Biological molecules recall questions Flashcards
(119 cards)
1
Q
What elements are common to all the molecules of life?
A
C, O, H
2
Q
What are the four main groups of carbon-based molecules common to all life forms?
A
Carbohydrates, Lipids, Proteins and Nucleic acids.
3
Q
What molecule forms part of the plasma membrane?
A
Phospholipids.
4
Q
Which biological molecules are required to make proteins?
A
Amino acids (and nucleic acids).
5
Q
Which two biological molecules are the main respiratory substrates?
A
Lipids and carbohydrates.
6
Q
What is a polymer?
A
A series of repeating units (monomers) joined together.
7
Q
Which reaction joins two monomers together?
A
Condensation reaction.
8
Q
What reaction breaks down polymers?
A
Hydrolysis.
9
Q
What type of chemical bond is formed between monomers?
A
Covalent bond.
10
Q
Why is it known as a condensation reaction?
A
A molecule of water is produced/released.
11
Q
Describe the process of hydrolysis.
A
A water molecule is used to break a covalent bond. An H and an OH group are joined to the monomers.
12
Q
What type of polymer is made from monosaccharides and what bond joins them together?
A
A Polysaccharide - Glycosidic bonds
13
Q
What type of polymer is made from amino acids and what bond joins them together?
A
A polypeptide - peptide bonds.
14
Q
What type of polymer is made from nucleotides and what bonds them together?
A
A polynucleotide - phosphodiester bonds
15
Q
What type of reaction joins monosaccharides together?
A
Condensation.
16
Q
What is a dissacharide? What type of bond is involved?
A
Two monosaccharides joined together by a glycosidic bond.
17
Q
What type of reaction breaks down maltose?
A
Hydrolysis.
18
Q
What disaccharide is made by joining glucose and glucose?
A
Maltose
19
Q
What are the two monosaccharides that join up to make sucrose?
A
Fructose and glucose.
20
Q
What disaccharide is made by joining glucose and galactose?
A
Lactose
21
Q
What are the 3 types of polysaccharides that α-glucose can form?
A
- Amylose
- Amylopectin
- Glycogen
22
Q
What type of reaction breaks polysaccharides apart?
A
Hydrolysis
23
Q
Describe the structure of glycogen
A
Polymer of alpha glucose - highly branched
24
Q
State the two structures that make up starch.
A
Amylose + Amylopectin
25
Describe the structure and properties of starch
A mixture of two polysaccharides of alpha glucose. Amylose is a lomg branched chain of a glucose. The angles of the glycosidic bonds give it a coiled structure which makes it compact so good for storage. Amylopectin is a long branched chain of a glucose. Its side branches allow enzymes to get at the glycosidic bonds easily so glucose can be released quickly. It is insoluble in water.
26
What's the differences and similarities between starch and glycogen?
Glycogen is always branched, starch isn't. Starch found in plants, glycogen in animals. Both are energy stores, both made of alpha glucose.
26
Why are different enzymes needed to digest starch and glucose?
Different shape molecule requires a different enzyme as they have different active site shapes. Cellulose is made of β-glucose and starch of α-glucose. 1,6-glycosidic bonds are only in starch. Starch is made of amylose and amylopectin, celleulose is linear and starch is branched.
27
Based on the arrangement of cellulose molecules, explain why cell walls provide strength and support to plant cells.
* Cellulose molecules form hydrogen bonds with eachother to make microfibrils.
* Fibres are tough and flexible.
28
1,6-glycosidic bonds are found in ..................
Amylopectin/Glycogen
29
β-glucose can only be found in...............
Cellulose
30
Describe the structure of amylopectin, including the bonds involved and the shape.
Amylopectin is a long branched chain of α-glucose. Its side branches, 1,4 and 1,6 glycosidic bonds, branched.
31
State 4 roles of lipids
1. Source of energy
2. Waterproofing
3. Insulation
4. Protection
32
What does a triglyceride consist of? Which type of bonds hold it together?
Glycerol and 3 fatty acids - ester bonds.
33
How is a phospholipid different to a triglyceride? And how are they similar?
Only 2 fatty acids (Triglyceride has three). Phosphate head (triglyceride has no phosphate). Both have fatty acids.
34
How many water molecule(s) is/are needed when breaking down a triglyceride?
3
35
What is the term for the reaction that makes lipids?
Condensation
36
What does a triglyceride consist of? Which type of bonds hold it together?
Glycerol and 3 fatty acids - ester bonds.
37
How is a phospholipid different to a triglyceride? And how are they similar?
Only 2 fatty acids (triglyceride has three). Phosphate head (triglyceride has no phosphate). Both have fatty acids.
38
Describe how phospholipid can form a bilayer arrangement.
- Hydrophilic heads point outwards.
- Hydrophobic tails point inwards (shielded from aqueous environment).
39
State the monomer of a protein.
amino acids
40
What are the components that make up an amino acid?
Central carbon + H atom + Amine group + Carboxyl group
41
Which part of the amino acid is variable? And how many different types are there?
