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Aqa a level biology > Section 1: biological molecules > Flashcards

Section 1: biological molecules Flashcards

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1
Q

What is a monomer

A

Monomers are the smaller repeating units from which larger molecules (polymers) are made

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2
Q

Give the number of carbon, hydrogen and oxygen atoms in a molecule of raffinose

A

carbon = 18
hydrogen = 32
oxygen = 16

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3
Q

Describe a biochemical test to show that raffinose solution contains a non-reducing sugar

A

1) heat the raffinose solution with an acid and neutralise
2) heat with benedicts solution
3) a red precipitate should form

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4
Q

what substances can dissolve in water

A

ATP, globular proteins, ions

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5
Q

What is one similarity between lactulose and lactose

A

both have glycosidic bonds

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6
Q

Suggest why lactulose can help people suffering from constipation

A

Lactulose lowers the water potential of faeces. This means that water is retained and enters the faeces by osmosis so the faeces soften.

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7
Q

How are polymers formed

A

from monomers by the process of polymerisation

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8
Q

What are condensation reactions

A

reactions that joins monomers and involves the elimination of a water molecule

formation of a chemical bond

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9
Q

What are reactions called that are broken down through the addition of water

A

hydrolysis

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10
Q

What is starch

A

starch is a polysaccharide that is found in plants. It is made of chains of alpha glucose monosaccharides link by glycosidic bonds (1,4,6) . Starch is insoluble so doesnt affect water potential or diffuse out of cells as it is a large molecule

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11
Q

What is glycogen

A

glycogen is found in animals and bacteria. It is similar to starch but has smaller chains and is more highly branched. In animals it is found in the muscles and liver. Glycogen is insoluble and compact and can be broken down to form glucose used in respiration

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12
Q

What is cellulose

A

Cellulose is made of monomers of beta glucose. It has long straight unbranched chains that run parallel to one another thus allowing hydrogen bonds to form cross linkages. Cellulose molecules are grouped together to form microfibrils. Cellulose exerts inward pressure to stop the influx of water (it is insoluble)

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13
Q

What are triglycerides

A

three fatty acids combined with glycerol. Each fatty acid forms an ester bond with glycerol in a condensation reaction. Variation comes from the different fats and oils as glycerol molecules are the same. They are large, non-polar molecules

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14
Q

What are phospholipids

A

two fatty acids, one phosphate molecule and glycerol. Phospholipids has a hydrophillic (attracts water) head and hydrophobic tail as fatty acids repel water. They form a bilayer along cell membranes

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15
Q

What are proteins

A

amino acids are monomers from which proteins are made. Amino acids are joined by peptide bonds in a condensation reaction. There is a primary, secondary, tertiary and quaternary structure to proteins. Proteins can either be globular or fibrous (long)

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16
Q

What is DNA

A

DNA is a polymer of nucleotides. Deoxyribonucleic acid and ribonucleic acid are polymers of nucleotides. Nucleotides consist of pentose, a nitrogen organic base and a phosphate group. They join together by phosphodiester bonds

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17
Q

What are the 4 organic bases of DNA

A

thymine, adenine, cytosine, guanine

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18
Q

How are disaccharides formed

A

by the condensation of 2 monosaccharides

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19
Q

What is sucrose

A

disaccharide of one glucose and one fructose molecule

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20
Q

What is maltose

A

disaccharide of two glucose molecules

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21
Q

what is lactose

A

disaccharide of a glucose and galactose molecule

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22
Q

What forms a glycosidic bond

A

a condensation reaction between two monosaccharides of carbohydrates

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23
Q

what is a 1-4 linkage

A

a glycosidic bond that has a covalent bond between the -OH group on carbon 1 on one sugar and -OH on a carbon 4 of the other

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24
Q

What is a 1-2 linkage

A

1 carbon of glucose connected to 2 carbon of fructose

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25
Q

Define covalent bonding

A

when atoms share a pair of electrons in their outer shell. As a result 2 stable compounds are formed

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26
Q

Define ionic bonding

A

ions with opposite charges attract one another with electrostatic forces of attraction. Ionic bonds are weaker than covalent bonding

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27
Q

Define hydrogen bonding

A

the electrons within a molecule are not evenly distributed but tend to spend more time at one position (more negatively charged). A molecule with an uneven distribution of charge is said to be polarised. The negative region and the positively charged region attract forming a weak electrostatic bond

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28
Q

What are the monomers of a polymer usually based on

A

carbon

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29
Q

Name 2 polymers that are industrially produced

A

polythene and polyesters

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30
Q

Name 3 natural polymers

A

polysaccharides, polynucleotides, polypeptides

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31
Q

What are polysaccharides formed from

A

monosaccharides or a single sugar molecule

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32
Q

What are polynucleotides formed from

A

mononucleotide sub units

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33
Q

What are polypeptides formed from

A

peptides that have amino acids as their basic sub unit

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34
Q

nucleotides condense to form what

A

polynucleotides

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35
Q

What do polysaccharides hydrolyse to form

A

monosaccharides

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36
Q

What do fatty acids and glycerol condense to form

A

lipids

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37
Q

What do polypeptides hydrolyse to form

A

amino acids

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38
Q

Define metabolism

A

all the chemical processes that take place in living organisms

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39
Q

What does mol mean

A

amount of the substance (6.022x10^23)

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40
Q

What is a molar solution

A

a solution that contains one mol of solute in each litre of solution

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41
Q

What is 1 mol equal to

A

12g of carbon-12 atoms

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42
Q

Essentially what are carbohydrates

A

carbon molecules combined with water

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43
Q

what are carbon containing molecules known as

A

organic molecules

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44
Q

what are most polymers made of (chemical elements)

A

carbon, hydrogen, oxygen and nitrogen

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45
Q

what is the basic monomer unit in carbohydrates

A

saccharide (sugar)

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46
Q

what is the general formula for monosaccharides

A

(CH2O)n

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47
Q

what are monosaccharides

A

sweet tasting, soluble substances

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48
Q

what are examples of monosaccharides

A

glucose, galactose, frucose

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49
Q

describe glucose

A

glucose is a hexose (6-carbon) sugar but the atoms can be arranged in different ways. Glucose has two isomers; a-glucose and b-glucose

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50
Q

what is reduction

A

a chemical reaction involving the gain of electrons or hydrogen.

