Core Concepts

Question 1

Name 4 inorganic ions and their uses

Answer 1

• Mg2+, constituent of chlorophyll
• Fe2+, constituent of haemoglobin
• PO4 3-, Making nucleotides e.g. ATP
• Ca2+, structural component of bones and teeth

Question 2

What is the difference between alpha glucose and beta glucose?

Answer 2

The first -OH group points down in alpha glucose but up in beta glucose

Question 3

What are the functions of glucose?

Answer 3

• Energy source in respiration
• Intermediate in reactions
• Constituent of nucleotides

Question 4

glucose + glucose =?

Answer 4

Maltose

Question 5

Glucose + Fructose = ?

Answer 5

Sucrose

Question 6

Glucose + Galactose = ?

Answer 6

Lactose

Question 7

Describe a test for reducing sugars

Answer 7

Add benedicts reagent to the sample and heat at 70°c

A positive result will show a colour change from blue to red

Question 8

How can you test for the presence of starch?

Answer 8

Add iodine solution

Positive result will show a colour change from Orange/Brown to black

Question 9

Describe a test for fats and oils

Answer 9

Mix sample with pure ethanol and shake with an equal volume of water. Positive result will show a cloudy white precipitate.

Question 10

What is the effect of a diet high in saturated fats?

Answer 10

Low density lipoproteins build up, atheromas get deposited in the coronary arteries, restricting blood flow. If the vessel becomes completely blocked a myocardial infarction occurs.

Question 11

What is the effect of a diet high in unsaturated fats?

Answer 11

More high density lipoproteins are produced which carry harmful fats to the liver for disposal.

Question 12

Describe the primary and secondary structure of proteins

Answer 12

Primary: The order of amino acids in the polypeptide chain
Secondary: Hydrogen bonding between molecules on the polypeptide chain forming alpha-helices and beta-pleated sheets.

Question 13

Describe the tertiary and quaternary structures of proteins

Answer 13

Tertiary: further folding of the secondary structure
Quaternary: combination of more than one polypeptide group eg. Haemoglobin

Question 14

How can you test for proteins?

Answer 14

Mix sample with biuret reagent

Postivie result will show a purple colour

Question 15

Explain the naming of the ‘fluid mosaic model’

Answer 15

Fluid: phospholipid molecules can move
Mosaic: Proteins embedded in the bilayer vary in shape, size and pattern.
Model: We can not be entirely sure how accurate this representation of a membrane is.

Question 16

Explain the arrangement of molecules within a cell membrane

Answer 16

Phospholipids form a bilayer with with the hydrophobic tails pointing inwards towards eachother.
Extrinsic proteins on the surface of the bilayer.
Intrinsic proteins extend across both layers of the phospholipid bilayer.

Question 17

What is the function of extrinsic and intrinsic proteins?

Answer 17

Extrinsic: Provide structural support and act as receptor sites.
Intrinsic: Form carriers or channels to allow molecules to cross the membrane.

Question 18

Explain the permeability if the cell membrane in terms of both lipid soluble and water soluble substances.

Answer 18

Lipid-soluble:
Can diffuse across the membrane
Water-soluble:
Polar molecules must pass through intrinsic proteins.

Question 19

What is diffusion?

Answer 19

The movement of molecules down a concentration gradient, no energy is required.

Question 20

Give 3 factors that will affect the rate of diffusion

Answer 20

1) Concentration gradient
2) Diffusion distance
3) Surface area of membrane

Question 21

What is facilitated diffusion?

Answer 21

A form of diffusion that allows insoluble substances to cross a membrane. Occurs through intrinsic proteins.

Question 22

Describe the 2 types of intrinsic protein

Answer 22

Channel Protein:
Hydrophilic channels allowing polar molecules to pass through the membrane according to the needs of the cell.
Carrier Protein:
Allow diffusion of larger molecules. A molecule attaches to a binding site on the carrier protein, changing its shape and releasing molecules on the other side of the membrane.

Question 23

What is active transport?

Answer 23

The exchange of substances across a membrane using energy in the form of ATP.

Question 24

Describe the process of Active Transport.

Answer 24

• A molecule/ion binds to the carrier protein
• ATP transfers a phosphate to the carrier protein
• The carrier protein changes shape, allowing the molecule to cross the membrane.
• The phosphate recombines with the ADP to form ATP

Question 25

What is co-transport?

Answer 25

A type of facilitated diffusion that brings molecules/ions into cells on the same transport protein.

Question 26

What is meant by the term ‘metabolism’?

Answer 26

All the reactions that occur in the body

Question 27

Give 4 properties of enzymes

Answer 27

1) They are not used up
2) They speed up reactions
3) They are not changed
4) They have a high turnover rate

Question 28

Name 3 sites of enzyme action

Answer 28

• Extracellular
• Intracellular (solution)
• Intracellular (membrane bound)

Question 29

How do enzymes speed up a reaction?

Answer 29

They lower the activation energy, increasing the number of collisions with enough energy to react.

Question 30

Name and explain 3 factors that affect enzyme activity

Answer 30

Temperature: High temperatures enzymes will denature, low temperatures the enzyme will not have enough energy
pH: small changes in pH can cause irreversible changes in enzyme structure
Substrate concentration: If theres too much substrate, all the active sites will be full

Question 31

How does a competetive inhibitor work?

Answer 31

They have a molecular shape complementary to the active site, meaning the substrate must compete with the inhibitors for the active sites.

Question 32

How does a non-competitive inhibitor work?

Answer 32

Bind to the enzymes allosteric site, forming covalent bonds. This changes the shape of the enzyme so the substrate no longer fits to the active site.

Question 33

How can enzymes become immobilised?

Answer 33

When they are fixed, bound or trapped on an inert matrix.

Question 34

Give 4 Benefits of immobilised enzymes

Answer 34

• Increased stability
• Dont contaminate products
• Easily recovered
• Several enzymes can be used at the same time
• Enzymes can be added or removed

Question 35

Name and explain 2 uses of immobilised enzymes

Answer 35

Lactose-free milk:
Milk is passed down a column containing immobilised lactase.
Biosensors:
The formation of enzyme-substrate complexes produces an electrical current which can be detected by an electrode.