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AQA A Level Biology > 1-1 Biological molecules > Flashcards

1-1 Biological molecules Flashcards

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1
Q

Glucose + Glucose

A

Maltose

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2
Q

Glucose + Fructose

A

Sucrose

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3
Q

Glucose + Galactose

A

Lactose

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4
Q

Where are ester bonds?

A

Between fatty acids and glycerol

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5
Q

Where are peptide bonds?

A

Between amino acids

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6
Q

What is the test for reducing sugars?

A

Goes brick red with benedicts due to the precipitate of copper (1) oxide
If no change, hydrolysed with HCL then neutralised with HCO3 then add more benedicts to get the brick red colour

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7
Q

What is the role of starch and 5 reasons why?

A

Energy storage in plants

  • Insoluble, doesn’t affect water potential
  • Doesn’t diffuse out of cells
  • Compact
  • Uses alpha glucose with is used for respiration
  • Branching allows quick hydrolysis
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8
Q

What is the role of glycogen and 4 reasons why?

A

Energy storage in animals

  • Insoluble, doesn’t affect water potential
  • Doesn’t diffuse out of cells
  • Compact
  • More branching than starch, allows quick hydrolysis
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9
Q

What is the role of cellulose and why?

A

Provides rigidity to cell walls and prevents bursting

  • Made with beta glucose instead, so form straight unbranched chains
  • Running parallel with lots of h bonds make it very strong
  • Creates microfibrils
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10
Q

What is the test for proteins?

A

Biuret test - add sample and equal parts NaOH, add biuret, lilac if protein present

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11
Q

Which factors affect the rate at which enzymes work?

A

Temp – denatured if too hot
The pH can break the tertiary structure
Enzymes concentration
Substrate concentration

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12
Q

What are reducing sugars?

A

Sugars that donate electrons to other chemicals

All monosaccharides and some disaccharides are reducing sugars

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13
Q

How do you test for starch?

A

Iodine test: iodine turns starch black

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14
Q

What are the properties of lipids?

A
  • A source of energy as when oxidised, they produce twice the amount of energy as carbohydrates
  • Insoluble in water but soluble in solvents such as alcohol and acetone- used for waterproofing
  • Slow conductors of heat, useful for insulation
  • Stored around organs for protection
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15
Q

How are triglycerides formed?

A

By the condensation reaction of a molecule of glycerol and three molecules of fatty acid: OH of the glycerol joins with the H of the fatty acid

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16
Q

Why are triglycerides used in the body?

A

High ratio of energy storing carbon-hydrogen bonds to carbon atoms: release lots of energy
Low mass to energy ratio: good storage molecules
Large non-polar molecules: don’t affect water potential
Produce water when formed: valuable source of water

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17
Q

What does a condensation reaction between glycerol and a fatty acid create?

A

An ester bond

18
Q

Is the R group of a fatty acid saturated or unsaturated?

A

It can be either

19
Q

What is a saturated molecule?

A

A molecule that has the maximum amount of hydrogen atoms bonded to its carbon atoms/ single c-c bonds only

20
Q

What is the structure of a phospholipid?

A

It is a triglyceride molecules where one of the fatty acids is replaced by a phosphate head
The phosphate head is hydrophilic and doesn’t interact with fat

The fatty acid tail is hydrophobic and mixes readily with fat

21
Q

What is the emulsion test?

A

Add sample to a grease-free test tube
Add ethanol and water, then shake gently
A cloudy white substance indicates a lipid presence
The lipid is finely dispersed in the water to form an emulsion, light passing through the emulsion is refracted as it passes from oil droplets to water droplets, making it cloudy

22
Q

What are the monomers that makeup proteins?

A

Amino acids

23
Q

How many naturally occurring amino acids are there?

A

20

24
Q

What changes from amino acid to amino acid?

A

The R group

25
Q

How are two amino acids joined?

A

By a peptide bond via a condensation reaction

26
Q

What is the primary structure of proteins?

A

The order of the amino acids in the polypeptide chain

27
Q

What changes the properties of a protein?

A

The order of the amino acids

28
Q

What is the secondary structure of proteins?

A

The alpha helix or beta pleated sheet

This is created by hydrogen bonds which aren’t bonded but are attracted which bend the polypeptide chain

29
Q

What is the tertiary structure of proteins?

A

The further folding of the alpha helix or beta pleated sheet

It is held together by hydrogen bonding, ionic bonding, a disulfide bridge and hydrophobic interactions

30
Q

What are hydrophobic interactions in the tertiary structure of proteins?

A

When clusters of hydrophobic molecules bend the chain around them to block any water

31
Q

What is a disulfide bridge?

A

When sulfur atoms in the side chains bond

This is one of the strongest types of bond

32
Q

What is the quaternary structure of proteins?

A

When 2 or more polypeptide chains are joined together in a fibrous or globulous structure

33
Q

What is an enzyme?

A

A globular protein that acts as a catalyst

34
Q

What is the structure of enzymes?

A

The structure is a result of the sequence of amino acids
The active site is the functional area of the enzyme that the substrate fits into
The substrate is specific to the enzyme because of the specific shape of the active site

35
Q

What are the two mechanisms for how enzymes work?

A

Induced fit: proximity of the substrate leads to a change in the enzyme which forms the functional active site, the enzyme is malleable
Lock and key: each enzyme has a specific active site that can only be activated by one substrate, the enzyme is rigid

36
Q

What are the stages of an enzyme reaction?

A

Start: lots of substrate, easy for substrate to find empty active sites, all active sites are filled, substrate is rapidly broken up
Middle: amount of substrate decreases, product increases, more difficult for substrate molecules to find an active site, product molecules gets in the way
End: rate of reaction slows until change in rate can’t be measured, all substrate hasn’t been used up

37
Q

How do you measure the rate of enzyme reaction?

A

Pick a point on the line, draw a tangent, work out the gradient of the line

38
Q

What do enzymes do?

A

Speeds up the rate of a chemical reaction without undergoing permanent changes themselves
They do this by lowering the activation energy

39
Q

How does enzyme/substrate concentration change the rate of an enzyme reaction?

A

Concentration increases as rate increases

Once the number of active sites equals the number of substrate molecules, the rate of reaction doesn’t increase

40
Q

How do you measure the rate of enzyme reaction?

A

For a graph with rate on the axis: plot the point and read off the graph
For a graph with something else on the axis: draw a tangent and measure the gradient of the line

41
Q

What is a competitive inhibitor?

A

A competitive inhibitor has a complimentary shape to the enzyme
Increasing the amount of competitive inhibitor competes against the substrate to find an active site

42
Q

What is a non-competitive inhibitor?

A

It attaches themselves to a binding site and alters the shape of the active site so that the substrate and active site are non-complimentary
Increasing the amount of substrate doesn’t affect rate
Increasing the amount of inhibitor decreases the rate of reaction

AQA A Level Biology (19 decks)

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