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51
Q

What is the test for a reducing sugar

A

benedicts test

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52
Q

What is the benedicts test

A

reducing sugar is heated with benedicts reagent to form an insoluble red precipitate of copper oxide

1)food sample dissolved in water
2)equal volume of benedicts reagent is added
3)heated in water bath and turns red

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53
Q

what is the bond called that is formed when monosaccharides join

A

glycosidic bond

a condensation reaction occurs

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54
Q

What can be added to a disaccharide to break the glycosidic bond

A

water

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55
Q

give an example of non-reducing sugars

A

disaccharides like sucrose (not maltose) so they do not change colour of benedicts reagent

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56
Q

How can you detect a non-reducing sugar

A

it must be hydrolsed into its monosaccharide
1)sample must be ground up in water or liquid
2)add benedicts reagent and filter
3)heat up solution
4) add dilute hydrochloric acid and heat again –> test with pH paper to see if alkaline as benedicts doesnt work in acidic conditions
5) add sodium hydrogencarbonate to neutralise solution
6) turn brown/orange

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57
Q

true or false –> polysaccharides are insoluble and why

A

true –> large molecules

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58
Q

what is a carbohydrate

A

an organic compound consisting of carbon, hydrogen and oxygen

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59
Q

What are the 5 monosaccharides of carbohydrates

A

glucose
galactose
fructose
ribose
dexoyribose

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60
Q

What is the general formula for monosaccharides

A

(CH2O)n

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61
Q

what are the 3 hexose sugars

A

glucose, galactose, fructose

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62
Q

What are the 2 pentose sugars

A

ribose and deoxyribose

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63
Q

what are isomers

A

e.g alpha and beta glucose –> same molecular formula but different structure

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64
Q

how are the OH groups arranged in alpha glucose

A

both OH groups are at the bottom

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65
Q

define a disaccharide

A

2 monosaccharides held by a glycosidic bond formed during a condensation reaction

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66
Q

what are the 3 types of carbonhydrates

A

monosaccharides, disaccharides, polysaccharides

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67
Q

what is the difference between hydrolysis and condensation

A

-condensation reaction forms a chemical bond by releasing water

-hydrolysis uses water to break down a chemical bond

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68
Q

what enzyme catalyses hydrolysis reactions of disaccharides

A

-carbohydrase (amylase) is the enzyme that catalyses the hydrolysis reactions of disaccharides to monosaccharides

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69
Q

what does the condensation of fatty acids and monoglycerides produce

A

lipids

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70
Q

what is ATP

A

adenosine triphosphate
provides energy

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71
Q

what are reducing sugars

A

all monosaccharides and some disaccharides like lactose and maltose
(alkaline solution capable of acting as a reducing agent)

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72
Q

what is an example of a non-reducing sugar

A

sucrose (disaccharide)

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73
Q

What is the test for starch

A

iodine
orange to blue/black

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74
Q

what are the two types of starch

A

amylopectin –> branched and useful for quick energy release
amylose –> unbranched and good for energy storage

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75
Q

what is glycogenolysis

A

glycogen is broken down to release glucose

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76
Q

true or false –> cellulose can be broken down by digestive enzymes

A

false

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77
Q

What occurs in a condensation reaction between 2 monosaccharides

A

a glycosidic bond forms between the 1st carbon on one glucose and the 4th carbon on the other

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78
Q

what is the difference between a pentose and hexose sugar

A

pentose –> only 5 carbon atoms
hexose –> 6 carbon atoms

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79
Q

what do the properties of a polysaccharide depend on

A

length
extent of branching
folded
whether chain is straight or coiled

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80
Q

where is starch found

A

in plants (chloroplasts and seeds) and tubers like potatoes

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81
Q

what is starch

A

polysaccharide of alpha glucose containing 2 isomers -> amylose and amylopectin

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82
Q

what type of glycosidic bonds does starch and glycogen have

A

1,4 and 1,6

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83
Q

is starch insoluble

A

yes starch is insoluble so doesnt affect water potential of cell

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84
Q

what is amylose

A

straight chain (coiled helical structure) 1,4 glycosidic
compact so is energy dense
unbranched

makes up 20% of starch

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85
Q

What is amylopectin

A

makes up 80% of starch
1,6 glycosidic bond and 1,4
compact and highly branched
quick energy release through breakdown by enzymes
long chains

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86
Q

what is glycogen

A

key energy store in animals
1,4 and 1,6 bonds
stored in liver and muscle cells
insoluble
highly branched and compact (coiled)

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87
Q

what is cellulose

A

-chains of beta glucose but every other beta glucose is inverted in order to create straight chains

-1,4 glycosidic bonds through condensation reaction

-hydrogen bonding of alternating branches –> positive hydrogen attracted to negative oxygen on hexose structure

-intermolecular forces of attraction

-microfibrils are strongest vertically

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88
Q

what are microfibrils

A

the chains are held together by weak hydrogen bonds between the –OH groups in neighboring cellulose chains

