Biological Molecules 3.1 Flashcards
1
Q
Carbohydrates AO1
Test for starch
A
1. Add (two drops of) iodine solution to the sample solution.
2. A blue/black/purple colour indicates the presence of starch.
2
Q
Monomers & Polymers AO1
Define a monomer (1 mark)
A
Small repeating units from which larger molecules called polymers are made
3
Q
Monomers & Polymers AO1
Define a polymer (1 mark)
A
Molecules made from a large number of monomers (3 or more) joined together
4
Q
Monomers & Polymers AO1
Give 3 examples of monomers
A
Glucose / Galactose / Fructose
Nucleotides
Amino acids
5
Q
Monomers & Polymers AO1
Give 3 examples of polymers
A
Starch
Glycogen
Cellulose
DNA
RNA
Proteins / Polypeptides
6
Q
Monomers & Polymers AO1
Which of the below molecules is NOT a polymer?
Glycogen
Triglyceride
Cellulose
Starch
DNA
Polypeptides/proteins
A
Triglyceride
7
Q
Monomers & Polymers AO1
Molecules with carbon-carbon and carbon-hydrogen bonds are referred to as ……………………
A
Organic molecules
8
Q
Monomers & Polymers AO1
What type of reaction joins two molecules together with the formation of a chemical bond and involves the elimination of a molecule of water (H2O)?
A
Condensation
9
Q
Monomers & Polymers AO1
Hydrolysis reaction
A
Breaks a chemical bond between two molecules & involves the use of a water molecule (H2O).
10
Q
Monomers & Polymers AO1
If 2 monomers are joined together via condensation reaction, how many molecules of water form?
A
1 molecule of water
For every bond formed, a condensation reaction produces one molecule of water.
11
Q
Monomers & Polymers AO1
If 3 monomers are joined together via condensation reactions, how many molecules of water form?
A
2 molecules of water
For every bond formed, a condensation reaction produces one molecule of water.
12
Q
Monomers & Polymers AO1
TRUE or FALSE:
Enzymes are required to catalyse the formation of bonds via condensation reactions
A
TRUE
13
Q
Monomers & Polymers AO1
TRUE or FALSE:
Enzymes are required to catalyse the breaking of bonds via hydrolysis reactions
A
TRUE
14
Q
Carbohydrates AO1
Monomers which form polysaccharides
A
Monosaccharides
15
Q
Carbohydrates AO1
Common monosaccharides
A
(alpha & beta) glucose,
galactose,
fructose
16
Q
Carbohydrates AO1
Which isomer of glucose?
A
Alpha glucose
Remember: Alpha Below Beta Above (ABBA) on C1
17
Q
Carbohydrates AO1
Which isomer of glucose?
A
Beta glucose
Remember: Alpha Below Beta Above (ABBA) on C1
18
Q
Carbohydrates AO1
Draw out the full chemical structure of alpha glucose
A
Remember: Alpha Below Beta Above (ABBA) on C1
19
Q
Carbohydrates AO1
What bond is formed as result of a condensation reaction between two monosaccharides?
A
Glycosidic bond
20
Q
Carbohydrates AO1
What disaccharide is formed by condensation reaction with two glucose molecules?
A
Maltose
21
Q
Carbohydrates AO1
What monosaccharides are joined by a condensation reaction to form lactose?
A
Glucose
Galactose
22
Q
Carbohydrates AO1
What disaccharide is formed by condensation reaction with glucose and fructose?
A
Sucrose
23
Q
Carbohydrates AO1
TRUE or FALSE:
Many glycosidic bonds are found in a disaccharide?
A
FALSE
There is only 1 glycosidic bond in a disaccharide
24
Q
Carbohydrates AO1
Draw out the formation of a glycosidic bond between two alpha glucose molecules
A
25
# **Carbohydrates AO1**
Write out a chemical equation for the formation of a disaccharide (*1 mark*)
## Footnote
For every bond formed, a condensation reaction produces one molecule of water.
