Cell Structure and Function: Topics to be discussed
❖Where are the “Molecules of Life” located in the cells?
❖What are common between different types of cells?
❖Are there differences between cells of different
organisms?
❖Why is cell size so small?
❖What are the experimental techniques that help us to
understand the cell structure and organization?
❖What are the different cellular organelles?
E. Coli O157:H7 strain is harmful to humans
oIntestinal bacteria that
live in cattle, deer, goats,
sheep and humans
oSeverely damage the
lining of human intestine
http://everything-pr.com/ecoli-germany-spain/228647/
oComplications: Bloody
diarrhea, kidney failure,
blindness, paralysis and
death
oWhat makes bacteria sticky?
oWhy do people but not cows get sick
with E. coli O157:H7?
oWe need to learn about cells and how
they work?
Cell is the smallest unit that shows properties of life
oCells vary dramatically in shape and function
oHowever, all cells share certain organizational and functional
features
Examples of cells
Traits common to all cells
1665: Antoni van Leeuwenhoek first
observed tiny moving organisms in rainwater,
insects, fabric, sperm and other samples
Robert Hooke coined the term cell
Robert Brown first identified
a cell nucleus in 1820s
Matthias Schleiden first hypothesized
that a plant cell is an independent living
unit even when it is part of a plant
Theodor Schwann together with Schleiden
concluded that tissues of animals and plants
are composed of cells and their products
Rudolf Virchow realized that all cells
descended from another living cell
Cell Theory
• 1. All living things are made of cells.
• 2. New cells are produced from existing cells
• 3. Cells are the basic unit of structure and function in
living things.
Surface-to-volume limits also affect the
body plan of multicelled species
http://voer.edu.vn/c/comparing-prokaryotic-and-eukaryotic-cells/a64457a4/6b98166e
A sense of scale
https://www.jic.ac.uk/microscopy/scale.html
Prokaryotes vs. Eukaryotes
• Prokaryotes
(bacteria)
have no nucleus
and very few
organelles. DNA is
not contained
• Eukaryotes
(protists, fungi, plants and
animals) larger,more
complex,DNA is inside the
nucleus
Eukaryotic Cell : Animal Cell
Plant Cell
Vacuole
Smooth endoplasmic
reticulum
Ribosome
(free)
Chloroplast
Cell
Membrane
Ribosome
(attached)
Nuclear
envelope
Cell wall
Nucleolus
Golgi apparatus
Mitochondrion
Nucleus
Rough endoplasmic reticulum
Compare and Contrast
Animal Cells
Centrioles
Plant Cells
Cell membrane
Ribosomes
Nucleus
Endoplasmic reticulum
Golgi apparatus
Lysosomes
Vacuoles
Mitochondria
Cytoskeleton
Cell Wall
Chloroplasts
Internal Organization
• Cells contain
ORGANELLES.
• Cell Components that
PERFORMS SPECIFIC
FUNCTIONS FOR THE
CELL.
Cellular Organelles
• The Plasma
membrane
– The boundary of the
cell.
– Composed of three
distinct layers.
– Two layers of fat and
one layer of protein.
The Nucleus
• Brain of Cell
• Bordered by a porous
membrane - nuclear envelope.
• Contains thin fibers of DNA
and protein called Chromatin.
• Rod Shaped Chromosomes
• Contains a small round
nucleolus
– produces ribosomal RNA which
makes ribosomes.
The nucleus controls access to DNA and permits easier
packing of DNA during cell division.
Ribosomes
• Small non-membrane
bound organelles.
• Contain two sub units
• Site of protein synthesis.
• Protein factory of the cell
• Either free floating or
attached to the Endoplasmic
Reticulum.
Cells also contain non-membranous structures:
Ribosomes, "free" or attached to membranes, participate in assembly of
polypeptide chains.
Endoplasmic Reticulum
•
Complex network of
transport channels.
• Two types:
1. Smooth- ribosome free
and functions in poison
detoxification.
2. Rough - contains
ribosomes and releases
newly made protein from
the cell.
The endoplasmic reticulum (ER) modifies newly formed
polypeptide chains and is also involved with lipid synthesis.
Golgi Apparatus
• A series of flattened
sacs that modifies,
packages, stores, and
transports materials
out of the cell.
• Works with the
ribosomes and
Endoplasmic
Reticulum.
The Golgi body modifies, sorts, and ships proteins; they also play a role
in the synthesis of lipids for secretion or internal use.
Lysosomes
• Recycling Center
– Recycle cellular debris
• Membrane bound
organelle containing a
variety of enzymes.
• Internal pH is 5.
• Help digest food particles
inside or out side the cell.
Centrioles
• Found only in animal cells
• Paired organelles found
together near the
nucleus, at right angles to
each other.
• Role in building cilia and
flagella
• Play a role in cellular
reproduction
Cell membrane
Cytoskeleton
Endoplasmic
reticulum
Microtubule
Microfilament
Ribosomes
Mitochondrion
Main Components
1. The cytoskeleton is an interconnected system of fibers, threads, and lattices that
extends between the nucleus and the plasma membrane.
2. It gives cells their internal organization, overall shape, and capacity to move.
3. The main components are microtubules, microfilaments, and intermediate
filaments: all assembled from protein subunits.
4. Some portions are transient, such as the "spindle" microtubules used in
chromosome movement during cell division; others are permanent, such as filaments
operational in muscle contraction.