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89
Q

how many molecules does each microfibril contain

A

60-70 cellulose molecules wound in a helical arrangement laid down at different angles forming a composite structure

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90
Q

what are 2 uses of lipids

A

storage and insulation

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90
Q

what are similarities between carbohydrates and lipids

A

-Both formed during condensation reactions

-both contain carbon, hydrogen and oxygen

-both act as a energy source

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91
Q

What are some differences between carbohydrates and lipids

A

-carbohydrates contain glycosidic bonds whereas lipids contain ester bonds

-Carbohydrates form polymers including starch etc whereas lipids form macromolecules e.g triglycerides

-Carbohydrates are soluble as monomers whereas lipids are insoluble in water but soluble in alcohol/acetone

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92
Q

what are triglycerides

A

-macromolecules consisting of one glycerol molecule and three fatty acids

-elimination of 3 water molecules

-3 ester bonds formed between each fatty acid and glycerol

-Carboxyl group (COOH) = defining factor of triglyceride

-number of squigly lines represents one carbon this can change for each fatty acid. The long chains can be replaced by the letter R

-ester bond (C-O=C)

-triglycerides are non polar (hydrophobic)

-R groups can either be saturated or non saturated

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93
Q

what is unsaturated fatty acids

A

carbon carbon double bond between carbon atoms so can bond with other hydrogens (c=c)

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94
Q

what are saturated fatty acids

A

single bond between carbon atoms so cannot bond with other hydrogens (c-c)

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95
Q

what is the difference between a glycosidic and ester bond

A

glycosidic bond is between 2 hydroxyl groups whereas an ester bond is between one carboxyl and one hydroxyl group

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96
Q

what is a phospholipid

A

-macromolecule consisting of a glycerol molecule attached to a phosphate head (polar) and two fatty acids

-formed in condensation reaction

-ester bond R-C-O-C=O-H

-hydrophobic tail (repels water)

-hydrophillic phosphate head (attracts water as it is slightly charged – polar)

-R group can either be saturated or not saturated

-forms bilayer on plasma membrane

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97
Q

define a fatty acid

A

long chain of carbon/hydrogen with a carboxyl group on the end

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98
Q

How is a tryiglyceride molecule formed

A

-A triglyceride is formed through the condensation reaction of one glycerol molecule and 3 fatty acids involving the removal of 3 water molecules. This creates an ester bond between each fatty acid and glycerol.

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99
Q

how do you test for lipids

A

ethanol and distilled water, shake and milky emulsion forms

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100
Q

what is the difference between saturated and unsaturated fatty acids

A

A saturated fatty acid doesn’t contain double carbon bonds so is unable to be saturated with more hydrogens whereas an unsaturated fatty acid can

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101
Q

what is the general formula of a carboxyl group

A

COOH

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102
Q

what is the general formula of a fatty acid

A

RCOOH

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103
Q

What forms the cell surface membrane

A

a phospholipid bilayer which consists of a hydrophilic head and a hydrophobic tail

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104
Q

true or false the cell surface membrane is selectively permeable

A

true

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105
Q

what surrounds the cell surface membrane

A

fluid

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106
Q

what type of molecules can and cant pass through a cell surface membrane

A

non polar molecules like oxygen and carbon dioxide can easily pass through diffusion

polar molecules like sugars and ions require channel proteins to move

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107
Q

what is cholesterol

A

four carbon based ring structures joined together
-small molecule that fits into lipid bilayer giving strength and stability
-used to form steroid hormones

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108
Q

how do phospholipids form cell surface membranes

A

Phospholipids have a hydrophilic head and a hydrophobic tail which forms the bilayer of cell surface membranes. The hydrophilic head faces outwards and the hydrophobic tail is inwards. There is water present in and out of the cell.

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109
Q

what are the main roles of proteins

A

-structural role –> main component of body tissues such as muscle, skin, ligaments and hair

-catalytic role –> all enzymes are proteins catalyzing many biochemical reactions

-Signalling role –> many hormones and receptors are proteins

-immunological role –> all antibodies are proteins

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110
Q

what are amino acids

A

the monomers from which proteins are made

111
Q

what do proteins contain

A

an amine group (NH2), R group which represents a side chain of anything and a carboxyl group (COOH)

112
Q

how do peptide bonds form

A

-condensation reaction between amino acids

-amino acid 1 + amino acid 2 = dipeptide bond +
H2O

-C-N = peptide bond

-an amine and carboxyl group undergo a condensation reaction to create a peptide bond. The bond produces an amino acid and water

113
Q

what are the 4 structures of proteins

A

primary, secondary, tertiary and quaternary

114
Q

what is the primary structure

A

-specific sequence of amino acids that are held together by peptide bonds which form a polypeptide chain.

-the sequence of amino acids determines its structure

-Ribosomes builds the primary structure of proteins

-DNA determines the sequence of amino acids in a polypeptide chain

-Amino acids have different R groups which interact in different ways to form specific shapes (secondary structure)

115
Q

what is the secondary structure

A

-hydrogen bonds form between the N-H and C=O on amino acids

-These hydrogen bonds cause the structure to bend and twist to form a 3D structure – either beta pleated sheets or alpha helix structure

116
Q

what are the types of bonds in the tertiary structure

A

disulfide bridges between sulfur molecules in the R group of cysteine amino acids –strong and not easily broken

-ionic bonds –> these form between carboxyl and amino acid groups, not involved in forming peptide bonds. They are weaker than disulfide bonds and are easily broken by changes in pH

-hydrogen bonds –> numerous, but easily broken. Form between O,H and N atoms due to difference in electronegativley