26
# **Carbohydrates AO2**
Carbon = 18
Hydrogen = 32
Oxygen = 16
| Two glycosidic bonds formed, so two molecules of water produced
27
# **Carbohydrates AO1**
Polymer formed by the condensation of many glucose units
Polysaccharides
28
# **Carbohydrates AO1**
Polysaccharides formed by condensation of α-glucose
Glycogen
Starch
29
# **Carbohydrates AO1**
Polysaccharide formed by condensation of many β-glucose units
Cellulose
30
# **Carbohydrates AO1**
Location of glycogen in animals
Liver
Muscle
31
# **Carbohydrates AO1**
**Explain** how starch is related to its function (*3 marks*)
Any **three** from:
1. **Insoluble** (in water), so doesn’t affect water potential/osmosis;
2. **Coiled** / (α-)helix / helical structure, so makes molecule compact;
3. **Polymer of (α-)glucose** so provides glucose for respiration;
4. **Branched** / more ends for fast breakdown / enzyme action;
5. **Large** (molecule), so can’t cross the cell membrane
32
# **Carbohydrates AO1**
Bonds contained in cellulose
Beta (1,4) glycosidic
(many weak) Hydrogen
33
# **Carbohydrates AO1**
**Explain** how the structure of cellulose is related to its function in plant cell walls *(3-4 marks)*
1. Long / straight / unbranched chains of **beta** glucose
2. (joined by weak) **hydrogen bonds**;
3. Forms **microfibrils**;
4. Provide rigidity / strength;
34
# **Carbohydrates AO1**
**Compare** the structure of starch and cellulose
1.**Both** polysaccharides;
OR Both are glucose polymers
OR Both are made of glucose monomers;
2. **Both** contain glycosidic bonds (between monomers);
3. **Both** contain carbon, hydrogen and oxygen/C, H and O;
35
# **Carbohydrates AO1**
**Contrast** the structure of starch and cellulose
1. Starch made of α-glucose **whereas** cellulose made of β-glucose;
2. Starch (molecule) is helical/coiled **whereas** cellulose (molecule) is straight;
3. Starch (molecule) is branched **whereas** cellulose is not/unbranched;
4. Cellulose has microfibrils **whereas** starch does not;
36
# **Carbohydrates AO1**
Bonds contained by starch AND glycogen
alpha (1,4) glycosidic
alpha (1,6) glycosidic
37
# **Carbohydrates AO1**
**Explain** how glycogen is related to its function *(4 marks)*
1. Helix/**coiled** so compact;
2. **Polymer of (alpha) glucose** so easily hydrolysed;
3. (Highly) **branched** so more ends for faster hydrolysis;
4. (alpha) Glucose (polymer) so provides **respiratory substrate for energy** (release);
5. **Insoluble** so does not affect osmosis / water potential;
38
# **Carbohydrates AO1**
What term is used to describe the different structures of α-glucose and β-glucose
Isomer
| Isomers have same molecular formula but different arrangement of atoms
39
# **Carbohydrates AO2**
Galacto-oligosaccharides (GOS) are polymers of galactose.
Explain why GOS are described as polysaccharides (*2 marks*).
**1.** Galactose is a monosaccharide/monomer;
**2.** Polysaccharide is a carbohydrate polymer;
**3.** Several monosaccharides / monomers / galactose joined by condensation reactions
OR monosaccharides / monomers / galactose joined by glycosidic bonds;
40
# **Carbohydrates AO2**
Galacto-oligosaccharides (GOS) are polymers of galactose.
Give two differences between the structures of GOS and lactose.
**1.** Lactose contains (alpha) glucose and GOS does not
OR Lactose contains (alpha) glucose + galactose and GOS contains only galactose;
**2.** Lactose is a disaccharide and GOS is a polysaccharide;
**3.** Lactose has one glycosidic bond and GOS has many glycosidic bonds;
41
# **Carbohydrates AO1**
Describe the biochemical test for a reducing sugar (*3 marks*).
**1.** Add equal volumes of **Benedict’s** solution and sample to a test tube
**2.** **Heat** to 95⁰C.
**3.** Formation of a **brick red precipitate** if a reducing sugar is present.
42
# **Carbohydrates AO1**
List all the reducing sugars
Glucose
Fructose
Galactose
Maltose
Lactose
43
# **Carbohydrates AO1**
Rank the below colours of **precipitate** by concentration - lowest to highest - of reducing sugar following the Benedict's test.
Brick red
Green/yellow
Orange
**Lowest:** green/low
**Medium:** orange
**Highest concentration:** brick red
44
# **Carbohydrates AO1**
Following the Benedict's test for a reducing sugar, what would a negative result look like?
Solution remains blue
45
# **Carbohydrates AO1**
**TRUE or FALSE:**
The Benedict's test is quantitative
FALSE
| The different coloured precipitates are semi-quantitative
46
# **Carbohydrates AO1**
**TRUE or FALSE:**
A sample containing sucrose will produce a coloured precipiate following the Benedict's test
FALSE
| Sucrose is a non-reducing sugar
47
# **Carbohydrates AO1**
**Describe** a biochemical test to show that a solution contains a non-reducing sugar (*3 marks*)
**1.** **Boil** with acid **AND** neutralise;
Accept named examples, eg hydrochloric acid (HCl), sodium hydrogen carbonate (NaHCO3)
**2.** Heat (to 95oC) **with Benedict's** (solution);
**3.** Red **precipitate**
(indicates non-reducing sugar is present);
Accept other colours eg. green/orange
48
# **Carbohydrates AO1**
Describe how scientists produce a calibration curve to obtain estimates maltose concentration for an unknown sample (*4 marks*)
*Do not include details of how to perform a Benedict’s test in your answer.*
**1** Make/use maltose solutions of **known/different** concentrations
**2.** Carry out **Benedict’s** test on each solution;
**3.** (Use colorimeter to) **measure colour/colorimeter value (e.g. absorbance)** of each solution and plot calibration curve;
**4.** Details of curve:
concentration on x-axis,
colorimeter value on y-axis,
draw a line of best fine.
**5.** Estimate concentration of sample by using calibration curve i.e. read off Y axis value to estimate concentration using the x axis
49
# **Carbohydrates AO1**
A student carried out the Benedict’s test. Suggest a method, other than using a colorimeter, that this student could use to measure the quantity of reducing sugar in a solution (*2 marks*).
**1.** Filter **AND** dry (the precipitate);
Accept: correct reference to evaporation after filtration
**2.** Find mass/weight;
50
# **Carbohydrates AO1**
Explain how you would use the below graph to determine the maltose concentration with a light absorbance of 0.45 arbitary units.
