Biochemistry 2.1-2.4

Question 1

What is the difference between covalent and ionic bonds?

Answer 1

• covalent share electrons (stable)
• ionic bonds easier to separate
  
  • dissociation
  • electrons move

Question 2

Why is water bipolar?

Answer 2

• oxygen negative
• hydrogen positive
• polarity

Question 3

What are hydrogen bonds?

Answer 3

• intermolecular force
• dipole-dipole force
  
  • strongest
• between water molecules
  
  • or bases of DNA

Question 4

What are properties of water?

Answer 4

• cohesion
  
  • water holds it shape (H-bonds)
  • surface tension
    
    • water “membrane” withstands pressure from air
• adhesion
  
  • water reacts with polar substances (also solid)
  • capillary action
    
    • water hold together and sticks to glass
    • forces pull water upwards
• thermal
  
  • water holds heat
  • high boiling point (H-bonds)
• solvent
  
  • for polar and ionic substances
  • hydration shells

Question 5

Why is water more dense than ice?

Answer 5

• in liquid state molecules are densely packed
• in ice water molecules are arranged in crystal lattice
  
  • more space between them
• highest density at 4ºC
• normally substances in liquid state have more space
• hexagonal structure maximises the amount of hydrogen bonds between molecules
• water reservoirs freeze at the top
  
  • organisms live underneath
  • isolates water from further freezing

Question 6

Boiling point of water vs methane

Answer 6

• hydrogen bonds are stronger and don’t allow for movement
• b.p. of water higher
  
  • more energy to break H bonds

Question 7

What is specific heat capacity and heat of vaporisation?

Answer 7

• specific heat capacity
  
  • energy needed to raise temp of 1g by 1ºC
  • conductivity regulates temperature of living things
• heat of vaporisation
  
  • energy needed for 1g to change from liquid to gas
  • no dehydration

Question 8

Water as a coolant

Answer 8

• water evaporation needs a lot of energy
• sweat cools down body

Question 9

Why are biological membranes wet?

Answer 9

• alveoli, villi and capillaries
• substances dissolve quickly
  
  • prevent collapsing

Question 10

Benefits of living in water?

Answer 10

• high density of water
  
  • swimming and floating
    
    • ice on top, underneath not frozen
• transparent
  
  • photosynthesis

Question 11

Why is carbon necessary for living things?

Answer 11

> 4 covalent bonds
complex molecules
gives and receives e-

Question 12

How are polymers formed?

Answer 12

• few molecules combined
  
  • large molecule
  • releasing small ones
• ex.: water - dehydration reaction

Question 13

What is hydrolysis?

Answer 13

• hydrolysis → opposite of dehydration
• polymer split into monomers + H2O

Question 14

Anabolism vs catabolism

Answer 14

• anabolism
  
  • formation of molecules from monomers
• catabolism
  
  • breakdown of complex molecules into monomers

Question 15

How are carbohydrates, proteins and triglycerides synthesised?

Answer 15

• carbohydrate
  
  • monosaccharides → disaccharides → polysaccharides
• proteins
  
  • amino acids → dipeptides → polypeptides
• triglycerides
  
  • 3 fatty acids + glycerol → triglyceride

Question 16

Examples of saccharides

Answer 16

• sucrose → glucose + fructose
• maltose → glucose + glucose
• lactose → glucose + galactose

Question 17

How are peptide bonds created?

Answer 17

• condensation reaction
• carboxyl group connects to amino group
  
  • water is released

Question 18

What are properties of glucose, fructose, sucrose and lactose?

Answer 18

• glucose
  
  • producing ATP
  • transported in blood
• fructose
  
  • fruit sugar
  • energy source
• sucrose
  
  • table sugar
  • transported in plants (plant sap)
• lactose
  
  • milk sugar
  • energy for infants
  • digested by lactase

Question 19

What are bonds between 2 monosaccharides

Answer 19

• glycosidic bonds

Question 20

What are functions of carbohydrates?

Answer 20

• energy source
• energy storage
  
  • starch - plants
  • glycogen - animals
• structure
  
  • cellulose
• cell membranes
  
  • glycoproteins
  • proteins + sugar = antigens

Question 21

What are the properties of glycogen and starch?

Answer 21

• glycogen
  
  • stores energy in muscles and liver
  • mobilised when blood glucose level drops
  • lots of branches and 2 glycosidic bonds
• starch
  
  • stored in plants
  • starch has less glycosidic bonds and therefore less branches (or none)

Question 22

What is amylose and amylopectin?

Answer 22

• building blocks of starch
• amylose = single strand
• amylopectin = branched
  
  • plant growth

Question 23

What are the properties of cellulose?

Answer 23

• multiple B-glucose molecules
  
  • plant cell walls
  • put at 180º to previous → stable structure (wall)
• digested by cellulase
• humans can’t digest → fibre (pushes faeces out)

Question 24

What is the difference between unsaturated and saturated fats?

Answer 24

• saturated = single bonds only
• unsaturated = double and single bonds
  
  • bent

Question 25

What is the difference between cis and trans fats?

Answer 25

- unsaturated fats → double bonds - difficult to rotate 2H+ mol. - on the same side → cis → bent - on opposite sides → trans

Question 26

What are phospholipids?

Answer 26

- fats with phosphate group - hydrophobic tails and hydrophilic heads → form plasma membrane

Question 27

Why are fats good energy storage?

Answer 27

- don’t affect osmosis of cell - long-term energy storage - harder to break down - more energy per unit of fat than sugar - thermal isolation and shock absorber

Question 28

What are LDL and HDL?

Answer 28

- LDL = low density lipoprotein (“bad cholesterol”) - more dense in cholesterol than proteins - used when fat deficiency - HDL = high density lipoprotein - carries excess cholesterol to liver

Question 29

How does cholesterol accumulate in blood vessels?

Answer 29

- LDL sticks to wall of vessels - endothelium destroyed - monocytes detect, macrophages destroy build-up - die from overeating - cholesterol builds up → cloth - fibrous cap covers the clot - calcium hardens - plaque (mountain) restricts blood flow

Question 30

How is insulin synthesised?

Answer 30

- preproinsulin (polypeptide) → proinsulin - chain C released → insulin created

Question 31

What are the levels of protein structure?

Answer 31

- primary (chain) - secondary (α helix or β sheets) - hydrogen bonds - tertiary (3D) - hydrophobic bonding (not an actual bond) - disulphide bridges - salt bridges (ions) - quaternary (more than one chain)

Question 32

What is the function of rubisco?

Answer 32

- enzyme (catalyst) for light-independent phase of photosynthesis - RuBP + CO2

Question 33

What is the function of insulin?

Answer 33

- animal hormone - secreted in β cells of pancreas - lower blood glucose level - triggers uptake by cells

Question 34

What is the function of immunoglobulins?

Answer 34

- immunoglobulins = antibodies - destroy foreign cells - recognise antigens - produced by lymphocytes - different structures

Question 35

What is the function of rhodopsin?

Answer 35

- light-sensitive protein - produced by rods (photoreceptors in retina) - B&W vision

Question 36

What is the function of collagen?

Answer 36

- building structure (connective tissue) - elastic

Question 37

What is the function of spider silk?

Answer 37

- resistant to pulling apart - used by spiders to make webs

Question 38

What is proteome?

Answer 38

- complete set of proteins expressed by an organism