-hydrophobic and hydrophillic interactions –> numerous and formed between polar R groups (not a type of bond)

117
Q

what is the tertiary structure

A

-leads to specific shapes e.g active site of enzymes and shape of antibodies

-the tertiary structure is when the secondary structure can be twisted and folded even more

-3 types of bonds –> disulfide bridges, ionic bonds, hydrogen bonds

118
Q

what is the quaternary structure

A

-large proteins made of more than one polypeptide chain e.g haemoglobin

-Quaternary proteins can have prosthetic groups attached e.g iron in haemoglobin

119
Q

explain how a change in amino acid sequence results in changes of protein tertiary structure

A

-a change in amino acid sequence means change in the sequence of R groups

-this means that there will be changes to the alpha helixes and the beta pleated sheets in the secondary structure which are held by hydrogen bonds

-this also means that there will be changes to the bonding in tertiary structure e.g disulfide bridges

120
Q

describe how the secondary structure of a polypeptide is produced

A

-hydrogen bonds between the N-H and C=O of amino acids cause the structure to bend and twist forming a 3D structure of either alpha helix or beta pleated sheets

121
Q

explain why proteins that have the same type of amino acids and number have different tertiary structures

A

-sequence of amino acids is different which forms ionic, hydrogen and disulfide bonds in different places

122
Q

what is water

A

H2O is a simple covalent molecule which is a dipolar molecule

-slight negative charge from electrons on oxygen

-slight positive charge from H atoms at an angle (protons + neutrons)

123
Q

define a hydrogen bond

A

an electrostatic attraction between hydrogen and an electronegative atom such as nitrogen, oxygen and fluorine

124
Q

how does hydrogen bonding in plants benefit plants

A

helps create the transpiration stream

125
Q

what is the importance of water having a high specific heat capacity

A

-buffers changes in temperature as a lot of energy is required to overcome the bonds

126
Q

what would happen to enzymes rate of reaction if pH changes

A

The pH will change the charges present on the amino acids that make the enzyme, which will alter the tertiary structure of the enzyme. Change in the tertiary structure leads to a change in the shape of the active site. The rate of reaction decreases as substrate can no longer fit in the active site.

127
Q

why is it important that water has a high latent heat of vaporisation

A

for homeostasis (Sweating) –> cooling effect

has high latent due to hydrogen bonding which absorbs a lot of energy

128
Q

what is the importance of water as a solvent

A

due to its dipole nature, other substances are able to dissolve in water which is important with water being the main transport medium for living organisms –> water a solvent

129
Q

what substances can dissolve in water

A

-oxygen, carbon dioxide, NaCl dissolve in water

130
Q

what in blood allows us to carry dissolved substances

A

water

131
Q

how is water involved in metabolism

A

condensation, hydrolysis and is a key reactant in photosynthesis

132
Q

what is the importance of water being amphoteric (acts as a base and acid)

A

acts as a buffer and prevents reactions from altering the pH inside the cell

133
Q

The formation of an enzyme substrate complex increases the rate of reaction. Explain how

A

Enzymes lower the activation energy by bending bonds which increases rate of reaction

134
Q

what is one similarity and one difference between induced fit and lock and key model

A

similarity –> both form enzyme substrate complexes

Differences –> active site changes in induced fit model whereas it is rigid and complimentary in the lock and key model

135
Q

Describe the induced fit model of enzyme action and how an enzyme acts as a catalyst

A

The substrate binds to the active site of the enzyme
the active site changes shape to be complimentary to the substrate so an enzyme substrate complex can form
This lowers the activation energy by bending bonds so rate of reaction increases

136
Q

what are enzymes

A

proteins with a specific tertiary structure

137
Q

what does the sequence of amino acids determine in terms of enzymes

A

-The sequence of amino acids determines the bonding in the tertiary structure, this means that the enzymes active site is a specific shape that is only complimentary to a specific substrate

138
Q

how do enzymes increase rate of reaction

A

-Enzymes are biological catalysts that catalyse different reactions without undergoing permanent change

-Enzymes lower the activation energy of reactions by bending the bonds in the molecule (weakens bonds)

139
Q

what are the two models for enzyme action

A

induced fit
lock and key

140
Q

what is the lock and key model

A

-enzyme’s active site is complimentary to the substrate (ridgid)

-reduces the activation energy to catalyse the reaction by bending bonds

-forms an enzyme-substrate complex

141
Q

what is the induced fit model

A

Induced fit model:

-Active site molds (changes shape) to be complimentary to the shape of the substrate so an enzyme substrate complex can form so is more flexible

-Lowers the activation energy by bending bonds to catalyse reactions

142
Q

Explain how the position of disulphide bridges plays a role in the specificity of the enzymes active site

A

-disulphide bridges are a key determining factor in the formation of an enzymes tetiary structure. This dictates the sequence of amino acids that cause the 3D shape of the active site of enzymes.

143
Q

State and explain the property of water that can help to buffer changes in temperature

A

high specific heat capacity so can gain energy without changing the temperature.

144
Q

What are 5 properties of water that make it important for organisms

A

-metabolite for condensation reactions
-solvent so metabolic reactions can occur and acts as a transport medium
-high specific heat capacity so buffers changes in temperature
-large latent heat so provides cooling effect
-cohesion to support transpiration stream in plants

145
Q

Give two properties of water that are important in the cytoplasm of cells

A

polar molecule –> acts as a universal solvent

reactive –> takes place on hydrolysis/condensation

146
Q

explain how two enzymes with different amino acid sequences can catalyse the same reaction

A

both active sites have similar tertiary structures so form an enzyme substrate complex with the same substrate

147
Q

explain why using a colorimeter would improve the repeatability of the experiment

A

Quantative method –> standardizes the procedure

148
Q

what is a glycosidic bond

A

A covalent bond between a carbohydrate molecule and a hydroxyl group on another molecule, resulting from a condensation reaction.