R group - 20.
42
Name the bond formed between two amino acids.
Peptide bond.
43
What is the primary structure of a protein?
Amino acid sequence.
44
What is the secondary structure of a protein?
alpha-helix + beta-pleated sheets
45
What is the tertiary structure of a protein?
Folding into a 3D shape.
46
What is the quaternary structure of a protein?
Binding with other subunits.
47
What is the difference between primary and secondary structure of polypeptides?
Primary = sequence of amino acids.
Secondary = the shape in which the chain forms due to hydrogen bonds.
48
State the bond involved in the tertiary structure of a protein.
ionic, covalent, hydrogen, hydrophobic interactions, disulphide bridges.
49
Name the reaction that breaks down proteins.
hydrolysis
50
Name the three bonds that maintain the tertiary structure in a protein.
Hydrogen bonds, ionic bonds and disulphide bridges.
51
Why are enzymes described as catalysts?
They are not used up in the reaction.
52
What do we mean by the term "enzymes are specific"?
They only catalyse certain reactions due to the shape of their active site.
53
How do enzymes speed up reactions?
They lower the activation energy.
54
How do we describe the shape of an enzyme's active site?
It is 3D and complimentary to the substrate.
55
Describe the lock and key model.
An analogy for how enzymes work - only the correctly sized key (substrate) fits into the keyhole (active site) of the lock (enzyme) to form an ES complex.
56
What is the most up to date model used to describe enzyme action? Explain how it was changed.
The shape of the active site of an enzyme is not exactly complimentary to the substrate molecule like a key in a lock. When the substrate collides with the enzyme, the active site can change shape slightly to fit around the substrate and form an ES complex.
57
If a substrate successfully collides with an enzyme, what is said to have formed?
An enzyme substrate complex.
58
How are the monosaccharides in cellulose arranged?
Alternative β-glucose molecules are turned upside down
59
If an enzyme successfully collides with an enzyme, what is said to have formed?
An enzyme-substrate complex.
60
Why does increasing the temperature of a reaction increase the rate of reaction?
Temperature increases so does the rate of reaction because there is more kinetic energy so the molecules move faster increasing the number of collisions and therefore the number of ES complexes formed.
61
If you were to increase the concentration of substrate in a reaction, but the rate of reaction did not increase, what would you suggest is the limiting factor?
The Concentration of enzyme.
62
How can the pH affect the rate of an enzyme controlled reaction?
Above and below the optimum pH for each enzyme, the H+ ions and the OH- ions, disrupt the ionic and hydrogen bonds holding the enzymes tertiary structure in place. At extremes of pH the active site changes shape and no more ES complexes can be formed as the substrate no longer fits. The enzyme is permanently denatured, the reaction stops.
63
Describe competitive inhibition.
Competitive inhibitor molecules have a similar shape to the substrate of the enzyme meet inhibit. They compete with the substrate to bind to the active site of the enzyme. They block the active site so the substrate cannot bind, and no ES complexes are formed.
64
Where does a non-competitive inhibitor bind?
Site away from the active site known as the allosteric site.
65
What’s the difference between competitive and non-competitive inhibition?
Do not binds to the active site as have different shape of the substrate so do not compete. Find to site away from the active site so doesn’t block the enzyme. Course is the active site of the enzyme to change shape so it is no longer complimentary to the substrate. Not affected by increasing substrate concentration.
66
How can you tell if a inhibitor is competitive or non-competitive?
Change the concentration of the substrate end if the rate of reaction increases of substrate increases, then the inhibitor is competitive. If increasing the substrate concentration has little Effect on the rate of reaction it is Non-competitive.
67
Describe test for reducing sugar and state the positive result.
Add Benedict’s reagent, heat, positive result = turns from blue to orange-brown
68
What can be done if the test for reducing sugar produces a negative result of sugar should be present?
Take another sample, add HCL and heating the water bath, then add an NaOH to neutralise. Add Benedict’s and boil.
69
Why is the Benedict’s test known as a semi quantitive test?
Because it tells you how much sugar there is, but not exactly how much (i.e. it’s not quantitive).
70
How can we use a Colorimeter to do a quantitive Benedict’s test?
- Colorimeter measure the absorbance or transmission of light by a coloured solution.
- More concentrated Solution as more light, absorbed/less light transmitted.
- Compare to data table (Known concentration versus abs/trans value.
71
Describe the test and result for starch.
Add iodine solution. If starch is present, it will change from orange/brown to blue/black.
72
What is the solution used to test for the presence of proteins?
Biuret Solution
73
Describe the test and result for proteins
If the blue solution turns purple, then it’s a positive test
74
Describe the steps in identifying lipids and state the positive result.
- Mix sample with ethanol.
- Mix solution with water and shake
- White emulsion layer formed as lipid present
75
Name the four bases found in DNA, name the bonds that form between them.
- Adenine thymine, Guanine, Cytosine
- Hydrogen Bonds
76
Draw a nucleotide.
