UNIT 3 Flashcards
Outline the thermal, cohesive and solvent properties of water
water has a high specific heat capacity;
a large amount of heat causes a small increase in temperature;
water has a high latent heat of vaporization;
a large amount of heat energy is needed to vaporize/evaporate water;
hydrogen bonds between water molecules make them cohesive/stick together;
this gives water a high surface tension / explains how water rises up xylem;
water molecules are polar;
Describe the significance of water to living organisms
surface tension - allows some organisms (e.g. insects) to move on water’s surface
polarity / capillarity / adhesion - helps plants transport water
(excellent) solvent - capable of dissolving substances for transport in organisms
(excellent) thermal properties (high heat of vaporization) - excellent coolant
Describe the use of carbohydrates and lipids for energy storage in animals
stored as glycogen (in liver)
short-term energy storage
more easily digested than lipids so energy can be released more quickly
more soluble in water for easier transport
lipids: 3 max
stored as fat in animals
long-term energy storage
more energy per gram than carbohydrates
lipids are insoluble in water so less osmotic effect
List three functions of lipids
energy storage / source of energy / respiration substrate
(heat) insulation
protection (of internal organs)
water proofing / cuticle
Outline the role of condensation and hydrolysis in the relationship between amino acids and dipeptides. 4 marks
diagram of peptide bond drawn
condensation / dehydration synthesis: water produced (when two amino acids joined)
hydrolysis: water needed to break bond
List four functions of proteins, giving an example of each.
storage - zeatin (in corn seeds)/casein (in milk)
transport - hemoglobin/lipoproteins (in blood)
hormones - insulin/growth hormone/TSH/FSH/LH
receptors - hormone receptor/neurotransmitter receptor/receptor in chemoreceptor cell
movement - actin/myosin
Explain three reasons for converting lactose to glucose and galactose during food processing
t allows people who are lactose intolerant/have difficulty digesting lactose to consume milk (products);
galactose and glucose taste sweeter than lactose reducing need for additional sweetener (in flavoured milk products);
galactose and glucose are more soluble than lactose / gives smoother texture / reduces crystalization in ice cream;
(bacteria) ferment glucose and galactose more rapidly (than lactose) shortening production time (of yoghurt/cottage cheese);
Suggest reasons for using lactase at relatively low temperatures.
less denaturation / enzymes last longer at lower temperatures;
lower energy costs / less energy to achieve 5 °C compared to 48 °C;
reduces bacterial growth / reduces (milk) spoilage;
Outline how enzymes catalyse reactions.
they increase rate of (chemical) reaction;
remains unused/unchanged at the end of the reaction;
substrate joins with enzyme at active site;
to form enzyme-substrate complex;
active site/enzyme (usually) specific for a particular substrate;
Explain the effect of pH on enzyme activity
enzymes have an optimal pH
lower activity above and below optimum pH / graph showing this
too acidic / base pH can denature enzyme
change shape of active site / tertiary structure altered
Describe the structure of proteins.
primary structure is a) chain of amino acids/sequence of amino acids
(each position is occupied by one of) 20 different amino acids
linked by peptide bonds
secondary structure formed by interaction between amino and carboxyl/-NH and -C=O groups
(weak) hydrogen bonds are formed
(α-) helix formed / polypeptide coils up
or (ß-) pleated sheet formed
tertiary structure is the folding up of the polypeptide
using one named example, the effect of a competitive inhibitor on enzyme activity
competitive inhibitor has similar shape/structure to the substrate
therefore it fits to the active site
no reaction is catalyzed so the inhibitor remains bound
substrate cannot bind as long as the inhibitor remains bound
only one active site per enzyme molecule
substrate and inhibitor compete for the active site
Explain how proteins act as enzymes, including control by feedback inhibition in allosteric enzymes.
enzymes are globular proteins there is an active site substrate(s) binds to active site shape of substrate (and active site) changed / induced fit bonds in substrate weakened activation energy reduced binding causes the enzyme / active site to change shape substrate no longer fits the active site Allosteric inhibition is non-competitive
