Higher Human Biology Flashcards
1
Q
Are somatic cells haploid or diploid?
A
Non-sex cells that have two sets of chromosomes, so somatic cells are diploid cells.
2
Q
What is differentiation?
A
The process which results in cells becoming specialises (they have their own specific structure and function)
3
Q
What do somatic cells do?
A
Divide by mitosis to form more somatic cells.
4
Q
What are epithelial cells?
A
These cells cover the body surface and line body cavities like the bladder and windpipe etc.
5
Q
What is a connective cell?
A
A connective cell includes bone, cartilage, muscle and nerve cells. These cells form tissues and the body organs are formed from a variety of these tissues.
6
Q
What happens during cell division?
A
During cell division the nucleus of a somatic cell divides by mitosis to maintain the diploid chromosome number.
7
Q
What do human diploid cells have?
A
Human diploid cells have 23 pairs of homologous chromosomes.
8
Q
What are germline cells?
A
Germline cells are diploid cells that can divide to form gametes.
9
Q
What can the nucleus of a germline cell divide by?
A
MITSOSIS - to produce more diploid germline cells.
Or
MEIOSIS - to produce haploid gametes.
10
Q
What are the two different types of stem cells?
A
• Embryonic stem cells
• Adult (or tissue) stem cells
11
Q
What does a multipotent and a pluripotent stem cell mean?
A
MULTIPOTENT- cells do growth and repair
PLURIPOTENT- can become any cell type
12
Q
What is a stem cell?
A
Stem cells are relatively unspecialised cells that can continue to divide and can differentiate into specialised cells of one or more cell types.
13
Q
What can embryonic stem cells do?
A
Embryonic stem cells can differentiate into any type of human cell and this because most of their genes are still switched on (or expressed).
14
Q
What can adult stem cells do?
A
Adult stem cells replenish differentiated cells that need to be replaced and they can only produce a limited range of cell types.
15
Q
What do adult stem cells differentiate into?
A
Different types of blood cells like red blood cells, platelets and lymphocytes.
16
Q
What happens once a cell differentiates?
A
Once a fell differentiates, it can only express the genes that produce the proteins that in turn makes cells different.
17
Q
what does stem cell research provide?
A
Stem dell research provides information on how cell processes such as cell growth, differentiation and gene regulation work and stem cells can also be used as model cells to see how diseases develop and for drug testing.
18
Q
What are examples of therapeutic uses of stem cells?
A
Therapeutic uses of stem cells include:
• bone marrow transplants
• skin grafts (for burns)
• repair of damaged or diseased organs (or tissues).
19
Q
What is the ethical issue with stem cell use?
A
Since one source of stem cells is embryonic tissue, their use can be controversial. The current Uk Law states that embryonic cells cannot be allowed to develop beyond 14 days ( the time an embryo would implant to the uterus).
20
Q
What have ethical concerns of stem cell use led to?
A
Ethical concerns have led to regulations on the use of embryonic stem cells.
21
Q
What happens to cancer cells?
A
Cancer cells do not respond to signals that regulate them which causes these cells to divide excessively to produce a mass of abnormal cells (a tumour).
22
Q
What is a tumour?
A
A mass of abnormal cells.
23
Q
What happens if cancer cells fail to attach to each other?
A
If cancer cells fail to attach to each other, they can spread throughout the body where they form secondary tumours.
24
Q
What is DNA?
A
DNA is an example of a nucleic acid.
25
What are nucleic acids like DNA made from?
Nucleic acids like DNA are made from repeating units called nucleotides.
26
What makes the nucleotides different from one another?
It is only the bases which make one nucleotide different from another.
27
How many nucleotides are in the DNA?
Since there is only 4 different bases, there can only be four different nucleotides in DNA.
28
What do nucleotides join together to form?
Nucleotides join to form a sugar-phosphate backbone.
29
What are bases held together by?
The bases pair off and are joined by weak hydrogen bonds.
30
What does anti-parallel mean?
The two strands of DNA run in opposite directions which means they are anti-parallel.
31
What ways do the DNA strands run?
