Biological Molecules,,

Question 1

Basic functions of water

Answer 1

A reactant in a chemical reactions (hydrolysis)
Solvent
Transports substances
Habitat

Question 2

Functions of water related to its structure

Answer 2

High specific heat capacity – hydrogen bonds between molecules can absorb a lot of energy, it takes a lot of energy to heat it up
High latent heat of vaporisation – takes a lot of energy to break the bonds between molecules, a lot of energy is used when water evaporates
Cohesive – due to polarity
Solvent – ions can be totally surrounded by water molecules (dissolved)
Less dense when solid – water molecules are held further apart in ice than liquid, useful for habitats

Question 3

Structure of water

Answer 3

One oxygen atom and two hydrogen atoms
Water is polar The oxygen nucleus is slightly negative charged and the hydrogen nucleus is slightly positively charged
Atoms are connected by hydrogen bonds

Question 4

Carbohydrate structure

Answer 4

Mostly polymers Made from monosaccharides
Made from carbon hydrogen and oxygen

Question 5

Polymer

Answer 5

A molecule made from smaller molecules (monomers)

Question 6

Glucose

Answer 6

A hexose monosaccharide
Two forms – alpha and beta
Soluble

Question 7

Ribose

Answer 7

Pentose monosaccharide

Question 8

Disaccharides and polysaccharides

Answer 8

Monosaccharides joined together by glycosidic bonds
Hydrogen atom on one monosaccharide bonds to a hydroxyl group on the other releasing a molecule of water (condensation reaction)
A disaccharide is two monosaccharides joined together
A polysaccharide is when more than two monosaccharides joined together
Hydrolysis breaks the glycosidic. 

Question 9

Starch

Answer 9

Main energy store in plants.
Cells get energy from glucose and plants store excess glucose as starch
Starch is a mixture of two polysaccharides of alpha glucose - amylose and amylopectin.
Starch is insoluble in water so it doesn’t cause water to enter cells by osmosis which makes it good for storage

Question 10

Amylose

Answer 10

Long unbranched chain of alpha glucose
Coiled structure
Compact therefore good for storage

Question 11

amylopectin

Answer 11

Long branched chain of alpha glucose
Side branches allow enzymes to break glycosidic bonds easily so glucose can be released quickly

Question 12

Glycogen

Answer 12

Main energy store in animals
Animals get energy from glucose and starch excess glucose as glycogen (polysaccharide of alpha glucose)
Lots of branches so starch glucose can be released quickly
Very compact – good for storage

Question 13

Cellulose

Answer 13

Component of cell wall implants
Long on branched chain of beta glucose
Beta glucose molecules bond and form straight cellulose chains linked by hydrogen bonds to form strong microfibrils to provide structural support

Question 14

Triglycerides

Answer 14

Contain carbon hydrogen and oxygen
Have one molecule of glycerol with three fatty acids
Fatty acid molecules have long tails of hydrocarbons, tails or hydrophobic (repel water molecules) making lipid insoluble in water
Ester bond forms between fatty acid and glycerol by a condensation reaction
Triglycerides can be broken down by hydrolysis which breaks the ester bond

Can be saturated or unsaturated

Question 15

Ester bond

Answer 15

In triglycerides between fatty acid and glycerol

Question 16

Phospholipids

Answer 16

One glycerol, two fatty acids and a phosphate group
Phosphate group is hydrophilic (attracts water molecules) and fatty acid tails a hydrophobic

Question 17

How is triglycerides structure related to the function

Answer 17

Mainly used as an energy store
Long hydrocarbon tails contain lots of chemical energy – lots of energy is released when they’re broken down
Insoluble so they don’t cause water to enter the cells by osmosis making them swell

Question 18

How is phospholipids structure related to their function

Answer 18

Found in the cell membrane is making up the phospholipid bilayer
Hydrophilic heads and hydrophobic tails from a double layer with the heads facing out towards the water
The centre is hydrophobic so water soluble substances can easily passed through acting as a barrier

Question 19

How is the structure of cholesterol related to its function

Answer 19

Structure has a pole hydroxyl group attached to it
In eukaryotic cells it helps strengthen the cell membrane by interacting with the phospholipid bilayer
Cholesterol is small which allows it to fit in between the phospholipid molecules in the membrane
They bind to the hydrophobic tails of phospholipids causing them to pack closely together – make the membrane less fluid and more rigid

