Biological Molecules - Biological Molecules

Question 1

Monomers?

Answer 1

They are the individual molecules that make up a chain such as carbohydrates. Examples of monomers are monosaccharides, amino acids and nucleotides.

Question 2

Polymers?

Answer 2

When monomers join together to form long chains. (Polymers)

Question 3

What elements make up carbohydrates?

Answer 3

Carbon, hydrogen, oxygen

Question 4

Monosaccharides?

Answer 4

A single monomer. 
General formula (CH2O)n

Question 5

Disaccharides?

Answer 5

When two monosaccharides join together. When they join, a molecule of water is removed so it is a condensation reaction. The bond that is formed is a glycosidic bond.
When water is added to disaccharides, it breaks the glycosidic bonds to release the constituent monosaccharides. This is hydrolysis.

Question 6

Monosaccharides that form disaccharides?

Answer 6

Glucose + Glucose -> Maltose
Glucose + Fructose -> Sucrose
Glucose + Galactose -> Lactose

Question 7

Polysaccharides?

Answer 7

They are polymers. They are formed when more than two monosaccharides join together by condensation reactions.
E.g. Lots of glucose joined by glycosidic bonds forms amylose.

Question 8

Types of polysaccharide

Answer 8

Starch
Glycogen
Cellulose

Question 9

Amino acids

Answer 9

These are the monomers that make up proteins.
20 different forms naturally occurring.
All have a central carbon and 4 attached to groups.
The R group varies between amino acids.

Question 10

Di-peptides

Answer 10

2 amino acids joined (several = polypeptide)
When 2 join, water is released (condensation reaction)
The two amino acids then link with a peptide bond (between the C&andN)
To separate the bond, water is needed (hydrolysis)

Question 11

Primary structure

Answer 11

Chains consisting of hundreds of amino acids (polypeptides) can be formed by polymerisation.
The primary structure of a protein refers to the order/sequence of amino acids in a polypeptide chain.

Question 12

Secondary protein structure

Answer 12

Two types: Alpha helix and beta pleated sheets
The secondary structure of a protein refers to the shape that the polypeptide chain forms as a result of hydrogen bonding.

Question 13

Alpha helix

Answer 13

Hydrogen bonds from between them - causes chain to coil. The hydrogen bonds that keep alpha helices together are vulnerable to fluctuations on pH and temperature.

Question 14

Beta plated sheets

Answer 14

Hydrogen bonds hold adjacent primary chains together.

Question 15

Tertiary structure

Answer 15

The alpha helices of the secondary protein structure can be twisted and folded even more to give the complex 3-D structure of each protein. This structure is maintained by a number of different bonds.
Disulfide bonds
Ionic bonds
Hydrogen bonds

Question 16

Quaternary structure

Answer 16

Only in proteins with more than 1 polypeptide chain. (Haemoglobin)
It refers to the combination of a number of different polypeptide chains and associated non-protein groups into a large, complex protein.

Question 17

Biological catalysts

Answer 17

Enzymes are catalysts so they speed up the rate of reaction without being used up. They allow reactions to take place at lower temperatures.

Question 18

Activation energy

Answer 18

It is the minimum amount of energy needed for reactants to collide.

Question 19

Enzyme structure

Answer 19

Globular proteins
Have a 3-D structure determined by the order of amino acids and the subsequent bonds between them (tertiary structure).
The active site is the functional part of the enzyme. This is where the substrate binds to (forms an enzyme-substrate complex)
Active site is specific to one type of substrate.

Question 20

Lock and key model

Answer 20

Explains how enzymes act. Suggests it is like a lock and key.
Each key has a specific shape that only fits one lock.
The shapes are complimentary.

Question 21

Induced fit model

Answer 21

The enzyme changes it’s shape slightly to fit the substrate. This change puts a strain on bonds in the substrate causing the lowering of activation energy.

Question 22

Starch

Answer 22

Major energy source. Made up of chains of alpha glucose monosaccharides linked by glycosidic bonds that are formed by condensation reactions.
The chains may be beached or unbranched. The unbranched chain is wound into a tight coil that makes the molecule compact.

Question 23

Why starch fits its role of energy storage

Answer 23

Insoluble so doesn’t affect water potential,so water is not drawn into cells by osmosis.
It does not diffuse into other cells as it is large and insoluble.
When hydrolysed it forms alpha glucose, which is easily transported and readily used in respiration.
The branched form has many ends which can be acted upon simultaneously by enzymes meaning that glucose monomers are released very rapidly.
It is compact so lots can be stored in a small space.

Question 24

Glycogen

Answer 24

Glycogen is found in animals and bacteria but never in plants. Glycogens structure has shorter chains than starch but has more highly branched ends. It is the major carbohydrate storage of animals and is stored in small granules in the muscles and liver.

Question 25

Why glycogen’s structure suits it’s storage role

Answer 25

It’s insoluble and so does not draw water into the cells by osmosis.
Being insoluble it doesn’t diffuse out of cells.
It’s compact, so a lot can be stored in a small space.
It is more highly branched than starch so has more ends that can be acted on simultaneously by enzymes. It is therefore more rapidly broken down to form glucose monomers, which are used in respiration.