149
Q

what amino acid does not have carbon in its R group

A

glyceine

150
Q

Name what type of sugar monosaccharides are and
describe
how the sugar is arranged differently

A

monosaccharides are reducing sugars
Glucose has two isomers - alpha and beta glucose

151
Q

Describe 2 ways dipeptides may be similar and one way they might be different

A

similarity –> two R groups, all contain C, N, O, H

Difference –> variable R groups

152
Q

Explain the positions of amino acid spots on the diagram

A

-amino acids move towards negative electrode as they are positivley charged
-spots move at different distances because they have different charges
-one spot has 2 amino acids due to same charge

153
Q

what are polymers

A

molecules made from a large number of monomers joined together

154
Q

how do amino acids differ

A

their side groups (R) are different

155
Q

what is a functional protein

A

contains one or more polypeptides

156
Q

how does a change in pH affect enzymes

A

Changing the pH changes the number of hydroxide ions and hydrogen ions (OH− and H+) surrounding the enzyme.
These interact with the charges on the enzyme’s amino acids, affecting hydrogen bonding and ionic bonding, so resulting in changes to the tertiary structure.

157
Q

what does increasing enzyme concentration mean

A

Increasing the concentration of enzyme in a solution means there are more enzyme molecules available to catalyse the substrate in a given amount of time

158
Q

what does increasing substrate concentration mean

A

Increasing the concentration of the substrate increases the numbers of substrate molecules that can form enzyme-substrate (ES) complexes at any one time.
This increases the initial rate of reaction but when all the enzyme molecules are engaged in ES complexes the rate cannot increase any further.
The rate will then plateau because the enzyme is said to be saturated

159
Q

what are inhibitors

A

Inhibitors are chemicals that slow down the rate or stop the reaction altogether.
Enzyme-substrate complexes cannot be formed or are formed at a much lower rate.

160
Q

what are the two types of inhibitors

A

competitive and non-competitive

161
Q

what does a non-competitive inhibitor do

A

Non-competitive inhibitors affect another part of the enzyme molecule causing a change to the shape of the active site.
The active site is no longer complementary to the substrate molecules

162
Q

what does a competitive inhibitor do

A

Competitive inhibitors are similar in shape to the usual substrate and affect the active site directly, blocking access for the formation of ES complexes.
Increasing the substrate concentration can compensate for the effects of a competitive inhibitor as there is no permanent damage to the shape of the active site.

Malonate ions are similar in shape to succinate ions and act as a competitive inhibitor of succinate dehydrogenase, an important enzyme in the Krebs cycle.

163
Q

how is enzyme activity calculated

A

by calculating the gradient of increase in products over time or decrease in reactants over time.

164
Q

Suggest and explain a procedure the scientists could have used to stop each reaction

A

place in a cold solution / ice so enzyme activity reduces

165
Q

what type of proteins are enzymes

A

globular proteins

166
Q

what is the active site made out of

A

a small number of amino acids

167
Q

what is a metabolic pathway

A

a series of reaction in which each step is catalysed by an enzyme

168
Q

how does temperature affect enzyme action

A

-increasing temperature increases kinetic energy which increases rate of successful collisions which means that more enzyme substrate complexes form.

-At enzymes optimum temperature the rate of reaction is high

-As temperature goes past the optimum bonds within the tertiary structure break so active site changes shape (enzyme denatured)

169
Q

how does pH affect enzyme action

A

-At optimum pH the enzymes active site is complimentary to the substrate. This means that lots of enzyme substrate complexes are formed

-At extreme pH bonds within the tertiary structure break. This means that the enzyme’s active site changes shape so fewer enzyme substrate complexes form (denatures)

-The arrangement of the active site is particulary determined by ionic and hydrogen bonds between amine and carboxyl groups so change in H+ ions affects this bonding causing the active site to change shape

-Changes in pH affects charges on amino acids

170
Q

how do you calculate rate of reaction

A

draw a tangent and do change in y / change in x

mass / temperature

171
Q

how does enzyme concentration affect activity

A

-Initially the substrate is in excess. As enzyme concentration increases rate of reaction increases as enzymes are saturated with the substrate forming enzyme substrate complexes. Eventually, it plateaus as all the substrates have binded to an active site and the enzyme is in excess. It becomes more difficult for substrate molecules to come into contact with an enzyme as there are product molecules which may get in the way

172
Q

how does substrate concentration affect enzyme activity

A

-Initially, rate of reaction increases as enzymes can now form e-s complexes with the substrate. At the point of saturation all active sites are occupied so increasing substrate concentration remains a limiting factor as there are no enzymes to catalyse a reaction.

173
Q

what do inhibitors do

A

inhibitors work to prevent an enzyme from catalysing a reaction, They bind to enzymes and prevent them from carrying out their function e.g can naturally control the rate of an enzyme catalysed reaction

174
Q

how do competitive inhibitors affect enzyme action

A

-binds to the active site of the enzyme prevent enzyme substrate complexes from forming. A competitive inhibitor is usually a similar shape to the substrate so is also complimentary to the active site of an enzyme. Competitive inhibition is reversible –> as concentration of competitive inhibitor decreases the rate of enzyme catalysed reactions can increase again. It can also be overcome by increasing the concentration of substrate molecules as they out-compete the inhibitor.

