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A Level Biology > Biomolecules > Flashcards

Biomolecules Flashcards

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1
Q

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)

A

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

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2
Q

Different sequences of bases code for different proteins explain how

A

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

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3
Q

Monosaccharides

A

(CH2O)n
Soluble

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4
Q

reducing sugars

A

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

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5
Q

Test for reducing sugars

A

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)

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6
Q

Benedict’s solution

A

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

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7
Q

Semi quantitative use of Benedict’s test

A

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

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8
Q

More accurate method for Benedict’s test

A

Filter the solution and weigh the precipitate

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9
Q

Test for non reducing sugars

A

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

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10
Q

Alpha glucose

A

OH at bottom

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11
Q

Solubility of polysaccharides

A

Insoluble

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12
Q

Starch

A

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

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13
Q

Test for starch

A

Add iodine in potassium iodide solution to sample
+ blue black

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14
Q

Glycogen

A

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)

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15
Q

Cellulose

A

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

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16
Q

Lipids

A

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)

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17
Q

Fatty acid
Glycerol

A

RCOOH
CH2OH

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18
Q

Triglycerides

A

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)

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19
Q

Phospholipids

A

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

20
Q

Emulsion test for lipids

A

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

21
Q

Explanation of emulsion

A

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)

22
Q

Amino acids as indirect evidence for evolution

A

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

23
Q

Formation of peptide bond

A

OH from carboxyl group
H from amine group

24
Q

Secondary structure of a protein

A

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

25
Q

Tertiary structure of a polypeptide

A

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)

26
Q

Biuret test for proteins

A

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

27
Q

Enzymes

A

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

28
Q

Antibodies

A

Two short and two long polypeptide chains bonded together
Variable regions

29
Q

Transport proteins

A

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

30
Q

Structural proteins

A

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

31
Q

Induced fit model

A

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

32
Q

Lock and key mechanism

A

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

33
Q

Effect of increased temperature on enzyme reaction

A

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

34
Q

Effect of pH on enzyme action

A

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

35
Q

Calculating pH with hydrogen ion concentration

A

pH= -log10[H+]

36
Q

Effect of enzyme concentration on enzyme action

A

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

37
Q

Effect of increasing substrate concentration on rate of enzyme action

A

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

38
Q

Competitive inhibitors

A

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

39
Q

Non competitive inhibition

A

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

40
Q

Measuring enzyme catalysed reactions

A

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

41
Q

Measuring amount of a gas produced to measure rate of reaction

A

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

42
Q

Measuring how fast a substrate is broken down

A

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

43
Q

Altering the methods for other variables

A

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

44
Q

Position of bands dna replication

A

“Denser so move further”

45
Q

Use of detergent

A

Dissolved membranes/ organelles

A Level Biology (23 decks)

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