ch2: 15 signs you're an alpha glucose

Question 1

state 1 role in living organisms for the following: sulphur, calcium, phosphorus and iron (4)

Answer 1

sulphur: proteins
calcium: bones, signal for neurotransmitter release and muscle contraction
phosphorus: ATP, DNA, phospholipids
iron: carries oxygen in haemoglobin
these are minerals needed by living organisms

Question 2

draw ɑ-D-glucose (1)
state what it makes as a long chain (1)
state its linkage and properties (3)

Answer 2

long chain → polysaccharide

glycogen: mostly alpha 1,4 some alpha 1,6

starch:
amylose
alpha 1,4
linear and unbranched
broken down by amylase to maltose

amylopectin
mostly alpha 1,4 some alpha 1,6
branched
cannot be broken down by amylase → dextrins
broken down by dextrinase to glucose

Question 3

draw β-D-glucose and state its linkage (2)

Answer 3

cellulose: beta 1,4

Question 4

outline how the structure of cellulose makes it suitable as a component of cell walls (2)

Answer 4

1-4 glycosidic linkages between beta glucose
cross linkage between cellulose molecules holds them together
alternating orientation of glucose units → forms straight chains
rigid: provides support

Question 5

draw deoxyribose (1)

Answer 5

google docs

Question 6

draw ribose (1)

Answer 6

google docs

Question 7

draw a general amino acid (1)

Answer 7

google docs

Question 8

explain how the properties of water are significant to living organisms (9)

Answer 8

polar molecule:
oxygen has a partial -ve charge + hydrogen has a partial +ve charge
hydrogen bonds form between adjacent water molecules
water remains liquid over wide range of temperatures
makes water a good solvent for polar/ionic substances
blood transport solutes in water
adhesive properties → transpiration stream in xylem
cohesive properties → high surface tension allowing insects to live on the surface

high specific heat capacity: moderates temperature fluctuation
high heat of vaporisation: sweating/transpiration cools organisms

transparent:
allows organisms to live below the surface
plants can photosynthesise

ice is less dense than water:
surface of a body of water freezes first → organisms to survive in the water below

Question 9

outline the properties of water molecules that permit them to move upwards in plants (3)

Answer 9

water molecules: polar → form hydrogen bonds
cohesion between water molecules → continuous water column → form transpiration stream in xylem
adhesion of water to the walls of xylem vessel → helps water rise
water evaporates at environmental temperatures → transpiration pull

Question 10

distinguish between anabolism, catabolism and metabolism (3)

Answer 10

metabolism = all enzyme-catalysed reactions in a cell
anabolism + catabolism
anabolism = synthesis of polymers/larger molecules from monomers/smaller molecules
catabolism = break down polymers/larger molecules into monomers/smaller ones

Question 11

outline the role of hydrolysis and condensation in the relationships between (monosaccharides, disaccharides and polysaccharides/fatty acids, glycerol and triglycerides/amino acids and polypeptides) (4)

Answer 11

hydrolysis: addition of water to break down a large molecule into smaller molecules
condensation: removal of water to form a large molecule from smaller molecules

lipids:

hydrolysis: fatty acids and glycerol produced by the hydrolysis of triglycerides through the breaking of ester bonds
condensation: up to 3 fatty acids linked to each glycerol to through formation of ester bonds

carbohydrates:
monosaccharides are single sugars and disaccharides are two sugars and polysaccharides are multiple sugars
disaccharides break into monosaccharides
polysaccharides break into disaccharides/monosaccharides
e.g. maltose → 2 glucose
-OH and -H are added or removed

protein:

hydrolysis: breaking of a polypeptide (large molecule) → amino acids (smaller units)
condensation: joining of 2+ amino acids (small molecules) → polypeptide (large molecule)

process depends on enzyme control

Question 12

outline the use of carbohydrates and lipids in energy storage (5)

Answer 12

google docs

Question 13

describe the structure and function of starch in plants (4)

Answer 13

structure: polysaccharide composed of glucose molecules
amylose: linear and unbranched molecule
amylopectin: branched molecule

function:
storage of glucose/energy in plants
no draw water

Question 14

distinguish between the structures of the different types of fatty acids in food (4)

Answer 14

fatty acids can be saturated or unsaturated
saturated fats have no double bonds
unsaturated can be monounsaturated or polyunsaturated
cis-form has hydrogen atoms on same side of carbon double bond
have kinks (no shame)
lower boiling/melting points
healthier
trans-form has hydrogens on opposite sides of carbon double bond
length of hydrocarbon chain can vary

Question 15

briefly explain the concept of proteome (4)

Answer 15

genome: same in all the cells of an organism
instructs the production of proteins

proteome = all the proteins produced by a cell
every individual has a unique proteome
proteins made vary over time depending on the cell’s activities
varies with the function of the cell
specific genes are expressed in different cells according to a required function

Question 16

list 3 functions of proteins, giving a named example of each (3)

