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Biology A-level > Biological Molecules > Flashcards

Biological Molecules Flashcards

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1
Q

Definition of a monomer

A

Small repeating units that can join together to form a polymer.

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2
Q

Definition of a polymer

A

Produced by multiple monomers joined together.

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3
Q

Definition of polymerisation

A

The process of small molecules joining together to form a polymer.

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4
Q

Definition of condensation

A

When water molecules are formed from amino acids forming a protein.

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5
Q

Definition of hydrolysis

A

To break peptide bonds, a water molecule is added.

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6
Q

Definition of metabolism

A

All the chemical processes that take place within cells of an organism.

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7
Q

Definition of an isomer

A

Different structural formulaes with the same chemical formulae.

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8
Q

Properties of monosaccharides (3 points)

A
  1. Dissolve in water and are reducing sugars.
  2. Same chemical formulae: isomers.
  3. Alpha and beta glucose, fructose, galactose.
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9
Q

List 3 properties of a disaccharide.

A
  1. Dissolve in water and can be reducing or non-reducing sugars.
  2. Made from two monomers joined by a condensation reaction.
  3. Forming a covalent bond; glycosidic.
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10
Q

Rules for drawing a condensation reaction (3 points).

A
  1. Always show groups involved.
  2. Always show water is released.
  3. Always circle and label the bond formed.
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11
Q

Rules for drawing a hydrolysis reaction (4 points).

A
  1. Always show the groups involved.
  2. Always show where the water is added.
  3. Always circle and label the bond broken.
  4. Name the monomers formed.
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12
Q

Starch structure (3 points).

A
  1. Alpha-glucose monomers
  2. 1-4 and 1-6 glycosidic bonds
  3. Branches and and coiled shape held by hydrogen bonds.
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13
Q

Describe the glycogen structure (3 points).

A
  1. Alpha-glucose
  2. 1-4 and 1-6 glycosidic bonds
  3. Branched and coiled shape held by hydrogen bonds.
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14
Q

5 Functions and explanations of starch and glycogen

A
  1. Insoluble- deosn’t affect water potential.
  2. Branched- compact
  3. Polymer of alpha-glucose- provides glucose for respiration.
  4. Large- cannot leave cell.
  5. Branched- many ends for enzymes to attach to and hydrolyse.
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15
Q

2 contrasts between starch and glycogen

A
  1. Starch contains less branches as less glucose is needed for plant respiration; glycogen contains more branches to be hydrolysed by enzymes for aerobic respiration in mammals.
  2. Starch has less 1-6 glycosidic bonds due to fewer branches; glycogen has more 1-6 glycosidic bonds due to more branches.
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16
Q

Describe cellulose structure (5 points).

A
  1. Polysaccharide of beta-glucose.
  2. Every other beta-glucose is upside down.
  3. 1-4 glycosidic bonds only.
  4. Straight chains.
  5. Many hydrogen bonds between chains forming microfibrils.
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17
Q

Explain the effect that many hydrogen bonds forming between microfibrils in cellulose has on the structure?

A

Provides rigidity/strength to plant cell walls.

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18
Q

2 Lipid properties

A
  1. Contains carbon, hydrogen and oxygen.
  2. Insoluble in water/non-polar.
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19
Q

What are the 2 main groups of lipids and their functions?

A
  1. Triglycerides- fats and oils.
  2. Phospholipids- plasma membranes.
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20
Q

Defintion of saturated

A

No C=C double bonds in the hydrogen chain.

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21
Q

Definition of unsaturated

A

C=C double bond in the hydrogen chain.

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22
Q

5 Functions and explanations of triglycerides

A
  1. Energy store- many crabon and hydrogen atoms so more energy per g than carbohydrates.
  2. Lrge, insoluble and non-polar molecules- doesn’t affect water potential of cell.
  3. Storage below dermis of skin in adipose tissue- insulation.
  4. Metabolic source of water- from respiration, due to high hydrogen:oxygen ratio.
  5. Buoyancy- low density.
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23
Q

Definition of amphipathic

A

Have polar and non-polar regions.

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24
Q

2 Properties of phospholipids

A
  1. Fatty acids repel water- hydrophobic.
  2. Phosphate group is attached to water- hydrophilic.
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25
Q

Describe the function of phospholipids (3 points).

