Cell Membrane Diagram

Draw a diagram of the cell membrane. Please include (and label):

- Phospholipid bilayer (hydrophilic and hydrophobic)- Protein channel- An ion pump- Cholesterol- Gylcoproteins*

Define the function of each as it relates to the function of the membrane and cell

(You will have some time on block day to work on this as well)

Block day

1. Grade quizzes2. Organelle partner quiz3. Finish cell membrane diagram4. Membrane transport notes *5. Transport and application in body

Cell Structure and FunctionHuman cells share the common features of:

1. Plasma membrane2. Cytoplasm

3. Nucleus structure

Which all operate together to provide cellular functions.

The Plasma Membrane1. Separates the extracellular and intracellular compartments of the body2. Regulates the movement of materials between these compartments

How does the plasma membrane relate to homeostasis?

Membrane Structure● Equal amounts--by weight-- lipid and protein molecules, with a small amount of

carbohydrates● The lipid component

○ Phospholipids ■ Two parts

● HEAD=hydrophilic TAIL=hydrophobic■ Usually liquid and fluid

○ Cholesterol■ Provide the stabilizing influence

and increase the strength of the membrane

Membrane Structure● Equal amounts--by weight-- lipid and protein molecules, with a small amount of

carbohydrates● The protein component

○ Peripheral■ Attached to the outside

and inside SURFACES○ Integral

■ More numerous■ Have at least some portion

WITHIN the membrane■ Most extend all the way through

● These would be channels for transport

Membrane Structure● Equal amounts--by weight-- lipid and protein molecules, with a small amount of

carbohydrates● The carbohydrate component

○ May be attached to the proteincomponent and help in communication■ The two together would be

GLYCOPROTEINS■ Serve as receptors to

distinguish between the different cell types● Think LABELS● Hormones, growth factors, antibodies, etc.

Membrane Function● Why is it necessary to regulate what enters and leaves a cell?● The membrane is SELECTIVELY PERMEABLE

○ Only some things can enter or leave● Various transport mechanisms, grouped by the amount of energy needed1. Passive processes2. Active processes

Which one uses energy? Which one does not use energy? What kind of energy?

Membrane Function● Passive Processes1. Diffusion

○ Molecules move from an area of HIGH concentration to LOW concentrationi. Try drawing a diagram of this in a way that makes sense to you

○ Movement will continue until EQUILIBRIUM○ A difference in one concentration (amount) from one area to another is

called a concentration gradient○ Examples?

2. Facilitated diffusion○ Same idea as diffusion but the molecules that are

trying to move are too large to cross the membrane and need assistance

○ Which molecules can help with this process?

Membrane Function● Passive Processes● 3. Osmosis: the movement of WATER molecules only, across the membrane

○ Still from an area of high concentration to low concentration--BUT OF WATER!○ Water concentration = the amount of

solutes present■ Many solutes = low water

concentration ■ Vice versa

○ ISOTONIC SOLUTION: concentration of solutes is the same on both sides (of the barrier,membrane, etc.)

○ HYPERTONIC SOLUTION: the solution on the outside has MORE solutes (high concen.) than whatever is in the solution

○ HYPOTONIC SOLUTION: the solution on the outside has LESS solutes (low concen.) than whatever is in the solution

○ EXAMPLE: a cell in a beaker of salt water...

Membrane Function● Passive Processes● 4. Filtration: movement of molecules from an area of high PRESSURE to low

PRESSURE○ In the cell, small molecules are physically pushed through the plasma membrane by a

pressure gradient○ EXAMPLE: in the kidneys, where

blood pressure forces small molecules such as water, small ions and waste (urea) between the plasma membranes of the thin cells of the blood vessels and kidney tubules

Membrane Function● Active Processes● Use energy supplied by the cell● In the form of….ATP!● Usually against the concentration gradient (from LOW concen. To HIGH concen.)

○ Think… UPHILL

1. Active Transport: requires ATP and integral proteins, called carriers

Ex: Sodium-potassium pump in neurons

Neurons need a concentration gradient in order

to function

Membrane Function● Active Processes

Membrane Function● Active Processes

2. Cytosis: the transport of large volumes of materials and large particles across the plasma membrane

● Two types○ Endocytosis: INTO the cell (Think...ENTER)○ Exocytosis: OUT of the cell (Think...EXIT)

● This happens by extending part of the membrane around the material and enclosing it