Line of best fit drawn;
Read off Y axis value at 0.45 (to estimate concentration using the x axis)
51
# **Carbohydrates AO1**
Arbitary unit (AU)
A relative unit of measurement to show the ratio of amount of substance;
This allows comparisons.
52
# **Carbohydrates AO1**
Using a colorimeter rather than relying on the Benedict's test results alone improves the repeatability of the student’s results.
Give one reason why.
**1.** Quantitative OR
(Colour change is) subjective;
Accept: accurate/precise
**2.** Standardises (the) method;
53
# **Lipids AO1**
Two groups of lipids
Triglycerides
Phospholipids
54
# **Lipids AO1**
Triglyceride components
One glycerol molecule
&
three molecules of fatty acid
55
# **Lipids AO1**
Tryglyceride bond
Ester
56
# **Lipids AO1**
Number of ester bonds in a triglyceride
3
57
# **Lipids AO1**
Identify the carboxyl group and hydrocarbon chain in the fatty acid
58
# **Lipids AO1**
Everything other than the COOH inside drawn box;
59
# **Lipids AO1**
Complete the diagram to produce a triglyceride
60
# **Lipids AO1**
Saturated OR unsaturated fatty acid
Saturated fatty acid
61
# **Lipids AO1**
Saturated or unsaturated fatty acid?
Unsaturated fatty acid
62
# **Lipids AO1**
Unsaturated fatty acid
Fatty acids with **double bonds** between the carbon atoms **in the hydrocarbon chain**.
63
# **Lipids AO1**
Saturated fatty acid
Fatty acids have **no double bonds** between carbons in the hydrocarbon chain.
64
# **Lipids AO1**
Describe the emulsion test for a lipid
(*3 marks*)
**1.** Add **ethanol** to sample and **mix**
(to dissolve the lipid)
**2.** Then **add water** and mix
**3.** **A white emulsion** will be visible if fat is present
65
# **Lipids AO1**
If the sample is a seed - which contains oils - what must you first do before starting the emulsion test?
Crush seeds before adding ethanol.
66
# **Lipids AO1**
Describe how a triglyceride molecule is formed (*3 marks*)
**1.** One glycerol and three fatty acids;
**2.** Condensation (reactions) and removal of **three molecules of water**;
**3.** Ester bond(s) (formed);
67
# **Lipids AO1**
What molecules are represented by P and Q?
P = Glycerol
Q = Fatty acids (chains)
68
# **Lipids AO1**
**Compare** the structure of triglycerides and phospholipids.
**Both** contain ester bonds (between glycerol and fatty acid);
**Both** contain glycerol;
Fatty acids on **both** may be saturated or unsaturated;
**Both** contain C, H and O **whereas** phospholipids also contain P; Must relate to element.
69
# **Lipids AO1**
**Compare** the properties of triglycerides and phospholipids.
**Both** are insoluble in water;
70
# **Lipids AO1**
**Contrast** the structure of triglycerides and phospholipids.
Triglyceride has three fatty acids **whereas** phospholipid has two fatty acids;
Triglyceride has no phosphate group **whereas** phospholipids has 1 phosphate group;
Triglycerides have 3 ester bonds **whereas** phospholipids have 2;
**Both** contain C, H and O **whereas** phospholipids also contain P; Must relate to element.
71
# **Lipids AO1**
**Contrast** the properties of triglycerides and phospholipids.
Triglycerides are hydrophobic/non-polar **whereas** phospholipids have hydrophilic/polar and hydrophobic region;
Phospholipids form bilayer **whereas** triglycerides don’t;
72
# **Lipids AO1**
Triglycerides are hydrophobic or hydrophilic
Hydrophobic
73
# **Lipids AO1**
**TRUE or FALSE**
Phospholipids are hydrophobic AND hydrophilic
TRUE
| Hydrophobic fatty acids tails and hydrophilic phosphate head
74
# **Lipids AO1**
Explain the arrangement of phospholipids in a cell-surface membrane (*3 marks*)
**1.** As a **bilayer**
**2**. Phospholipid **both** hydrophobic and hydrophilic
OR Phospholipid polar
**3.** Triglycerides **only** hydrophobic
OR Fatty acid/triglyceride is non-polar;
**4.** Hydrophilic/phosphate group **attracts water** (to either side of bilayer)
OR **Hydrophobic** (fatty acid) tails point away/are repelled from water
75
# **Lipids AO1**
Draw and label a simple diagram of the phospholipid bilayer
76
# **Lipids AO1**
Draw and label a simple diagram of a single phospholipid molecule
77
# **Lipids AO1**
The general structure of a fatty acid is RCOOH.
Name the group represented by COOH.
Carboxyl
78
# **Lipids AO1**
Explain why phospholipids can form a bilayer but triglycerides cannot (*3 marks*)
**1.** Phospholipid both hydrophobic and hydrophilic
OR Phospholipid polar
OR Phosphate group is charged;
**2.** Triglycerides only hydrophobic
OR Fatty acid/triglyceride is non-polar;
**3.** Hydrophilic/phosphate group attracts water (to either side of bilayer);
79
# **Lipids AO1**
**1.** 3 fatty acids rather than 2;
**2.** 3 ester bonds rather than 2;
**3.** No phosphate group;
80
# **Lipids AO1**
Describe the hydrolysis reactions involved in the digestion of triglycerides.