Deoxyribose is at 3’ end and phosphate is at the 5’ end of each strand. ( one strand runs in 3’ to 5’ direction and the other runs in 5’ to 3’ direction).
32
What type of DNA do chromosomes consist of?
Chromosomes consist of DNA that is tightly coiled around histone proteins.
33
Why is DNA tightly coiled around histone proteins?
This is so that all 2 metres of it can fit into the nucleus of a cell.
34
What is DNA replication?
Before cells divide, an exact copy of the DNA must be made and this process s called DNA replication.
35
Why is DNA replication important?
it ensures that each new cell receives a full set of chromosomes and therefore no genetic information will have been lost.
36
What are the enzymes involved in DNA replication?
The two enzymes involved in DNA replication are:
• DNA polymerase
• ligase
37
When does DNA replication begin?
DNA replication begins when DNA is unwound and unzipped from two single template strands.
38
What does DNA polymerase use to start DNA replication?
DNA polymerase needs a primer to start DNA replication.
39
What can DNA polymerase only add to DNA?
DNA polymerase can only add free complementary DNA nucleotides to the deoxyribose 3’ end to a DNA strand.
40
What does DNA polymerase only being able to add complementary nucleotides result in?
This results in one of the strands of DNA being repeated continuously.
41
What is the leading strand?
The strand of DNA which is being replicated continuously.
42
What happens to the lagging strand?
The leggings strand is replicated in fragments and these fragments are then joined together by the enzyme ligase.
43
What does ligase join?
Ligase joins replicated fragments form the lagging strand of DNA and ligase also joins single nucleotides together in the continuous leading strand.
44
What is mRNA?
mRNA is a messenger molecule which carries the genetic code from DNA in the nucleus to a ribosome.
45
What is rRNA?
rRNA is a ribosomal RNA that forms the ribosome along with proteins.
46
What is tRNA?
tRNA is transfer RNA and each tRNA carries a specific amino acid to a ribosome.
47
Where does transcription happen?
Nucleus
48
What are all three types of RNA made of?
Nucleotides
49
What is a nucleotide made of?
Phosphate - ribose sugar - base
50
What is the difference between DNA and mRNA?
• DNA has deoxyribose sugar and mRNA has ribose sugar
• DNA has base thymine and mRNA has base uracil
• DNA is double stranded and mRNA is single stranded
51
What does RNA polymerase do during transcription?
RNA polymerase moves along the DNA unwinding s section of the double helix and synthesises a primary transcript of mRNA by complementary base pairing.
52
What do genes have?
Genes have introns and exons
53
What are introns and exons?
Introns are the non coding region of a gene;
Exons are the coding region of the gene.
54
What is RNA splicing?
During transcription the introns in the primary transcript are removed and this process is called RNA splicing.
55
What happens to the exons after RNA splicing?
The exons are then joined together to form the mature transcript mRNA.
56
What makes transcription take place?
RNA polymerase.
57
What does mRNA hold?
mRNA holds the genetic code which provides the recipe to make a protein e.g. haemoglobin, insulin etc.
58
What do three bases in a row (codon) code for?
There bases in a row on the mRNA strand “code” for one specific amino acid.
59
What is a codon?
A codon is a triplet of bases on an mRNA strand.
60
What is the genetic code called?
The genetic code is called a triplet code.
61
Why are different mRNA molecules produced from the same primary transcript?
Different mRNA molecules are produced from the same primary transcript and this is due to the fact that during RNA splicing, exons are sometimes removed along with the introns next to them.
62
What is alternative RNA splicing?
alternative RNA splicing is when exons are removed along with introns next to them.
63
Where are introns always removed from?
All the introns are always removed from the primary RNA transcript.
64
What does alternative RNA splicing mean?
This means that the same primary mRNA transcript has the potential to produce several different mRNA molecules.
65
What does each mRNA molecule have?
Each mRNA molecule will have a different sequence of base triplets and each mRNA molecule will code for a different polypeptide/protein.
66
What can one gene code for?
One gene can code for several different proteins.
67
What does gene coding depend on?
