Biological membrane structure

Question 1

what are the components of membranes?

Answer 1

lipid bilayer = structural backbone made up phospholipids, glycolipids, and cholesterol

proteins = transport, enzymatic, and signal transduction

carbohydrates = attached to proteins and lipids

Question 2

Are carbohydrate chains found on the inside or outside of the cell membrane?

Answer 2

They are found on the outside of the cell membrane

Question 3

how many rings does a sterol have?

Answer 3

4 rings

Question 4

How do membranes contain different phospholipids?

Answer 4

phospholipids differ in their esterification to serine, ethanolamine, choline or inositol

Question 5

What is cholesterol used for?

Answer 5

it maintains the fluidity fo the membrane and acts as a precursor to steroid hormones and Vitmain D

Question 6

Is lateral diffusion or transverse diffusion faster?

Answer 6

Lateral and transverse diffusion of lipids in the bilayer (where they switch spots)

lateral difussion is faster

Question 7

what is the fluid mosaic model of the membrane?

Answer 7

membranes are two dimensional solutions of oriented globular proteins and lipids

Question 8

What are integral proteins?

Answer 8

integral proteins are fully integrated in the lipid bilayer - spanning the entire double layer

Question 9

what are peripheral proteins?

Answer 9

They are proteins that only cushion into the bottom layer of the lipid bilayer

Question 10

What are the functions of membrane proteins?

Answer 10

anchoring = attach cell membranes to eachtoerh or to external/internal structures

recognition proteins = identify the cell and prevent attack by immune system

enzymes = catalyze intracellular or extracellular reactions

receptors = bind to specific ligands in the extracellular matrix

carrier proteins = move solutes across membrane (may require ATP)

leak channels = permit continuous movement of water and ions

gated channels = close or open to regulate ion movement

Question 11

Which membrane protein requires ATP to function?

Answer 11

carrier proteins

Question 12

What is passive diffusion?

Answer 12

the unaided spontaneous movement of solute molecules down their concentration gradient, from high to low, until solutes equilibrate across the bilayer - entropically driven

Question 13

When is maximum entropy reached?

Answer 13

at equilibrium… which is why equilibrium is the equilibrium

Question 14

What types of faciliated diffusion occur in a lipid bilayer?

Answer 14

They occur down a concentration gradient and are dependent on integral proteins

we can have

• uniport - one molecule in one direction
• symport - two types of molecules in one direction
• antiport - two different molecules in opposite directions

Question 15

What are the three forms of active transport?

Answer 15

• primary
• secondary
• group translocation

Question 16

Give an example of a primary active transport

Answer 16

the Na+ K + pump/ ATPase ion pump

Where the sodium binds, then ATP is dephosphorylated giving the energy needed for the protein to change conformation and drive the sodium extracellularly

Question 17

What classifies as a primary active transport?

Answer 17

requires ATP to move molecule against a concentration gradient

Question 18

What type of transport does the hydrogen potassium ATPase require?

Answer 18

dead give away that the protein requires ATP

exchages K+ in the stomach for H+ in cytoplasm - works against con. gradient - therefore

PRIMARY active transport

Question 19

What is the definition of a secondary active transport?

Answer 19

carrier protein that moves a specific substance against it’s concentration gradient, but uses the concentration gradient for one substance as the driving force

so the second substance gets a ‘free ride’

Question 20

What is the definition of group translocation?

Answer 20

solute changes during transport -

ex) in the phosphotransferase system where the sugar is phosphorylated during transport into the cell therefore, it becomes sugar phosphate

Question 21

What sort of transport does the glucose transport follow?

Answer 21

it follows secondary active transport because it tags along with the sodium that is moving with it’s normal concentration gradient

Question 22

What is phagocytosis? How about Pinocytosis?

Answer 22

phagocytosis = cell bringing in material “eating”

pinocytosis = cell “drinking” fluid