2.1.2 Biological molecules

Question 1

Define monomer

Answer 1

Smaller units that join together to form larger molecules

Question 2

Define polymer

Answer 2

Molecules formed when many monomers are joined together

Question 3

Define condenstion reaction

Answer 3

A chemical bond forms between to molecules and a water molecule is produced

Question 4

Define hydrolysis reaction

Answer 4

A chemical bond is broken between two molecules and a water molecule is used

Question 5

Describe how hydrogen bonding occurs between water molecules

Answer 5

Hydrogen bonding is the intermolecular force of attraction between the partially positive hydrogen of one water molecule and the partially negative oxygen atom of another water molecule.

Water is polar as oxygen is more electronegative than hydrogen

Question 6

Define cohesion and adhesion of water

Answer 6

Cohesion is the hydrogen bonding between water molecules

Adhesion is the attraction between water molecules and other polar molecules

Question 7

Explain the importance water as a transport medium in organisms

Answer 7

Cohesion and adhesion lead to capillary action in an organism.

This is the movement of water up a narrow tube against gravity

Question 8

Explain the importance of water as a habitat for organisms

Answer 8

• Temperature of water is stable, providing a constant environment
• Floating ice insulates water for aquatic organisms
• Surface tension is strong enough to support small insects

Question 9

Explain the importance of water as a solvent in organisms

Answer 9

• Water is polar
• Water dissolves and transports many biological molecules
• This allows these molecules to undergo metabolic reactions

Question 10

Explain the importance of water as a coolant in organisms

Answer 10

• High latent heat capacity
• This helps to maintain a stable internal temperature and protect cells from heat damage
• High latent heat of vapourisation
• Evaporation of water cools the surface of organisms

Question 11

Define high latent heat of vaporisation of water and high specific heat capacity.

Answer 11

The hydrogen bonding between water molecules is very strong

Vaporisation - the thermal energy required for a liquid to vaporize to a gas or the amount that is released when a gas condenses to a liquid

Heat capacity - the energy required to raise the temperature of 1 gram of water by 1 degree Celsius

Question 12

Explain why ice floats

Answer 12

• Hydrogen bonds fix positions of water molecules further apart when water is solid
• This forms a giant, rigid, open structure
• Ice is therefore less dense than water
• This causes ice to float

Question 13

State the biological elements that make up carbohydrates

Answer 13

• Carbon
• Hydrogen
• Oxygen

Question 14

Draw the structures of an α- and a β-glucose molecule

Hexose monosaccharides - 6 carbon monosaccharides

Answer 14

Look up answer to confirm

Question 15

Draw the structure of a ribose sugar

Pentose monosaccharide - 5 carbon sugar

Answer 15

Look up answer to confirm

Question 16

State the important properties of glucose

Answer 16

• Glucose is polar and soluble
• This is due to hydrogen bonding between hydroxyl groups and water molecules
• Glucose can dissolve in the cytoplasm of a cell

Question 17

State the bond formed between monosaccharides and the chemical reaction

Answer 17

Glycosydic bond
Condensation reaction

Question 18

State three disaccharides
Explain how they are formed

Answer 18

Maltose = glucose + glucose
Lactose = glucose + galactose
Sucrose = glucose + fructose

A condesation reaction between two monosaccharides forms a glycosydic bond

Question 19

State the function and structure of starch

Amylopectin and Amylose

Answer 19

Energy store for plants

Amylopectin
* 1-4 and 1-6 glycosydic bonds
* Branched shape

Amylose
* 1-4 glycosydic bonds
* Helix shape with intermolecular hydrogen bonding

Alpha glucose polysaccharide

Question 20

State the function and structure of glycogen

Answer 20

Energy store for animals
* 1-4 and 1-6 glycosydic bonds
* Branched shape

Alpha glucose polysaccharide

Question 21

State the function and structure of cellulose

Answer 21

Cellulose provides strength and rigidity to plant cell walls
* 1-4 glycosydic bonds
* Straight chain molecules
* Microfibrils form due to hydrogen bonding between parallel chains

Beta glucose polysaccharide

Question 22

Explain how the structure of glycogen relates to it’s function

Answer 22

Branching
* Many free ends where glucose can be added or removed - speeds up release and storage of glucose
* Compact - ideal for storage

Large and insoluble
* No osmotic effect on cells
* Does not diffuse out of cells

Question 23

Explain how the structure of starch relates to it’s function

Answer 23

Helix shape
* Compact - ideal for storage

Branching
* Many free ends for removal and addition of glucose - speeds up release and store of glucose
* Compact - ideal for storage

Large and insoluble
* No osmotic effect on cells
* Does not diffuse out of cells

Question 24

Explain how the structure of cellulose relates to it’s function

Answer 24

Microfibrils - hydrogen bonding between parallel chains of cellulose
* Microfibrils form fibres
* Fibres are strong and insoluble
* Fibres provide high tensile strength to plant cell wall
* Unreactive molecule
* Flexible molecule