This depends on which exons have been discarded during RNA splicing.
68
What does bae pairing in tRNA cause?
base pairing causes tRNA to fold
69
What does tRNA have at each end?
Af one end tRNA molecule is an anticodon and at the opposite end is an amino acid which the tRNA molecule is responsible for carrying to a ribosome .
70
What does an anticodon determine?
The anticodon determines the sequence of amino acid that each tRNA molecule will pick up and then carry to a ribosome.
71
What is mRNA translated into?
mRNA is translated into a polypeptide chain at a ribosome.
72
What must ribosome bind to?
Ribosome must bind to one end of the mRNA strand.
73
What is a start codon?
A start codon is the first three bases on the mRNA strand.
74
What is a stop codon?
The stop codon is when the final codon in the mRNA is reached and the ribosome releases the newly synthesised polypeptide chain.
75
What does translation require?
this Provences required energy which is provided by ATP
76
What does the sequence do codons determine?
The sequence of the codons on the mRNA strand will determine the sequence of the amino acids in the polypeptide that will be synthesised.
77
What are anticodons on the tRNA complementary to?
The anticodons on the tRNA are complementary to the mRNA strand.
78
What happens after a peptide bond is formed?
After a peptide bond has formed between two adjacent amino acids, the tRNA molecule is released from the amino acid.
79
Where does the tRNA leave the ribosome to do?
The tRNA molecule is released from the amino acid and it then leaves the ribosome to go and pick up another one of its specific amino acid present in the cytoplasm.
80
What happens after translation?
After translation, the structure of the protein is modified.
81
How is a protein modified?
This is done through the cutting and joining of polypeptide chains or by the addition of a carbohydrate or a phosphate group to the final protein molecule.
82
Where does translation happen?
Ribosome
83
What are the similarities of mRNA and tRNA?
Both tRNA and mRNA contain bases Adenine, Uracil, Guanine, Cytosine.
84
What are the differences between mRNA and tRNA?
• tRNA is folded and mRNA is not;
• tRNA has base pairing,mRNA doesnt;
• mRNA is single-stranded and tRNA is double stranded.
85
What is gene expression?
Whether a gene is “switched on” or “switched off”
86
What is gene expression controlled by?
Gene expression is controlled by regulating the processes of transcription and translation.
87
What is mRNA transcribed from?
mRNA is transcribed form DNA in the nucleus and then it is translated into a protein by ribosomes in the cytoplasm.
88
What is an organisms function determined by?
An organisms function is determine by the proteins produced as a result of genes being expressed (switched on).
89
How many genes are expressed in each cell?
Only a fraction of the genes in any one cell are actually expressed.
90
What are expressed genes influenced by?
The genes that are expressed are influenced by intra and extra-cellular environmental factors.
91
What does proteins have a large variety of structures and shapes result in?
This results in them having a wide range of functions.
92
What are amino acids linked to?
Amino acids are linked by peptide bonds to form a polypeptide chain.
93
What happens to polypeptide chains?
Polypeptide chains fold to form a particular 3 dimensional shape.
94
What are polypeptide chains held together by?
These chains are held together by peptide bonds, hydrogen bonds and other interactions that form between different amino acids.
95
What is an example of a start codon?
AUG
96
what are examples of stop codons?
mRNA codons UAA, UAG and UGA are all stop codons.
97
What are you altering when you alter DNA?
If you alter DNA you are altering the protein.
98
What is a mutation?
changes to genes or chromosomes
99
What do mutations result in?
Mutations result in proteins either not being synthesised at all or proteins which are synthesised not functioning properly.
100
Why do single gene mutations happen?
Single gene mutations happen when the sequence/order of bases (nucleotides) in the DNA that a gene is made of is altered.
101
What are three different types of single gene mutations?
• substitution
• insertion
• deletion
Of DNA bases/nucleotides
102
What are three examples of diseases/conditions that are caused by a single gene mutation?
• Duchenne muscular dystrophy
• cystic fibrosis
• PKU
103
What can mutations result in?