A
  1. Forms a bilayer within a cell surface membrane so hydrophobic barrier formed between the inside and outside of cell.
  2. Forms membranes inside the cell, for example; mitochondria, to isolate metabolic reactions.
  3. Controls the exchange of substances.
26
Q

1 Similarity and 5 differences between phosphlipids and triglycerides

A
  1. Triglycerides have 3 ester bonds; phospholipids have 2 ester bonds.
  2. Triglycerides have 1 molecule of glycerol; phospholipids have 1 molecule of glycerol.
  3. Triglycerides contain carbon, hydrogen and oxygen atoms; phospholipids have a hydrophilic head and a hydrophobic tail.
  4. Triglycerides are insoluble; phospholipid tails repel water and they have a hydrophilic head.
  5. Triglycerides have no bilayer; phospholipids have a phospholipid blayer.
  6. Triglycerides have 3 fatty acids; phospholipids have 2 fatty acids.
27
Q

3 Properties of proteins

A
  1. Contains carbon, hydrogen, oxygen, nitrogen and sometimes sulfur.
  2. 20 naturally occurring amino acids.
  3. Proteins can be: 1. Globular- spherical and soluble. Have a metabolic function. Examples: insulin, haemoglobin, enzymes. 2. Fibrous- long,thin and insoluble. Have structural function. Examples: collagen and keratin.
28
Q

Describe the structure of proteins (4 points).

A
  1. Amine group- NH2.
  2. Carboxyl group- COOH.
  3. Hydrogen atom- H.
  4. R group- differs in all amino acids.
29
Q

Describe the structure of dipeptides (3 points).

A
  1. Dipeptides formed by condensation reactions.
  2. Peptide bonds.
  3. Forms between the amine group of one amino acid and the carboxyl group of another.
30
Q

Definition of primary structure

A

The order in which the amino acids are arranged in a protein chain.

31
Q

State and describe the bond(s) that are present in a primary protein ( 2 points).

A
  1. Peptide bonds.
  2. These are very strong bonds and form via condensation reactions between two amino acids.
32
Q

Definition of secondary structure

A

Polypeptide chain folds into either: alpha-helix or beta-pleated sheet.

33
Q

State and describe the bond(s) present in a secondary protein (2 points).

A
  1. Peptide bonds.
  2. Hydrogen bonds which are weak, so can break with a slight positive or negative charge or temperature change.
34
Q

Definition of tertiary structure

A

Polypeptide chain folds further to produce a specific structure.

35
Q

State and describe the bond(s) present in a tertiary protein ( 4 points).

A
  1. Peptide bonds.
  2. Hydrogen bonds between the polar R groups of the amino acids, which are easily broken by temperature and pH changes.
  3. Ionic bonds between amino acids with opposite charges.
  4. Disulfide bridges between amino acids that contain sulfur in their R group- strong covalent bonds but broken by reducing agents.
36
Q

How is tertiary structure determined?

A

By where the bonds form in the polypeptide chain, determined by the sequence of amino acids.

37
Q

What does tertiary structure determine?

A

3D shape and function of protein.

38
Q

Definition of quaternary structure

A

More than one polypeptide chain.

39
Q

State and describe the bond(s) present in a quaternary protein (4 points).

A
  1. Peptide bonds.
  2. Hydrogen bonds between the polar R groups of the amino acids, which are easily broken by temperature and pH changes.
  3. Ionic bonds between amino acids with opposite charges.
  4. Disulfide bridges between amino acids that contain sulfur in their R group- strong covalent bonds but broken by reducing agents.
40
Q

Describe the test for proteins (2 points).

A
  1. Add Biuret.
  2. Result: Blue-lilac.
41
Q

Describe the test for carbohydrates- reducing sugars (monosacchraides and disaccharides) ( 2 points).

A
  1. Heat to 80 degrees with Benedict’s.
  2. Result: Blue- brick-red precipitate.
42
Q

Carbohydrates- non-reducing sugars (polysaccharides) test (5 points).

A
  1. Heat to 80 degrees with Benedict’s but solution stays blue.
  2. Fresh sample.
  3. Boil with acid, then neutralise with alkali.
  4. Heat to 80 degrees with Benedict’s.
  5. Results: Blue-brick-red precipitate.
43
Q

Lipids test (3 points).

