Biomolecules

Question 1

Biological washing powders often contain a number of different enzymes. This enables them to remove a wider range of stains from clothes. Explain why a number of enzymes are requires to remove a wider range of stains
(General enzyme question layout)

Answer 1

Stains caused by different substances
Enzymes are specific
Active site specific to substrate/ other substances cannot fit active site

Question 2

Different sequences of bases code for different proteins explain how

Answer 2

Protein made of chain of amino acids
Each amino acid has its own base/ triplet code

Question 3

Monosaccharides

Answer 3

(CH2O)n
Soluble

Question 4

reducing sugars

Answer 4

All monosaccharides and some disaccharides (maltose)
Can donate electrons to another chemical (reduces that chemical)

Question 5

Test for reducing sugars

Answer 5

Add Benedict’s reagent to sample
Heat in water bath that’s being brought to the boil
+ will form coloured precipitate (red copper 1 oxide)

Question 6

Benedict’s solution

Answer 6

Alkaline solution of copper (ll) sulfate
Reduced by reducing sugars to produce copper (l) oxide (red)

Question 7

Semi quantitative use of Benedict’s test

Answer 7

Estimate the approximate amount of reducing sugar in sample as colour of precipitate depends on concentrations of sugar

Question 8

More accurate method for Benedict’s test

Answer 8

Filter the solution and weigh the precipitate

Question 9

Test for non reducing sugars

Answer 9

New sample, add dilute HCl (breaks down into monosaccharides by hydrolysis) and heat in water bath brought to boil
Add sodium hydrogencarbonate to neutralise it (Benedict’s reagent doesn’t work in acidic conditions) test with pH paper to check solution is alkaline
Add Benedict’s solution and heat in water bath brought to boil
+ coloured precipitate

Question 10

Alpha glucose

Answer 10

OH at bottom

Question 11

Solubility of polysaccharides

Answer 11

Insoluble

Question 12

Starch

Answer 12

Plant cells
Small granules/ grains
(Long)Chains may be branched or unbranched, the unbranched chain (amylose) is wound into a tight coil to make the molecule compact. Branched chain (amylopectin) has many ends which can be acted in by enzymes simultaneously so glucose monomers are released rapidly and can be easily transported and readily used.
Insoluble so doesn’t affect water potential
Large and insoluble do doesn’t diffuse out of cells
Compact, lots stored in small space

Question 13

Test for starch

Answer 13

Add iodine in potassium iodide solution to sample
+ blue black

Question 14

Glycogen

Answer 14

Animals and bacteria
Shorter chains than starch and more branched
Stored as small granules mainly in the muscle and liver
Insoluble so doesn’t affect water potential and doesn’t diffuse out of cells
Compact
Highly branched (higher metabolic rate than plants)

Question 15

Cellulose

Answer 15

Straight unbranched long chain
Run parallel to each other, allowing hydrogen bonds to form cross linkages between adjacent chains (collective strength)
Cellulose molecules grouped together to form microfibrils, then fibres
Provides rigidity
Turgid- exerts an inward pressure that stops any further influx of water. Also provides maximum surface area for photosynthesis

Question 16

Lipids

Answer 16

CHO
Insoluble in water
Soluble in organic solvents
Energy source when oxidised
Waterproofing (waxy lipid cuticles on plants and insects and mammals produce oily secretions from glands in skin)
Insulation (slow conductors of heat so retain heat, electrical insulators)
Protection (stored around delicate organs like kidneys)

Question 17

Fatty acid
Glycerol

Answer 17

RCOOH
CH2OH

Question 18

Triglycerides

Answer 18

High ratio of energy storing carbon hydrogen bonds to carbon atoms and are therefore an excellent source of energy
Low mass to energy ratio
Insoluble as large and non polar
High ratio of hydrogen to oxygen atoms so release water when oxidised (water source)

Question 19

Phospholipids

Answer 19

Phosphate molecule
Amphiphilic
Polar so form a bilayer in aqueous environments
Can form glycolipids by combining with carbohydrates within the cell surface membrane, for cell recognition
Provide flexibility to membrane

Question 20

Emulsion test for lipids

Answer 20

Add ethanol to sample then shake
Add water then shake
Milky emulsion

Question 21

Explanation of emulsion

Answer 21

Lipid in the sample is finely dispersed in the water to form an emulsion
Light passing through the emulsion is refracted as it passes from oil to water droplets ( cloudy)

Question 22

Amino acids as indirect evidence for evolution

Answer 22

The same 20 amino acids occur in all living organisms, different only in their side groups

Question 23

Formation of peptide bond

Answer 23

OH from carboxyl group
H from amine group

Question 24

Secondary structure of a protein

Answer 24

H on NH has overall + and O on C=O has - so from weak hydrogen bonds causing chain to twist and fold into a 3D shape

