Topic 2: Molecular Biology

Question 1

What is polarity?

Answer 1

The slight difference in charge that occurs at different poles of a molecule, the covalent bonds between O atom and H atoms are polar covalent bonds (water), electrons are not shared equally therefore water is polar.

Question 2

What pole in water is slightly positive?

Answer 2

Hydrogen, H atoms have a weaker attracts electrons more strongly, forming a slightly positive charge.

Question 3

What pole in water is slightly negative?

Answer 3

Oxygen, attracts electrons more strongly, forming a slightly negative charge.

Question 4

What is hydrogen bonding in water?

Answer 4

Polarity of water allows it to form weak associations with other polar molecules or charged ions through hydrogen bonds, these bonds form when hydrogen atom is attracted to a fluorine, oxygen or nitrogen atom of another molecule.

Question 5

When does cohesion occur?

Answer 5

When molecules of the same type are attracted to each other.

Question 6

What does the hydrogen bonding in water molecules allow?

Answer 6

Allows liquids to resist low levels of external force which creates surface tension. High surface tension is sufficiently dense allowing smaller organisms to move along its surface.

Question 7

What is adhesion?

Answer 7

Attraction between polarity of water and polar substances. Water molecules form hydrogen bonds between each other and polar molecules.

Question 8

What is a solvent?

Answer 8

Liquid that dissolves solute

Question 9

What is a solute?

Answer 9

Dissolves in liquid

Question 10

What is a solution

Answer 10

Solvent and solute

Question 11

What kind of substances are attracted to water?

Answer 11

Substances with a positive or negative charge - they can easily dissolve because of their ionic composition.

Question 12

What is a ‘hydration shell’?

Answer 12

Water forms hydrogen bonds with solute which forms a hydration shell around a solute.

Question 13

Why do polar molecules dissolve in water?

Answer 13

Because they are hydrophilic and form hydrogen bonds with water

Question 14

What region of a solute is the positive water hydrogen atoms attracted to?

Answer 14

The negatively charged region

Question 15

What region of a solute is the negative water oxygen atom attracted to?

Answer 15

The positively charged region

Question 16

Why do charged ions dissolve in water?

Answer 16

Because they are hydrophilic

Question 17

What is water electrostatically attracted to?

Answer 17

Ions

Question 18

Why do non-polar or uncharged atoms not dissolve in water?

Answer 18

Because they are hydrophobic - these substances are insoluble

Question 19

What is a metabolic medium?

Answer 19

Water is a medium for metabolic and enzyme manipulated reactions

Question 20

What is water’s role in cytosol?

Answer 20

Water makes up 80% of the cytosol and contains salts, fatty acids, amino acids and proteins - water dissolves the reactants and enzymes for metabolism

Question 21

What is transported in xylem from roots to leaves in vascular plants?

Answer 21

Dissolved mineral ions

Question 22

What is transported in the phloem from source to sink?

Answer 22

Dissolved sugars produced in photosynthesis.

Question 23

What is carried in animal blood plasma?

Answer 23

Dissolved solutes transported in solution around the body; salt ions, amino acids, proteins, glucose, waste products of metabolism, small amount of dissolved sugars

Question 24

What is buoyancy?

Answer 24

Upward force on an object placed in or on it - depends on density, object density lower than fluid the object will float.

Question 25

Examples of buoyancy?

Answer 25

Bony fish have airfield swim bladders which are used to control overall density. Organisms that fly have to generate lift to stay airborne as buoyancy in air is much less than in water.

Question 26

What is viscosity?

Answer 26

Resistance of a fluid to flow due to internal friction. Water is more viscous than air as it forms hydrogen bonds which inc. the friction of flowing molecules. water can dissolve solutes with inc. viscosity of the solution

Question 27

What is thermal conductivity?

Answer 27

Measure of a material’s ability to move heat across a temp. grad. Water absorbs and transfers heat more rapidly than air because water particles are packed more tightly tgthr.

Question 28

What is specific heat capacity?

Answer 28

Quantity of heat needed to raise temp. of 1g of substance by 1C. Water has a higher SPC than air as its hydrogen bonds require additional energy to break - makes it an efficient coolant in sweat

Question 29

What are covalent bonds?

Answer 29

Sharing of electrons to form electron pairs btwn atoms

Question 30

Why does carbon form the basis of all organic compounds?

Answer 30

Due to its ability to form large and complex molecules via covalent bonding.

Question 31

How many covalent bonds does carbon make?

Answer 31

4

Question 32

What are monomers?

