1. Biological Molecules Flashcards
1
Q
Describe how calibration curve is carried out:
A
-reducing tests of known glucose concentrations carried out (6 different concentration)
-colorimeter used on all of them to quantify amount of glucose
-reducing test done on unknown concentration solution
-colorimeter used to quantify by comparing results of unknown to known solutions to predict concentration of unknown
2
Q
Two molecules of glucose can react during a ……. ……. to form a ……. …… and lose a water molecule, forming a disaccharide. This forms a …. …..
A
Two molecules of glucose can react during a condensation reaction to form a glycosidic bond and lose a water molecule, forming a disaccharide.
This forms a 1-4 bond.
3
Q
A primary structure is ……. ….. (3)
A
- specific sequence of amino acids
- joined by peptide bonds
- by cond. reaction
4
Q
A secondary structure is
A
-folding of the polypeptide chain due to h-bonds betw/ NH and C=O ➜ folds into alpha helix / beta pleated sheet
5
Q
Tertiary structure:
A
- further folding into 3D shape betw/ multiple amino acids joined by pep bonds
- due to bonds forming betw/ diff R groups in amino chain (h-bonds, ionic, disulfide)
6
Q
quaternary structure:
A
- folding & bonding betw/ >=2 polypep chains
- forms fibrous/ globular structures
7
Q
cellulose is a polymer of
A
beta glucose
8
Q
Define reducing sugars:
A
Reducing sugars can donate an electron to another molecule, eg:
-all monosaccharides
-maltose, lactose
9
Q
describe how a triglyceride is formed
A
- one molecule of glycerol and 3 fatty acids
- condensation reaction, 3 molecules of water removed
forms ester bonds
10
Q
glycogen is made w
A
alpha glucose
11
Q
describe test for lipid
A
- add ethanol
- add water
- shake
- white emulsion
12
Q
Describe the structure of starch and explain how it’s adapted for its function in cells: (6 marks)
A
- coiled in a tight helix
➔makes it compact and allows for maximum glucose storage to be used as energy during respiration - Insoluble in water
➔doesn’t affect water potential so doesn’t cause water to move into the cells through osmosis - Large polymers
➔can’t diffuse out of the cell membrane - has a lot of ends from a lot of branches
➔many ends for enzymes to act on during hydrolysis, starch is broken down rapidly
13
Q
Explain one other effect on the plant caused by the evaporation of water from its leaves
A
- Cools leaves
- Evaporation uses heat from leaves
14
Q
Explain why a change in primary structure can affect the structure of a protein: (4)
A
- means diff amino acids in the sequence
- different R groups in different places
- changes in bonding in tertiary structure between R groups (ionic, h-bonds, disulfide)
- protein will fold into a different shape and function will change
15
Q
Explain why this column of water doesn’t break (3 marks)
A
Water molecules polar
Form hydrogen bonds betw water molecules
Cohesion prevents breakage of columns
16
Q
Give properties of water that are important in Biology (5)
A
- Polar molecules: Acts as an universal solvent
- Metabolite: Involved in metabolic reactions such as condensation and hydrolysis
- Water molecules stick together, cohesive bonds between water molecules: Provides surface tension/ prevents columns of water breaking
- High specific heat capacity: Reduces fluctuations in temperature (of water bodies)
- High latent heat of evaporation: Evaporation of small amount of water cools an organism
17
Q
how is cellulose adapted for function in plant cells
A
- straight and long chains
- many hydrogen bonds between chains form fibrils
- makes cell wall very strong, resistant to osmotic pressure
18
Q
how is starch adapted for function in plant cells
A
- Insoluble;
- Don’t affect water potential;
- Helical;
- Compact;
- Large molecule;
- Cannot leave cell.
19
Q
If there is a reducing sugar present then:
A
The Cu2+ from the Benedicts solution will gain an electron and form C+ ions.
- These form a red precipitate.
- If concentration of reducing sugars is low then: less precipitate, more Cu2+ ions left in the solution (less transmission, more absorption)
- Solution will be bluer
20
Q
lactose formed by cond. of
A
glucose and galactose
21
Q
2 major stores of glycogen in humans
A
liver and muscle cells
22
Q
Test for non-reducing sugars: (sucrose)
A
- take boiling tube, add dilute HCl (to hydrolise)
- add Sodium hydrogen carbonate (to neutralise it)
(pH should be 7) - add Ben’s solution
- heat by putting boiling tube in beaker w/ boiling water
observe color change
23
Q
hydrolysis reaction to reverse a peptide bond is carried out by
A
protease enzymes in digestive system
24
Q
what is a monomer
A
small repeating unit from which a larger molecule is made
25
Why is starch a good storage molecule (4)
1. Insoluble, doesn’t affect water potential;
2. Branched / coiled so makes molecule compact;
3. Polymer of (α-)glucose so provides glucose for **respiration**;
4. Branched / more ends for fast breakdown / enzyme action;
26
benefits of immobilised enzymes: (5)
* allows for continuous process
* avoids end product inhibition
* doesn't need to seperate enzyme form product
* makes enzymes more stable
* enzymes can be reused
27
Describe process of non-competitive inhibitor:
* **doesn't bind to active site**
* binds to an allosteric site
* changes the tertiary structure of enzyme
* shape of active site changes, no longer complimentary to substrate
* sub can't bind to form E-S complex, **reduces rate of reaction**
28
Processes in the cell that require energy from hydrolisis of ATP to ADP:
muscle contraction
active transport
formation of large molecules eg. proteins
29
What is an enzyme?
