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