Chapter 5 Membranes

Question 1

Intrinsic proteins information

Answer 1

• TRANSMEMBRANE embedded both layers of membrane
• Amino acids with HYDROPHOBIC r groups in their external surfaces, so this can interact with the hydrophobic fatty acid core of bilayer

Question 2

Intrinsic channel protein

Answer 2

• hydrophilic channel that allows passive movement of POLAR molecules/ ions down a concentration gradient through membranes
• held in POSITION ( by hydrophobic R group on amino acid outside and interaction with hydrophobic fatty acid outside stated previously…)

Question 3

Intrinsic carrier protein

Answer 3

• allows BOTH passive and active transport (against concentration gradient )
• shape of protein changes for active transport
• atp

Question 4

Extrinsic glycoprotein

Answer 4

• role is of cell adhesion ( cells joining in tissues)
• is also A receptors for chemical signal = roll in CELL SIGNALLING
• has attached carbon chain of varying length and embedded in one layer of bilayer

Question 5

Cell signalling and examples (this is to do with glycoprotein receptors) what is it

Answer 5

• chemical binds to the receptors , releases a response from cell: either direct or chain of events in cell
  Ex
  1) receptors for neurotransmitters (ones thst diffuse )at nerve synapses (triggers or prevent impulse for next neurone remember)
  2) Peptide hormones , like insulin glycogen (maintaining glucose concentrations)

Question 6

Glycolipids

Answer 6

• lipids with varying carbohydrate chains
• act as cell markers = ANTIGENS, allowing immune system either recognises as self or non self (belonging to other organism)
• also form hydrogen bonds with water molecules to stabilise membranes

Question 7

Extrinsic proteins information

Answer 7

• hydrophilic r groups on their outer layer so they can interact with polar heads of phospholipids (or with intrinsic proteins )
• can move layers

Question 8

Cholesterol
Structure
Function how does it regulate fluidity
How does it give stability?

Answer 8

=lipid that regulates fluidity of membranes , gives stability

• cholesterol has hydrophilic OH- group on ONE END so interact with heads and hydrophobic end of carbon ring
  THIS IS WHAT IT BINDS WITH the fatty acid tails

2) in low temps makes them fluids by not allowing phospholipids from coming too close and Crystal aight to become a solid
- in high temps stops phospholipids from becoming too fluid aswell, interactions between head and tail PULL THE PHOSPHOLIPIDS TOGETHER
- causes phospholipids to pack closely together, making them MORE STABLE without rigid.

Question 9

What proteins need to be for chemical reactions to happen

What example - you got this wrong in test

Answer 9

In specific places

• for example electron carriers and protein enzyme ATP synthase has to be on inner membrane mitochondria, CRISTAE and in correct positions so respiration Can take place.
• remember Cristae contain all enzymes needed for light dependent reactions 😪

Question 10

What is compartmentalisation?

Why is it important (3)

Answer 10

The formation of separate membrane bound areas in a cells

2) 1: incompatible reactions occur within the cell , compartmentalisation isolates them allowing them to happen
2: it allows different conditions to be set for Esch reaction, like gradients etc to get best reaction
3: protects cell components from harmful Hydrolytic enzymes from lysozyme potentially

Question 11

What is the use of a plasma membrane?

Answer 11

• separates cell contents fro, the outside (barrier)
• controls passage in and out of cells
• allows cells to communicate ,
• recognition of other cells is possible here

Question 12

What is the function of organelle bound membranes ?

Answer 12

• also helps isolate dna
• acts as an intracellular transport system
• site of chemical reactions, form vesicles for transport etc

Question 13

Describe the arrangement of the phospholipid bilayer?

Answer 13

Phospholipids contain a polar, and thus hydrophilic phosphate head and two hydrophobic fatty acid tails .

-Thus two layers of phospholipids form such that the polar hydrophilic phosphate heads orientate themselves to be on the outside whilst the fatty acid hydrophobic tails are SANDWICHED on the inside.

• This allows the bilayer to be able to interact with both the interior and exterior aqueous environment
• whilst still protecting the hydrophobic fatty acid core.

Question 14

What makes the membrane known as a fluid mosaic model?

Answer 14

Fluid = phospholipids and proteins are free to move throughout the layer  relative to Esch other 
Mosaic = because the various different proteins embedded in the protein vary in shape and size, forming a mosaic like pattern in the membrane  (just like a mosaic).

Question 15

How do the phospholipids move!

Why can they move around!

Answer 15

Side to side like 10^7 times per second
- flip flopping once per month

2) they ade held together by weak hydrophobic interactions which allows them to be fluid