Cell structureLecture 2
A. Cell Membranea. The cell membrane regulates what enters and leaves the
cell and also provides protection and supportb. Takes in water and food and eliminates wastec. The membrane is a double-layered sheet called a lipid
bi-layeri. Polar heads face outwards and non-polar tails face
inwardsd. Embedded in the membrane are protein channels/pumps
and carbohydrates
B. Cell Walla. Where is it found?
i. Found in almost all prokaryotesii. Found in plants, fungi, and algaeiii. NOT found in animals
b. Lies outside of the cell membranec. 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. Cell walls are made of carbohydrates produced by the celli. Plants use cellulose
C. Nucleusa. Discovered by a botanist named
Robert Brown in 1831b. The nucleus controls most cell
processes and contains the hereditary information of DNA
c. Consists of 4 partsi. 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 nucleus1. Chromosomes – the
condensed form of chromatin just before a cell divides
D.Cytoskeletona. A network of protein filaments that helps the
cell keep its shape, also used in many forms of cell movement
b. Made up of microtubules and microfilamentsi. Microtubule – hollow tubes of protein which
also serve as tracks for organelles to moveii. Microfilament – Long thin fibers that function
in the movement and support of the cell
E. Organellesa. Ribosomes
i. Ribosomes assemble proteins following the coded instructions that come from the nucleus
ii. Ribosomes are made of protein and RNA
b. Endoplasmic Reticulumi. The organelle in which components of the cell
membrane are assembled and some proteins are modified
ii. Smooth ER – contains collections of enzymes that perform specialized tasks, such as the synthesis of lipids
iii. Rough ER – the part that is involved in the synthesis of proteins; has ribosomes embedded in the membrane
c. Golgi Apparatusi. Proteins made
by the ER move to the Golgi apparatus where enzymes attach carbohydrates and lipids
ii. Discovered by Camillo Golgi
d. Lysosomesi. 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. Vacuolesi. Storage for the
cell1. Stores
materials such as water, salts, proteins and carbohydrates
ii. Plants have a single large vacuole
iii.Vesicles are the animals cell equivalent to vacuoles
f. Chloroplastsi. Found in
photosynthetic organisms
ii. Use energy from sunlight to make energy-rich food molecules in a process known as photosynthesis
iii. Enclosed by two envelope membranes
iv. Contains thylakoids and chlorophyll
v. Contains its own DNA
g. Mitochondriai. Releases energy
from stored food molecules in a process called cellular respiration
ii. Enclosed by two envelope membranes
iii. Found in nearly all cells
iv. Contains its own DNA
h. Organelle DNAi. 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 membranea. Facilitated diffusion
i. Molecules such as glucose 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 transporti. When a molecule has to move against the concentration gradientii. Uses energyiii. Each pump is used to move a specific molecule across the membrane
1. Example: sodium potassium pump moves sodium out and potassium in
iv. Endocytosis1. The process of taking materials into the cell by means of infolding
or pockets of the cell membrane2. The resulting pocket breaks loose from the outer portion of the
membrane creating a vesicle within the cytoplasm3. Phagocytosis is then used to break up the vesicle and use the
molecules insidev. Exocytosis
1. The removal of large amounts of material from a cell2. The membrane of the vesicle surrounding the material fuses with
the cell membrane forcing the contents out of the cell