Do **not** write about the activity of lipase.
**1.** Breaking of ester bonds;
**2.** By addition of water;
81
# **Lipids AO1**
How many molecules are produced following the complete hydrolysis of a triglyceride
4
| 1 glycerol + 3 fatty acids
82
# **Lipids AO1**
**Type of R group** = Unsaturated (fatty acid);
**Explanation** = Double bond (between carbons);
Accept for ‘double bond’, C=C
83
# **Water AO1**
Explain the importance of water as a **metabolite**
Involved in metabolic reactions such as condensation and hydrolysis.
84
# **Water AO1**
Explain the importance of water as a **solvent**
This allows metabolic reactions to occur
AND
also allows the transport of substances.
85
# **Water AO1**
Explain the importance of the **high specific heat capacity** of water
This ‘buffers’ changes in temperature.
| It requires lots of energy to break the hydrogen bonds in water
86
# **Water AO1**
Explain the importance of the **large latent heat of vaporisation** of water
This provides a cooling effect
(through evaporation)
87
# **Water AO1**
Explain the importance of **cohesion** between water molecules
This supports the formation of **continuous columns of water** (which is needed to move water up the xylem).
OR
Produces **surface tension** which supports small organisms on the surface of water e.g., pond skaters.
88
# **Carbohydrates AO1**
The student controlled variables in the test using Benedict’s solution.
Give **two** variables the student controlled.
1. Benedict’s (solution) **volume**;
2. Benedict’s (solution) **concentration**;
3. (Fruit) juice **volume**;
4. (Water bath/water/solution) **temperature**;
5. **Duration** of heating (in water bath);
89
# **Proteins AO1**
Draw out and label an amino acid
90
# **Proteins AO1**
Monomers of proteins
(aka polypeptides)?
Amino acids
91
# **Proteins AO1**
**Describe** how a peptide bond is formed between two amino acids to form a dipeptide (*2 marks*).
1. Condensation (reaction) / loss of water.
2. Between amine/NH2 and carboxyl/COOH groups.
92
# **Proteins AO1**
List the levels of organisation of protein structure
The **PRIMARY** structure
The **SECONDARY** structure
The **TERTIARY** structure
The **QUATERNARY** structure
93
# **Proteins AO1**
Describe the primary structure of all proteins
**1.** **number** AND **sequence/order** of amino acids (in a polypeptide chain);
**2.** Joined by **peptide bonds**;
94
# **Proteins AO1**
**Describe** how monomers join to form the primary structure of a protein (*3 marks*).
1. Condensation reaction between amino acids
2. Forming peptide bond
3. Creating a specific number **AND** sequence of amino acids
95
# **Proteins AO1**
Bond in secondary structure of protein
(Many weak) hydrogen bonds
96
# **Proteins AO1**
The secondary structure of a polypeptide is produced by bonds between amino acids. **Describe** how (*2 marks*).
1. Hydrogen bonds
2. Between **NH** (amine) and **C=O** (carboxyl groups) groups of amino acids
3. This forms alpha helix / beta pleated sheets
97
# **Proteins AO1**
Which level of protein structure?
Secondary
98
# **Proteins AO1**
The tertiary structure is held together by bonds between the ____________ of different amino acids.
R groups
99
# **Proteins AO1**
Tertiary structure bonds
Hydrogen
Ionic
Disulphide bridges
100
# **Proteins AO1**
**TRUE or FALSE:**
The R group is the same in all amino acids
FALSE
101
# **Proteins AO1**
Properties of amino acid
R groups
Positively charged
Negatively charged
Polar and non-polar
Hydrophophic and hydrophilic
102
# **Proteins AO1**
Level of protein structure?
Tertiary
103
# **Proteins AO1**
**Fill in the blank:**
Quatenary proteins contain ....................... polypeptide chains
two or more
OR
more than one
104
# **Proteins AO1**
The quaternary structure is held together by which bonds between the polypeptide chains.
Hydrogen
Ionic
Disulphide bridges
105
# **Proteins AO1**
Two proteins have the same number and type of amino acids but different tertiary structures. **Explain** why (*2 marks*).
1. Different primary structure / **different sequence** of amino acids
2. Forms ionic / hydrogen / disulphide **bonds** in different places
106
# **Proteins AO1**
**Describe** the structure of a protein (*5 marks*).
**1.** Polymer of amino acids
**2.** Amino acids joined by peptide bonds
**3.** Formed by a condensation reaction
**4.** Primary structure is number AND order/sequence of amino acids
**5.** Secondary structure is **folding** of polypeptide chain due to hydrogen bonding
**6.** Tertiary structure is **3D folding** formed by interactions between R groups e.g. due to hydrogen / ionic / disulphide **bonds**
**7.** Quaternary structure more than one OR two or more polypeptide chains
107
# **Proteins AO1**
Biochemical test for proteins
Add Biuret reagent
Positive result = purple/lilac (solution)
108
# **Proteins AO1**
A dipeptide consists of two amino acids joined by a peptide bond.
Describe **two** other ways in which all dipeptides are similar.
1. Amine/NH2 (group at end);
2. Carboxyl/COOH (group at end);
3. Two R groups;
4. All contain C and H and N and O;
109
# **Proteins AO1**
A dipeptide consists of two amino acids joined by a peptide bond.