• no protein
• altered protein that still functions
• affects a few bases - single gene mutations causes a change to a single nucleotide.
104
Can you develop diseases caused by mutations?
These are not diseases that can develop, people are born with them because they have inherited a mutated gene from one or both of their parents.
105
What do single base/nucleotide substitution mutations include?
• missense
• nonsense
• splice-site.
106
What is missense?
Missense is where one amino acid codon is replaced with another different amino acid codon.
107
What is an example of substitution mutation?
CUG is replaced by the amino acid CHG which results in only one amino acid in the sequence being changed.
108
What is a nonsense mutation?
A nonsense mutation is when one amino acid codon is replaced with a premature stop codon. The effect of this type of mutation is to bring the process of translation and transcription to a premature stop and the polypeptide chain will be shorter than it should be.
109
What type of mutation causes duchenne muscular dystrophy?
Nonsense mutation
110
What is controlled at the splice-site?
RNA splicing is controlled by specific base/nucleotide sequences found at a splice site on the primary RNA transcript where introns flask exons.
111
What happens if a mutation occurs in the RNA transcript?
If a mutation occurs in an intron in the primary transcript it will not be removed and instead it will be retained in error and so will end up in the mature RNA transcript which results in the production of a protein that doesn’t function properly.
112
What does insertion and deletion mutations result in?
Insertion and deletion mutations result in frameshift mutations.
113
What is mRNA read as during translation?
mRNA is read as a series of codon (triolets) during translation.
114
What happens if a base/nucleotide is inserted or deleted from a gene(DNA)?
If a base/nucleotide is inserted or deleted from a gene every codon after where the mutation has occurred will be altered during transcription.
115
What does codons being altered result in?
This results in every amino acid being altered after the mutation site.
116
What happens to the protein formed form alteration of amino acids?
The protein formed is almost certain to be non-functional (the protein will not work).
117
What will a protein being produced and not working result in?
This will result in a protein being synthesised that is almost certain to be non-functional.
118
What can gene mutations affect?
These gene mutations can affect the phenotype of individuals as they can result in conditions such as Tay-Sachs syndrome.
119
When does a chromosome mutation occur?
A chromosome mutation occurs when the structure of a chromosome is altered.
120
What are the three main types of chromosome mutation?
• deletion
• duplication
• translocation
• inversion
121
What is a deletion mutation?
Deletion is the loss of a segment of a chromosome.
122
What is a duplication mutation?
Duplication is the repetition of a segment of a chromosome.
123
What is a translocation mutation?
A translocation when a section of one chromosome breaks off and becomes attached to another chromosome that is not it’s homologous partner.
124
What do substantial changes in chromosome structure result in?
substantial changes in chromosome structure often result in these mutations being lethal.
125
What is inversion?
Inversion is when a section of chromosome is reversed.
126
What has made it possible to determine the sequence of bases for individual genes?
Advances in faster and cheaper computer processing has made it possible to determine the sequence of DNA bases for individual genes and entire genomes.
127
What is a genome?
A genome is a complete DNA of an organism.
128
What is bioinformatics?
Bioinformatics is when computers are used to analyse the sequence of bases in DNA and sequence of amino acids in proteins.
129
What is personalised medicine based on?
Personalised medication is based on an individual’s genome.
130
What can lead to personalised medication?
By understanding the link between a persons genes and certain diseases could lead to personalised medication.
131
What is an example of understanding the link between a persons genes and certain diseases?
It may be that Ma individuals carrying a particular allele of a gene have an increased risk of developing a particular gene like breast cancer.
132
What happens after the link between a persons genes and certain diseases is known?
A patients medicines will be specifically geared to them resulting in increased drug efficiency whilst reducing side effects.
133
What does human genomics mean for the future?
This means that in the future the “one size fits it all” approach would be recognised as history.
134
What is PCR/sequencing DNA?
Many copies of a specific segment of DNA can be produced using a technique called polymerase chain reaction (PCR).
135
Where is the copying of DNA segment done?
The copying/amplification of this DNA segment is done in vitro (outside the body).
136
What must be present to amplify DNA?
