Introduction to Botany
Thursday, July 21, 2022
11:19 AM
PRINCIPLES OF THE SCIENTIFIC METHOD
➢ Information derived from documented and
controlled observations
➢ Tangible phenomenon studied
➢ Constant and universal- therefore reproducible
results
➢ Based on skepticism
CLASSIFICATION OF PLANTS
HOW DOES ONE CONDUCT A SCIENTIFIC
STUDY?
1.
2.
3.
4.
5.
6.
7.
8.
Identify the statement of the problem
Formulate hypothesis
Define data to collect
Devise experimental design
Conduct the experiment
Record and analyze the data
Write the results and conclusions
Evaluate the study in relation to similar
investigations
< 400,000 plant species
< around 391,000 vascular plants
< and over 3000 endangered species
WHAT ARE SOME OF THE TRENDS IN BOTANICAL RESEARCH?
1. Pharmaceutical research
- This involves drug discovery, development, evaluation, and
regulatory approval
i. Ampalaya (Momordica charantia )
○ Used to treat diabetes
○ leaf extract is a folkloric remedy for stomach
problems
○ could decrease cholesterol levels
ii. Coconut (Cocos nucifera)
○ VCO was found to inhibit the growth of
Staphylococcus aureus
○ promotes blood sugar control; has powerful
antioxidants
iii. Lagundi (Vitex negundo) [Chinese chastetree]
○ Used for cough and asthma relief; relaxant of the
air passages in the lungs
iv. Malunggay (Moringa oleifera)
○ Has antioxidants; has 7 times more Vit. C than
oranges, and 15 times more potassium than bananas
○ helps treat stomach disorders (e.g. constipation,
gastritis)
v. Mangosteen (Garcinia mangostana )
○ contains chemicals that might act as antioxidants
and fight infections
○ may help lower blood pressure
i. Papaya (Carica papaya )
○ contain high levels of antioxidants
vitamin A, vitamin C, and vitamin E
○ reduced risk of heart disease,
diabetes, cancer
ii. Avocado (Persea americana )
○ source of vitamins C, E, K, and B6
○ Improves digestion
○ Natural detoxifier
iii. Aloe vera (Aloe vera)
○ Usually used to relieve sunburns
○ Serves as heartburn relief
○ Lowers blood sugar
○ Natural laxative
iv. Cashew (Anacardium occidentale )
○ Rich in protein, healthy fats, and
antioxidants
○ Reduces cholesterol
○ May help prevent heart diseases
2. How environmental changes affect plant life
3. Researches that assist agriculture productivity and food security
- Golden Rice is a genetically-modified type of rice that was
approved in the Philippines. Developed by the International Rice
Research Institute (IRRI), the goal was to help curb the vitamin A
deficiency in developing nations.
IMPORTANCE OF PLANTS TO MAN
1. Air
a. Plants produce oxygen
2. Water
a. Plants are regulators of the water cycle
b. They are responsible for 60% of the flow of
water from land to atmosphere
3. Shelter and clothing
4. Health and well-being
Module 1 Page 1
Part II
Wednesday, October 12, 2022
8:00 AM
 Plant Biology Specialties
 Applied Botany
○ Agronomy
▪ Application of plant and soil science to
crop production
○ Horticulture
▪ Science and art of cultivating fruits,
vegetables, flowers, and ornamental
plants
○ Postharvest science
▪ study of plant physiology of living plant
tissues after picking; establishes the
storage and transport conditions that
best prolong shelf life
○ Biotechnology
▪ Harnessing cellular and biochemical
processes to develop technologies
○ Plant Breeding
▪ The science of developing new plant
varieties
○ Plant Tissue Culture
▪ Science of cultivating plant
cells/tissues/organs on specifically
formulated nutrient media
○ Plant Pathology
▪ Studies the causes of plant diseases
and how they can be managed and
controlled
○ Agrostology/Graminology
▪ Studies grasses and their classification
○ Phycology
▪ Study concerned with seaweeds and
other algae
○ Forestry
▪ Science related to creating, managing,
planting, using and conserving forests
○ Anatomy
▪ study of the tissue and cell
structure of plant organs, internal
structure
○ Morphology
▪ a.k.a. phytomorphology studies the
physical form and external
structure of plants
○ Plant Physiology:
▪ study of plant function and
behavior, including processes of
growth, metabolism, reproduction,
defense, etc.
○ Cytology:
▪ the study of cells as the
fundamental units of living things
○ Genetics:
▪ study of genes, genetic variation,
and heredity in plants
○ Taxonomy:
▪ science of naming organisms
○ Ecology:
▪ studies the distribution and
abundance of plants, interaction
among plants and other organisms
○ Ethnobotany:
▪ how people of a particular culture
make use of native plants
○ Paleobotany:
▪ study of ancient plants using plant
fossils in sedimentary rocks
EXAMPLES OF NEW PLANT SPECIES
DISCOVERED IN THE PHILIPPINES:
➢ Nepenthes cabanae
○ It is a new species of pitcher plant from Central Mindanao
○ Resource: Noel E. Lagunday & Victor B. Amoroso, 2019.
Nepenthes cabanae (Caryophyllales, Nepenthaceae), a new
species of pitcher plant from Central Mindanao, Philippines.