175
Q

how do non-competitive inhibitors affect enzyme action

A

-binds to the allosteric site on the enzyme which affects bonds in the tertiary structure causing the shape of the active site to change. This shape change means that the active site is no longer complimentary to the substrate so the substrate and enzyme are unable to form enzyme substrate complexes. Non-competitive inhibition is permanent.

176
Q

what is a single molecule of ATP

A

a nucleotide derivative and is formed from a molecule of ribose, a molecule of adenine and three phosphate groups

177
Q

What enzyme catalyses the hydrolysis of ATP to ADP and an Pi

A

ATP hydrolyase

178
Q

what does the inorganic phosphate released during hydrolysis of ATP do

A

used to phosphorylate other compounds making them more reactive

179
Q

How is ATP resynthesised

A

by the condensation of ADP and Pi. This reaction is catalysed by the enzyme ATP synthase during photosynthesis or respiration

180
Q

What forms adenosine

A

adenine + ribose

181
Q

what is ATP

A

a molecule of adenine, ribose and 3 phosphate molecules

182
Q

what is adenine

A

is an organic base of DNA (containing nitrogen)

183
Q

what is ribose

A

pentose sugar - 5 carbon ring which acts as a backbone for ATP

184
Q

ATP equation

A

ATP + H2O –> ADP + Pi + energy (hydrolysis reaction) which is catalysed by ATP hydrolayse

185
Q

what is Pi

A

inorganic phosphate molecule

186
Q

what are some differences between glucose and ATP

A

-ATP releases a small amount of energy so it is not wasted

-ATP is small and soluble so is easy to transport

-only one bond has to be hydrolysed in ATP is an immediate source of energy

-ATP can transfer energy to another molecule by transferring phosphate group

-ATP cant pass/diffuse out of cells so always provides constant supply of energy

187
Q

what functions do organisms need energy for

A

-metabolism

-movement

-active transport

-secretion

-activation of molecules

-homeostasis

188
Q

what enzyme synthasises ATP
ADP + Pi –> ATP + H2O

A

ATP synthase

189
Q

what enzyme hydrolyses ATP

A

ATPase

190
Q

where does ATP come from

A

the energy supplied in respiration

191
Q

what are some issues with ATP

A

-phosphate bonds are unstable and sometimes unpredictable

-ATP cannot be stored

192
Q

what are some advantages of ATP

A

-intermediate source of energy

-releases less energy than glucose so is more manageable

-not a long reaction

-Doesn’t take up storage space

-phosphorlyates other reactions making them more reactive

-can be reformed

-insoluble

-cannot leave the cell

193
Q

what is DNA

A

(deoxyribonucleic acid) –> One phosphate group, one base (ACTG) and a deoxyribose pentose sugar

194
Q

what is RNA

A

(ribonucleic acid) –> One phosphate group, one base (ACUG) and a ribose pentose sugar

195
Q

what is DNA

A

a polymer of nucleotides with a double helix structure and phosphate backbone

-Polynucleotides are formed through a condensation reaction

196
Q

what bond holds polynucleotides together

A

phosphodiester bonds

197
Q

what are the 4 bases of DNA

A

adenine, guanine, cytosine, thymine

198
Q

what are the 4 bases of RNA

A

adenine, guanine, cytosine, uracil

199
Q

what do the bases of DNA pair with

A

adenine with thymine
cytosine with guanine

200
Q

structure of DNA

A

-The sugar phosphate backbone of DNA protects the bases in the middle from chemical reactions. Hydrogen bonds hold the chain together

-Cytosine and guanine contain 3 hydrogen bonds (stronger and more stable)

-Adenine and thymine contain 2 hydrogen bonds

201
Q

what are the functions of DNA

A

-stable to avoid mutation

-hydrogen bonds can be overcome for DNA replication

-large and therefore carrier a lot of information

-compact so can store large amounts of information in small places

-double helix which allows one strand to act as a template for semi-conservation replication

202
Q

explain a property or iron that allows it to carry its role in red blood cells

A

. (Is) charged/polar
OR
(Is) part of haem(oglobin);
2. (So) binds/associates/loads (with) oxygen
OR
(So) forms oxyhaemoglobin
OR
(So) transports oxygen;

203
Q

Describe what the scientist should place in the control tubes

A

-same volume of buffer solution
-same concentration of substrate at start
-same concentration of denatured enzyme

204
Q

what happens to rate of hydrolysis as concentration of starch increases

A

increases

205
Q

How can eating stale bread reduce weight gain

A

less hydrolysis of starch to maltose
less glucose is absorbed by small intestine and stored as glycogen

206
Q

what forms during a condensation reaction between 2 nucleotides

A

A condensation reaction between two nucleotides forms a phosphodiester bond.

207
Q

inorganic ions

A

-Inorganic ions occur in solution in the cytoplasm and body fluids of organisms some in high concentrations and others in very low concentrations

-Each type of ion has a specific role depending on its properties

-For example, iron is found in haemoglobin where they play a role in the transport of oxygen

208
Q

process for semi conservative replication

A

1) Enzyme DNA helicase breaks hydrogen bonds linking the base pairs
2) double helix unwinds and seperates into 2 strands
3) Each polynucleotide strand then acts as a template binds to a complimentary base
4) Nucleotides join together in a condensation reaction by the enzyme DNA polymerase (phosphodiester bond)
5) semi conservative replication is the formation of DNA containing one strand of original template DNA

209
Q

describe how the seperation of DNA strands occurs

A

The strands of DNA are seperated by the enzyme DNA helicase which hydrolyses the hydrogen bonds between complimentary base pairings

210
Q

describe the role of DNA polymerase in the semi conservative replication of DNA

A

DNA polymerase forms phosphodiester bonds between adjacent mononucleotides during a condensation reaction

