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A-level Biology > Biological Molecules and enzymes > Flashcards

Biological Molecules and enzymes Flashcards

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1
Q

Examples of reducing sugars

A

All monosaccharides such as glucose fructose and galactose

Lactose and maltose

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2
Q

What is a reducing sugar

A

Donates electrons to other chemicals

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3
Q

Reducing sugar test and result

A

Benedict’s test

  • add benedict’s reagent to 2cm3 of sample
  • heat mixture for two minutes

Positive = orange/green

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4
Q

What are isomers

A

Glucose has two isomers which have the same molecular formula but different structural formula

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5
Q

Maltose is made up of…

A

Glucose and glucose

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6
Q

Sucrose is made up of…

A

Glucose and fructose

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7
Q

Lactose is made up of…

A

Glucose and galactose

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8
Q

What reaction are disaccharides and polysaccharides formed

A

Condensation reaction, releases water to form glycosidic bonds between the monosaccharides

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9
Q

What reaction can break the bonds between the monosaccharides

A

Hydrolysis, uses water to break glycosidic bonds

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10
Q

Name of the bond between monosaccharides

A

Glycosidic bond

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11
Q

Example of non-reducing sugar

A

Sucrose

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12
Q

Test for non-reducing sugar and result

A

Only do if reducing sugar test is negative

  • heat sample with acid
  • neutralise acid by adding alkali
  • add benedict’s reagent
  • reheat for two minutes

Positive = orange/ green

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13
Q

What are made from alpha glucose

A

Glycogen and starch

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14
Q

What are made out of ß glucose

A

Cellulose

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15
Q

Where is starch found and what is it for

A

Plants for energy store

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16
Q

Types of starch and their structures

A

Amylopectin is slightly branched

Amylose is a helix

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17
Q

Why is it good that starch is insoluble

A

Osmosis is not affected and it can’t diffuse out of cells

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18
Q

What is good about starch

A

Able to coil up a large amount into a small space in the amyloplasts in the cell

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19
Q

Test for starch and result

A

Iodine test

-add iodine

Positive = blue/black

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20
Q

Where is glycogen found and what is it used for

A

Animals (liver and muscles) and bacteria

Used for energy store (can be broken down into glucose for energy)

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21
Q

Structure of glycogen and benefit

other properties and benefits (2)

A

Highly branched alpha glucose polypeptide
Higher surface area so can be more easily broken down
insoluble - no osmotic effects
compact - can store more energy per unit volume

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22
Q

Where is cellulose found and use

A

Cell walls of plants

Prevents cells from bursting from turgor pressure

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23
Q

How do ß glucose molecules bond together

A

Alternate molecules have to rotate to bond to form a straight polymer
bonded by glycosidic bonds

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24
Q

How do the ß glucose chains arrange themselves

A

Parallel to one another and have strong hydrogen bonds between the chains

Cellulose molecules group to form microfibrils which join into bundles called fibres

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25
Q

Difference between saturated and unsaturated fatty acids

A

Saturated do not have a double bond in the R group (hydrocarbon chain)
Saturated are bad fats

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26
Q

Uses of lipids (4)

A

Release energy and water when oxidised (more energy per gram than carbohydrates) C-H bonds
Water proof (eg waxy cuticles)
Insulation underneath skin and myelin sheath around neurones
Protects organs

27
Q

Test for lipids and results

A

Emulsion test

  • add ethanol
  • shake
  • add water
  • filter

Positive = milky emulsion

28
Q

Name two groups of lipids

A

Triglycerides and phospholipids

29
Q

What is triglyceride made out of

A

One glycerol and three fatty acids from a condensation reaction

30
Q

Bonds in lipids

A

Ester bonds

31
Q

What do fatty acids end in

A

COOH

32
Q

What is a phospholipid made out of

A

One glycerol, two fatty acids and one phosphate

33
Q

How are phospholipids arranged

A

In two parallel layers called a phospholipid bilayer

34
Q

What are phospholipids used for

A

Cell membranes

35
Q

Features of a phospholipid molecule

A

One end is hydrophilic, the other is hydrophobic

36
Q

Primary structure of proteins

A

Amino acids join by peptide bonds during a condensation reaction
DNA determines the sequence of amino acids

