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Cell structure
Lecture 2
A. Cell Membrane – all cells
a. FUNCTION- The cell membrane regulates what enters
and leaves the cell and also provides protection and
support
b. Takes in water and food and eliminates waste
c. STRUCTURE - The membrane is a double-layered sheet
called a lipid bi-layer
i. Polar heads face outwards and non-polar tails face
inwards
d. Embedded in the membrane are protein
channels/pumps and carbohydrates
B. Cell Wall – plants and bacteria
a. Where is it found?
i. Found in almost all prokaryotes
ii. Found in plants, fungi, and algae
iii. NOT found in animals
b. Lies outside of the cell membrane
c. Allow for movement of certain molecules
i. Water, carbon dioxide, oxygen and some other
substances
d. The main function of the cell wall is to provide support
and protection to the cell
e. Structure - Cell walls are made of carbohydrates i.e.
cellulose fiber
C. Nucleus - eukaryotes
a. Function - The nucleus controls
most cell processes and contains the
hereditary information of DNA
b. Structure - Consists of 4 parts
i. Nucleolus – small densely packed
region where ribosomes are
created
ii. Nuclear Envelope – double
membrane layer surrounding the
nucleus
iii. Nuclear Pores – a perforations
within the nuclear membrane
iv. Chromatin – this is the granular
material within the nucleus
1. Chromosomes – the
condensed form of chromatin
just before a cell divides
D.Cytoskeleton – all cells
a.Function - A network of protein filaments that
helps the cell keep its shape, also used in many
forms of cell movement (in the documentary
the virus traveled along these filaments)
b.Structure - Made up of microtubules and
microfilaments
Ribosomes - eukaryotes
i. Function Ribosomes assemble
proteins following
the coded
instructions that
come from the
nucleus
ii. Structure Ribosomes are made
of protein and RNA
b. Endoplasmic Reticulum - eukaryotes
i. Function - The organelle in which components of the
cell membrane are assembled and some proteins are
modified
Structure Types
i. Smooth ER – contains collections of enzymes that
perform specialized tasks, such as the synthesis of
lipids (fats)
ii. Rough ER – the part that is involved in the synthesis
of proteins; has ribosomes embedded in the
membrane
c. Golgi Apparatus eukaryotes
i. Function -Proteins
made by the ER
move to the Golgi
apparatus where
enzymes attach
carbohydrates and
lipids
ii. Structure – folded
sacs involved with
modifying and
packaging proteins
d. Lysosomes – animal
cells
i. Structure - Are
small organelles
filled with enzymes
ii. Main function is to
break down lipids,
carbohydrates and
proteins into
particles that can
be used by the cells
iii. Also helps to break
down old
organelles, remove
debris from the cell
e. Vacuoles – all cells
i. Function Storage for the cell
1. Stores materials
such as water,
salts, proteins
and
carbohydrates
ii. Plants have a
single large vacuole
(mostly water)
f. Chloroplasts – plant cell
Found in photosynthetic
organisms
i. Function - Use
energy from sunlight
to make energy-rich
food molecules in a
process known as
photosynthesis
ii. Structure – Light
capturing pigment
Contains thylakoids
and chlorophyll
iii. Contains its own
DNA
g. Mitochondria –
eukaryotes
i. Function Releases energy
from stored food
molecules in a
process called
cellular respiration
ii. Found in
eukaryotes
iii.Structure – Small
organelle that
contains its own
DNA (you get it
from your momma)
h. Organelle DNA
i. Lynn Margulis
suggested that
mitochondria and
chloroplasts were
originally
prokaryotic
organisms that
were enveloped by
a eukaryotic cell
ii. The DNA in
mitochondria
comes almost
exclusively from
the mother
F. Movement through the membrane
a. Facilitated diffusion – no energy required
i. Molecules such as glucose sugar that cannot cross the
cell membrane’s lipid bilayer directly can move
through protein channels from an area of high
concentration to an area of low concentration with the
concentration gradient
b. Active transport – energy required
i. When a molecule has to move against the
concentration gradient
ii. Each pump is used to move a specific molecule across
the membrane
1. Example: sodium potassium pump moves sodium
out and potassium in (
v. Endocytosis
1. The process of taking materials into the cell by
means of infolding or pockets of the cell membrane
vi. Exocytosis
1. The removal of large amounts of material from a
cell
exocytosis
ANIMAL AND PLANT