Crossing the Plasma Membrane

Question 1

Lipids are made of which elements?

Answer 1

Carbon, Hydrogen and Oxygen.

Question 2

State three examples of lipids

Answer 2

Fats, oils and waxes.

Question 3

How are lipids different to carbohydrates in terms of their molecular structure?

Answer 3

Lipids contain less oxygen atoms. Lipids also have long tails made up entirely of C and H.

Question 4

Difference between fats and oils?

Answer 4

Fats are solid at room temperature whilst oils are liquid.

Question 5

State two properties of lipids.

Answer 5

Non-polar and insoluble in water. Poor conductors of heat, which means they are good insulators.

Question 6

What are the subunits of a triglyceride molecule?

Answer 6

One glycerol and three fatty acids.

Question 7

What is the name of chemical bond that holds the subunits of a triglyceride together?

Answer 7

Ester bond

Question 8

How many hydroxyl groups does a glycerol contain?

Answer 8

Three hydroxyl groups allowing three fatty acids to attach to the glycerol molecule.

Question 9

How do fatty acids attach to the glycerol?

Answer 9

The carboxyl group of the fatty acid joins with the hydroxyl group of the glycerol.

Question 10

Difference between saturated and unsaturated fats?

Answer 10

Saturated fats have no double bonds between carbon atoms in their fatty acid tails, whereas unsaturated fats have double bonds between carbon atoms in their fatty acid tails.

Question 11

Describe the structure of a phospholipid

Answer 11

Hydrophilic polar phosphate head
Hydrophobic non-polar fatty acid tails

Question 12

Difference between phospholipids and triglycerides

Answer 12

A phospholipid contains a phosphate group and two fatty acid tails, whereas a triglyceride contains three fatty acid tails.

Question 13

What is the function of phospholipids?

Answer 13

They form an integral part of all cell membranes.

Question 14

How do phospholipids form a bilayer?

Answer 14

Two layers of phospholipids come together with phosphate heads facing the water rich environments (i.e. extracellular space and cytoplasm) and fatty acid tails facing towards the centre, forming the core of the phospholipid bilayer.

Question 15

What is the function of cholesterol?

Answer 15

It is a lipid found in the plasma membrane that provides stability and flexibility.

Question 16

What is the function of triglycerides? State at least three functions.

Answer 16

Any three of the following:
Source of energy, Insulation, Protection of vital organs, To prevent evaporation in plants, form myelin sheath around neurons, Source of water (metabolic water produced in respiration).

Question 17

What are steroids?

Answer 17

Steroids are lipid-based hormones; they act as signalling molecules that cause a response in the body of an organism.

Question 18

How do steroids move into or out of the cell?

Answer 18

Because they are lipid-based, they can freely move across the phospholipid bilayer.

Question 19

Protein channels are involved in?

Answer 19

Facilitated diffusion

Question 20

Protein pumps are involved in?

Answer 20

Active transport

Question 21

How are glycoproteins and glycolipids formed?

Answer 21

When a carbohydrate chain attaches to a protein & When a carbohydrate chain attaches to a phospholipid.

Question 22

What is the function of glycoprotein and glycolipid?

Answer 22

Cell communication and recognition.

Question 23

What is the fluid mosaic theory about?

Answer 23

It states that membranes are made up of small, varying components like a mosaic. In addition, these components are able to move across the plasma membrane.

Question 24

Define diffusion

Answer 24

Net movement of particles from a high concentration to a low convention down a concentration gradient

Question 25

Define facilitated diffusion

Answer 25

Facilitated diffusion is the net movement of particles from a high concentration, to a low concentration, down a concentration gradient, through a protein channel.

Question 26

State the properties of molecules that will pass through a protein channel or pump and how you know if they will cross by facilitated diffusion or active transport

Answer 26

Hydrophilic (either charged or polar).
Large in size.

If down a concentration gradient = facilitated diffusion through a protein channel

If up a concentration gradient = active transport through a protein pump

Question 27

Describe which types of molecules can cross the phospholipid bilayer directly

Answer 27

Small, non-polar, hydrophobic molecules can pass through the phospholipid bilayer directly.

Small, polar molecules (like water and ethanol) can also pass through the phospholipid bilayer directly.

Question 28

Describe a hypertonic solution.

Answer 28

A solution that is higher in solute in comparison to another solution.

Question 29

Describe a hypotonic solution.

Answer 29

A solution that is lower in solute in comparison to another solution.

Question 30

Describe steps in osmosis using the scaffold provided (OTTO).

Answer 30

1. osmosis has occurred.
2. Water has moved from the hypotonic solution (+ context)
3. through the partially membrane of (+ context)
4. to the hypertonic solution (+ context)
5. outcome (e.g. the animal cell swells and lyses)

Question 31

Describe an isotonic solution.

Answer 31

A solution that has the same solute concentration as another solution.

Question 32

Define osmosis

Answer 32

The net movement of water molecules from a hypotonic solution to a hypertonic solution.

Question 33

Define active transport

Answer 33

the net movement of particles from a low concentration, to a high concentration, against the concentration gradient, through a protein pump using ATP .

Question 34

Define exocytosis

Answer 34

Bulk movement of large molecules OUT of the cell. (This is primarily proteins but can be other polymers or molecules too big to pass through a protein pump or channel)

Question 35

Define endocytosis

Answer 35

Bulk movement of large molecules INTO the cells.

Question 36

Define pinocytosis

Answer 36

Bulk movement of liquids into the cell.

Question 37

Define phagocytosis.

Answer 37

Bulk movement of solids into the cell.