[answer](https://www.thesciencehive.co.uk/nucleic-acids-ocr)
77
Draw a polynucleotide. label the phosphodiester bond.
[answer](https://www.thesciencehive.co.uk/nucleic-acids-ocr) x 2 phosphodiester bond in the middle of the two nucleotides
78
Which molecules make up the backbone of a polynucleotide?
Phosphates and pentose sugars.
79
Describe the difference between bacterial DNA and eukaryotic DNA.
Bacterial DNA is short, circular and not associated with proteins. Eukaryotic DNA is long, linear and associated with proteins to form chromosomes.
80
What are the three differences between DNA and RNA?
Tea is replaced with a different base called yourself, the sugar is ribose, not deoxyribose. The nucleotide strand is a single strand, not double.
81
What does the hydrolysis of ATP produce?
ADP + Pi
82
Give the equation for the formation of ATP.
ADP + Pi -> ATP
83
What are the differences between ATP and a DNA nucleotide?
- DNA can also have guanine, thymine and cytosine but ATP always has adenine.
- DNA has deoxyribose sugar, but ATP has ribose sugar.
- ATP has three phosphate groups, but DNA only has one.
84
What type of reaction joins nucleotides?
Condensation.
85
What is semiconservative replication?
Half of the strands in each new DNA molecule are from the original DNA molecule.
86
Why is it known as semiconservative replication?
Because the original strand Is split into and half of each new strand comes from the original. Half is conserved.
87
What evidence do we have to prove there are two strands?
The Meselson and Stahl experiment.
88
What enzyme breaks the hydrogen bonds between the bases?
DNA Helicase.
89
What enzyme adds new nucleotides to the new strand?
DNA polymerase.
90
Why is one strand known as the template strand?
Because it acts as a template for new nucleotides to create a new strand with the correct complementary base pairing.
91
State the enzymes involved in DNA replication.
DNA Helicase, DNA polymerase.
92
Which enzyme separates the strands in DNA replication?
DNA Helicase.
93
State the role of DNA polymerase.
Joins nucleotides together in condensation reactions.
94
State the steps of DNA replication in order
1. DNA Helicase separates the two strands by breaking the hydrogen bonds between the bases.
2. Each strand acts as a template.
3. Free nuclear tides attached to template strand through complementary base pairing.
4. DNA, polymerase joins nucleotides by reforming hydrogen bonds between bases.
5. Replication of semiconservative as new DNA molecules contain one old strand and one new strand.
95
The free nuclear tides pair up with exposed bases on the DNA strands based on……(which principle)?
Complementary base pairing
96
Where does transcription occur in the cell?
In the nucleus.
97
Name the enzymes involved in transcription and explain what they do.
DNA Helicase - unwinds DNA section and exposes nucleotides.
RNA polymerase - adds complimentary RNA nucleotides to form pre-mRNA
98
What happens when the RNA polymerase attaches to the DNA at the start codon?
The hydrogen bonds between the DNA strands break separating the strands and the DNA molecule unwinds.
99
What happens when RNA polymerase reaches a stop codon?
It stops making mRNA and attaches from the DNA.
100
What is pre-mRNA?
MRNA that contains introns and exons - before it has been spliced.
101
What happens during mRNA splicing?
Introns are removed and exons are joined and possibly rearranged, to Form mRNA.
102
Why does pre-mRNA need to be spliced?
To remove introns (non coding sections).
103
Even though DNA codes for proteins directly, why is mRNA needed to be made for making proteins?
Because DNA is too large to move out of the nucleus, so a section is copied onto mRNA.
104
Define proteome
The full range of proteins that a cell is able to produce.
105
What is a ribosome made of?
Proteins, RNA (NO MEMBRANE)
106
What is a protein made of?
A polymer of amino acids.
107
What is a codon?
Triplet of bases that codes for an amino acid.
108
What does it mean by non-overlapping?
Each codon is read in sequence, separate from the code on before and after it. Codons do not share bases.
109
Explain the term ‘degenerate’?
There are more possible combinations of codons than there are amino acids. Some amino acids are coded for by more than one codon.
110
What is the product of translation?
A polypeptide chain.
111
Where does translation take place?
The ribosomes in cytoplasm or RER.
112
What is tRNA?
Found in cytoplasm, has an amino binding site at one end and an anticodon on the other end, carries amino acids that are used to make proteins to the ribosomes.
113
Describe the structure of tRNA.
tRNA is folded, has hydrogen bonds holding the structure together, is a fixed site, has an anticodon, has an amino acid binding site.
114
What is an anticodon?
Triplet of bases on tRNA which is complementary to binding site on mRNA.
115
Which part of tRNA bonds to the mRNA?
the anticodon binding site/loop.
116
What are the stop and start codons for?
Triplets that tell the cell when to start and stop production of the protein. Found at the beginning and end of the gene.
117
What is a mutation?
Change in the base sequence of DNA.
118
How can a gene mutation result in a protein not being synthesised properly?
Mutation changes sequence of bases so that it no longer codes for the same protein sequence.