A
  1. Shake with ethanol
  2. Then add water.
  3. Results: white/milky emulsion.
44
Q

Starch test (2 points).

A
  1. Add iodine.
  2. Results: yellow- blue-black.
45
Q

What is the purpose of the acid in the non-reducing sugars test?

A

The acid hydrolyses the glycosidic bonds producing monosaccharides (reducing sugars).

46
Q

What is the purpose of the alkali in the non-reducing sugars test?

A

Benedict’s works in alkaline solutions, so the solution mustbe neutralised.

47
Q

Definition of quantitative data

A

Numerical measurement of a variable, can be statistically analysed.

48
Q

Definition of qualitative data

A

Judgement, cannot be statistically analysed.

49
Q

Describe the method for a qualitative Benedict’s test (7 points).

A
  1. Calibrate colorimeter using water = 0% absorption.
  2. Place sample into cuvette into colorimeter.
  3. Turn on light source.
  4. Light passes through sample.
  5. Light is absorbed by precipitate in solution.
  6. Detects light that is not absorbed.
  7. Quantitative reading for each glucose solution concentration.
49
Q

Describe the method for a qualitative Benedict’s test (7 points).

A
  1. Calibrate colorimeter using water = 0% absorption.
  2. Place sample into cuvette into colorimeter.
  3. Turn on light source.
  4. Light passes through sample.
  5. Light is absorbed by precipitate in solution.
  6. Detects light that is not absorbed.
  7. Quantitative reading for each glucose solution concentration.
50
Q

Describe how the student would use a calibration curve to work out the glucose concentration of an unknown solution (3 points).

A
  1. Heat to 80 degrees.
  2. Place cuvette in colorimeter.
  3. Plot % absorption graph to calculate the concentration.
51
Q

Structure of water (6 points).

A
  1. Major component of cells.
  2. Made up of two atoms of hydrogen and 1 atom of oxygen.
  3. Covalent bonds.
  4. Electrons are not shared equally- oxygen has a slight negative charge, hydrogen atoms have a slight positive charge. Therefore, this molecule is dipolar.
  5. Each water molecule is attracted to each other.
  6. Hydrogen bonding.
52
Q

Explain how water being a polar molecule is an advantage to organisms.

A

Water is a universal solvent that can transport ions around the body for faster reactions.

53
Q

Explain how water being a universal solvent is an advantage to organisms.

A

Water is polar, allowing ions to dissolve for transportation of ions around the body for faster reactions.

54
Q

Explain how water being reactive/a metabolite is an advantage to organisms.

A

Water is involved in hydrolysis/condensation reactions.

55
Q

Explain how water having a high heat capacity is an advantage to organisms (3 points).

A
  1. Water takes a lot of energy to break hydrogen bonds- acts as a buffer.
  2. External: stable environment for organisms, example: fish.
  3. Internal: maintains stable temperature for enzymes and reactions.
56
Q

Explain how water having a large latent heat of vaporisation is an advantage to organisms (3 points).

A
  1. Water takes a lot of energy to break hydrogen bonds.
  2. Energy is used to change liquid to gas when it evaporates carrying away the heat energy.
  3. Heat energy is lost through evaporation allowing animals to cool down.
57
Q

Explain how water cohesion is an advantage to organisms (5 points).

A
  1. Attraction between water molecules.
  2. Water forms a column of support.
  3. Water has a high surface tension when in contact with air.
  4. Column: transports ions in plants.
  5. Surface tension: provides habitat, for example: pond skaters.
58
Q

*Draw the condensation reaction for maltose

A

Two alpha-glucose monomers.
1,4 glycosidic bond.
A water molecule.
*Refer to old Biological Molecules notes.

59
Q

*Draw the condensation reaction for sucrose

A

1 alpha-glucose monomer and fructose monomer.
1,4 glycosidic bond.
A water molecule.
*Refer to old Biological Molecules notes.

60
Q

*Draw the formation of lactose

A

*Refer to old Biological Molecules notes

61
Q

*Draw the hydrolysis reaction for maltose

A

Forms 2 monomers of alpha-glucose.
*Refer to old Biological Molecules notes.

Biology A-level (27 decks)

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