Describe **one** way in which they might differ.
Variable/different R group(s);
110
# **Proteins AO2**
A solution contained a mixture of three different amino acids. A scientist passed an electric current through the solution to separate the amino acids.
Explain what the positions of the spots in the below diagram show about these amino acids.
1. Moved to negative (electrode) because positive(ly charged);
2. (Spots move) different distances/rates because (amino acids) different charge/mass;
3. Two spots (not three) because (amino acids) same charge/mass
111
# **Proteins AO1**
**TRUE OR FALSE:**
All proteins have a **specific tertiary structure** which gives them a specific shape which is necessary for them to carry out their function.
True
112
# **Proteins AO1**
Rank the bonds found in the tertiary structure of protein by strength
Disulphide = strongest
Ionic (broken by changes in pH)
Hydrogen = weakest (broken by changes in temperature)
113
# **Proteins AO1**
What is denaturation of proteins?
A permanent change in its tertiary structure
114
# **Proteins AO1**
If you added the Biuret reagent to a solution containing enzymes, what would the result be?
Purple/lilac = positive result
because enzymes are proteins.
115
# **Enzymes AO1**
Enzymes lower the ______________________ of the reaction they catalyse
activation energy
116
# **Enzymes AO1**
Enzymes are proteins which have a specific ___________ structure
tertiary
117
# **Enzymes AO1**
Enzyme active sites have a unique shape which is _______________ to only one substrate
complementary
118
# **Enzymes AO1**
When an enzyme active site binds to a substrate it forms an _______________
enzyme substrate complex
119
# **Enzymes AO1**
In humans, the enzyme maltase breaks down maltose to glucose. Explain why maltase only breaks down maltose (*2 marks*).
1. Maltase has a **specific tertiary structure** that contains an active site;
2. Active site **complementary** to only maltose / substrate
120
# **Enzymes AO1**
Describe the induced fit model of enzyme action (*3 marks*)
1. Active site is initially **NOT complementary** to the substrate
2. The substrate enters the enzyme's active site and **induces the change in the shape of the active site** so now complementary
3. Enzyme substrate complex forms which **stresses the bonds in the substrate** and **lowers the activation energy**
4. When the product leaves the active site, active site returns to its previous shape
121
# **Enzymes AO1**
Describe one **similarity** between the induced-fit model of enzyme action and the lock and key model of enzyme action
Substrate binds to active site
OR
Enzyme-substrate complex (formed);
122
# **Enzymes AO1**
Describe one **difference** between the induced-fit model of enzyme action and the lock and key model of enzyme action
Active site **changes shape** with induced-fit, **whereas** does not change in lock and key
OR
(Initially) active site not complementary to substrate with induced-fit, **whereas** is complementary in lock and key
123
# **Enzymes AO1**
In humans, the enzyme maltase breaks down maltose to glucose. This takes place at normal body temperature. Explain why (*3 marks*).
**1.** Description of induced fit - binding of substrate causes **active site to change shape** (now complementary to substrate);
**2.** This forms an **enzyme-substrate complex which stresses bonds in the substrate** (so more easily broken);
**3.** Which **lowers activation energy** required for reaction;
124
# **Enzymes AO1**
Explain how the active site of an enzyme causes a high rate of reaction (*3 marks*)
**1.** Description of induced fit - **binding of substrate causes active site to change shape **(now complementary to substrate);
**2.** This forms an **enzyme-substrate complex which stresses bonds in the substrate** (so more easily broken);
**3.** Which **lowers activation energy** required for reaction;
125
# **Enzymes AO1**
How can you measure the rate of enzyme-controlled reactions?
formation of products OR
disappearance or breakdown of the substrate
(in a defined period of time)
| **KEY POINT:** Calculating the rate of any process ALWAYS requires time
126
# **Enzymes AO1**
How to calculate the rate of an enzyme controlled reaction
DY (substrate or product) /
DX (always time)
| (Change in Y over change in X)
127
# **Enzymes Maths**
Calculate the rate of reaction using the below triangle
## Footnote
**Clue:** DY / DX
128
# **Enzymes AO1**
Explain how two enzymes with different amino acid sequences can catalyse the same reaction (*2 marks*)
**1.** Both active sites have similar/identical tertiary structures
OR
Both have active sites that are complementary to different parts of the substrate;
**2.** Form enzyme-substrate complexes (with the same substrate);
129
# **Enzymes AO1**
Factors affecting enzyme controlled reactions
Temperature
pH
Substrate concentration
Enzyme concentration
130
# **Enzymes AO1**
**Fill in the gaps:**
As the temperature increases the enzymes and substrates have more [1].
Therefore they move around more and are more likely to successfully collide and form [2].
1. knetic energy
2. enzyme-substrate complexes
131
# **Enzymes AO1**
Enzyme denaturation
A **permanent change to the tertiary structure**;
**Active site no longer complementary** to substrate;
**fewer enzyme substrate complexes form**.
132
# **Enzymes AO1**
Bonds broken in enzyme tertiary structure by increasing temperature
(mainly) weak hydrogen
ionic
133
# **Enzymes AO1**
pH is a measure of________________.
hydrogen ion concentration
| Increase H+ ions (low pH) , decrease H+ ions (high pH)
134
# **Enzymes AO1**
**TRUE or FALSE:**
Both increases and decreases in pH can denature an enzyme
TRUE
135
# **Enzymes AO1**
Describe and explain the effect of increasing substrate concentration on the rate of an enzyme controlled reaction (*2 marks*).