211
Q

what does the semi conservative replication of DNA ensure

A

genetic continuity between generations of cells

212
Q

prime location

A

-Prime location –> 3’ - 5’ carbon atoms –> how carbon atoms in a pentose molecule are numbered

-The 5 prime carbon atom has an attached phosphate group and the 3 prime carbon atom has a hydroxyl group

213
Q

why can nucleotides only be synthasised antiparallel

A

-Nucleotides can only be synthesized in vivo 5’ to 3’ because the enzyme DNA polymerase that assembles the nucleotides into a DNA molecule can only attach nucleotides to the hydroxyl group on the 3’ carbon molecule (antiparallel)

214
Q

what are the requirements for semi conservative replication

A

-4 types of nucleotide bases must be present

-Both strands of the DNA molecule that act as a template

-enzyme DNA polymerase

-source of chemical energy

215
Q

what are the two models for DNA replication

A

-Conservative model –> new double stranded molecule of DNA was constructed from nucleotides which would be an exact copy

-Semi conservative model –> One original strand, one new strand

216
Q

why did the scientist conclude that pectin is a non-competitive inhibitor

A

-with the inhibitor rate of reaction does not change and an increase in substrate concentration does not overcome change

217
Q

How does lyxose help increase rate of reaction in this scenario (exam question)

A

-lyxose binding alters tertiary structure
-causes active site to change shape
-more successful enzyme substrate complexes form

218
Q

Name the two types of molecule from which a ribosome is made

A

RNA and proteins

219
Q

Describe how the scientists would remove large organelles from this suspension of cell contents

A

-test tubes must be placed in a cold, isotonic and buffered solution
-Spin homogenised solution at different speeds using a centrifuge

220
Q

Describe how one amino acid is added to a polypeptide that is being formed at a ribosome during translation

A

-tRNA brings specific amino acids to the ribosome
-Anticodon on RNA binds to codon on mRNA
-Amino acids join through condensation reaction to form a peptide bond using ATP

221
Q

outline the role of organelles in the production, transport and release of proteins from eukaryotic cells

A

-DNA in nucleus codes for the protein
-ribosomes synthesise the protein
-golgi apparatus packages and modifies the proteins into vesicles for transportation
-vesicles fuse with cell surface membrane

222
Q

what enzyme is used in this DNA replication

A

DNA polymerase

223
Q

what is the role of

single stranded DNA

DNA nucleotides

A

template that determines the order of nucleotides

forms complimentary base pairs

224
Q

Explain why the arrows point in different directions (DNA)

A

-DNA has antiparallel strands
-shape of nucleotides is different
-enzyme active sites have specific shapes
-only 3’ end can bind with enzyme

225
Q

true or false - cellulose and starch have a Quaternary structure

A

false –> starch and cellulose are polysaccharides not proteins

226
Q

what is the formula for lactose

A

C12H22O11

227
Q

name the monomer from which nucleic acids are made

A

nucleotides

228
Q

what is an enzyme

A

a protein with a specific tertiary structure. Catalyses reactions and lowers activation energy

229
Q

explain how a change in a sequence of DNA bases could result in a non-functional enzyme

A

change in primary sequence of amino acids
this changes hydrogen bonding in tertiary structure
enzyme substrate complexes cannot be formed

230
Q

name the monomer from which nucleic acids are made

A

nucelotides

231
Q

4 structural differences between DNA and RNA

A

-DNA has thymine whereas RNA has uracil
-DNA is long whereas RNA is short
-DNA has deoxyribose whereas RNA has ribose
-DNA is double stranded whereas RNA is single stranded

232
Q

describe how monomers join together to form the primary structure of a protein

A

-amino acids join together in a condensation reaction
-forms peptide bond
-thus creating a new specific sequence of amino acids

233
Q

what are the two main things with a specific tertiary structure

A

-antibodies
-enzymes

234
Q

describe complete digestion of starch by a mammal

A

-hydrolysis of glycosidic bonds by enzyme amylase converting starch to maltose
-maltose into glucose monosaccharide

235
Q

how could you use the Michaelis constant to determine the type of inhibition occuring in an enzyme-catalysed reaction

A

reaction with non-competitive inhibitor has same value of Km than with no inhibitor

236
Q

explain how the structure of DNA is related to its functions

A

-long molecule = holds lots of information
-specific base sequence which codes for specific sequence of amino acids
-double stranded so DNA replication occurs
-sugar phosphate backbone for strength and stability
-Weak hydrogen bonds between complimentary base pairs

237
Q

iron

A

polar/charged so associates with oxygen

238
Q

why are fats solid at room temperature but oils are liquid

A

-fats are made of saturated fatty acids which have straight hydrocarbon chains
-oils are unsaturated with bends in their hydrocarbon chain which take up a lot of space and cannot be tightly packed together

239
Q

what type of structure is ATP

A

quaternary (made of several polypeptides)

240
Q

suggest how GOS is a preobiotic

A

-provides galactose
-bacteria use galactose for respiriation
-bacteria use galactose for binary fisson

241
Q

describe and explain 2 features you would expect to find in a cell specialised for absorption

A

microvilli –> increased SA

large no. of co-transporter proteins

242
Q

explain the function of this ATP hydrolase

A

-releases energy
-allows ions to be moved against concentration gradient

243
Q

describe how amino acids join to form a polypeptide so thee is always NH2 at one and COOH at the other end

A

-one amine group joins to a COOH group to form a peptide bond
-so in the chain there is a free amine group at one end and a free carboxyl group at the other

244
Q

saturated vs unsaturated fats

A

unsaturated have lower melting points bc of double carbon bond which creates “kinks or bends”

