2.5 bio membranes

Question 1

What is facilitated diffusion?

Answer 1

The movement of large of polar molecules through the phospholipid bilayer using channel proteins and carrier proteins.

Question 2

What is a carrier protein?

Answer 2

a transport molecule that changes shape to allow the molecule to pass across the membrane

Question 3

What is a channel protein?

Answer 3

Transport protein that provides a tube-like opening in the plasma membrane through which particles can diffuse

Question 4

What is crenation?

Answer 4

When the cell shrivels. This is due to there being a more negative water potential outside the cell than inside so water leaves the the cell via osmosis

Question 5

What is cytolysis?

Answer 5

This is when the cells split. This is due to there being a less negative water potential outside the cell than inside, so water enters the cell via osmosis.

Question 6

What is plasmolysis?

Answer 6

When the cytoplasm of the plant cell shrinks and the membrane pulls away from the cellulose cell wall. The cells are described as plasmolysed

Question 7

What is turgidity?

Answer 7

In a plant cell, the rigid strong cellulose wall will prevent bursting. The cell will swell up to a certain size when it’s contents push against the cell wall, which will resist any further swelling.

Question 8

What is active transport?

Answer 8

The movement of molecules against the concentration gradient, from low to high, using atp and carrier proteins.

Question 9

How does temperature affect enzyme activity?

Answer 9

a. as temperature increases, so does the rate of reaction because the molecules are moving faster and have a higher chance of hitting each other. At extremely high temperatures, the enzyme is denatured due to a change in the tertiary structure. At lower temperatures the substrate molecules do not have enough kinetic energy for the reaction to take place even in the presence of the enzyme

Question 10

How does pH affect enzyme activity?

Answer 10

Each enzyme has an optimal pH at which it can perform at its maximum rate. Too high or too low of a pH, the H+ and OH- ions mess up the ionic bonds so the enzyme denatures

Question 11

How does enzyme concentration affect enzyme activity?

Answer 11

The more enzyme molecules there are, the more likely there are to be collisions between enzyme and substrate molecules, forming more enzyme-substrate complexes

Question 12

How does substrate concentration affect enzyme activity?

Answer 12

The rate increase initially and then levels off because all enzymes are constantly occupied and adding more substrate will not make a difference.

Question 13

What is the role of membranes at the surface of cells? (Plasma membrane)

Answer 13

They separate the cells components from its external environment, regulates transport on materials into and out of the cell, and contains receptors for cell communication.

Question 14

What is the role of membranes within cells.

Answer 14

Separates the organelles contents from the cytoplasm. In some organelles, metabolic processes occur on membranes.

Question 15

How is a mitochondria’s membrane specialized?

Answer 15

They have folded inner membranes called cristae, which give a large surface area for some of the reactions of aerobic respiration and localise some of the enzymes needed for respiration to occur.

Question 16

How is a chloroplast’s membrane specialised?

Answer 16

The inner membrane, called thylakoid membranes, house chlorophyll. On these membranes some of the reactions for photosynthesis occur.

Question 17

What does the fluid mosaic model propose?

Answer 17

That the fabric of the membrane consisted of a phospholipid booster with proteins floating in it making up a mosaic pattern. The lipid molecules can change places with each other and some of the proteins may move, giving fluidity.

Question 18

What is bulk transport?

Answer 18

Transporting molecules that are too large to diffuse through the plasma membrane. They do this through bulk transport, using ATP. This involves enclosing substances to be moved in their own small globes of membrane, which can then fuse with the membrane.

Question 19

What is endocytosis?

Answer 19

This is how large particles are brought into the cell. A segment of the membrane surrounds and encloses the particle and brings it into the cell enclosed in a vesicle

Question 20

What is exocytosis?

Answer 20

This is how large molecules are moved out of a cell. They don’t pass through the cell, but instead a vesicle containing them is moved towards and fused with the plasma membrane. ATP is needed.

Question 21

What is the role of cholesterol in the membrane?

Answer 21

Cholesterol is a type of lipid. Molecules fit between the phospholipids. They bind to the hydrophobic tails, causing them to pack more closely together. This makes the membrane less fluid and more rigid.

Question 22

What is the role of proteins in a membrane?

Answer 22

Some proteins form channels in the membranes. These allow small or charged particles through. Other proteins transport molecules across the membrane by active transport and facilitated diffusion. Thy also act as receptors for molecules in cell signalling.

Question 23

What is the role of glycolipids and glycoproteins?

Answer 23

They stabilise the membrane by forming hydrogen bonds with surrounding water molecules. They are a site where drugs, hormones and antibodies bind. They act as receptors for cell signalling and are also antigens.