Philippine Journal of Systematic Biology 13(1); 39-45; doi:
10.26757/pjsb2019a13005
Medinilla malabrigoi
➢ Amorphophallus calcicollus
○ Resource: Tamayo, M. N., Magtoto, L. M., Sumalinog, M. S., Jr.,
Reyes, T. D., Jr., & Austria, C. M. (2021). Amorphophallus
calcicolus (Thomsonieae, Araceae), a new species from the Bohol
island, Central Visayas, Philippines. Phytotaxa, 489(2), 229–235.
https://doi.org/10.11646/phytotaxa.489.2.12
Nepenthes cabanae
Amorphophallus calcicollus
➢ Medinilla malabrigoi
○ Adorador, J. T., Meneses-Adorador, Z. D., & Quakenbush, J. P.
(2021). Medinilla malabrigoi (Melastomataceae), a new species
from forests over limestone in Samar Island, Philippines.
Phytotaxa, 483(2), 95–105.
https://doi.org/10.11646/phytotaxa.483.2.2
➢ Tristaniopsis flexuosa
○ Resource: Fernando, Edwino & Wilson, Peter. (2021).
Tristaniopsis flexuosa (Myrtaceae), a new species from
ultramafic soils in the Philippines. Telopea. 24. 345–349.
10.7751/telopea15588.
Module 1 Page 2
Tristaniopsis flexuosa
The Plant Cell
Friday, July 22, 2022
10:47 AM
THE ORIGIN OF LIFE
Theory of Spontaneous Generation
- Living organisms develop from non-living matter
- Has been disproved by Louis Pasteur in 1850
How did life on Earth begin?
2. Formation of more complex organic polymers (large
Stage 1. Organic molecules formed from inorganic molecules. (Abiotic synthesis) Stage
molecules).
 Reducing atmospheric hypotheses
○ Proposed by Oparin and Haldane (1920)
▪ The atmosphere of early Earth was electron adding (reducing)
□ Which was actually found to be a neutral atmosphere;
contained CO, CO2, N2, and H2O
▪ Contained water vapor, H2, CH4, NH3
▪ Had "primordial soup"
▪ Energy came from lightning and UV radiation
○ Stanley Miller's Experiment (1953)
▪ With Harold Urey; simulated the situation proposed by Oparin and
Haldane
 Organic molecules can eventually polymerize to DNA, RNA, or
proteins
 Can react in hot sand, clay, or rock
Stage 3. Polymers become enclosed by a boundary
(membrane).
 Called protocell/protobionts
○ Coacervates: droplets of protein and carbohydrate
surrounded by a skin of water
○ Liposomes: vesicles surrounded by phospholipid bilayer
▪ RNA on the surface of clay were enclosed in
the liposomes; genetic material found in
protocells
▪ Features of protocells that make it precursor
of living cells
□ Contains boundary that separates
internal contents from external
environment
□ Contains polymers that could contain
information (DNA or RNA)
□ Contain polymers that have catalytic
ability
□ Capable of self-replication by division
Stage 4. Cells evolve by chemical selection.
 Deep Sea Hypothermal Vent Hypothesis
○ Organic matter can be produced in deep sea hypothermal vent
○ Vent produces hot hydrogen sulfide
▪ Black smokers: water is extremely hot, unstable organic compounds
▪ Alkaline vent: water is warm, pH 911, more suitable for origin of life
 Extraterrestrial hypothesis
○ Meteorites brought organic matter to Earth
○ e.g. Murchison meteorite; had >80 amino acids, lipids, simple sugars
○ Tagish lake meteorite; 3% of weight is organic matter; glycine most
abundant
 RNA world: hypothetical period in early Earth where
information needed for life were contained only in RNA
molecules
○ RNA molecules:
▪ Has ability store information through its
nucleotide bases
▪ Has capacity for self-replication: nucleotide
sequence
▪ Perform catalytic actions
○ Chemical selection:
▪ Chemical within a mixture has special
properties that cause it to increase in number
relative to other chemicals in the mixture (like
natural selection)
□ Leads to chemical evolution
 Population of molecules
changes over time to become
a new population with a
different chemical composition
➢ Formaldehyde and hydrogen cyanide were
formed
➢ Later experiments showed sugars, amino
acids, lipids, and nitrogenous bases
Module 1 Page 3
The First Living Cells
Wednesday, October 12, 2022
8:13 AM
THE FIRST LIVING CELLS
1. Were heterotrophic
a. Fed organic molecules in primordial soup
b. Used chemicals in the sea vents to produce
energy
2. Anaerobic
a. Very little O2 in early Earth
3. Prokaryotic
a. No nucleus
b. Free-floating DNA
Evolution of Autotrophy
➢ When the supply of organic food decreased resulting in
famine
○ With famine, there becomes competition for
resources, threatening heterotrophs
➢ Some cells then developed the capacity to produce
organic compounds through photosynthesis
○ Before it was anoxygenic photosynthesis (using
hydrogen sulfide H2S), which later evolved to
oxygenic photosynthesis
Evolution of aerobic organisms
➢ Cyanobacteria were able to photosynthesize and
pumped O2 in the atmosphere, causing a rise in O2 level
➢ This caused the evolution of aerobic respiration
Origin of Eukaryotic cells
➢ Eukaryotic cells appeared about 1.8 billion years ago,
presumably from prokaryotes
➢ These eukaryotic cells have membrane-bound organelles
○ Mitochondria
○ ER
○ Golgi apparatus
○ Chloroplasts
▪ Nuclear, mitochondrial, and chloroplast
genomes are derived from separate cells
that came together via endosymbiotic
relationship
□ Nuclear genome came from
bacteria and archaea; while the
mitochondria and chloroplast may
have come from bacterium that
was eaten by a primordial
eukaryotic cell
□ Endosymbiont theory: smaller
organisms (endosymbiont) lives
inside a host
CELL THEORY
In 1665, Robert Hooke published Micrographia, a book filled with
drawings and descriptions of the organisms he viewed under the
recently invented microscope (invented by Zacharias Janssen).
