Cells Membranes

Question 0

Functions of membranes within cells

Answer 0

Divide into different compartments, makes different functions more efficient.
Increasing surface area to make reactions more efficient.
Can form vesicles for transport within cells.
Control what goes in and out of an organelle.

Question 1

How would you describe a cell membrane?

Answer 1

Partially permeable

Question 2

What is the name given to the structure of a cell membrane?

Answer 2

Fluid Mosaic

Question 3

What is the fluid mosaic made up of.

Answer 3

Phospholipids, cholesterol, proteins and glycolipids and glycoproteins.

Question 4

function of phospholipids

Answer 4

Hydrophilic head sticking out and hydrophobic tails attract together. They form a bilayer with a very hydrophobic region in the centre. The don’t let water soluble molecules, charged, ions or polar molecules to pass through.

Question 5

function of cholesterol

Answer 5

Fits in-between the phospholipids binding to the hydrophobic tail. Less fluid more stable, further barrier to substances. Increasing membrane stability.

Question 6

function of proteins in cell membrane

Answer 6

Some form channels allowing small charged particles through and carrier proteins allows large charged particles through. Also act as a receptor in cell signalling.

Question 7

Functions of Glycolipids and glycoproteins

Answer 7

Stabilises the molecule by forming hydrogen bonds with surrounding water molecules. Act as receptors in cell signalling. Also act as antigens involved in self recognition and immune response.

Question 8

Effects of temperature below 0 degrees on membranes

Answer 8

Phospholipids don’t have as much energy, channel proteins and carrier proteins denature, increasing permeability of the membrane. Ice crystals may form and pierce the membrane, making it have a high permeability when it thaws.

Question 9

Effects of temperature between 0 and 45 degrees on membranes

Answer 9

Can move around, membrane is partially permeable. As temp increases the permeability will increase as they have more energy.

Question 10

Effects on membranes with temperature above 45 degrees

Answer 10

Bilayer begins to break down. Water inside cell expands putting pressure on membrane. Channel proteins and carrier proteins inside the cell denature increasing permeability.

Question 11

How do cells communicate?

Answer 11

By signalling via messenger molecules.

Question 12

Explain cell signalling.

Answer 12

This starts when one cell releases a messenger molecule, this molecule travels to another cell. This messenger molecule is detected by the cell because it binds to a receptor. This triggers off changes in that cell. Then a series of chemical signals are set off.

Question 13

What is a cell called the responds to particular messenger molecule?

Answer 13

A target cell.

Question 14

Why do some cells respond and others don’t?

Answer 14

Receptor proteins have specific shapes - only messenger molecules with specific shapes will bind to them. The shape must be complementary.

Question 15

Define diffusion.

Answer 15

The overall net movement of particle from an area of high concentration to an area of low concentration.

Question 16

What are the factors affecting the rate of diffusion?

Answer 16

The concentration gradient - higher the better
Thickness of the exchange surface - thinner the better
The surface area - bigger the better

Question 17

What is water potential?

Answer 17

The likelihood of water molecules diffusing in and out of a solution.

Question 18

What is the water potential of pure water in kPA?

Answer 18

0

Question 19

How does the water potential change as you add solute?

Answer 19

It lowers.

Question 20

What is an isotonic solution?

Answer 20

When the water potential is the same on both sides.

Question 21

What is a hypotonic solution?

Answer 21

When the water potential is higher on the outside of the cell compared to inside. Water will move out of the cell.

Question 22

What happens to cells in hypotonic solutions?

Answer 22

Animal will swell and burst and plant cells will become turgid.

Question 23

What is a hypertonic solution?

Answer 23

A solution where the water potential is lower on the outside of the cell compared to the inside of a cell.

Question 24

What will happen to cells in a hypertonic solution?

Answer 24

The water will rush out of the cell, animal cells will become cremated. Plants cells will become flaccid and cytoplasm and cell membrane will pull away from cell wall, it’ll become plasmolysed.

Question 25

Proteins involved in facilitated diffusion

Answer 25

Carrier and channel proteins

Question 26

Why are proteins used.

Answer 26

Most larger, polar molecules and ions can’t diffuse directly through the bilayer.

Question 27

Explain how carrier proteins allow molecules to diffuse

Answer 27

A large molecule attaches itself in the membrane, protein changes shape and releases molecule on the other side.

Question 28

Explain how channel proteins allow molecules to diffuse

Answer 28

The form pores for smaller ions and polar molecule to diffuse through.

Question 29

Explain active transport.

Answer 29

It move vole clues against the concentration gradient and involve carrier proteins. Attaches to the carrier proteins at the binding site, protein changes shape and this moves the solute against the concentration gradient.

Question 30

What is endocytosis?

Answer 30

When a molecule is too large to be taken in by a protein. The membrane wraps it self round the molecule and pinches off the membrane to form a vesicle inside the cell containing an ingested substance. Requires energy.

Question 31

What is exocytosis?

Answer 31

When substances are produced by an organelle in a cell, they move towards the cell membrane in a vesicle. Vesicle fuses with the plasma membrane and releases it’s contents outside the cell. Requires energy.