Answer 16

catalysts/digestion: amylase
defense: immunoglobulin
movement: actin and myosin
transport: hemoglobin
synthesis: ligase/DNA polymerase
hormonal communication: insulin/LH

Question 17

outline enzyme-substrate specificity (6)

Answer 17

enzyme shape is specific to substrate
shape of active site matches substrate → active site change to induce fit of substrate
active site has specific 3D shape essential to functioning
substrate and active site are complementary due to chemical attraction
form enzyme-substrate complex
denaturation changes enzyme’s binding ability

Question 18

explain how enzymes catalyse reactions and how a change in pH could affect this (8)

Answer 18

enzymes speed up the rate of chemical reactions
lock and key model: substrate fits into active site due to enzyme-substrate specificity

enzymes work best at optimal pH
increase/decrease from optimum pH decreases activity
change in pH changes structure of active site + 3D structure of enzyme
not allow substrate to fit in active site
enzymes can be denatured if change is extreme
denaturing = loss of its biological properties
changes the ionisation of amino acids

sketch graph showing pH versus enzyme activity

Question 19

explain the use of pectinase in fruit juice production (2)

Answer 19

substrate: pectin
pectin hydrolysed into soluble sugars
enzyme action makes clear juice
↑ yield of fruit juice production

Question 20

explain the factors that can affect enzymes (8)

Answer 20

substrate conc:
substrate concentration ↑ → more frequent collisions between enzyme and substrate → enzymatic activity ↑
up to a maximal level of action → plateau → all active sites are occupied

temp:
enzymes have an optimal temp
more frequent collisions between enzyme and substrate at higher temperatures → enzymatic activity ↑ as it gets closer to optimal temperature
high temperatures stop enzyme activity due to denaturation by changing active site shape

pH:
enzymes have an optimal pH
enzymatic activity ↑ as pH gets closer to optimal pH
extreme pH stop enzyme activity due to denaturation by changing active site shape

Question 21

describe the use of biotechnology in the production of lactose-free milk (6)

Answer 21

a particular yeast contains lactase
biotech companies culture the yeast → extract lactase from it

natural milk contains lactose
lactose: disaccharide
provide energy (for young mammals)
lactase added to milk are immobilised on beads
lactose hydrolysed to glucose and galactose → easily absorbed
increases sweetness/solubility/smooth texture

lactose-free milk allows some people who are lactose intolerant to be nourished by milk without discomfort
many Asians are lactose intolerant but this is less common among other groups
a commercial market exists for lactose-free milk
biotech produced in one part of world is more useful in another

Question 22

describe cell respiration in terms of metabolism (2)

Answer 22

catabolic: complex molecules become simpler
energy is released from complex food molecules to make ATP
enzymes control the reactions

Question 23

outline anaerobic cell respiration (5)

Answer 23

absence of oxygen
glycolysis: glucose is partially oxidised in the cytoplasm
net gain of 2 ATP + 2 3C pyruvate

human: lactate fermentation
pyruvate ⇌ lactic acid

yeast: alcoholic fermentation
pyruvate → ethanol + CO2

(in plants: waterlogged roots, peat + omit human part)

Question 24

outline the process of aerobic respiration/explain how ATP is generated in animal cells (6)

Answer 24

generated in cells by cell respiration
glycolysis: glucose is partially oxidised in the cytoplasm
net gain of 2 ATP + 2 3C pyruvate

anaerobic: no require oxygen
aerobic: pyruvate is broken down in the mitochondrion
requires oxygen
carbon dioxide is produced
link reaction: pyruvate → acetyl CoA + CO2
Krebs cycle releases CO2
water is produced

38 ATP molecules per glucose molecule → net gain 36
a form of energy currency immediately available for use
​​ADP changes into ATP with the addition of a phosphate group

Question 25

explain how the rate of photosynthesis can be measured (5)

Answer 25

measure production of oxygen: oxygen is a by-product of photosynthesis
e.g. count bubbles under water

measure uptake of carbon dioxide: carbon dioxide is used during photosynthesis
e.g measure aquatic pH shift

measure biomass of plants: ↑ in biomass gives indirect measure of rate of photosynthesis

Question 26

explain the process of photosynthesis (8)

Answer 26

autotrophs perform photosynthesis
require water + CO2 + light
occurs in chloroplasts

chlorophyll is the main photosynthetic pigment
different pigments absorb different wavelengths
absorbs red and blue light
greatest absorption in blue light
red light absorbed in high amounts
green light is reflected

light energy absorbed is converted into chemical energy
some energy used for ATP production
photolysis: water split to form oxygen and hydrogen
oxygen released as waste product through stoma
ATP and hydrogen used to fix carbon dioxide to make glucose

CO2 concentration + temperature + light intensity are limiting factors

Question 27

explain the relationship between the absorption spectrum for chlorophyll and action spectrum of photosynthesis for green plants (3)

Answer 27

action spectrum higher than absorption spectrum
peaks in action spectrum correspond to peak absorption by chlorophyll
least absorption in green range as most light reflected
light absorbed by other pigments is also used for photosynthesis
differences due to absorption by other pigments