Membranes

Question 1

What is the structure of a phospholipid?

Answer 1

Glycerol, two fatty acids and a phosphate group

Question 2

What is the width of the cell membrane?

Answer 2

7nm

Question 3

How are phospholipids arranged in a cell membrane?

Answer 3

As a bilayer. Phospate heads are dissolved in water, fatty acid tails interact with each other away from water.

Question 4

What are the functions of the cell membrane?

Answer 4

Controlling entry and exit of molecules to the cell, secreting chemicals, cell recognition.

Question 5

What is an intrinsic protein?

Answer 5

Intrinsic proteins sit within the phospholipid bilayer

Question 6

What do you call a protein that spans the entire membrane, like a carrier or channel protein?

Answer 6

Transmembrane intrinsic proteins

Question 7

What is an extrinsic protein?

Answer 7

Extrinsic proteins are on the outside of the phospholipid bilayer

Question 8

Name the layer above the membrane consisting of carbohydrate chains from glycoproteins and glycolipids

Answer 8

Glycocalyx

Question 9

What does “fluid” mean in the fluid mosaic model?

Answer 9

The model is called fluid because the phospholipid and protein molecules move around each other.

Question 10

What does “mosaic” mean in the fluid mosaic model?

Answer 10

The model is called a mosaic because proteins embedded between the phospholipids vary in shape, size and pattern

Question 11

What is the function of glycoproteins and glycolipids in the cell membrane?

Answer 11

Cell to cell communication and recognition

Question 12

What is the function of cholesterol in the cell membrane?

Answer 12

To maintain fluidity

Question 13

How do lipid soluble substances pass through the cell membrane?

Answer 13

They can dissolve in the fatty acid tails and move through the membrane by simple diffusion

Question 14

How do ions pass through the cell membrane?

Answer 14

They must pass through a channel protein by facilitated diffusion

Question 15

What is diffusion?

Answer 15

It is the movement of molecules or ions from a region of high concentration to one of low concentration.

Question 16

Which factors can affect the rate of diffusion through a membrane?

Answer 16

Surface area, the concentration gradient, temperature, size of the molecule, lipid solubility, availability of specific ion channels, and thickness of the membrane.

Question 17

What is facilitated diffusion?

Answer 17

Diffusion through channel or carrier proteins. Molecules move from an area of high concentration to low concentration. This is passive and does not need ATP

Question 18

What is co transport?

Answer 18

A type of facilitated diffusion in which two substances are simultaneously transported across a membrane by one protein. This is passive and does not need ATP

Question 19

What is active transport?

Answer 19

Movement from an area of low to high concentration, against a concentration gradient. This is done through a carrier protein and requires ATP

Question 20

Which transport proteins are used for facilitated diffusion?

Answer 20

Channel and carrier proteins

Question 21

Which transport proteins are used for active transport?

Answer 21

Carrier proteins

Question 22

What is a channel protein for water called?

Answer 22

An aquaporin

Question 23

What is the specific term for bulk transport of a solid into a cell?

Answer 23

Phagocytosis

Question 24

What is the term for bulk transport of a liquid into a cell?

Answer 24

Pinocytosis

Question 25

What is the term for bulk transport out of a cell?

Answer 25

Exocytosis

Question 26

What are the steps in phagocytosis?

Answer 26

Receptors on the cell surface bind to the object. The cell membrane invaginates to fold around the object. The object is now contained within a phagosome. The phagosome fuses with a lysosome to form a phagolysosome. Digestive enzymes break down the object. Useful products are absorbed, the rest is removed from the cell by exocytosis

Question 27

What do you call the vesicle formed in phagocytosis and what does it fuse with?

Answer 27

The vesicle is called a phagosome. It fuses with a lysosome which contains digestive enzymes.

Question 28

Why do endocytosis and exocytosis require ATP?

Answer 28

ATP is required to provide energy to move the cell membrane

Question 29

What is water potential?

Answer 29

The potential for water to move out of a solution by osmosis.

Question 30

What is osmosis?

Answer 30

Water molecules moving down a water potential gradient through a selectively permeable membrane.

Question 31

What is the water potential of pure water?

Answer 31

0 Kpa, the highest water potential can be

Question 32

What happens to the water potential when solute is added to a solution?

Answer 32

The water potential goes down (becomes more negative)

Question 33

In a plant cell the water potential=

Answer 33

solute potential + pressure potential. The solute potential is the effect of solutes lowering the water potential of the cytoplasm. This value is negative. Pressure potential is provided by the cell wall and is usually positive

Question 34

Hypotonic means

Answer 34

A solution with a higher water potential than a cell

Question 35

Hypertonic means

Answer 35

A solution with a lower water potential than a cell

Question 36

Isotonic means

Answer 36

A solution with the same water potential as a cell

Question 37

When in hypertonic solution, what will happen to a plant cell and why?

Answer 37

Water will move out of the cell, down a water potential gradient by osmosis. The plant cell is plasmolysed

Question 38

When in hypertonic solution, what will happen to an animal cell and why?

Answer 38

Water will move out of the cell, down a water potential gradient by osmosis. The animal cell is crenated

Question 39

When in hypotonic solution, what will happen to a plant cell and why?

Answer 39

Water will move into the cell, down a water potential gradient by osmosis. The plant cell will become turgid

Question 40

When in hypotonic solution, what will happen to an animal cell and why?

Answer 40

Water will move into the cell, down a water potential gradient by osmosis. The animal cell will swell and possibly lyse (burst)

Question 41

When a plant cell is in incipient plasmolysis, what is happening to water movement?

Answer 41

There is no net water movement into or out of the cell

Question 42

How would you recognise a plant tissue in incipient plasmolysis?

Answer 42

50% of cells are plasmolysed, 50% are turgid

Question 43

How would you recognise a plant cell in incipient plasmolysis?

Answer 43

The cell membrane is just beginning to move away from the cell wall

Question 44

Why would cyanide stop active transport?

Answer 44

Because it is a non competitive respiratory inhibitor, which would prevent production of ATP. ATP is required to provide energy for active transport

Question 45

What does increasing temperature do to the cell membrane?

Answer 45

As temperature increases the membrane becomes more fluid, and slightly more permeable. When the temperature increases too much proteins will denature and lost their shape, creating pores that make the membrane even more permeable.