245
Q

describe the biochemical tests that you would use to confirm presence of a lipid, non reducing sugar and amylase

A

Lipid = emulsion test -> add ethanol then water and shake to form milky emulsion

Non reducing sugar = do benedicts and stays blue. Boil with acid and neutralise with alkali. Head with benedicts and red precipitate forms

Amylase = add buiret and become lilac. Add starch and test for reducing sugar

246
Q

Watson + Crick

A

DNA model

247
Q

role of single stranded DNA and nucleotides

A

strand = template strand = order of nucelotides

nuclotides = forms complimentary base pairs

248
Q

explain how a competitive inhibitor decreases ROR

A

-inhibitor is similar shape to substrate
-binds to active site
-prevents enzyme substrate complex from forming

249
Q

describe the role of the enzymes of the digestive system in the complete breakdown of starch

A

-amylase = starch to maltose
-maltase = hydrolsysis of glycosdic bonds (maltose to glucose)

250
Q

describe the processes involved in the absorption of the products of starch digestion

A

-glucose moves with Na+ ions
-Na-K pump
-conc gradient
-glucose moves into blood via facilitated diffusion

251
Q

triglycerides vs phospholipids

A

-triglycerides = hydrophobic
-phospholipids = hydrophobic and hydrophillic
-3 vs 2 fatty acids
-both have ester bonds
-both are insoluble in water
-both have C, H and O

252
Q

why does maltose allow breakdown at normal body tmeperature

A

-E-S complex lowers Ea
-induced fit

253
Q

describe and explain how the structure of DNA results in accurate replication

A

-2 strands
-base pairing
-weak H bonds
-template

254
Q

explain why ATP is useful in many biological processes

A

-release energy in small, managable amounts
-can be reformed
-phosphorlaytes othe rreactions
-broken down in one step

255
Q

suggest how different cells can develop from genetically identical cells

A

-different genes expressed producing different enzymes

256
Q

vaccines

A

-vaccine contain antigen from pathogen
-macrophage presents antigens
-T cell with complimentary receptor binds antigen
-T cell stimulates B cell

257
Q

difference between active and passive immunity

A

-passive = faster, no memory cells, external source, short term

-active = slower, memory cells, internal antibodies, long term

258
Q

adaptations of lungs

A

-many alveoli = large SA for diffusion
-flattened walls
-ventilation maintains conc gradient

259
Q

sunken stomata
waxy cuticle
rolled leaves

A

-saturated still air
-impermeable
-less S.A for water loss

260
Q

compare structure of bacterial and human cell

A

-bacterial = circular DNA, cell wall of murien, smaller ribosomes, no membrane bound organelles, no histones

human = nucleus, cellulose cell wall, larger ribosomes, membrane bound organelles, histones

261
Q

why did the student press down firmly on the cover slip

A

so cells are flattened/thin layer of cells

262
Q

describe and explain what the student should have done when counting cells to ensure the mitotic index was accurate

A

-examine large field of view to ensure the sample is representative
-repeat count to ensure figures are correct

263
Q

why does a high mutation rate make it difficult to develop a vaccine

A

-antigen variability
-vaccines contain specific antigens
-antibodies are not complimentary to the changed antigen

264
Q

describe how an ATP molecule is formed from its component molecules

A

-condensation reaction
-adenosine + 3 phosphate molecules
-ATP synthase
-ADP and Pi

265
Q

dilution series -> 1 in 10 then used to make 1 in 1000

A

1 in 10:
-1 part bacteria
-9 part sterile liquid
-mix

1 in 1000:
-add in 1 in 10 dilution to 99 parts of sterile liquid

266
Q

similarities between starch and cellulose

A

Both contain C, H, O

Both are polysaccharides

Both contain glycosidic bonds

267
Q

importance of starch and glucose being large molecules

A

cannot leave cell membrane

268
Q

3 models of DNA replication

A

conservative = 2 new strands of DNA

semi-conservative = 1 new 1 old

dispersive = random sharing of 2 strands of DNA (overlapping)

269
Q

role of nitrogen

A

Nitrogen has a lot of different roles in organisms.

One of the most important roles of nitrogen is to create an organism’s DNA, and this means that nitrogen is an essential substance for a huge range of organisms, from blue whales, to humans, to flowers and bacteria.

However, these organisms can’t just create nitrogen themselves. Instead, nitrogen is taken from an organism’s environment , just like other essential substances such as carbohydrates and lipids.

For example, plants absorb nitrogen from soil and we absorb nitrogen by eating these plants.

Next, as we’ve seen, different types of nitrogen exist.

The type of nitrogen a plant absorbs will determine the type of nitrogen we absorb from the plant. This in turn will determine which type of nitrogen is available in our body to build new DNA molecules.

So, if a plant only absorbs N-14, and then we eat the plant, we’ll only get N-14 from it.

In turn, this would mean that any new DNA molecules in our bodies are all built with N-14.

270
Q

replicate twice =

A

only 14N = conservative

271
Q

both triglycerides and phospholipids

A

-insoluble in water
-fatty acids can be saturated or unsaturated
-both = glycerol
-both = ester bond

272
Q

where in the cell would lactose be attached to a polypeptide

A

golgi apparatus

273
Q

biochemical test to show sucrose is a non-reducing sugar

A

-heart sucrose with benedicts = remains blue (no colour change)
-heat solution with acid and neutralise with alkali
-heat solution again with benedicts
-colour change to red precipitate

274
Q

arrganement of genetic material in figure 1

A

-chromosomes condense and become visible
-random arrangement

Aqa a level biology (9 decks)

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