Unit 4 - Cell membranes and transport

Question 1

Active transport

Answer 1

The active movement of substances from a low concentration to a higher concentration (up their concentration gradient) with the use of energy in the form of ATP.

Question 2

Antigen

Answer 2

Marker molecule on the cell surface membrane (usually a protein or glycoprotein) that can be detected by antibodies and triggers an immune response.

Question 3

Carrier protein

Answer 3

Protein involved in active transport that uses energy in the form of ATP to change conformation.

Question 4

Cell signalling

Answer 4

Cells release chemicals which bind to complementary receptors on their target and trigger specific responses.

Question 5

Cell surface receptor

Answer 5

A component on the cell membrane which binds to extracellular signals.

Question 6

Channel proteins

Answer 6

Transmembrane proteins for transporting large or charged substances. Some are involved in facilitated diffusion and do not use ATP; others are involved in active transport and do require energy in the form of ATP.

Question 7

Cholesterol

Answer 7

A steroid hormone which adds stability and fluidity to the lipid bilayer. it prevents breaking of the cell in harsh temperatures.

Question 8

Diffusion

Answer 8

The passive spreading out of substances from a high concentration to a lower concentration (down their concentration gradient) without the use of energy.

Question 9

Endocytosis

Answer 9

A method of bulk transport into a cell which relies on invagination of the cell membrane and requires energy in the form of ATP.

Question 10

Exocytosis

Answer 10

A method of bulk transport out of a cell which occurs when vesicles fuse with the cell membrane and release their contents. It requires energy in the form of ATP.

Question 11

Facilitated diffusion

Answer 11

The passive movement of substances from a high concentration to a lower concentration (down their concentration gradient) through transport proteins without the use of energy.

Question 12

Fluid mosaic model

Answer 12

A model that describes membrane structure as a sea of mobile phospholipids studded with various proteins.

Question 13

Glycolipid

Answer 13

A lipid which is bound to a monosaccharide.

Question 14

Glycoprotein

Answer 14

A protein which is bound to a carbohydrate chain.

Question 15

Ligand

Answer 15

An ion or molecule that transmits signals within or between cells. It has a role in cellular signalling and recognition.

Question 16

Osmosis

Answer 16

The passive diffusion of water molecules from a region of high water potential to a region of lower water potential (down a water potential gradient) through a selectively permeable membrane without the use of energy.

Question 17

Phospholipid

Answer 17

The type of lipid which forms the cell surface membrane bilayer. It is formed by the condensation of one molecule of glycerol, two molecules of fatty acid and a phosphate group. The two fatty acid chains are the non-polar hydrophobic tails whilst the phosphate group is the polar hydrophilic head.

Question 18

Phospholipid bilayer

Answer 18

hydrophobic tails face each other and hydrophillic phophate group heads ward outward to the watery environment of the cell.

Question 19

Surface area to volume ratio

Answer 19

The volume of an object compared with the amount of area where it contacts its environment. Calculated by dividing the surface area of an object by its volume.

Question 20

Water potential

Answer 20

A measure of the tendency of water molecules to move from one area to another measured in kilopascals (kPa) and given the symbol.

Question 21

Describe channel proteins

Answer 21

• the central tube is lined with polar r groups
• channel proteins can be opened or closed depending on certain stimuli
• can be a single protein or multiple arranged together

Question 22

describe carrier proteins

Answer 22

• molecules bind to the protein
• the protein can flip between two shapes
• binding site is open to both sides of the membrane
• diffusion affected by number of carrier proteins in the cell membrane

Question 23

Whats the order of cell signalling

Answer 23

1. stimulus/signal
2. receptor
3. transmission of signal
4. target/ effector
5. response

Question 24

Ligands

Answer 24

• secreted from a cell into extracellular space
• transported through that space to target
• bind to surface receptors
• message in ligand is transmitted to cell through a chain of chemical messengers

Question 25

high water potential

Answer 25

lower solute conc. (more pure water)

Question 26

low water potential

Answer 26

higher solute conc. (impure water)

Question 27

describe the process of osmosis

Answer 27

• water molecules on the side with a higher water potential are freeer to move around than the other side.
• this causes them to hit the membrane more often which allows them to diffuse through to the other side.

Question 28

active transport process

Answer 28

1. particle enters the pump from the side with lower concentration
2. particle binds with the specific site
3. energy from atp is used to change the shape of the pump
4. the particle is released on the side w/ higher conc. and returns to its orginal shape

Question 29

where is active transport used

Answer 29

In root hair cells for inorganic ions and reabsorption in kidneys

Question 30

hypertonic

Answer 30

has a higher amount of solute

Question 31

hypotonic

Answer 31

has a lower amount of solute

Question 32

isotonic

Answer 32

has the same amount of solute

Question 33

what happens if you put a red blood cell into a hypertonic solution

Answer 33

it becomes crenated as the water content of the cell rushes out.

Question 34

what happens if you put a plant cell in hypertonic solution

Answer 34

it becomes plasmolysied