The invention of the microscope led to the discovery of the cell
by Hooke. While looking at cork, Hooke observed box-shaped
structures, which he called “cells“ as they reminded him of the
cells, or rooms, in monasteries. This discovery led to the
development of the classical cell theory.
The classical cell theory was proposed by Theodor Schwann in
1839. There are three parts to this theory. The first part
states that all organisms are made of cells. The second part
states that cells are the basic units of life. These parts were
based on a conclusion made by Schwann and Matthias Schleiden
in 1838, after comparing their observations of plant and animal
cells. The third part, which asserts that cells come from
preexisting cells that have multiplied, was described by Rudolf
Virchow in 1858, when he stated omnis cellula e cellula (all cells
come from cells).
Since the formation of classical cell theory, technology has
improved, allowing for more detailed observations that have led
to new discoveries about cells. These findings led to the
formation of the modern cell theory, which has three main
additions:
1. DNA is passed between cells during cell division;
2. The cells of all organisms within a similar species are
mostly the same, both structurally and chemically;
3. Finally, that energy flow occurs within cells.
Antonie van Leeuwenhoek made descriptions of various cells
that laid the foundation for the cell theory
Module 1 Page 4
Prokaryotic vs. Eukaryotic Cells
Wednesday, July 27, 2022
10:17 AM
THE PROKARYOTIC CELL
➢ Etymology: pro- meaning before, karyon meaning nucleus
➢ These cells lack a nucleus and other membrane-bound organelles
THE EUKARYOTIC CELL
➢ eu- meaning true, karyon meaning nucleus ("true nucleus"
➢ Unlike prokaryotic cells, these have a true nucleus and membrane-bound
organelles
 What are some benefits of the existence of prokaryotic cells?
THE DIFFERENCES BETWEEN PROKARYOTIC & EUKARYOTIC CELLS
PROKARYOTES
EUKARYOTES
Free-floating in the cytoplasm
Found in the nucleus
Location of genetic material
No nucleus and membrane-bound organelles
Has a nucleus and membrane-bound organelles
Organelles
Usually unicellular
Can be unicellular or multicellular
Number of cells
From Domain Bacteria and Archaea
From Doman Eukarya; animals, plants, protists, fungi
Organisms
Simpler and smaller
Complex and larger
Size of cells
THE SIMILARITIES BETWEEN PROKARYOTIC & EUKARYOTIC CELLS
Genetic material
Jelly-like region within the cell
Structures that synthesize proteins
Outer covering
DNA | deoxyribonucleic acid
Cytosol
Ribosomes
Cell membrane
Module 1 Page 5
Parts of the Eukaryotic Plant Cell
Wednesday, July 27, 2022
10:52 AM
THE PLANT CELL
WHAT ORGANELLES
ARE EXCLUSIVE
PARTS
OF THE PLANT
CELL TO EACH
TYPE OF CELL?
Animal Cell
Plant Cell
Lysosome
Centriole
Centrosome
Chloroplast
Central vacuole
Cell wall
Plasmodesmata
WHICH CELL PARTS ARE NOT
CONSIDERED ORGANELLES?
◊ Nucleus
◊ Cytoskeleton
◊ Ribosomes
SUBUNITS OF THE CELL
Whole Cell
Cell Wall
Protoplasm - substance that
makes up cells; protoplasm of
single cell is protoplast
Nucleus
Vacuole
Cytoplasm - combination
of cytosol and
organelles
Organelles
Cell Junctions:
Cytosol
- jelly-like substance holding the organelles
Tight Junctions
- Forms a barrier
that prevents
leakage of
extracellular fluid
across a layer of
epithelial cells
Desmosomes
- Function like
rivets; fastens
cells together
Gap Junctions
- a.k.a.
communicating
junctions; acts
similar to
plasmodesmata
- Necessary for
communication
between cells
Module 1 Page 6
]
Part I
Wednesday, October 12, 2022
8:23 AM
 Cell wall
○ maintains the cell's shape and protects it from damage; it is composed of
polysaccharide cellulose
○ An extracellular structure of plant cell
Primary cell wall: what a young plant cell
secretes first; flexible and thin
Secondary cell wall: sturdier than the
former; deposited between the primary
cell wall and the plasma membrane
• Made with lignins, which
resists chemical, fungal, and
bacterial attacks
> Middle lamella: an adhesive layer that
glues one cell wall to other cell walls
>
>
○
▪ Plasmodesmata - from desma meaning bond; the channels that connect
cells together
 Endomembrane system
○ Serves a variety of purposes from protein synthesis, protein transport,
metabolism and movement of lipids, etc.
▪ Plasma membrane
□ Is also called the plasmalemma; completely covers the surface
of the protoplasm
□ It is selectively permeable; keeps harmful substances out, lets
beneficial ones in
□ A phospholipid bilayer: hydrophobic tail, hydrophilic head
 Fluid Mosaic Model: the currently accepted model of the
arrangement of molecules in the plasma membrane; membrane
is a mosaic of protein molecules bobbing in a fluid bilayer of
phospholipids
▪ Nuclear membrane
□ This separates the nucleus from the rest of the cell
▪ Endoplasmic Reticulum (E.R.)