Question 25

State the biological molecules which make up lipids

Answer 25

* Carbon * Hydrogen * Oxygen

Question 26

Describe the structure of a triglyceride | State the molecules, bonds and chemical reaction

Answer 26

Condesation reaction between a glycerol molecule and three fatty acids which form ester bonds | Example of a macromolecule

Question 27

Constrast unsaturated and saturated fatty acids

Answer 27

Unsaturated * Contain at least one C=C double bond * Bent molecule Saturated * Only contain C-C single bonds * Straight chain molecule

Question 28

Describe the structure of a phospholipid | State the molecules, bonds and chemical reaction

Answer 28

Condensation reaction between a phosphate head and two fatty acids forming ester bonds | Example of a macromolecule

Question 29

Outline the properties of triglycerides related to their function in organisms

Answer 29

* Energy store * Thermal insulation to reduce heat loss * Waterproofing/physical protection of organism surfaces * buoyancy for aquatic animals

Question 30

Define the term macromolecule

Answer 30

Macromolecules are large complex molecules. Lipids are a macromolecule.

Question 31

Outline the properties of phospholipids in related to their function in organisms

Answer 31

* Fatty acid tails are hydrophobic, point away from water, inward/towards each-other * Phosphate group is hydrophilic, forms H-bonds with water and points outwards * Formation of phopholipid bilayer in the cell membrane

Question 32

Describe the structure and function of cholesterol

Answer 32

Structure * Four hydrocarbon rings * Hydroxyl (OH) group at one end Function * Adds stability to the cell membrane by reducing the fluidity of the phospholipid bilayer

Question 33

State the biological elements that make up proteins

Answer 33

* Carbon * Hydrogen * Oxygen * Nitrogen * Sulphur

Question 34

Draw the general structure of an amino acid

Answer 34

Look up answer to confirm

Question 35

Outline the synthesis of peptide chains | State the monomer, chemical reaction and bond

Answer 35

Condesation reaction between amino acids forms polypeptide chains with peptide bonds

Question 36

Describe the primary structure of a protein

Answer 36

The sequence of amino acids in a peptide chain

Question 37

Describe the secondary structure of a protein | State bonding present

Answer 37

Hydrogen bonding in the peptide chain form alpha-helix or beta pleated sheet structures

Question 38

Describe the tertiary structure of a protein | State bonding present

Answer 38

The 3D structure of a protein * Hydrophobic and hydrophilic interactions - between polar and non-polar R-groups * Hydrogen bonding * Ionic bonding - between oppositely charged R groups * Disulphide bonding - covalent bonding between R groups containg sulphur atoms (cysteine amino acids)

Question 39

Describe the quarternary structure of a protein

Answer 39

Two or more polypeptide chains

Question 40

Describe the properties and function of globular proteins

Answer 40

Properties: * Spherical and compact * Water soluble - hydrophilic R-groups face outwards and hydrophobic R-groups face inwards * Have a tertiary shape complimentary to another molecule * May be conjugated proteins Functions: * Involved in metabolic processes * Examples include: enzymes such as catalase, hormones such as insulin, and molecules such as haemoglobin

Question 41

Describe the structure and function of Haemoglobin | Haemoglobin is a named example of a globular conjugated protein

Answer 41

Haemoglobin * 2 alpha subunits, 2 beta subunits * Each subunit contains a prosthetic haem group * Fe2+ ion in the haem group can bind an to oxygen molecule * Haemoglobin can transport oxygen around the body

Question 42

State the definition of a conjugated protein

Answer 42

A globular protein with a non-protein component - known as a prosthettic group

Question 43

Describe the structure and function of catalase | Catalase is a named example of an enzyme globular protein

Answer 43

* Quaternary structure * Four prosthetic haem groups * Fe2+ ions allow catalase to break down hydrogen peroxide which is damaging to cells

Question 44

Describe the structure and function of insulin

Answer 44

Hormone which regulates blood glucose concentration Water soluble - hydrophilic R groups point outwards. Hydrophobic R groups point inwards Specific shape caused by hydrophilic, hydrophobic interactions and bonding in the tertiary structure - to fit into specific cell surface receptors

Question 45

Why must every other beta glucose moleucle be oriented oppositely in a beta glucose polysaccharide

Answer 45

Due to the position of the OH group and the H atom on carbon 1 of a beta glucose molecule, alteernate molecules must be oriented 180 degrees for a glycosydic bond to form.

Question 46

Why do unsaturated triglycerides have a low boiling point?

Answer 46

Fewer hydrogen atoms/more carbon carbon double bonds Kinked chain, unable to uniformly pack together

Question 47

Describe the function and properties of fibrous proteins (give names examples)

Answer 47

Properties: * Insoluble * elongated strands * strong and tough * flexible Functions: * Structure: Collagen in bones * Protection: Keratin in skin, hair and nails * Elasticity: Elastin in blood vessels * Contraction: muscle movement, movement in cilia/flagella