1. Many of the four free nucleotides of DNA
2. Primers
3. DNA polymerase
137
What is a primer?
These are complementary to a specific target sequence of bases at the two ends of the region of DNA that is to be amplified.
138
What is DNA polymerase?
This is a heat-tolerant enzyme which synthesises two complementary strands of DNA by joining the free DNA nucleotides together.
139
What are the stages of PCR?
1) DNA is firstly heated in order to seperate or split the two strands by breaking the hydrogen bonds between the complementary bases and this is called denaturing.
2) the DNA is then cooled which allows the primers to bind to the complementary target sequences which is called annealing.
3) Heat-tolerant DNA polymerase replicates the DNA by joining free DNA nucleotides together using the primer as a starting point.
140
What temperatures to each stages of PCR happen at?
Stage 1 : 92-98 degrees Celsius
Stage 2: 50-65 degrees Celsius
Stage 3: 70-80 degrees Celsius
141
What are repeated cycles used for?
Repeated cycles of heating and cooling are used to amplify this section of DNA.
142
How many cycles does it take to produce 64 molecules of DNA from one DNA double helix.
It would take 6 cycles to produce 64 molecules of DNA from one DNA double helix.
143
What happens after 21 cycles?
After only 21 cycles, one molecule of DNA can be amplified to produce over a million copies!
144
What is amplification?
One molecule of DNA can be amplified to produce over a million copies.
145
What are uses of PCR?
• helps solve crimes
• settles paternity suits
• diagnose genetic disorders
146
What does PCR require?
• DNA nucleotides
• DNA polymerase
• a primer
147
What do DNA probes do?
DNA probes are used to detect the presence of specific DNA base sequences in a samples of DNA this is called DNA sequencing/profiling.
148
What is a DNA probe?
A DNA probe is a short single-stranded man-made fragment of that is complementary to the specific sequence of DNA bases that are being tested for.
149
What happens if the target sequence is present on the DNA probe?
If the target sequence is present, the probe will bind to it via complementary base pairing and the probe can then be detected.
150
What is a DNA probe detected by?
The DNA probe can be detected by fluorescent or radioactive label.
151
What are DNA probes used for?
DNA probes can be used to determine the father/parent of a child or for solving crimes.
152
What can DNA probes be used on?
Many different DMA probes can be used on a microarray (1000s) of genes to give a fuller DNA profile.
153
What are the stages of a DNA probe?
1) DNA is cut into fragments of varying lengths
2) the fragments are separate according to their length.
3) a probe with a known base sequence is added. If it is complementary to a base sequence on a fragment via complementary base pairing.
4) if there is a match, it shows up.
154
What is the result of screening a cell sample from a patient?
By screening a cell sample from a patient for the presence or absence of a particular nucleotide/base sequence (called DNA profiling) a diagnosis of a disease can be made of how at risk they might be of getting a disease or passing a disease onto their children can be worked out.
155
What does DNA profiling allow?
DNA profiling allows the identification of individuals through comparison of regions of the genome highly variable numbers of repetitive sequences of DNA.
156
Where are the variable number of repetitive sequence in DNA located?
Highly variable number of repetitive sequences of DNA are located on chromosomes.
157
What is an example of a repeated sequence of DNA bases?
Two homologous chromosomes each have a different number of the same repeated sequences of bases.
158
What are repetitive sequences of DNA useful for?
These repeated sequences of DNA have been useful for forensic crime investigations as the possibility of two people having the same number of these repeated sequences is extremely low.
159
Hat are the numbers of repeated sequences of DNA like?
The number of repeated sequences even between homologous chromosomes are usually different.
160
What happens ik since these repetitive sequences are part of a chromosome?
Since these repetitive sequences are a part of a chromosome they are inherited from both parents.
161
What can family relationships be confirmed by?
Family relationships can be confirmed by the number of repetitive sequences that they share.
162
What is cell metabolism
Metabolism is all the enzyme controlled reactions that occur in a cell at the same time
163
What do enzyme controlled reactions and cell metabolism involve?