□ A system of narrow tubes and membrane sheets that form a
network around the cytoplasm
□ Rough ER:
 Responsible for protein synthesis; has a "rough" look
because of the ribosomes attached to it
 Has transport vesicles that move the proteins that
need to be secreted from the cell
□ Smooth ER:
 Involved in lipid synthesis and membrane assembly
(folding membranes); has a "smooth" look due to the
lack of ribosomes
 Can also detoxify drugs and poisons (like in liver cells)
Module 1 Page 7
▪ Golgi apparatus
□ Products of the ER are sent here and
then sent to other destinations
□ Consists of a group of associated,
flattened membranous sacs (called
cisternae)
 Has the cis face (faces the ER,
receives the proteins) and
trans face (ships off the
proteins via vesicles)
▪ Vacuole
□ Store mostly water and salts; also
crystals, starch, protein, and various
types of granules or fibrous materials
□ Helps in cell growth, stores nutrients
and waste products
 A large central vacuole is
formed by the merging of
numerous little vacuoles
□ Has a vacuole membrane called the
tonoplast
Part II
Wednesday, October 12, 2022
8:20 AM
 Nucleus
 Plastids
○ Where the cell's genetic information is stored
○ The nucleus carries out information retrieval by making copies of
specific parts of the DNA whenever the information is needed
▪ Nuclear envelope
□ Composed of an inner and outer membrane; this
separates the nuclear material from the rest of
the cell
▪ Nuclear pores
□ This allows transport of materials in and out of
the nucleus
▪ Nucleoplasm
□ Like the "protoplasm" of the nucleus
▪ Nucleolus (plural, nucleoli)
□ Areas where the components of ribosomes are
synthesized and partially assembled
▪ Nuclear lamina
□ Netlike array of protein filaments that maintains
the shape of the nucleus by giving mechanical
support to the nuclear envelope
▪ Nuclear matrix
□ Protein filaments that extend throughout the
nuclear interior
○ Organelles that perform a variety of functions
▪ Chloroplast
□ Contain the green pigment chlorophyll
□ Important in photosynthesis; converts solar energy
to chemical energy
 Ribosomes
○ Are responsible for protein synthesis
○ Are complex aggregates of three molecules of RNA and
approximately 50 types of protein
▪ Membrane-bound
▪ Free-floating
▪ Chromoplast
□ Contain abundant colored lipids; in flowers and
fruits
▪ Amyloplasts
□ Stores starch (amylose); considered to be
leucoplasts
▪ Etioplasts
□ Specific stage in the transformation of proplastids
to chloroplasts; occur when tissues are grown
without light
▪ Leucoplasts
□ colorless plastids; synthesize lipids and other
materials
▪ Protoplastids
□ Small, undifferentiated plastids
Elaioplasts (Figure 2(c)) are plastids that specialize in oil
synthesis and storage
 Mitochondria
○ Carry out cell respiration
○ Generates adenosine triphosphate (ATP) by extracting energy
from sugars, fats, and other fuels
▪ Cristae - folded mitochondrial membranes
▪ Matrix - where reactions that do not involve highly
reactive intermediates take place
▪ Outer mitochondrial membrane - gives shape and rigidity
to mitochondrion
▪ Inner mitochondrial membrane - forms the cristae;
selectively permeable
Module 1 Page 8
From <https://www.google.com/search?
q=elaioplast&oq=elaioplast&aqs=chrome.0.69i59j0i512l9.3034j0j9
&sourceid=chrome&ie=UTF-8>
Part III
Wednesday, October 12, 2022
8:21 AM
 Cytoskeleton
○ Gives mechanical support to the cell
○ Maintains the shape; made of a network of fibers
○ Is also involved in some types of cell motility (movement of cell and cell parts)
▪ Microtubules
□ Most abundant and easily-studied of the structural elements of the cell
□ Maintains cell shape, motility
▪ Microfilaments
□ Have been implicated in different types of structure and movement
 Microbodies
○ Has two classes:
▪ Peroxisomes
□ Detoxifies certain byproducts of photosynthesis
□ Also found in animal cells (in liver and kidney cells)
▪ Glyoxysomes
□ Converts stored fats into sugars
□ Found only in plants
 Lysosomes
○ Hydrolytic enzymes that digest macromolecules (like in phagocytosis, by engulfing
smaller organisms)
 Peroxisomes
○ Used in oxidation
○ contain enzymes that remove hydrogen atoms from various
substrates and transfer them to oxygen (O2), producing
hydrogen peroxide (H2O2)
Module 1 Page 9
Types of Transport
Thursday, August 4, 2022
7:07 PM
CELL TRANSPORT
➢ A fundamental aspect of life which allows the movement of specific substances to
particular sites within organisms
➢ They are categorized into two types:
○ Short-distance transport - transport distances of a few cell diameters or less
○ Long-distance transport - transport distances between cells that are not close