Question 25

Tertiary structure of a polypeptide

Answer 25

Further twisting and folding Hydrogen bonds, easily broken Ionic bonds- form between carboxyl and amino groups. Easily broken by changes in pH Disulfide bridges- strong, between two cysteine amino acids (bond between 2 sulfur atoms)

Question 26

Biuret test for proteins

Answer 26

Add sodium hydroxide to sample Add dilute copper (ll) sulfate solution + purple - blue (Can just say biuret reagent)

Question 27

Enzymes

Answer 27

Spherical due to tight folding of polypeptide chains Soluble Roles in metabolism

Question 28

Antibodies

Answer 28

Two short and two long polypeptide chains bonded together Variable regions

Question 29

Transport proteins

Answer 29

Channel proteins- contain hydrophobic and hydrophilic amino acids which cause the protein to fold up and form a channel Transport molecules and ions across the membrane

Question 30

Structural proteins

Answer 30

Long polypeptide chains lying parallel to each other with cross links between them Physically strong Keratin (hair and nails) Collagen (connective tissue)

Question 31

Induced fit model

Answer 31

Active site forms as the enzyme and substrate interact The enzyme is flexible and can mould itself around the substrate The enzyme has a certain general shape but this alters in the presence of the substrate As it changes shape the enzyme puts a strain on the substrate molecule which distorts a particular bond or bonds in the substrate and consequently lowers the activation energy needed to break that bond

Question 32

Lock and key mechanism

Answer 32

Shape of substrate (key) exactly fits the active site of the enzyme (lock) Enzyme has a rigid structure

Question 33

Effect of increased temperature on enzyme reaction

Answer 33

Increases kinetic energy of the molecules— more frequent and successful collisions Causes hydrogen and ionic bonds to break, substrate less able to form complex Denatured

Question 34

Effect of pH on enzyme action

Answer 34

Change in pH alters the charges on the amino acids that make up the active site of the enzyme so alters active site Affects hydrogen and ionic bonding

Question 35

Calculating pH with hydrogen ion concentration

Answer 35

pH= -log10[H+]

Question 36

Effect of enzyme concentration on enzyme action

Answer 36

More frequent collisions Proportionate increase long as there is excess substrate Until amount of substrate is limited and graph levels off

Question 37

Effect of increasing substrate concentration on rate of enzyme action

Answer 37

More frequent collisions so proportional increase Until saturation point when all active sites are full Rate will decrease over time too if no more substrate is being added

Question 38

Competitive inhibitors

Answer 38

Have a molecular shape similar to that of the substrate Occupy active site of enzyme, no reaction occurs and eventually detaches Block- substrate must compete with the inhibitor If substrate concentration is increased then the effect of the inhibitor is reduced All substrates will eventually occupy active site

Question 39

Non competitive inhibition

Answer 39

Bind to enzyme at a site that isn’t the active site Alters shape of active site so that substrate molecules can no longer occupy it Increase in substrate concentration has no effect on the inhibitor

Question 40

Measuring enzyme catalysed reactions

Answer 40

Formation of products or loss of substrate 1. Lots of substrate so easy for enzyme substrate complexes to form 2. Amount of substrate decreases as its broken down and amount of product increases 3. More difficult for substrate to bind to enzyme as there are fewer substrate molecules and product molecules get in the way so rate increases at decreasing rate 4. Graph flattens when all substrate has been broken down into product

Question 41

Measuring amount of a gas produced to measure rate of reaction

Answer 41

Upside down measuring cylinder in trough of water, connected with a delivery tube to a boiling tube sealed with a bung Add buffer solution to boiling tube to keep pH constant Fill each boiling tube with equal volumes and concentrations of the solution Put each boiling tube in a water bath set to different temperatures along with another tube of catalase Use pipette to add same volume of set concentration of catalase to each boiling tube and replace bung Time oxygen production Repeat at each temp 3 times to get average volume of oxygen produced Calculate average rate if reaction at each temp

Question 42

Measuring how fast a substrate is broken down

Answer 42

Drop of iodine in potassium iodide added to each well in spotting tile Known concentration of starch and amylase added to test tube Dropping pipette to add this to a well and observe colour change Do this at regular intervals Stop when well remains browny orange Repeat with different concentrations of amylase

Question 43

Altering the methods for other variables

Answer 43

pH- adding buffer solution with different pH to each tube Substrate conc Temp Enzyme conc

Question 44

Position of bands dna replication

Answer 44

“Denser so move further”

Question 45

Use of detergent

Answer 45

Dissolved membranes/ organelles