Answer 32

Organic compounds are typically composed of recurring subunits which are covalently joined to form polymers. Monomeric subunits of carbohydrates, nucleotides, proteins, lipids; monosaccharide, fatty acid, nucleotide, amino acid

Question 33

What is polymerisation?

Answer 33

Polymers can be formed from monomers via condensation reactions. A strong covalent bond is formed between monomers and a molecule of water is released. Anabolic reaction.

Question 34

What can polymers be broken down into?

Answer 34

Their monomeric subunits via hydrolysis reaction. A water molecule

Question 35

What are carbohydrates composed of?

Answer 35

Monomers called monosaccharide. These monomers link together by condensation reactions to form a disaccharide and polysaccharide polymers.

Question 36

What are glycoproteins?

Answer 36

Carbohydrate chain faces outwards and can be recognised by other receptors own other cells.

Question 37

Properties of lipids

Answer 37

substances that dissolve in non-polar solvents. E.g. fats, oils, waxes and steroids

Question 38

What are triglycerides?

Answer 38

Contain one glycerol molecule and three fatty acids molecules.

Question 39

What are saturated fatty acids?

Answer 39

Carbons are carrying as many hydrogen atoms as they can, no double bonds between the carbon atoms - straight molecule. Solid at room temp. because they can stack tightly.

Question 40

What are monounsaturated fatty acids?

Answer 40

One double bond within the hydrocarbon chain.

Question 41

What are polyunsaturated fatty acids?

Answer 41

At least two double bonds within the hydrocarbon chain.

Question 42

What are cis fatty acids?

Answer 42

Naturally curved. Hydrogen atoms are bonded to the carbon atoms on either side of the double bond are on the same side.

Question 43

What are trans fatty acids?

Answer 43

They are hydrogenated. H atoms one either side of the double bond are on opposite sides. Vast majority. of trans fats are the results of chemical processing in food processing factories.

Question 44

What are amino acids?

Answer 44

Proteins that are composed of long chains of recurring monomers. Each a.a. contains a central alpha carbon linked to an amino group, carboxyl group, H atom and a variable group.

Question 45

How many types of amino acids are there?

Answer 45

20

Question 46

What is an essential amino acid?

Answer 46

Cannot be produced by the body and must be present in diet.

Question 47

What is a non-essential amino acid?

Answer 47

Can be produced by the body.

Question 48

What is a conditional amino acid?

Answer 48

Can be produced by the body at lower rates.

Question 49

What is the function of haemoglobin?

Answer 49

Transporting oxygen from lungs to the tissues and facilitating the return transport of carbon dioxide. Composed of four polypeptides found in RBC/

Question 50

What is immunoglobulin?

Answer 50

Antibodies that bind to antigen.

Question 51

What is collagen?

Answer 51

Provides structural support to the extracellular space of connective tissues - proteins in dermis of the skin. Three polypeptides wound together.

Question 52

What is keratin?

Answer 52

Maintains elasticity in the skin - found in hair, nails, claws, hooves. Fibrous proteins composed of two polypeptide chains.

Question 53

What is a digestive enzyme?

Answer 53

Proteins that the body makes to break down food and aid digestion.

Question 54

What is insulin?

Answer 54

Peptide hormone responsible for uptake of glucose into cells reduces glucose conc. in blood secreted by the beta cells in pancreas

Question 55

What are enzymes?

Answer 55

Globular proteins which act as a biological catalysts by speeding up the rate of chemical reactions. Takes part in anabolic and catabolic reactions. are not changed or consumed by the reactions they catalyse.

Question 56

What is an anabolic reaction?

Answer 56

Build up complex molecules from simpler ones occurs via condensation reactions.

Question 57

What is a catabolic reaction?

Answer 57

Breaking down complex molecules molecules into simpler ones, occurs via hydrolysis reactions.

Question 58

What is an active sites?

Answer 58

The region on the surface of the enzyme which binds to the substrate molecule. The active site and the substrate compliment each other in terms of both shape and chemical properties. Composed of a few amino acids only but the interactions ensure the active site is complementary to the substrate.

Question 59

What is the induced fit model?

Answer 59

Enzymes active site is not a completely rigid fit for the substrate. The active site undergoes a conformational change when exposed to a substrate. explains how enzymes may exhibit broad specificity.

Question 60

What is an exergonic reaction?

Answer 60

If the reactants contain more energy than the products the free energy is released into the system. These reactions are usually catabolic as energy is released from broken bonds.

Question 61

What is an endergonic reaction?

Answer 61

Reactants contain less energy than the products, free energy is lost to the system. Reactions are usually anabolic as energy is required synthesise bonds between molecules.