neighbors
▪ e.g. from root hairs to leaves at the top of the plant
▪ This is adaptive for land plants
○ Isolation mechanisms - are also essential in the concept of cell transport
▪ These inhibit substance movement
□ e.g. epidermis with cutin-lined walls keeps water from leaving the
shoot
□ Casparian strips in the endodermis prevent substances from
diffusing from one part of a root to the other
SHORT-DISTANCE TRANSPORT TYPES
➢ Apoplastic route
○ The apoplast of the plant refers to the cell wall and the intracellular
spaces
▪ Route can pass through dead cells; external to plasma membrane
of living cells
○ Route: cell walls - extracellular space - interior of dead cells - extracellular
space - cell wall - extracellular space
➢ Symplastic route
○ The symplast is the one continuous mass of the protoplasm
○ Passes through cytosol of all living cells, and plasmodesmata; also passes
by cell membrane
○ Route: cytosol - plasma membrane - plasmodesmata - plasma membrane cytosol
TYPES OF MEMBRANES
> Freely-permeable
○ Allow all solutes to diffuse through it and have little biological significance
> Completely impermeable
○ Act as isolation barriers due to their impenetrable nature
> Selectively-permeable/Differentially permeable
○ Only allows certain substances to pass through
▪ All lipid/protein cell membranes are like this
Semipermeable membranes permit only some particles to depending on their size
TYPES OF TRANSPORT
 Passive Transport - does not require energy
○ Diffusion: movement of particles from high concentration to low concentration
▪ Dispersal from higher to lower concentration
▪ Principle way of movement within the cell
▪ Osmosis - diffusion through a membrane
□ Tonicity - ability of a surrounding solution to cause a cell to gain/lose water
 Isotonic
◊ Same solute concentration ; no net flow of water
◊ Flaccid (limp)
 Hypertonic
◊ Higher solute concentration ; water leaves the cell
◊ Causes cell lysis; plasmolysis (shrivel, plasma membrane gets pulled inwards)
 Hypotonic
◊ Lower solute concentration ; water enters the cell
◊ Causes cell to swell; increase in turgidity and turgor pressure
□ Water potential (Ψ) - the free energy of water
 Can be increased in several ways: heating water, increasing pressure, or elevating water
◊ Solute potential - also called osmotic potential; the effect solutes have on water potential
◊ Pressure potential - the effect pressure has on water potential
Osmosis:
The equation for water potential:
where:
➢ Transmembrane route
○ Passes by the plasma membrane
○ Route: cell wall - plasma membrane - cytosol - plasma membrane - cell
wall
LONG-DISTANCE TRANSPORT TYPES
 Phloem
○ Pressure-flow hypothesis (Munch Hypothesis)
▪ proposes that water containing food molecules flows under pressure through the
phloem
□ Phloem sap: mixture of vacuolar water and part of the cytoplasm
□ Mass transfer: amount of sugars and other nutrients excluding water
transported by the phloem per hour
○ Sources - sites from which water and nutrients are transported
○ Sinks - sites that receive transported phloem sap
▪ e.g. meristems, root tips, leaf primordia, growing flowers, fruits
 Xylem
○ Cohesion-tension hypothesis
▪ The movement of water through the xylem is based on a few of its properties:
□ Cohesive - water molecules interact strongly with other water molecules
□ Adhesive - it interacts with many substances (stick to other particles)
▪ Facilitated Diffusion - needs help from channel proteins to transport substances
□ Channel protein: a hydrophilic channel that certain molecules or ions use as a tunnel through the
membrane
 Ion channel: transport ions; function as gated channels which respond to stimulus
 Aquaporin: used by water molecules
□ Carrier protein: seem to undergo a subtle change in shape that somehow translocates the solute -binding
site across the membrane
 Active Transport - requires energy in the form of ATP (adenosine triphosphate )
○ Usually in the form of carrier proteins
▪ Sodium potassium pump: 3 Na+ out, 2 K+ in
▪ Proton pump: actively transports protons (hydrogen ions, H+) out of the cell. The pumping of H+ transfers
positive charge from the cytoplasm to the extracellular solution
▪ Co-transport: transport protein (a cotransporter) can couple the “downhill” diffusion of the solute to the
“uphill” transport of a second substance against its own concentration gradient
Module 1 Page 10
Facilitated diffusion:
Cell Division
Thursday, August 4, 2022
8:46 PM
THE CELL CYCLE
 Cell division plays an important role in asexual reproduction, cell growth and development, and tissue renewal
in organisms.