**(Describe)**
Increases then plateaus;
**(Explain)**
Because all enzyme active sites are occupied
Plateaus because all the substrate has been used up
136
# **Enzymes AO1**
Limiting factor at the red arrow
Substrate concentration
137
# **Enzymes AO1**
Limiting factor at the red arrow
Enzyme concentration
138
# **Enzymes AO1**
Why is the initial rate of reaction faster?
because there’s lots of substrate and therefore **more enzyme substrate complexes** form.
139
# **Enzymes AO1**
Why does the rate of reaction plateau?
because all enzyme active sites have been occupied by the substrate;
the concentration of enzyme is a limiting factor;
140
# **Enzymes AO1**
Inhibitors __________ the rate of reaction
decrease
141
# **Enzymes AO1**
Competitive inhibitors have a __________________________ shape to the substrate
similar
142
# **Enzymes AO1**
**Fill in the blanks:**
Because they have a similar shape to the substrate, competitive inhibitors can bind to the enzyme's [1].
.
Competitive inhibitors reduce [2] complexes forming.
This decreases the [3] of reaction.
1. active site
2. enzyme substrate
3. rate
143
# **Enzymes AO1**
___________________ substrate concentration can overcome competitive inhibition
Increasing
144
# **Enzymes AO2**
1. (Allopurinol) is a **similar shape** to xanthine;
2. (Allopurinol) enters active site / is a competitive inhibitor;
3. Less xanthine binds so fewer enzyme substrate complexes and therefore fewer uric acid crystals formed;
145
# **Enzymes AO1**
Which type of inhibitor binds to the allosteric site (away from the active site).
non-competitive
146
# **Enzymes AO1**
What happens after a non-competitive inhibitor binds to the allosteric site?
**1.** **Change the shape of the active site** so that it is **no longer complementary** to the substrate.
**2.** **Fewer enzyme substrate complexes form** and the rate of reaction is decreased.
147
# **Enzymes AO1**
**TRUE OR FALSE:**
Increasing substrate concentration can overcome non-competitive inhibition.
FALSE
| This is because the active site has changed shape
148
# **Enzymes AO2**
Explain the results in the below graph
(*2 marks*).
**1.** (Rate of) increase in concentration of maltose slows as substrate/starch is used up
OR
High initial rate as plenty of starch/substrate/more enzyme-substrate complexes;
**2.** No increase after 25 minutes/at end/levels off because no substrate/starch left;
149
# **Enzymes AO1**
What does the addition of a buffer do in an enzyme controlled reaction?
Maintains a constant pH
This prevents the enzyme from denaturing
150
# **Enzymes AO1**
A competitive inhibitor decreases the rate of an enzyme-controlled reaction.
Explain how (*3 marks*).
1. Inhibitor **similar shape** to substrate;
2. Binds to active site;
3. Reduces enzyme-substrate complex forming;
151
# **Enzymes AO1**
Describe how a non-competitive inhibitor can reduce the rate of an enzyme-controlled reaction (*3 marks*).
1. Attaches to the enzyme at the **allosteric site** (other than the active site);
2. **Changes shape of the active site**
OR Changes tertiary structure (of enzyme);
3. (So active site and substrate) **no longer complementary** so less/no substrate can fit/bind;
152
# **Enzymes AO2**
High substrate concentration does not overcome inhibition
*OR*
(With inhibitor) increase substrate/lipid concentration does not increase rate of reaction
*OR*
(With inhibitor) increase substrate/lipid concentration does not increase lipase activity
153
# **Enzymes AO3**
When investigating factors that affect enzyme-controlled reactions, enzymes are often ‘isolated’ from a cell (e.g. a bacterial cell).
Explain why this is a limitation?
.
The process of isolation **may change the enzyme's activity**
Outside the optimum conditions of the host cell, the enzyme's activity may also change.
154
# **Enzymes AO3**
What is a common control condition that proves a specific enzyme is needed for a reaction?
1. **Boiled** enzyme
2. At **same concentration** & volume
3. This denatures the enzyme and the reaction will not take place in this condition
155
# **Structure of DNA AO1**
DNA holds ____________ information
genetic
156
# **Structure of DNA and RNA AO1**
RNA transfers genetic information from ____________ to the ribosomes
DNA
157
# **Structure of DNA and RNA AO1**
Both DNA and RNA are polymers of ______________.
nucleotides
158
# **Structure of DNA AO1**
Draw out and label a DNA nucleotide
159
# **Structure of RNA AO1**
Pentose sugar in a RNA nucleotide
Ribose
160
# **Structure of DNA AO1**
Pentose sugar in a DNA nucleotide
Deoxyribose
161
# **Structure of RNA AO1**
Draw out and label a RNA nucleotide
162
# **Structure of RNA AO1**
Nitrogenous base specific to RNA
Uracil
163
# **Structure of DNA AO1**
Nitrogenous base specific to DNA
Thymine
164
# **Structure of DNA and RNA AO1**
Bond that joins together nucelotides
Phosphodiester
165
# **Structure of DNA AO1**
Enzyme that catalyses the formation of a phosphodiester bond via a condestation reaction of DNA nucleotides.