These reactions involve pathways for one compound is converted into a different compound
164
What can happen to compounds?
Compounds can either be broken down (catabolism) or synthesised (anabolism).
165
What do anabolic and catabolic reactions require or release?
Anabolic reactions require an input of energy; catabolic reactions, usually release energy
166
What is an example of catabolism?
Aerobic respiration is an example of catabolism which releases energy. This energy can then be used for the synthesis of proteins from amino acids, which is an example of anabolism.
167
When are metabolic, pathways, reversible or irreversible?
1. Pyruvate to lactic acid in animal cells is reversible
2. Pyruvate to ethanol and CO2 in plant/yeast cells, is irreversible
168
What are metabolic pathways control by?
1. By the presence or absence of particular enzymes in the metabolic pathway, and through the regulation of the rate (speeds) of reaction of key enzymes within the pathway (regulation can be controlled by intracellular or extra cellular regulatory molecules).
169
Why are enzymes specific?
Enzymes are specific because they only react with one substrate
170
I what does a basic mechanism by which enzymes catalyse reactions begin with?
The basic mechanism by which enzymes catalyse reactions begin with the binding of the substrate
171
Why does The active site have a unique shape?
The Active site has a unique shape that is complementary to the shape of the substrate molecule.
172
What happens when the enzyme and substrate form a complex?
Structural changes occur so that the active site fits precisely around the substrate and the substrate causes the active site to change shape.
173
How do enzymes speed up reactions?
Enzymes speed up reactions by orientating then holding the reactants close together and by reducing the activation energy required for the reaction to occur.
174
What do the end products of enzyme reactions have?
The end products of the reaction have a lower affinity for the enzyme than the substrate and are therefore released from the active site
175
What can the direction and speed of an enzyme-controlled reaction be affected by?
The direction and speed of an enzyme controlled reaction can be affected by the concentration of both the substrate and end product.
176
What are most metabolic reactions?
Most metabolic reactions are reversible and the presence of a substrate or the removal of a product will drive a sequence of reactions in a particular direction.
177
Where do enzymes often act?
Enzymes often act in groups, where the product of one reaction becomes substrate for the next
178
What happens when enzymes act as multienzyme complexes or as demonstrated by pyruvate dehydrogenase?
Multi-enzyme complexes where are number of enzymes work together at the same time on the same substrate molecule (S), as demonstrated by pyruvate dehydrogenase, where does a complex of three different enzymes that collectively catalyse the breakdown of pyruvate at the end of glycolysis?
179
What jeans are continuously expressed or switched on?
The genes are responsible for the production of some enzymes are continuously expressed (“switched on “); these enzymes are therefore always present in the cell.
180
How is the control of enzyme activity achieved?
The control of enzymes activity is achieved via regulating the rate of reaction that they catalyse
181
What is an enzyme inhibitor and how does it carry out what it does?
Is an enzyme inhibitor is a molecule that can affect the rate of reaction; it does this by either changing the active site of an enzyme or by joining the enzyme.
182
What is three ways can the control of metabolic pathways be achieved?
1. Competitive inhibition.
2. None – competitive, inhibition or stimulation.
3. Feedback inhibition
183
When does competitive inhibition occur?
This type of inhibition occurs with a molecule that resembles the shape of the substrate competes with the substrate for the active site.
184
Can competitive inhibition be reversed?
This can be reversed, and therefore the rate of reaction can be increased by increasing the concentration of the substrate molecules.
185
What happens with a competitive inhibitor is present?
When a competitive inhibitor is present, the rate of reaction is slower, compared to a reaction when no inhibitor is present.
186
How can you tell from a graph if an inhibitor is competitive or non-competitive?
With a competitive inhibitor when the substrate concentration is increase, the rate of the reaction increases, this does not happen with a non-– competitive inhibitor
187
What happens when the graph levels off?
When a graph level is off some factor other than substrate, concentration must be limiting the rate of the reaction for example, temperature, pH, enzyme concentration
188
What are noncompetitive inhibition do?
These molecules affect the activity of an enzyme by changing the shape of the enzymes active site.
