Biological Membrane and cell transport

Question 1

What is the main component of a membrane- describe it

Answer 1

• phospholipid (bilayer)
• 2 fatty acid tails; hydrophobic
• polar, phosphate head; hydrophilic

Question 2

Describe the type of proteins that help particles pass across the membrane.

Answer 2

• channel

- carrier

Question 3

Factors that affect diffusion?

Answer 3

• size; smaller diffuse quicker

- polarity; non-polar quicker

Question 4

What are the main roles of the cell surface membrane? (3)

Answer 4

• controls what exists and enters cell
• allows creation of concentration gradient
• contains receptors for cell signalling

Question 5

Main roles for membranes within cells? (5)

Answer 5

• compartmentalises cell organelles
• allows creation of concentration gradient
• controls what enters and exits the organelle
• provides sites for attachment for ribosomes and enzymes
• isolates metabolic reactions from each other

Question 6

What model is used to represent the cell surface membrane

Answer 6

• fluid mosaic model

Question 7

• what are the main components of membranes

Answer 7

• phospholipid (bilayer)
• proteins
• glycoproteins
• glycolipids
• cholesterol

Question 8

Phospholipids

Answer 8

• phospholipid with chain of sugar attached to it

Question 9

Describe how cholesterol relates to the membrane

Answer 9

• fatty substance located inbetween the phospholipids
• OH end with hydrophilic phosphate head
• hydrocarbon end with the hydrophobic fatty acid tail
• stabilises the membrane structure by keeping it fluid

Question 10

What is the width of the plasma membrane

Answer 10

• 7 nm

Question 11

Glycoproteins + glycolipids

Answer 11

• proteins attached to a sugar
  chain
• phospholipid attached to sugar chain
• receptors for hormones, drugs and signalling molecules
• stabilises membrane by forming hydrogen bonds with water
• cell signalling;

Question 12

How does high temperature affect the membrane

Answer 12

At high;
- high kinetic energy means that components move more= more fluidity

• membrane more permeable
• changes structure of protein which disrupts shape of membrane

Question 13

How do lower temperatures

Answer 13

• lower kinetic energy= less fluidity phospholipid layer

- membrane less permeable

Question 14

Describe membrane in Mitochondrion

Answer 14

• double membrane
• inner membrane folder to form cristae
• increases surface area for more enzymes and therefore increases rate of reaction

Question 15

Hypertonic

Answer 15

Water potential of the solution is higher/ less negative than

WP of cell

Question 16

Hypotonic

Answer 16

WP solution is lower/ more -/ve than that of cell

Question 17

Water potential

Answer 17

Net movement of water molecules

From high WP/ negation to low WP

Question 18

Water potential

Answer 18

Relative tendency of water to move from one are to another

Question 19

Turgid cell

Answer 19

Plant in hypotonic solution

Plant is full of water

Question 20

Crenated

Answer 20

Shrivelled animal cell

In hypertonic solution

Question 21

Plasmolysed

Answer 21

Cytoplasm shrinks from cell wall in plants

In hypertonic solution

Question 22

Cell burst

Answer 22

In hypotonic solution

Animal cells

Question 23

Diffusion

Answer 23

Passive movement of

Non polar substances

From high concentration to low

Question 24

Facilitated diffusion

Answer 24

Polar or slight larger substances

Cannot interact with the hydrophobic fatty acid tail

Require Channel or carrier proteins

Question 25

Transport of large substances

Answer 25

Active transport

Requires energy from ATP

Also uses carrier proteins

Question 26

Intrinsic proteins

Answer 26

• embedded on both sides of the bilayer

- eg Channel and carrier proteins

Question 27

Extrinsic proteins

Answer 27

• Embedded on one side of the bilayer.

- Eg glycoproteins and enzymes

Question 28

Endocytosis (4)

Answer 28

• Bulk transport of material into the cell. Therefore requires ATP
• Either pinocytosis with liquids or phagocytosis with solids
• Cell surface membrane invaginates around material and surrounds it until the membrane fuses to form a vesicle
• The vesicle then pinches off and moves into cytoplasm

Question 29

Exocytosis

Answer 29

• Bulk transport of material out of the cell. Therefore requires ATP
• Vesicle containing material moves to the plasma membrane and fuses with it.
• Contents in vesicle are then released out of the cell.

Question 30

When is ATP needed during bulk transport? (3)

Answer 30

• Movement of vesicles using cytoskeleton
• Changing the shape of membrane to engulf material in endocytosis.
• Fusion of cell membranes in both exocytosis and endocytosis

Question 31

Describe Active transport, including the role of ATP, Phosphate and ADP. (7)

Answer 31

• Using energy in the form of ATP to transport large or charge particles.

1- Ion/ molecule is recognised by protein and binds to receptor to outside the cell.

2- ATP binds to the protein inside the membrane. It is hydrolysed into Phosphate and ADP.

3- Phosphate binds to protein and causes a change in shape which creates opening inside the cell and close outside the cell.

4- Material is released into the cell.

5- Phosphate detaches from protein and combines with ADP to form ATP again

6- The protein returns to its original shape

Question 32

How does water travel through cell surface membrane (2)

Answer 32

• via phospholipid bilayer

- using aquaporins