DNA polymerase
166
# **Structure of DNA AO1**
Describe how a phosphodiester bond is formed between two nucleotides within a DNA molecule
(*2 marks*).
1. Condensation reaction;
2. Between phosphate and deoxyribose;
3. (Catalysed by) DNA polymerase;
167
# **Structure of RNA AO1**
Enzyme that catalyses the formation of a phosphodiester bond via a condestation reaction of **RNA** nucleotides.
RNA polymerase
168
# **Structure of DNA AO1**
**Fill in the blanks**
A DNA molecule is a double helix with two [1] chains held together by [2] bonds between specific [3] base pairs.
1 - polynucleotide
2 - hydrogen
3 - complementary
169
# **Structure of DNA AO1**
The double helix structure for DNA and its replication was proposed by which scientists?
James Watson &
Francis Crick
170
# **Structure of DNA AO1**
In the DNA double helix, adenine forms a complementary base pair with?
thymine
171
# **Structure of DNA AO1**
In the DNA double helix, guanine forms a complementary base pair with?
cytosine
172
# **Structure of DNA AO1**
Describe the structure of DNA
(*5 marks*)
**1.** Polymer of nucleotides;
**2.** Each nucleotide formed from deoxyribose, a phosphate group and a nitrogenous base;
**3.** Phosphodiester bonds (between nucleotides);
**4.** Double helix / 2 strands held by hydrogen bonds;
**5.** Complementary pairing between adenine, thymine **AND** cytosine, guanine;
173
# **Structure of DNA AO1**
Functions of the sugar-phosphate backbone and double helix structure
1. Provides strength and stability;
2. Protects information coded in the bases and hydrogen bonding between bases;
174
# **Structure of DNA AO1**
Function of DNA being a long molecule
Can store a lot of information
175
# **Structure of DNA AO1**
Function of helix structure in DNA
Makes it compact
| (more nucleotides can fit into a smaller space)
176
# **Structure of DNA AO1**
Function of the base sequence of DNA
Codes for the sequence of amino acids in the primary structure of proteins
177
# **Structure of DNA AO1**
Function of the DNA helix
being double stranded
Allows semi-conservative replication because both strands can act as a template;
178
# **Structure of DNA AO1**
Complementary base pairing between – adenine and thymine & cytosine and guanine allows ____________ .
accurate replication
179
# **Structure of DNA AO1**
Function of the weak hydrogen bonds between complementary bases in DNA
Easily broken by DNA helicase and allows separation of strands during semi-conservative replication;
180
# **Structure of DNA Maths**
Thymine = 18%
Guanine = 32%
181
# **Structure of DNA Maths**
182
# **Structure of DNA Maths**
183
# **Structure of DNA and RNA AO1**
Structural **differences** between a DNA molecule and a mRNA molecule (*4 marks*).
**1.** DNA has deoxyribose **whereas** mRNA has ribose;
**2.** DNA has thymine **whereas** mRNA has uracil;
**3.** DNA long **whereas** mRNA short;
**4.** DNA is double stranded / double helix whereas mRNA is single stranded
**5.** DNA has hydrogen bonds **whereas** mRNA has no hydrogen bonds
OR
DNA has (complementary) base pairing **whereas** mRNA does not;
184
# **Structure of DNA and RNA AO1**
Structural **similarities** between a DNA molecule and a mRNA molecule (*4 marks*).
**1.** **Both** polymers of nucleotides;
**2.** Nucleotides have pentose, (nitrogen-containing organic) base and a phosphate (group);
**3.** **Both** Cytosine, guanine and adenine (as bases);
**4.** **Both** have phosphodiester bonds;
185
# **Structure of DNA AO1**
1. Hydrogen bonds;
2. Phosphodiester bonds;
186
# **Biological Molecules AO1**
187
# **Structure of DNA AO1**
8
188
# **Structure of DNA AO1**
deoxyribose
189
# **DNA replication (AO1)**
The semi-conservative replication of DNA ensures ___________________ .
genetic continuity between generations of cells
OR
genetically identical cells following mitosis
190
# **DNA replication AO1**
Role of DNA helicase during semi-conservative DNA replication
Breaks hydrogen bonds;
between complementary base pairs;
To unwind DNA / separate strands;
191
# **DNA replication AO1**
Following semi-conservative replication, a new molecule of DNA will consist of _______________.
**half** “original” strand
AND
**half** “new” strand
192
# **DNA replication AO1**
In the process of semi-conservative DNA replication, the two strands within a DNA molecule are separated. Each then acts as a template for the formation of a new complementary strand.
Describe how the separation of strands occurs (*2 marks*).
1. DNA helicase;
2. Breaks hydrogen bonds between complementary base pairs
193
# **DNA replication AO1**
Role of the single-stranded DNA fragments (*2 marks*)
1. Act as template;
2. Determines order of nucleotides / bases;
194
# **DNA replication AO1**
Role of DNA nucleotides
Forms complementary pairs
e.g. Adenine to Thymine, Guanine to Cytosine
195
# **DNA replication AO1**
Bond catalysed by DNA polymerase
phosphodiester
196
# **DNA replication AO1**
Describe the role of DNA polymerase in the semi-conservative replication of DNA (*2 marks*).