* biological catalysts
* globular proteins
* have specific tertiary structures that shape their active site
30
compare and contrast structure of starch and cellulose
SIMILARITIES:
- both are polysacs
- both contain glycosidic bonds
DIFFERENCES:
- starch, alpha but cellulose, beta
- starch has **mainly** 1-4 and **some** 1-6 glyco bonds but cellulose only has 1-4
- starch forms coiled structure but cellulose forms linear fibre
31
explain 5 properties in water that make it useful in organisms (5)
* cohesion - supports water columns & provides surface ten
* high spec heat - buffers temp changes
* large latent - provides cooling effect through evap
* metabolite in cond. reactions
* solvent allows transport of substances
32
ATP useful properties: (4)
* releases energy in small amounts
* broken down in one step
makes energy rapidly available
* phosphorylates
makes substances more reactive / lowers act. en.
* reformed / made again
33
explain what causes arrangement of phosphate bilayer (2)
* **phosphate** head hydrophilic
* **fatty acid** tail hydrophobic
34
what is saturated
a molecule with only single bonds betw/ carbon atoms
35
desc. how monomer join to form primary structure of protein (3)
* condensation reaction betw/ amino acids
* forming peptide bond
* creating specific sequence of amino acids
36
curve levels off because
all substrate used up
37
Why does rate of reaction increase when sugar lyxose is added? (4)
* lyxose cause **tertiary structure of active site** to change
* active site changes shape to become comp. to substrate
* **more successful collisions** betw/ sub & active site, **more ES complexes** fomed
* activation energy reduced
38
Change from optimum pH effect on ROR (3)
* change in charges of R groups
* change in tertiary structure of enzyme so shape of active site
* less ES complexes formed
39
change in pH changes...
* charges of R groups
* ionic and hydrogen bonds disrupted
* tertiary structure of active site changes
* less successful collisions betw/ sub & a.s
* less ESc formed
40
describe test for lipids
* dissolve in ethanol
* add water, shake
* white emulsion
41
Contast saturated and unsaturated fatty acids (4)
saturated
* only single bonds betw/ carbon atoms
* straight chain molecules
* higher melting point
* found in animal fats
unsaturated:
* contain C=C
* kinked molecule
* lower melting point
* found in plant cells
42
relate structure of 3glyceride w/ function
* high energy:mass ratio = **high calorific value** from oxidation (energy store)
* insoluble hydrocarb chain = no effect on water potential and used for **waterproofing**
* slow conductor of heat;**thermal insulation**
* less dense than water; **buoyancy** of aquatic animals
43
desc. fatty acid
hydrocarbon+COOH
44
desc glycerol
hydrocarb+OH instead of H on one side
45
process of ester bond
esterification
46
triglycerides are
* hydrophobic
* non polar
* don't affect water potential
47
Describe the induced fit hypothesis.
* Initially, the active site isn't quite the right shape for the substrate to fit in.
* The substrate induces a change in the shape of the active site of the enzyme.
* The substrate is able to fit better into the active site of the enzyme.
* An enzyme-substrate complex is formed.
* Reaction occurs.
* Enzyme-product complex is formed.
* Product released from enzyme, and enzyme remains unchanged.
48
2 scientists who proposed DNA replication
watson & crick
49
explain difference in structure of starch and cellulose molecules
* cellulose formed from beta glucose **but** starch formed from alpha glucose
* position of H and OH group on carbon atom 1 **inverted**
50
explain how a starch molecule is adapted for its function (2)
1. helical
2. compact
OR
1. large molecule
2. cannot diffuse out of cell
OR
1. insoluble in water
2. doesnt affect water potential
51
Water is a major component of cells. It has several properties that are important in biology. In particular, water:
* is a metabolite in many metabolic reactions, including condensation and hydrolysis reactions
* is an important solvent in which metabolic reactions occur
* has a relatively high heat capacity, buffering changes in temperature
* has a relatively large latent heat of vaporisation, providing a cooling effect with little loss of water through evaporation
* has strong cohesion between water molecules; this supports columns of water in the tube-like transport cells of plants and produces surface tension where water meets air.
52
Describe how a gene is a code for the production of a polypeptide (3)
* base sequence
* in triplets
* determines sequence of amino acids
53
Define the term exon (1)
base sequence coding for sequence of amino acids
54
Define non-coding base sequences and describe where they are found in the genome (2)
* DNA that doesn't code for amino acids
* found betw/ genes
55
Describe how a peptide bond forms between 2 amino acids to form a dipeptide: (2)
* condensation
* betw/ amine and carboxyl
56
Features of starch that make it a good storage molecule (5)
1. Insoluble, so doesn’t affect water potential;
2. Branched / coiled, so makes molecule compact;
3. Polymer of (α-)glucose so provides glucose for respiration;
4. Branched / more ends for fast breakdown / enzyme action;
5. **Large (molecule), so can’t cross the cell membrane**
57
in enzyme questions ALWAYS mention
enzyme-substrate complexes
58
Describe how the structure of the protein depends on the amino acids it contains. (5)
1. Structure is determined by (relative) position of amino acids
2. Primary structure is sequence/order of amino acids;
3. Secondary structure formed by hydrogen bonding
4. Tertiary structure formed by interactions (between R groups);
5. Creates active site in enzymes
6. Quaternary structure contains >1 polypeptide chain
59
Why is rate of reaction lower at pH8 than pH6? (4)
pH6 is closer to the optimum
* at PH8 there are more OH- groups, this changes the charges on R groups
* tertiary structure of the enzyme changes
* so shape of active site changes
* fewer ES complexes formed at pH 8
60
What is the advantage of giving the results of the initial v final mass as ratios? (2)
* allows comparison
* as initial masses were different
61