Question 20

Proteins

Answer 20

Long chains of amino acids (Monomers)
Polymers
Dipeptide is when two amino acids join together
Polypeptide is one more than two amino acids join together
Proteins are made from one or more polypeptide

Question 21

Amino acids

Answer 21

Made from: a carboxyl group (minus COOH) and an amino group (minus NH2) attached to a carbon atom, Variable R group.
Contain carbon, oxygen, hydrogen and nitrogen. Sometimes sulphur

Joined by peptide bond to form dipeptides and polypeptides a condensation reaction
Hydrolysis reaction breaks the peptide bond

Question 22

Peptide bond

Answer 22

Joins amino acids together

Question 23

Structural levels of protein

Answer 23

Primary structure
Secondary structure
Tertiary structure
Quanternary structure

Question 24

Primary structure

Answer 24

Sequence of amino acids in the polypeptide chain
Different proteins have different sequences
Peptide bonds between amino acids

Question 25

Secondary structure

Answer 25

Hydrogen bonds formed between amino acids make a coil into an alpha helix or fold into a beta pleated sheet

Question 26

Tertiary structure

Answer 26

Chain of amino acids called and folded further
More bonds form between different parts (ionic bonds, disulphide bonds, hydrogen bonds)
If proteins are made from a single polypeptide chain the tertiary structure is the final structure

Question 27

Quaternary structure

Answer 27

If proteins are made from several different polypeptide chains the quaternary structure is the way that these chains are assembled together
(For example haemoglobin is made from four polypeptide chains)

Question 28

Globular proteins

Answer 28

Hydrophilic our groups are pushed to the outside of the molecule making globular proteins soluble so that easily transported in fluids

Haemoglobin
Insulin
Amylase

Question 29

Haemoglobin – globular protein function

Answer 29

Carries oxygen around the body in red blood cells
Conjugated protein – a protein with a non-protein group attached (prosthetic group)
In haemoglobin each of the four polypeptide chains has a prosthetic group called haem

Question 30

Insulin – globular protein function

Answer 30

Hormone secreted by the pancreas
Regulate blood glucose level
Solubility means it can be transported in the blood where it acts
Consists of two polypeptide chains held together by disulphide bonds

Question 31

Amylase – globular protein function

Answer 31

Enzyme that catalyses the breakdown of starch in the digestive system
Single chain of amino acids
Most enzymes a globular proteins

Question 32

Fibrous proteins

Answer 32

Insoluble and strong
Fairly unreactive

Collagen
Keratin
Elastin

Question 33

Collagen – fibrous protein

Answer 33

Found in animal connective tissues
Strong
Minerals can bind to the protein to increase rigidity

Question 34

Keratin – fibrous protein

Answer 34

Found in many external structures of animals
Can be flexible (Skin)
Can be Hard and tough (nails)

Question 35

Elastin – fibrous proteins

Answer 35

Found in elastic connective tissues
Elastic, so allows tissues to return to original shape after being stretched

Question 36

Inorganic ions

Answer 36

Ion is an atom that has an electrical charge
Positive charge is cation
Negative charge is anion

Question 37

Cations

Answer 37

Calcium – involved in the transmission of nerve impulses and the release of insulin from the pancreas. Important for bone formation. Acts as a cofactor for many enzymes.
Sodium – important for generating nerve impulses, muscle contraction and regulating fluid balance in the body.
Hydrogen – effects the pH of substances. Also important for photosynthesis reactions.
Ammonium – absorbed by the soil and plants and is important source of nitrogen.

Question 38

Anions

Answer 38

Nitrate – absorbed from the soil by plants, important source of nitrogen.
Hydrocarbonate – acts as a buffer which helps maintain the pH of the blood.
Chloride – involved in the chloride shift helps maintain pH of blood during gas exchange. cofactor for amylase. Involved in nerve impulses.
Phosphate – involved in photosynthesis and respiration reactions. Needed for synthesis of many biological molecules (nucleotides, Phospholipids and calcium phosphate.)
Hydroxide – affects the pH of substances.