37
Q

What is an amino acid made up of

A 
Anime group (H2N)
Variable group (R)
Carboxyl group (COOH)
38
Q

Secondary structure of proteins

A

Chain of amino acids fold depending on which amino acids are present
Held together by hydrogen bonds
Eg alpha helix or ß pleated sheet

39
Q

Tertiary structure of proteins

A

Secondary structure is twisted into a 3D shape called a ß polypeptide
Held by disulphides bridges, ionic bonds and hydrogen bonds
Maintains the shape so protein can do its function

40
Q

Quaternary structure of proteins

A

Many ß polypeptides join to form large complex molecules

Joined by hydrogen bonds

41
Q

Test for proteins

A

Biuret test

-add NaOH and dilute CuSO4

Positive = pale purple

42
Q

Structure of cellulose

A

ß-glucose chains arrange themselves parallel to one another held by strong hydrogen bonds

43
Q

Functions of proteins (5)

A 
Structural
Hormones
Antibodies
Enzymes
Transport
44
Q

What is an enzyme

A

Globular proteins lower the activation energy of the reaction it catalysed without being changed chemically themselves and can be reused

45
Q

What does the primary structure of an enzyme determine

A

The specific 3D structure

46
Q

What does the tertiary structure of the active site determine

A

The properties of the enzyme and it’s ability to combine with complementary substrates

47
Q

What is the functional part of an enzyme

A

Active site

48
Q

Lock and key theory

A

Enzymes have a rigid structure which substrates fit into

49
Q

Induced fit theory

A

Enzymes are flexible and can alter the shape of the active site so substrate can fit due to a change in the environment

50
Q

Factors affecting enzyme action (6)

A 
Temperature
pH
Concentration of competitive inhibitors
Concentration of non-competitive inhibitors
Enzyme concentration
Substrate concentration
51
Q

How does temperature affect enzyme action

A

Increase in temperature increases KE so frequency of collisions increaSes

After a certain temperature, bonds of the enzymes break causing a change in shape of active site
Active site shape becomes less complementary to the shape of the substrate
Less enzyme-substrate complexes formed
Lose their function and denature

52
Q

How does pH affect enzyme action

A

At optimum, ions such as H+ and OH- influence the shape of enzymes by interacting with hydrogen and ionic bonds
Shape becomes more complementary to shape of substrate

Above or below optimum would cause a decrease in rate of reaction

53
Q

How does concentration of competitive inhibitors affect enzyme action

A

Have similar shape to substrate so are able to fit into active site
Prevents substrate fitting into enzyme
Fewer enzyme-substrate complexes formed

54
Q

How does the concentration of non-competitive inhibitors affect enzyme action

A

Fits into another site of the enzyme which distorts the shape of the active site
Substrate no longer fits into active site
No enzyme-substrate complexes formed

55
Q

How does enzyme concentration affect enzyme action

A

Increase in enzyme concentration increases rate of reaction until it is no longer the limiting factor
More enzymes per unit volume so higher frequency of collisions

56
Q

How does substrate concentration affect enzyme action

A

Increase in substrate concentration increases rate of reaction until it is no longer the limiting factor
More substrate per unit volume to collide with enzymes so more product formed

57
Q

Reason for adding a buffer solution

A

Controls the pH for optimum reaction

A change in pH would cause the rate of reaction to slow down and denature enzymes

58
Q

Hydroxylating

A

Addition of hydroxyl group

59
Q

what are carbohydrates used for

A

provides/ stores energy

60
Q

what elements are carbohydrates made up of

A

C H O

61
Q

how does alpha and ß glucose differ from one another

A

ß-glucose has the OH and H inverted on the right so every alternate molecule would need to rotate to bond with each other

62
Q

how do triglycerides form

A

condensation reaction forms 3 ester bonds and 2 waters are lost

63
Q

how can the induced fit theory be proven

A

non-competitive inhibitors are able to alter shape of enzymes so prove they are flexible

A-level Biology (14 decks)

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