 The cell cycle is the life of a cell from its formation to its own division into two daughter cells
 INTERPHASE
○ Is the longest stage that takes about 90% of the cell cycle (the mitotic phase, which includes the
division and cytokinesis, takes a shorter amount of time)
○ This is divided into three stages:
▪ G1 phase - called the gap one or "first gap" phase
□ Cell grows in size; all the organelles duplicate, building blocks required in next stages
are made by the cell
▪ S phase - synthesis phase
□ DNA and nucleus is duplicated
G2
phase
- called gap two or "second gap" phase
▪
THE CHROMOSOME STRUCTURE
□
Allows
the cell to grow more in size; cell makes more proteins and organelles
➢ Chromosome - packaged DNA molecules; composed of one very long linear DNA molecules
associated with many proteins
 The G phases were misnamed as "gaps" because first observations believed
they appeared inactive
➢ Chromatin - the complex of DNA and proteins that is the building material of
chromosomes
▪ G0 phase - is optional for the cell; depends on resource availability
➢ Chromatid - one of the two identical halves of a chromosome
□ Thought as the resting phase
○ The pair is called "sister" chromatids (joined copies o the original chromosome)
□ Quiescent stage: when the cell enters G0 phase, shows metabolic activity and signs
of dividing
□ Senescent stage: when the cell enters G0 but does not show signs of dividing again
PLOIDY
➢ Is the number of chromosomes occurring in the nucleus of a
cell
○ Haploidy/Haploid - contains half of the
normal/somatic number of chromosomes (for humans,
the haploid cell has 23 chromosomes)
▪ Gametes/sex cells (e.g. egg and sperm)
○ Diploidy/Diploid - chromosomes in pairs (in humans,
there are 46 chromosomes in diploid cells)
▪ Body/somatic cells
○ Polyploidy/Polyploid: cell whose nuclei has three or
more times the number of chromosomes found in
haploid cells
Phase
G1 phase
S phase
G2 phase
M phase
➢ Centromere - constricted region of a chromosome where the cell's spindle fibers
attach
○ Separates the human chromosomes into the P (short) and Q (long) arm
➢ Kinetochore - the sister chromatids have this structure made of proteins that have
assembled on specific sections of DNA at each centromere
○ Where the microtubules attach during prometaphase to pull the chromatids
towards one of the poles
➢ Chromosome arms - the short arm is called the "p arm" and the long arm is called the
"q arm"
➢ Classification of chromosomes:
○ Metacentric - the centromere located midway between the ends of the
chromosome, separating the two arms of the chromosome
○ Acrocentric - centromere is located quite near one end of the chromosome
○ Telocentric - centromere is located at one end; the p arms would not, or
barely, be visible
○ Submetacentric - centromere is located near the middle; as such, p arm is
relatively shorter
Module 1 Page 11
What happens in the phase Amount of time it takes
Cell grows
~5-6 hours
Copying chromosomes
~10-12 hours
Preparing for cell division
~4-6 hours
Cell division
~less than 1 hour
PPT
Tuesday, August 9, 2022
11:09 AM
Prophase 1
➢ Leptotene stage
➢ Zygotene stage
➢ Pachytene stage
➢ Diplotene stage
➢ Diakinesis
Metaphase 1
Anaphase 1
Telophase 1
➢ One pair of chromosomes is called a homologue
1.
2.
3.
4.
➢ The one above is a karyotype of a human: haploid of humans
2
4
Gametes
Halves
Gametes don’t undergo meiosis because they are already
haploid
Only the somatic cells undergo this since they are originally
diploid
Consequences of meiosis include genetic diversity, since it
involves the "crossing over" of chromosomes
➢ Kinds of chromosomes corresponds to n
➢ Sets corresponds to the multiplier of n
n=23 (23 kinds)
2n=46 (2 sets)
Module 1 Page 12
Mitotic Division
Saturday, August 6, 2022
8:06 PM
 MITOSIS | Mitotic Phase
○ Prophase
▪ Chromatin fibers more tightly coiled, condensing into discrete observable
chromosomes
▪ Nucleoli disappear
▪ Duplicated chromosome appears as two identical sister chromatids attached
by the centromere
▪ Mitotic spindle forms (centrosomes + microtubules)
▪ Centrosomes move away from each other
○ Prometaphase
▪ Nuclear envelope disappears
▪ Microtubules from each centromere now invade the nuclear area
▪ The kinetochore is formed; some microtubules attach to the kinetochores
▪ Nonkinetochore microtubules interact with those from the opposite pole of the
spindle, lengthening the cell
○ Metaphase
▪ Centrosomes now at opposite poles
▪ The chromosomes are in the metaphase plate; chromosomes lined at the middle
of the cell
○ Anaphase
▪ Shortest stage of mitosis, lasting only a few minutes
▪ Cohesion proteins cleaved; sister chromatids separated, becoming an
independent chromosome
▪ Chromosomes start moving towards opposite ends of the cell
▪ Cell elongates; at the end two ends of the cell have identical and complete
collections of chromosomes
○ Telophase
▪ 2 daughter nuclei form in the cell; nuclear envelope forms
▪ Nucleoli reappear
▪ Chromosomes less condensed
▪ Mitosis is complete
 Cytokinesis
○ Division of cytoplasm
○ Involves the formation of the cleavage furrow which pinches the cell in two
Centrosomes are not in plant cells; they
are only microtubule organizing centers
n=23 (23 kinds)
2n=46 (2 sets)
0 chromatids at anaphase because the chromatids are considered chromosomes
The nuclear envelope is not the reason why the chromatins condense
Module 1 Page 13
Counting Chromosomes
Wednesday, October 12, 2022
9:25 AM
Genome(s)/Set(s) of chromosomes at G-1
two
Kinds of chromosomes at G-1
8
Chromatids at G-1
(0 - no chromatids at G-1 because the
16 chromatids
Chromosomes at G-1
16 chromosomes
Chromatids at G-2
32 chromatids
Functional centromeres at Prophase
16
Chromatids at Metaphase
32
Functional centromeres at Anaphase
32
Chromosomes at Anaphase
32
Chromatids at Anaphase
32 (dapat 0 na din? Kasi na divide na sila, and they are
now considered their own chromosome)
Genomes(s)/Set(s) of chromosomes moving toward one pole at
Anaphase 2
16
Genome(s)/Set(s) of chromosomes in each daughter nuclei at
Telophase. 2
16
Kinds of chromosomes in each daughter nuclei at Telophase.
8
Genome(s)/Set(s) of chromosomes prior to cytokinesis.
