Cell Membrane (Diffusion, Osmosis, Active Transport etc)

Question 1

Are the different substances that make up the cell membrane fixed?

Answer 1

No, they are not fixed in place

Question 2

Describe how the substances within the cell membrane are arranged

Answer 2

They are arranged in ‘mosaic’ but are also free to move around within the mosaic.

Therefore, we describe the cell membrane as ‘fluid’

Question 3

What 4 components make up the cell membrane?

Answer 3

Phospholipids

Cholesterol

Proteins

Glycolipids and Glycoproteins

Question 4

What is the role of the phospholipids in a cell membrane?

Answer 4

Form a barrier to dissolved substances

Question 5

What is the role of the cholesterol in a cell membrane?

Answer 5

Gives the membrane stability

Question 6

What is the role of proteins in a cell membrane?

Answer 6

Controls what enters and leaves the cell

Question 7

What is the role of the glycolipids and glycoproteins in a cell membrane?

Answer 7

Act as receptors for messenger molecules (hormones, drugs, antibodies)

For cell signalling

Question 8

What two kinds of proteins are there?

Answer 8

Extrinsic

Intrinsic

Question 9

Where are extrinsic proteins found in the cell membrane?

Answer 9

Found on one surface of the membrane only

Question 10

Where are the intrinsic proteins found in the cell membrane?

Answer 10

They span the entire membrane

Question 11

What are the functions of proteins in the cell membrane?

Answer 11

1. Act as enzymes (e.g. carbohydrase enzymes are found in the cell membranes of intestinal epithelial cells)
2. Act as receptors for hormones
3. Act as carrier proteins, controlling what enters and leaves the cell
4. Carbohydrates and lipids attached to proteins (forming glycolipids and glycoproteins) allow cells to recognise one another

Question 12

How to substances leave and enter the cell membrane?

Answer 12

Either by diffusion, osmosis or active transport

Question 13

Meaning of hydrophilic

Answer 13

Likes water

Question 14

Meaning of hydrophobic

Answer 14

Dislikes water

Question 15

Define diffusion

Answer 15

The movement of particles from an area of high concentration to an area of low concentration.

Question 16

Define osmosis

Answer 16

The diffusion of water particles across a semi-permeable membrane from an area of high water concentration to an area of low water concentration

Question 17

Passive transport

Answer 17

No energy needed. E.g. osmosis, diffusion

Question 18

Active transport

Answer 18

Where dissolved molecules more across a cell membrane from an area of low concentration to an area of high concentration

Requires energy as it goes against the concentration gradient

Question 19

Isotonic meaning

Answer 19

Concentration is the same both inside and outside of the cell

Question 20

Hypertonic meaning

Answer 20

Concentration of dissolves particles are higher outside the cell that inside.

Water will LEAVE the cell.

Question 21

Hypotonic meaning

Answer 21

Concentration of dissolved particles are lower outside the cell than inside.

Water will enter the cell.

Question 22

4 Functions of cell membrane

Answer 22

1. Cell signalling
2. Selective transport
3. Excretion of waste
4. Structural support

Question 23

Exocytosis

Answer 23

Vesicles release contents out of the cell

Question 24

Endocytosis

Answer 24

Vesicles release contents into the cell

Question 25

Aquaporins

Answer 25

Aquaporins are integral membrane pore proteins. AKA: water channels

Question 26

Pinocytosis

Answer 26

The ingestion of LIQUID into a cell by the budding of small vesicles from the cell membrane

Question 27

Phagocytosis

Answer 27

The ingestion of a SOLID into the cell | e.g. ingestion of bacteria

Question 28

Active Transport examples

Answer 28

Endocytosis Exocytosis Receptor Mediated Transport

Question 29

Types of osmosis

Answer 29

Hypotonic Hypertonic Isotonic

Question 30

Why are small cells more efficient at diffusion?

Answer 30

They have a HIGH SA:V ratio

Question 31

What size cells are most efficient at diffusion?

Answer 31

Small cells

Question 32

When an object is very small, what is its SA:V ratio like?

Answer 32

It has a large SA:V ratio

Question 33

When a cell grows, what happens to its SA:V ratio?

Answer 33

Its volume increases at a greater rate that its surface area. Therefore, its SA:V ratio decreases.

Question 34

How might a cell increase its SA:V ratio?

Answer 34

- long thin shape / elongated shape. e.g. nerve cells - folding the surface of the object / cell membrane. e.g. villi of the lining in the small intestines - plant cells are larger than animal cells, and have a large vacuole which pushes organelles to the edge of the cell where they get regular access to resources

Question 35

Are the heads in the cell membrane hydrophilic or hydrophobic?

Answer 35

Hydrophilic

Question 36

Are the tails in the cell membrane hydrophilic or hydrophobic?

Answer 36

Hydrophobic

Question 37

What do the hydrophobic tails and hydrophilic heads make?

Answer 37

A phospholid bilayer