Cell membranes

Question 1

What does the fluid mosaic model suggest about the structure of cell membranes?

Answer 1

phospholipid molecules arrange themselves in a bi layer which is fluid as the phospholipids molecules are constantly moving around. There are proteins withing the membrane as well as glycoproteins, glycolipids, and cholesterol (structural).

Question 2

role of proteins in membrane

Answer 2

channel proteins, carrier proteins

Question 3

role of glycoproteins and glycolipids

Answer 3

receptors and flags

Question 4

what substances can pass through the membrane by simple diffusion

Answer 4

non polar, lipid soluble (not water soluble) , small

Question 5

Describe and explain the relationship between membrane permeability and temperature.

Answer 5

Membrane permeability increases with increasing temperature because phospholipids move around more making the membrane more fluid. At high temperatures proteins will denature meaning that they no longer control what enters and leaves the cell.

Question 6

What is diffusion?

Answer 6

The net movement of particles from an area of higher concentration to an area of lower concentration. This is a passive process.

Question 7

What 3 factors affect the rate of diffusion?

Answer 7

Concentration gradient
Thickness of exchange surface
Surface area

Question 8

How are epithelial cells of the small intestine adapted for rapid diffusion?

Answer 8

Their cell surface membrane is highly folded into microvilli, increasing the surface area.

Question 9

Which type of substances can be moved by facilitated diffusion?

Answer 9

Large molecules, polar molecules and ions.

Question 10

How do channel proteins allow facilitated diffusion?

Answer 10

Channel proteins form pores in the membrane, allowing a specific charged particle to pass through.

Question 11

How can cells be adapted to allow for rapid facilitated diffusion across their membranes?

Answer 11

Some cells have many transport proteins in their cell membranes.

Question 12

What is osmosis?

Answer 12

The movement of water molecules across a partially permeable membrane from an area of high water potential to an area of low water potential.

Question 13

What is meant by an isotonic solution?

Answer 13

An isotonic solution has the same water potential as surrounding solutions.

Question 14

What would happen if a cell was placed into a hypertonic solution? Explain your answer.

Answer 14

Water would move out of the cell by osmosis because the hypertonic solution has a lower water potential than the cytoplasm of the cell.

Question 15

What is meant by a serial dilution?

Answer 15

A serial dilution is when you create a set of solutions that decrease in concentration by the dame factor each time.

Question 16

What is active transport?

Answer 16

Active transport uses energy to move molecules and ions across a membrane against a concentration gradient, using a carrier protein.

Question 17

How is energy supplied for the process of active transport?

Answer 17

ATP is hydrolysed into ADP and Pi releasing energy.

Question 18

What is a co-transport protein?

Answer 18

A co-transporter allows the facilitated diffusion of one substance down it’s concentration gradient across a cell membrane, whilst moving another molecule against it’s concentration gradient at the same time

Question 19

Describe the process of absorption of glucose and amino acids into the blood from the small intestine.

Answer 19

Na+ actively transported out of epithelial cells into the blood, lowering the concentration of Na+ in the cytoplasm
Na+ moves into the cell from the ileum by facilitated diffusion via a co-transporter, carrying either glucose of amino acids with it
Glucose diffuses out of the cell into the blood by facilitated diffusion