4
Genome(s)/Set(s) of chromosomes after cytokinesis
2
Module 1 Page 14
Meiosis
Saturday, August 6, 2022
MEIOSIS
➢ A type of cell division that
produces cells with half
the chromosomes of the
parent cell
8:07 PM
Meiosis I
 Prophase 1
○ Centrosome movement, spindle formation, nuclear envelope
breakdown
○ Chromosomes condense
○ Where crossing over occurs; DNA molecules of nonsister
chromatids are broken and rejoined to each other
○ Chiasmata forms, where the homologous pair joins and
does the crossing over
 Metaphase 1
○ Pair of homologous chromosomes now arranged at
metaphase plate, with one chromosome of each pair facing
each pole
○ Pairs lined up independently of other pairs (independent
assortment)
○ Both chromatids of one homolog (half of pair) attached to
kinetochore microtubules from one pole; same is to the
other homolog
 Anaphase 1
○ Homologs are separated; sister chromatids are still
attached by the centromere
○ Chromosome moves as a unit toward the same pole
 Telophase 1 and Cytokinesis
○ Each half of the cell has a complete haploid cell of
duplicated chromosomes
○ Each chromosome has 2 sister chromatids
○ Cytokinesis usually occurs simultaneously with telophase 1,
forming two haploid daughter cells
Meiosis II
 Prophase 2
○ Spindle apparatus forms
○ Chromosomes are moved by microtubules towards
metaphase 2 plate
 Metaphase 2
 Anaphase 2
 Telophase 2 and Cytokinesis
Module 1 Page 15
Figures
Wednesday, October 12, 2022
9:29 AM
Module 1 Page 16
Plant Tissues
Thursday, August 11, 2022
8:49 AM
What are meristems?
Levels of Organization
> Cells: the basic unit of life
> Tissues: a collection of cells that
performs specialized function
> Organs: a collection of tissues
that carry out particular functions
 These are regions of active cell division; mitosis
THE PLANT BODY
➢ Shoot system
○ Aerial portion of the plant body
▪ Includes the stem, leaves,
and flowers
➢ Root system
○ Are the plant's roots; roots are
almost never photosynthetic
There are also the types of plant bodies:
 Primary plant body
○ Derived from shoot and root apical
meristems
○ Made of primary tissues
○ The herbaceous parts of a plant
 Secondary plant body
○ Derived from meristems and other
apical meristems
○ Composed of secondary tissues:
wood and bark
happens here
- The cells in meristems are undifferentiated
 There are two types of meristems:
○ Apical Meristem
▪ Located at shoot and root tips
▪ Provide cells that enable primary growth
(growth in length)
□ Gives rise to the primary
meristems: protoderm, ground
meristem, and procambium
○ Lateral Meristem
▪ Responsible for secondary growth
(growth in width)
▪ In woody plants
□ Includes the vascular cambium and
cork cambium
Module 1 Page 17
Growth
Wednesday, October 12, 2022
8:27 AM
 Cell differentiation
➢ Plant growth and development may be defined as the
"increasing of plant volume and/or mass with or without
the formation of new structures."
➢ This is associated with development and reproduction
○
○
○
➢ The two types of growth:
○ Indeterminate growth
▪ Growth that occurs throughout the plant's
life
▪ e.g. the roots and stem
○ Determinate growth
▪ Stop growing after reaching a certain size
▪ e.g. leaves, flowers, fruits, thorns
Process by which cells with the same genes become
different from one another
The cells assume different functions
Cells differentiate from the meristem (meristematic
cells are undifferentiated or incompletely
differentiated)
○ All plant cells are grouped based on the nature of their
walls:
▪ Parenchyma cells
□ Have primary walls that remain thin
□ Relatively unspecialized plant cell that
carries out many functions
□ Typically alive at maturity
 Though some function by dying at
How does growth happen?
 Cell division
○ This enhances the potential for growth by
increasing the number of cells
▪ However, cell division alone does not
contribute to plant growth: it is accompanied
with cell expansion because it increases mass
maturity (e.g. stamens and some
fruits must open to release pollen or
seeds - this only happens when
parenchyma cells die and break
down/get torn apart)
▪ Collenchyma cells
 Cell elongation
○ When the cell expands in a direction mainly
perpendicular to the main orientation of the
microfibrils in the cell wall
○ During elongation, cell intakes water, vacuole
expands, cell elongates
▪ This is usually in response to the plant
hormone auxin
□ Have a primary cell wall that remains thin
in some areas, but unevenly thickened in
other areas
□ Typically alive at maturity
□ Mainly provides plastic support
 Found in shoot tips and young
petioles
▪ Sclerenchyma cells
□ Have primary and secondary cell walls
 Secondary wall is almost always
Parenchyma and collenchyma cells work together
when providing structural support
◊ Parenchyma acts as the air pressure inside
the collenchyma tire
○ Tendency of parenchyma to
expand is counterbalanced by
confinement by collenchyma
Module 1 Page 18
lignified (has lignin, a strengthening
polymer that accounts for most of
the dry mass of wood)
 Can develop from parenchyma cells
□ Many dead at maturity
□ Provides elastic support and some are
involved in water transport
□ These have two types:
 Mechanical (nonconducting)
sclerenchyma
◊ Sclereids: more or less
isodiametric; often dead at
maturity
◊ Fibers: long, with many types
dead, while others remain
alive and are involved in
storage
 Conducting sclerenchyma
◊ Tracheids
◊ Vessel Elements
Classification of Tissues
Thursday, August 11, 2022
10:38 AM
CLASSIFICATION OF TISSUES
There are different types of tissues :
Simple vs. Complex
➢ Simple tissues are only made of one type of cells
○ e.g. parenchyma, collenchyma, and sclerenchyma
tissues
➢ Complex tissues are made of multiple types of cells
○ e.g. xylem and phloem
Meristematic vs. Permanents
➢ Meristematic tissues continue to divide
➢ Permanent tissues, once they have differentiated,
they are permanently remain in that role
○ e.g. epidermis, xylem and phloem
Module 1 Page 19
Protoderm and Ground Meristem
Thursday, August 11, 2022
10:50 AM
PROTODERM
➢ The protoderm gives rise to the dermal tissue system.
