Membrane strucutre

Question 1

What molecules make up the plasma membrane?

Answer 1

• Lipids
• Carbohydrates
• Proteins
• The type and amount affect function

Question 2

What is the fluid mosaic model?

Answer 2

• The structure of the plasma membrane is described to be a mosaic of phospholipids, proteins, cholesterol, glycoproteins, and glycolipids
• These molecules can move around in the cell membrane

Question 3

What is the primary component of membranes?

Answer 3

• Phospholipids

Question 4

What direction do the head and tail of the phospholipids face and why?

Answer 4

• Head faces the outside because they are hydrophilic

- Tails face the inside of the cell because they are hydrophobic

Question 5

What molecules do the phospholipid bilayer not allow through and why?

Answer 5

• Polar molecules
• The hydrophobic tails do not allow polar molecules to diffuse through the membrane
• large molecules
• Too big to fit through the membrane

Question 6

How do phospholipids differ in strucutre?

Answer 6

• Fatty acid chain length
• Degree of saturation
• Kinds of polar groups present

Question 7

How are cholesterol molecules imbedded in the cell membrane?

Answer 7

• Hydroxyl groups interreact with the polar heads of the phospholipids
• The rest of the cholesterol interacts with the tails of the phospholipids
• Pretty much like a phospholipid, jus the hydroxyl group of the cholesterol is the head

Question 8

What is cholesterols function in the cell membrane?

Answer 8

Modulating membrane fluidity

Question 9

What structure makes the membrane fluid?

Answer 9

Fatty acids

Question 10

What influences membrane fluidity?

Answer 10

• Saturation (unsaturated increases fluidity)
• Length (short increases fluidity)
• Temperature (heat increases fluidity)

Question 11

Why do unsaturated lipids increase fluidity in a cell membrane?

Answer 11

The kinks and bends in the structure of a lipid creates more space for molecules to move in the cell membrane

Question 12

What are the types of proteins found in the phospholipid bilayer?

Answer 12

• Peripheral membrane proteins
• Integral membrane proteins
• Anchored membrane proteins
• Transmembrane proteins

Question 13

What is a peripheral membrane protein?

Answer 13

Proteins that lack a hydrophobic group and are not embedded in the bilayer,
- Found on the surface of the plasma membrane, either inside or outside of the cell

Question 14

What is an integral membrane protein?

Answer 14

Proteins with a hydrophobic group that are at least partly embedded into the bilayer
- Interact extensively in the bilayer

Question 15

What is an anchored membrane protein?

Answer 15

Proteins with hydrophobic lipid components that anchor them to the bilayer,
- the hydrophobic component has to stay inside the bilayer with the lipid tails, so the rest of the protein can be free from being embedded into the membrane while having an anchor secure inside

Question 16

What are transmembrane proteins?

Answer 16

Proteins that extend through the bilayer, they have areas with functions inside and outside of the membrane

Question 17

How are proteins distributed on the plasma membrane?

Answer 17

Asymmetrically, this is because proteins cannot flip from facing the inside of the cell to the outside, so they need to have proteins facing inside and outside of the cell,
- There is not necessarily an equal amount of proteins facing each direction, they are just not ordered to face one way

Question 18

Can all molecules move in the phospholipid bilayer?

Answer 18

No, some can while some are restricted, the cytoskeleton and other proteins inside the cell can restrict some membrane proteins from moving

Question 19

What is the function of carbohydrates in the bilayer?

Answer 19

Communication/ identification

Question 20

What carbohydrates can be found in the bilayer?

Answer 20

• Glycolipid
• Glycoprotein
• Proteoglycan

Question 21

What is a glycolipid?

Answer 21

Carbohydrates covalently bonded to a lipid

Question 22

What is a glycoprotein?

Answer 22

One or more oligosaccharides (small carbohydrates) covalently bonded to proteins

Question 23

What are proteoglycans?

Answer 23

Proteins with more and longer carbohydrates bonded to it

Question 24

What is an oligosaccharide?

Answer 24

Oli-go-saccharide

- A small chain of monosaccharides/ small carbohydrates

Question 25

How do cells attach to each other?

Answer 25

Proteins and carbohydrates can connect to each other across membranes and keep the cells close to each other

Question 26

Are cell membranes ever inactive?

Answer 26

No, they are constantly forming, transforming into other types, fusing, and breaking down

Question 27

What is plasmolysis?

Answer 27

The detaching of the cell membrane from the cell wall, and constriction of the membrane when a plant cell is in a hypertonic solution

Question 28

What is a selectively permeable membrane?

Answer 28

When the membrane only allows certain molecules to diffuse through, will others are unable to.

Question 29

What is a carrier protein?

Answer 29

A protein that changes shape in order to facilitate the diffusion through a cell membrane across a concentration gradient

Question 30

What is a channel protein?

Answer 30

A type of integral protein, a hollow protein that allows molecules to pass through across the plasma membrane.

Question 31

What is a concentration gradient?

Answer 31

The direction in which molecules move, from a high concentration of molecules to a lower one