Cytoskeleton
B. The Structural Basis of Cell Movements
1. Through the controlled assembly and disassembly of their subunits,
microtubules and microfilaments grow or shrink in length (example:
movement of chromosomes).
2. Microfilaments or microtubules actively slide past one another (example:
muscle movement).
3. Microtubules or microfilaments shunt organelles from one location to
another (example: cytoplasmic streaming).
Cytoskeleton
C. Flagella and Cilia
1. Flagella are quite long, are usually not numerous, and are found on one-celled
protistans and animal sperm cells.
2. Cilia are shorter and more numerous and can provide locomotion for free-living cells
or may move surrounding water and particles if the ciliated cell is anchored.
3. Both of these extensions of the plasma membrane have a 9 + 2 cross-sectional array
(arising from centrioles) and are useful in propulsion.
Mitochondrion
A. Mitochondria are the primary organelles for
transferring the energy in carbohydrates to ATP
under oxygen-plentiful conditions.
B. Hundreds of thousands of mitochondria occur in
cells.
1. It has two membranes, an inner folded
membrane (cristae) surrounded by a smooth
outer membrane.
2. Inner and outer compartments formed by the
membranes are important in energy
transformations.
3. Mitochondria have their own DNA and some
ribosomes, a fact which points to the possibility that
they were once independent entities.
Mitochondria are efficient factories of ATP production.
The Chloroplast
• Double membrane
• Center section contains
grana
• Thylakoid (coins) make up
the grana.
• Stroma - gel-like material
surrounding grana
• Found in plants and algae.
A. Chloroplasts and Other Plastids
1. Chloroplasts are oval or disk shaped, bounded by a double membrane, and
critical to the process of photosynthesis.
a. In the stacked disks (grana), pigments and enzymes trap sunlight
energy to form ATP.
b. Sugars are formed in the fluid substance (stroma) surrounding the
stacks.
c. Pigments such as chlorophyll (green) confer distinctive colors to
chloroplasts.
the
2. Chromoplasts have carotenoids, which impart red-to-yellow colors to plant parts,
but no chlorophyll.
3. Amyloplasts have no pigments; they store starch grains in plant parts such as
potato tubers.
Mitochondria vs.
Chloroplasts
• Mitochondria make energy from
chemicals (food molecules)
• Chloroplasts make energy
from light through
photosynthesis
The Vacuole
• Sacs that help in food
digestion or helping
the cell maintain its
water balance.
• Found mostly in plants
and protists.
1. In the mature plant, the central vacuole may occupy 50 to 90% of the cell interior!
a. stores amino acids, sugars, ions, and wastes.
b. enlarges during growth and greatly increases the cell’s outer surface area.
2. The cytoplasm is forced into a very narrow zone between the central vacuole and the plasma
membrane.
Cell Wall
• Extra structure surrounding its plasma
membrane in plants, algae, fungi, and
bacteria.
• Cellulose – Plants
• Chitin – Fungi
• Peptidoglycan - Bacteria
Smooth ER vs. Rough ER
• Rough ER - ribosomes on the ER make proteins,
the ER modifies the proteins
• Smooth ER - makes lipids
Cytoskeleton
• Network of
protein filaments
• Maintains shape
• Involved in cell
movement
Prokaryotes
DNA is
free
floating
Cell membrane
Contain DNA
Eukaryotes
Nucleus
Endoplasmic reticulum
Golgi apparatus
Lysosomes
Vacuoles
Mitochondria
Cytoskeleton
Cell Wall
• Provides support and
protection for plant
walls
• Made of porous cellulose
so it does not regulate
what enters and leaves
cell
Eukaryotic Cell Walls
1. Many single-celled eukaryotes have a cell wall, a supportive
and protective structure outside the plasma membrane
2. Microscopic pores allow water and solute passage to and
from underlying plasma membrane.
3. In plants, bundles of cellulose strands form the primary cell
wall, which is more pliable than the more rigid secondary
wall that is laid down inside it later.
Cell Membrane
• Regulates what enters and leaves the cell and
provides support and protection
• Structure – lipid bilayer with embedded
proteins
Diffusion through Cell Boundaries
• Particles move from an area of high
concentration to an area of lower
concentration
• No energy is required
Osmosis
• Diffusion of water through a selectively
permeable membrane
Isotonic
"ISO" means the same
• Concentration of
solutes (salts) is the
same inside and
outside of cell.
• Water flows in and
out in equal amounts
• No effect on cell
Hypertonic
“Hyper” means more
• Concentration of solutes is more
outside the cell than inside
• Water flows out of cell
• The cell shrivels and may die.
• This is why it is dangerous to drink
sea water
• This is also why "salting fields"
was a common tactic during war, it
would kill the crops in the field,
thus causing food shortages.
Hypotonic
"HYPO" means less
• Concentration of solutes
is less outside the cell
than in.
• Water flows in
• The cell swell with water
and becomes “turgid”
Active Transport
• Carried our by protein pumps found in
the membrane
• Energy is required
Facilitated Diffusion
• Molecules move through protein
channels.
• No energy required
Endocytosis
• Cell takes material into cell by infolding of the cell
membrane
• Phagocytosis – eating – cell engulfs large particles
• Pinocytosis – drinking – cell takes in liquid
• www.endocyte.com/ animation/animation.htm
Exocytosis
• Cell releases large
amounts of material
Cell Specialization
• The cells in multicellular organisms can develop in
different ways to perform different tasks.
Levels of Biological
Organization
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Organism
Organ system
Organ
Tissue
Cell
Organelle
DNA
Atoms