○ Dermal tissue system : covers the outer surface of plants
➢ The outermost primary meristem
➢ Has two tissue types: epidermis and periderm
EPIDERMIS
> Protective covering over the surface of the plant organs (e.g. stem, root,
leaf, flower, fruit, and seed) with primary growth
▪ Barrier against bacterial invasion, protection from abrasion,
reflective to prevent overheating
> Made of a single layer of parenchyma cells; all interchange of material
between the plant and the environment occurs by the epidermis
> Secretes a waxy cutin to make the wall impermeable to water (prevents
water loss)
▪ Builds up to form cuticle
▪ Cell types:
□ Epidermal cells
□ Guard cells
 Are gateways for CO2 to enter the impermeable
epidermis
 Has stomatal pores; the guard cell and stomatal
pore form the stoma (pl. stomata)
□ Trichomes
 The hairs that make it difficult for animals to land
on, walk on, or chew into a leaf; also provide
shade, and create a layer of immobile air next to a
leaf surface
PERIDERM
> Protective covering that replace the epidermis (only present in plants with
secondary growth)
> Created by the cork cambium
> In woody plants
▪ Cell types:
□ Cork cells
 non-living and has cell walls that are composed of a
waxy substance that is highly impermeable to gases
and water called suberin
□ Cambium cells
 divide to produce secondary xylem cells toward the
central axis of the stem and secondary phloem cells
toward the outside
□ Parenchyma cells
GROUND MERISTEM
➢ This comprises the bulk of the plant body
➢ Function for storage, secretion, photosynthesis, support, strength
○ Pith:
▪ Ground tissue that is internal to the vascular tissue in a
stem
○ Cortex:
▪ Interior to the epidermis, external to the vascular tissue
➢ Have different tissue types:
○ Parenchyma tissue
▪ permanent tissue that makes a major part of ground tissues
in plants, where other tissues like vascular tissues are
embedded; and
▪ are non-vascular and composed of simple, living and
undifferentiated cells, which are modified to perform
various functions.
○ Collenchyma tissue
▪ supporting tissue composed of more or less elongated living
cells with unevenly thickened, nonlignified primary walls
▪ in regions of primary growth in stems and leaves
○ Sclerenchyma tissue
▪ support tissue composed of any of various kinds of hard
woody cells
Module 1 Page 20
Guard cells swell by absorbing water; this causes the
cell to open
 This causes CO2 to enter and O2 to leave
the cell. But this increases the risk of
microbes entering the plant, so during
nighttime where photosynthesis is
impossible, the guard cells close to prevent
water loss.
Layers of a woody stem
(with the periderm)
Procambium
Wednesday, October 12, 2022
8:30 AM
➢ Gives rise to the vascular tissue system
○ The vascular tissue system allows organisms to transport
nutrients and oxygen around the system when the distance
between cells is too far
➢ Stele: vascular cylinder that serves as passage of water and minerals
XYLEM
 These tissues conduct water and minerals
 Are composed of:
▪ Tracheary elements: tubular, elongated cells that are
dead and lignified at functional maturity
□ Tracheids
 Long, thin cells with tapered ends
 Water moves from cell to cell through
pits
□ Vessel elements
 Generally wider, shorter, thinner walled,
and less tapered than tracheids
 Have perforated end walls/plates
enabling water to flow freely through
vessels Secondary walls of the tracheary elements
PHLOEM
 Distributes sugars and minerals
 Composed of:
▪ Sieve-tube elements
□ Collective term used to refer to the conducting cells
of the phloem tissues
Sieve Cells
Sieve Tube Members
Shape
Long/narrow Short/wide
Ends pointed Ends flat
Sieve areas Small, over
On side walls: small;
cell surface
on end walls, sieve
plate
Associated Albuminous
Companion cells
cells
cells
▪ Xylem parenchyma
□ Can store water
▪ Xylem fibers
□ Provide mechanical support to the xylem, and the
whole plant
□ Thick, lignified dead cells
 Have two types:
▪ Primary xylem: xylem that grows first during primary
growth
□ Protoxylem
□ Metaxylem
▪ Secondary xylem: xylem that grows during secondary
growth
□ The end of these elements have sieve plates that
facilitate fluid flow from cell to cell
▪ Companion cells
□ Non-conducting cells in the sieve-tube element
▪ Phloem parenchyma
□ Function in food transport, and food and substance
storage
▪ Phloem fibers
□ Provide mechanical support to the phloem
 Types of phloem tissues
▪ Primary phloem: phloem that grows first during primary
growth
□ Differentiates from the procambium
 Protophloem
 Metaphloem
▪ Secondary phloem: phloem that grows first during secondary
growth
□ Differentiates from vascular cambium
(lined with lignin) keeps the plant from
collapsing under tension of water transport
Module 1 Page 21