Joins adjacent DNA nucleotides between deoxyribose and phosphate;
Via condensation reactions to form phosphodiester bonds;
197
# **DNA replication AO1**
Describe the process of semi-conservative replication of DNA
(*5 marks*).
**1.** **DNA helicase** unwinds DNA/double helix OR DNA helicase breaks hydrogen bonds;
**2.** **Both strands act as templates**;
**3.** (Free DNA) nucleotides line up in **complementary base pairs** / Adenine to Thymine and Guanine to Cytosine;
**4.** **DNA polymerase** joins adjacent nucleotides (of new strand);
**5.** Forming **phosphodiester bonds**;
**6.** Each new DNA molecule consists of one
old/**original**/template strand and one **new** strand;
198
# **DNA replication AO1**
Name of scientisis who provided the evidence for the semi-conservative model of replication
Meselson & Stahl
199
# **DNA replication AO1**
What organism did Meselson and Stahl use for their experiment?
Bacteria (*E.coli*)
200
# **DNA replication AO1**
**Meselson & Stahl experiment**
In generation '0', all the bacteria (e.coli) were grown with which isotope of nitrogen?
N15
201
# **DNA replication AO1**
**Meselson & Stahl experiment**
In generation '1', all the bacteria (e.coli) were grown with which isotope of nitrogen?
N14
202
# **DNA replication AO1**
**Meselson & Stahl experiment**
Which nitrogen isotope is heavier?
N15
203
# **DNA replication AO1**
**Meselson & Stahl experiment**
Put ticks for which generation the different DNA molecules will be found.
204
# **Structure of DNA AO1**
DNA is a polymer of nucleotides. Each nucleotide contains an organic base.
Explain how the organic bases help to stabilise the structure of DNA (*2 marks*).
1. Hydrogen bonds between the complementary base pairs holds two strands together
2. Many hydrogen bonds provides strength
205
# **ATP AO1**
ATP stands for
Adenosine **tri**phosphate
206
# **ATP AO1**
Draw out and label the structure of adenosine triphosphate (ATP)
207
# **ATP AO1**
Products of ATP hydrolysis
adenosine **di**phosphate (ADP)
AND
an **inorganic** phosphate group (Pi)
208
# **ATP AO1**
Enzyme that catalyses ATP hydrolysis
ATP hydrolase
209
# **ATP AO1**
ATP is mostly produced in the mitochondria via which process?
Aerobic respiration
| Smaller amounts of ATP are produced by anaerobic respiration
210
# **ATP AO1**
Describe how an ATP molecule is formed from its component molecules (*4 marks*).
**1. and 2.** Accept for 2 marks correct names of three components: adenine, ribose, **three** phosphates;
*OR accept suitably labelled diagram*
**3.** Condensation reaction (releases 1 water molecule);
**4.** ATP synthase;
211
# **ATP AO1**
Adding an inorganic phosphate to a biological molecules is known as phosphorylation. This makes the molecule ______________ .
more reactive
212
# **ATP AO1**
ATP is useful in many biological processes. Explain why (*4 marks*).
**1.** Releases energy in **small** amounts;
**2.** One bond broken down in a single step so **immediate** energy compound / makes energy available rapidly;
**3.** **Phosphorylates** / adds phosphate makes molecules **more reactive** / lowers activation energy;
**4.** **Reformed** / made again / resynthesised;
213
# **ATP AO1**
**TRUE or FALSE**
Adding a phosphate group to an enzyme can help lower the activation energy.
TRUE
214
# **ATP AO1**
Give two ways in which the properties of ATP make it a suitable source of energy in biological processes (*2 marks*).
**1.** Energy released in small amounts;
**2.** One bond broken down in a single step so **immediate** energy compound / makes energy available rapidly;
**3.** Soluble;
215
# **ATP AO1**
Humans synthesise more than their body mass of ATP each day. Explain why it is necessary for them to synthesise such a large amount of ATP (*2 marks*).
**1.** ATP cannot be stored / is an immediate source of energy;
**2.** ATP only releases a small amount of energy at a time;
216
# **ATP AO1**
Adenosine triphosphate (ATP) is a nucleotide derivative.
**Contrast** the structures of ATP and a nucleotide found in DNA to give **two** differences.
**1.** ATP has ribose **whereas** DNA nucleotide has deoxyribose;
**2.** ATP has 3 phosphate (groups) **whereas** DNA nucleotide has 1 phosphate (group);
**3.** ATP – base always adenine **whereas** in DNA nucleotide nitrogenous base can be different / varies;
217
# **ATP AO1**
Quaternary
Condensation/phosphorylation
Release/loss/formation
(Aerobic) respiration
218
# **Biological Molecules AO1**
B - is a monomer in an enzyme’s active site
D - is a monomer in cellulose
C - is produced during photosynthesis and respiration
B - forms a polymer that gives a positive result with a biuret test
219
# **Inorganic ions (AO1)**
Describe the role(s) of phosphate ions in cells
**1.** Joins nucleotides/in phosphodiester bond/in backbone of DNA/RNA/in nucleotides;
**2.** Used in/to produce ATP;
**3.** Phosphorylates other compounds (usually) making them more reactive;
**4.** Hydrophilic/water soluble part of phospholipid bilayer/membrane;
**5.** Affects osmosis/water potential;
