The structure and function of membranes Flashcards Preview

Biology OCR (5, plasma membranes) > The structure and function of membranes > Flashcards

Flashcards in The structure and function of membranes Deck (33)
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1
Q

What does compartmentalisation mean

A

The formation of separate membrane-bound areas in a cell

2
Q

Why is compartmentalisation necessary

A

It allows for the different and specific environments for the chemical reactions to exist even if they are not compatible with one another

3
Q

What is the name for the cell surface membrane?

A

The plasma membrane

4
Q

What is the main function of the plasma membrane?

A

It separates the cell from its external environment

5
Q

What are membranes formed from?

A

Phospholipid bilayer

6
Q

Describe and draw how the phospholipids create a bilayer (and thus the cell wall)

A

The many phospholipids aramge themselves in a way in which the hydrophilic phosphate heads are both on the inner and outer surface of the membrane, sandwiching the hydrophobic, fatty acid tails in the middle

7
Q

What type of environment do cells normally live in?

A

An aqueous environment

8
Q

What evidence in 1950s arose which supported the theory of the lipid bilayer?

A

The invention of the electron microscope showed the cell membrane as two black lines.

9
Q

During 1972 what did the two scientists Singer and Nicolson propose?

A

The fluid-mosaic model

10
Q

Why was it called the fluid-mosaic model?

A

Because the phospholipids are free to move within the layer relative to each other and because the proteins within the layer vary in shape,size and position.

11
Q

Where are intrinsic proteins located on the membrane?

A

Through both layers of the membrane

12
Q

Draw a diagram of an intrinsic protein

A

e

13
Q

What is anther name for an intrinsic protein?

A

An integral protein

14
Q

How do intrinsic proteins keep themselves in place?

A

Hydrophobic R-groups on their external surfaces of the protein interact with the hydrophobic core of the membrane, keeping them in place

15
Q

What are the three different types of intrinsic proteins?

A

Channel, carrier proteins, glycoporoteins

16
Q

What are channel and carrier proteins both evolved with?

A

Transport across the membrane

17
Q

How do channel proteins allow the movement of polar molecules and ions into the cell?

A

They provide a hydrophilic channel that allows passive movement of polar molecules and ions down a concentration gradient through the membrane

18
Q

What type of molecule does channel proteins allow through?

A

polar molecules and ions

19
Q

What is the function of the carrier protein?

A

It plays a role in both passive and active transport into cells.

20
Q

What is the structure of glycoporoteins?

A

They are proteins with attached carbohydrate chains

21
Q

What do glycoproteins play a role in?

A

cell adhesion and as receptors for chemical signals

22
Q

What is meant by cell signaling?

A

When the chemicals bind to the receptor on a cell membrane which causes either a direct response or sets of a cascade of events inside of the cell.

23
Q

What is the structure of a glycolipid?

A

They are lipids with attached carbohydrate chains

24
Q

What are other names for glycolipids?

A

Cell markers or antigens

25
Q

What is the function of glycolipids?

A

They can be recognised by the cells of the immune system as self or non-self

26
Q

What are extrinsic proteins?

A

They are proteins which are only present on one side of the bilayer

27
Q

Draw a diagram of ab extrinsic protein

A

d

28
Q

What is another name for an extrinsic protein?

A

Peripheral proteins

29
Q

How are extrinsic proteins kept in place?

A

They have hydrophilic R-groups on their outer surfaces which interact with the polar heads of the phospholipids or intrinsic proteins.

30
Q

What is the structure of cholesterol?

A

They are a lipid with a hydrophilic end and a hydrophobic end.

31
Q

What is the function of cholesterol?

A

It regulates the fluidity of membranes

32
Q

How does cholesterol add stability to the membrane without making it too rigid?

A

The cholesterol molecules are positioned between two phospholipids with the hydrophilic end interacting with the heads and the hydrophobic ends interacting with the tails, pulling them together

33
Q

What do the cholesterol molecules act to prevent?

A

The membranes from becoming too solidly stopping the phospholipid molecules from grouping too closely and crystallising