transport

Question 1

what is the function of cell surface membrane

Answer 1

-Control the passage of substances into and out of cells and organelles
-Separate the content of cells from their environment
-Provide a surface for attachment of enzymes and receptors

Question 2

what is the cell surface membrane

Answer 2

a barrier that is partially permeable

Question 3

what model describes the cell surface membrane

Answer 3

fluid mossaic model-

Question 4

what does the cell membrane consist of

Answer 4

hospholipid bilayer - This is made up of phospholipids with hydrophilic heads and hydrophobic tails.
Cholesterol - This adds stability.
Proteins - These may be intrinsic and extrinsic proteins.
Glycoproteins - These are proteins attached to a carbohydrate.
Glycolipids - These are lipids attached to a carbohydrate.

Question 5

what is the role of the phospholipid bilayer

Answer 5

contains hydrophyllic heads-facing out- and hydrophobic tails-facing in which forms a bilayer and moves around.This arrangement creates a hydrophobic centre in the bilayer so that water-soluble substances cannot pass through

Question 6

what is the role of cholestrol

Answer 6

provides stability-Cholesterol molecules consist of a hydrophilic and hydrophobic region. The hydrophobic regions bind to phospholipid fatty acid tails, causing them to pack more closely together- regulates fluidity

Question 7

what are channel proteins

Answer 7

provide a channel for passive movement of substances through
facilitated diffusion. They do not change shape.

Question 8

what are carrier proteins

Answer 8

transport substances across membranes by changing their shape.
Movement can be passive (by facilitated diffusion) or active transport.

Question 9

proteins can be grouped in 2 categories what are they

Answer 9

intrinsic and extrinsic

Question 10

what is the role of intrinsic/intergral

Answer 10

embedded on both sides of phospholipid bilayer- ivolved in cell signalling-communicates with cells and cell adhesion- hold cells togther

Question 11

what is extrinsic/peripheral

Answer 11

only present on one side of bilayer -provide support to membrane

Question 12

what are 3 factors that affect permeability of membrane

Answer 12

-size- smaller molecu;es easier to get across as squeeze through
-molecule type-lipid based more easier than non-lipid based
-charge-uncharged easier

Question 13

what requires a channel protein or carrier protein to move across membrane

Answer 13

large, charged or protein based molecules

Question 14

what is equilibrium

Answer 14

when molecules move randomly due to kinetic energy-spread out evenly

Question 15

what is diffusion

Answer 15

the movement of molecules from an area of high to low conc until equilibrium is reached

Question 16

what affects the rate of diffusion

Answer 16

tempreture, conc gradient, surface area, diffusion pathway

Question 17

how many types of diffusion are there

Answer 17

2- simple and facilliated

Question 18

what is simple diffusion

Answer 18

Some molecules can diffuse directly across cell membranes in a process known as simple diffusion.This is because they are:

Small - This means that they can pass through the spaces between phospholipids.
Non-polar - This means that they can dissolve in the hydrophobic core of the cell membrane.

Question 19

what is facilliated diffusion

Answer 19

a passive process that involves carrier and channel proteins to move ions and polar molecules.

Question 20

why does temp affect diffusion

Answer 20

At higher temperatures, particles have more kinetic energy and diffuse faster.

Question 21

why does conc gradient affect diffusion

Answer 21

The steeper the concentration gradient, the faster the rate of diffusion.

Question 22

why does surface area affect diffusion

Answer 22

Larger surface areas mean more particles can cross the membrane at once, making diffusion faster.- microvilli

Question 23

what is a solution-osmosis

Answer 23

mixtures made up of a solute (e.g. glucose), dissolved in a solvent (e.g. water).

Question 24

what is water potential (Ψ)

Answer 24

the pressure exerted by water molecules on the membrane (or container) surrounding a solution. It is measured in kiloPascals

Question 25

what does high water potential mean

Answer 25

means the solution has a high water concentration

Question 26

what is osmosis

Answer 26

water moves from an area of high water potential to an area of lower water potential until equilibrium is reached

Question 27

what has the highest water potential / 0

Answer 27

pure water

Question 28

what happens when more solutes are dissolved in water

Answer 28

water potential becomes more negative

Question 29

what happens to an animal cell in a hypotonic solution

Answer 29

has a higher water potential than the cell. Water molecules move into the cell. The cell swells and bursts.

Question 30

what happens to an animal cell in a isotonic solution

Answer 30

An isotonic solution has the same water potential as the cell. There is no net movement of water into or out of the cell. The cell stays the same size.

Question 31

what happens to an animal cell in a hypertonic solution

Answer 31

has a lower water potential than the cell. Water molecules move out of the cell. The cell shrinks.

Question 32

what happens to an plant cell in a hypotonic solution

Answer 32

has a higher water potential than the cell. Water molecules move into the cell. The cell swells and becomes turgid

Question 33

what happens to an plant cell in a isotonic solution

Answer 33

has the same water potential as the cell. There is no net movement of water into or out of the cell. The cell stays the same size

Question 34

what happens to an plant cell in a hypertonic solution

Answer 34

has a lower water potential than the cell. Water molecules move out of the cell. The cell shrinks and becomes plasmolysed.

Question 35

what are 3 factors affect osmosis

Answer 35

Temperature - At higher temperatures, water molecules have more kinetic energy and diffuse faster. Water potential gradient - The steeper the gradient, the faster the rate of osmosis. surface area-

Question 36

what is active transport

Answer 36

movement of molceules or ions across a cell membrane against a conc gradient using carrier proteins and energy from ATP

Question 37

what is the carrier protein that brings about active transport of molecules called

Answer 37

a pump

Question 38

explain the process of active transport

Answer 38

The molecule/ion binds to receptors in the carrier protein (pump). 2. ATP binds to the carrier protein and is hydrolysed to ADP and Phosphate (Pi) 3. The phosphate binds to the carrier protein transferring energy to the protein. 4. The protein changes shape and the molecule/ion is released across the other side of the membrane 5. The phosphate is released and the carrier

Question 39

what do cells have that make them adapted to the role of active transport

Answer 39

have many mitochondria to provide the energy (ATP)

Question 40

what are the factors affecting active transport

Answer 40

temp, number of carrier proteins and thickness of membrane

Question 41

in bulk transport how does large molecules move across the membrane

Answer 41

in vesicles and do not pass through the plasma membrane

Question 42

what is bulk transport into cells called

Answer 42

endocytosis

Question 43

There are 2 types:

Answer 43

Uptake of solids is called phagocytosis.  Uptake of liquids is called pinocytosis

Question 44

what happens during endocytosis

Answer 44

The cell surface invaginates (bends inwards) around the material until it forms a vesicle The vesicle pinches off and moves into the cytoplasm. ATP is needed to provide energy to form vesicles and move them using molecular motor proteins and the cytoskeleton.

Question 45

Bulk transport OUT OF cells is called

Answer 45

exocytosis

Question 46

explain the co-transport of sodium ions and glucose in the ilieum

Answer 46

1. Sodium ions are actively transported out of epithelial cells, by the sodium-potassium pump carrier protein, into the blood. ATP is hydrolysed to release energy for this process. There is now a much higher concentration of sodium ions in the lumen than in the epithelial cells. 2. The sodium ions diffuse into the epithelial cells down their concentration gradient through a co-transport/symport protein in the cell surface membrane. As they diffuse through this co-transport protein they couple with glucose which is carried into the cell with them. 3. Sodium ions are again moved out of the cell via active transport to repeat the cycle

Question 47

what happens to the glucose next

Answer 47

it diffuses into the bloodstream by faciliated diffusion