BSPh 102
BOTANY WITH TAXONOMY
Midterms
CELL STRUCTURE
2.1
TRANSPORT PROCESSES
MIDTERM
COVERAGE
2.2
GROWTH AND DIVISION OF
CELL
2.3
PLANT ORGANS
2.4
SEXUAL REPRODUCTION
2.5
CELL
STRUCTURE
20XX
DISCOVERY OF THE CELL
• Robert Hooke – observed slices of cork
under a simple magnifying device in 1665
• He took slices of cork and observed it under a
microscope.
• Coined “cells”
• Dead cells
• Today, we know a lot more
about cells and their structure due
to the improved microscopes having
high magnification.
4
THE CELL
• Is the lowest level of structure capable of performing all the
activities of life
5
SOME PLANT CELL FUNCTIONS
• Water and salts are absorbed from soil by the ROOT CELLS
and are also transported by cells of the vascular tissues
• Energy of sunlight is used by leaf cells to convert CO2 and H2O
to carbohydrates
• Plant reproduction
• Cells in flowers produce pigments/nectar that attract insects
20XX
presentation title
6
THE CELL THEORY
• Was proposed by Matthias Schleiden and
Theodor Schwann in 1839:
1. All living things are made up of cells.
2. Cells are the smallest working unit of all living
things.
3. All cells come from pre-existing cells through
cell division.
7
CELL FUNCTIONS
• Some organisms consist of a single cell
(unicellular), others are multicellular aggregates
of specialized cells. But whether multi or
unicellular, all cells must accomplish the same
functions:
• Uptake and processing of nutrients
• Excretion of wastes
• Response to environmental stimuli
• Reproduction
20XX
presentation title
8
TYPES OF PLANT CELLS
1. Cells of shoot/root lips
2. Epidermis
3. Epidermal gland cells
4. Green leal cells
5. Root epidermal cells
6. Vascular cells
7. Flower cells
1. Cell division; produce new protoplasm
2. Water retention; cutin and wax are barriers against
fungi and insects
3. Protection: produce poisons that inhibit animals from
harming plants
4. Collect solar energy by photosynthesis
5. Collect water and minerals
6. Transport water, minerals, and organic molecules
7. Petal cells: pigments that attract pollinators
Scent cells: fragrances that attract pollinators
Nectary cells: sugars that attract pollinators
Stamen cells: indirectly involved in producing sperm
cells
Carpal cells: indirectly involved in producing egg cells
Fruit cells: produce sugars, aromas, flavorful compounds
that attract fruit-eating/seed-dispersing animals
9
TRANSPORT
PROCESSES
TRANSPORT OF SMALL MOLECULES
1. DIFFUSION
• molecules of substances move from their region of higher
concentration to the regions of lower concentration. This does not
require energy. Both solute and solvent moves.
Example : absorption of glucose in a cell
11
TRANSPORT OF SMALL MOLECULES
2. OSMOSIS
• movement of water molecules from the region of their higher
concentration to the region of their lower concentration through a
semipermeable membrane. There is no expenditure of energy in
osmosis. This kind of movement is along concentration gradient. Only
the solvent moves.
12
TRANSPORT OF SMALL MOLECULES
3. ACTIVE TRANSPORT
• When the direction of movement
of a certain molecule is opposite
to that of diffusion i.e., from region
of their lower concentration
towards the region of their higher
concentration, it would require an
“active effort” by the cell for which
energy is needed. This energy is
provided by ATP (adenosine
triphosphate). The active transport
may also be through a carrier
molecule.
13
TRANSPORT OF LARGE MOLECULES
1. ENDOCYTOSIS
2. EXOCYTOSIS
14
ENDOCYTOSIS (TYPES)
1. PHAGOCYTOSIS
• intake of solid particles
• membrane folds out going
round the particle, forming a
cavity and thus engulfing the
particle
2. PINOCYTOSIS
• intake of fluid droplets
• membrane folds in and forms a
cup-like structure and sucks in
the droplets
15
Match the following:
(i) hydrophilic end
(a) inner ends of
lipids
(ii) pinocytosis
(iii) fluid-mosaic model
(b) fluid droplets
(c) outer ends of
lipids
(iv) hydrophobic end
Singer
(d) Nicholson and
16
CELL PARTS
20XX
17
THE PLASMA MEMBRANE
• Is made of proteins and lipids and several models were
proposed regarding the arrangement of proteins and lipids
• The fluid mosaic model proposed by Singer and Nicholson
(1972) is widely accepted.
18
THE FLUID MOSAIC MODEL
According to the fluid mosaic model:
(i) The plasma membrane is composed of a lipid bilayer of
phospholipid molecules into which a variety of globular proteins are
embedded.
(ii) Each phospholipid molecule has two ends, an outer head
hydrophilic i.e., water attracting, and the inner tail pointing centrally
hydrophobic, i.e., water repelling
(iii) The protein molecules are arranged in two different ways:
(a) Peripheral proteins or extrinsic proteins: these proteins are
present
on the outer and inner surfaces of lipid bilayer.
(b) Integral proteins or intrinsic proteins: These proteins
penetrate the
lipid bilayer partially or wholly
19
THE PLASMA MEMBRANE (functions)
• Encloses the cell contents
• Act as surfaces that hold enzymes
• Allows transport of certain substances into and
out of the cell but not all substances so it is
termed as ‘selectively permeable’
20XX
presentation title
20
THE CELL WALL
• STRUCTURE:
• Outermost non-living layer present in all plant cells.
• Secreted by the cell itself.
• In most plants, it is chiefly made up of cellulose but may also
contain other chemical substances such as pectin and lignin.
• The substance constituting the cell wall is not simply
homogeneous, but it consists of fine threads or fibers called
microfibrils.
• It may be thin (1 micron) and transparent as in the cells of
onion peel. In some cases, it is very thick as in the cells of
wood.
20XX
THE CELL WALL
21
THE CELL WALL
• FUNCTIONS:
– The cell wall protects the delicate inner parts
of the cell.
– Being rigid, it gives shape to the cell.
– As it is rigid, it does not allow distension of the cell, thus leading
to turgidity of the cell that is useful in many ways
– It freely allows the passage of water and other chemicals into and
out of the cells
– There are breaks in the primary wall of the adjacent cells through
which cytoplasm of one cell remains connected with the other.
These cytoplasmic strands which connect one cell to the other one
are known as plasmodesmata.
– Walls of two adjacent cells are firmly joined by a cementing
material called middle lamella made of calcium pectinate
22
TRUE OR FALSE?
1. The plasma membrane is composed of a lipid bilayer
of fat molecules.
2. The fluid mosaic model proposed by Songer and
Nicholson (1962) is widely accepted.
3. Cells, whether unicellular or multicellular must
accomplish the same functions.
4. The cell theory was proposed by Matthias Schleiden in
1839.
5. Each phospholipid molecule has four ends.
20XX
presentation title
23