Membranes + Transport

Question 1

What are the 3 main functions of a plasma membrane?

Answer 1

-control the transport of substances in and out of the cell.
-To act as a receptor site to recognise chemicals which need to enter the cell or organelle.
-To separate off the cell from the environment

Question 2

What type of lipid is found in cell membranes?

Answer 2

Phospholipids

Question 3

What does it look like when phospholipids are arranged in a bilayer?

Answer 3

.

Question 4

Diffusion and osmosis are passive processes what does this mean

Answer 4

Do not require energy in the form of ATP

Question 5

What is simple diffusion?

Answer 5

Where molecules that are small enough and/or non polar can diffuse rapidly across the phospholipid bilayer

Question 6

What is the definition of diffusion?

Answer 6

Movement of substances from a region of their higher concentration to a ego on of their lower concentration- movement of molecules down a concentration gradient.

Question 7

What is dynamic equilibrium?

Answer 7

Where the particles are evenly spread, although still moving

Question 8

What factors affect the rate of diffusion?

Answer 8

-surface area
-thickness of exchange surface
-concentration gradient
-size of diffusing molecule
-temperature
-water solubility/polarity

Question 9

What is facilitated diffusion?

Answer 9

helps molecules diffuse through the membranes. requires channel adn carrier proteins.

Question 10

What does a graph for simple diffusion look like?

Answer 10

.

Question 11

Why does the graph on facilitated diffusion level off?

Answer 11

As all of the carrier proteins are occupied at any one time. Number of carrier/channel proteins are limiting.

Question 12

What is osmosis?

Answer 12

the movement of water molecules from an area of high water concentration to an area of low water concentration through a partially permeable membrane.

Question 13

What is active transport?

Answer 13

-movement against a concentration gradient.
-requires energy
-needs specific protein caries/pumps
-moves charges polar molecules
-not passive

Question 14

What is exocytosis?

Answer 14

Exporting material in vesicles

Question 15

What does facilitated diffusion diffuse?

Answer 15

Moves charges/ polar/ hydrophobic substances (channels for ions; carriers for other.)

Question 16

What is a hypotonic solution?

Answer 16

A dilute solution or pure water will have a higher concentration than the cell so water enters the cell by osmosis. the cell swells and eventually bursts (osmotic lysis)

Question 17

Membranes are partially permeable what does this mean?

Answer 17

They do not let water-soluble, charges or polar substances pass through easily and this is why the cell-surface membrane acts as an effective barrier to separate the cell from its environment.

Question 18

What does fluid mosaic mean?

Answer 18

Fluid- molecules can move around
Mosaic-different types of molecules

Question 19

What is a glycolipid?

Answer 19

these are made up of a carbohydrate covalently bonded to a lipid.

Question 20

What does a graph for facilitated diffusion look like?

Answer 20

.

Question 21

What is endocytosis?

Answer 21

The process of importing material in vesicles.

Question 22

What is a bilayer?

Answer 22

Acts as a barrier to polar/water-voluble/large molecules.

Question 23

What is a glycoprotein?

Answer 23

Short branching carbohydrate chains attached to proteins in the membrane.

Question 24

What is the function of a glycoprotein?

Answer 24

Acts as receptors for hormones and neurotransmitters or antigens

Question 25

What is the function of a glycolipid?

Answer 25

Acts as recognition sites, help to maintain stability of the membrane and help cells attach to one another, forming tissue

Question 26

What is a hypertonic solution?

Answer 26

A concentrated salt solution will have a lower water concentration than the cell so water leaves the cell by osmosis. this causes the cell to shrink (crenate)

Question 27

What does a graph for active transport look like?

Answer 27

.

Question 28

What is a lysosome?

Answer 28

-can hydrolyse all of the molecules
-specialised vesicles full of hydrolysis enzymes

Question 29

What is cytosol?

Answer 29

Aqueous solution in the cytoplasm

Question 30

What is Fick’s law?

Answer 30

Rate of diffusion-surface area x difference in concentration / thickness of exchange surface

-=little fish thing

Question 31

example and function of intrinsic proteins?

Answer 31

Channel protein, carrier proteins
Transport

Question 32

What is the function of cholesterol?

Answer 32

-restricts movement of other molecules making up the membrane.
-increases strength and stability
-prevents water loss and dissolved ions from the cell.

Question 33

What is an isotonic solution?

Answer 33

Same conc as cell. No net osmotic movement of water so cell remains the same

Question 34

Example and function of extrinsic proteins?

Answer 34

-enzymes-e.g. maltose
-receptors-for binding to hormones (e.g. role in cell signalling)
-antigens-for cell recognition

Question 35

What acts as a cognitive site?

Answer 35

Glycoprotein in fluid mosaic model.