189
What does noncompetitive inhibition prevent?
This prevents the binding of the substrate and can either inhibit or stimulate enzyme activity
190
Where is the non-competitive inhibition molecules bind to?
This type of molecule binds to a part of the enzyme molecule away from the active site
191
What happens when an activator binds the enzyme?
One type of molecule when it goes to the enzyme, stabilises the active form of the enzyme, and this increases the rate of the reaction
192
What happens when an inhibitor binds to an enzyme?
When a different type of molecule called an inhibitor binds to the enzyme stabilises, the inactive form of the enzyme, and this inhibits the rate of the reaction
193
When does feedback inhibition occur?
This occurs when the end product of a metabolic pathway binds to the first enzyme involved in the pathway, which reduces the enzymes activity
194
What does feedback inhibition do?
This slows down the metabolic pathway by preventing the production of more of the end product until its concentration falls, and the inhibition is removed
195
What does cellular respiration involve?
respiration involves a series of energy controlled metabolic steps, which releases the chemical energy in food
196
What does some of the energy from respiration go to?
Some of us energy from food ends up being transferred to a high energy compound called ATP
197
How is ATP made?
ATP is made by joining ADP with a single inorganic phosphate (Pi) molecule; to join us to molecules together, requires energy, this energy comes from glucose
198
What happens when cells require an immediate source of energy?
When cells require an immediate source of energy, the high energy bonds between the last two phosphate molecule breaks and energy is released from cellular processes.
199
What are examples of cellular processes?
Cellular processes include:
• muscle contraction
• active transport
• mitosis/meiosis (to separate the chromosomes)
• DNA replication
• protein synthesis
200
What does cells need?
Cells need a constant supply of ATP, so it is regenerated as quickly as it is broken down
201
What is the importance of ATP?
The importance of ATP to cells is that it transfers chemical energy by acting as a link between aerobic respiration and other cellular processes which require ATP to drive them E.g. protein synthesis.
202
When does phosphorylation occur?
Phosphorylation occurs when a phosphate group (supplied by the breakdown of ATP) is joined to a molecule.
203
What does the addition of a phosphate group do?
The addition of a phosphate group alters the reactivity of the molecule to which it has been added.
204
What does a cell use to synthesise a bulk of its ATP?
To synthesise the bulk of its ATP a cell uses a source of high energy electrons to pump hydrogen ions across the inner membrane of a mitochondrion along a concentration gradient.
205
What does phosphorylation help?
This helps to maintain a higher concentration of hydrogen ions on one side of the membrane.
206
What does the return flow of hydrogen ions do?
The return flow of these hydrogen ions (by diffusion) rotates part of an inner membrane protein which is called ATP synthase.
207
What is ATP synthase?
ATP synthase is an enzyme and it’s involved in the synthesis of ATP from ADP and Pi.
208
What is the point of respiration ?
The whole point of respiration is to break down glucose in a series of enzyme-controlled steps during which hydrogen and high energy electrons are removed from the original glucose molecules and then used to produce ATP.
209
What can respiration be divided into?
Respiration can be divided into 3 seperate but continuous processes:
• glycolysis
• the citric acid cycle
• the electron transport chain
210
Where does glycolysis take place and is oxygen required?
Glycolysis takes place in the cytoplasm and no oxygen is needed for glycolysis to occur.
211
What is glycolysis?
Glycolysis is a chain of enzyme controlled steps where glucose is broken down into pyruvate.
212
What are the 2 enzyme-controlled phases?
Phase 1 : investment phase
Phase 2 : Pay off phase
213
What happens in the energy investment phase?
2 ATP molecules are used up per molecule of glucose, this is because two intermediate compounds in the pathway are generated (i.e. a phosphate (Pi) from the breakdown of ATP is added to these compounds).
214
In the investment phase, what does the first phosphorylations lead to a product that can continue to a number of pathways.
215
What does the second phosphorylation lead to?
The second phosphorylation which is catalysed by an enzyme called phosphofructokinase is an irreversible reaction as the resulting compound only leads to the final stage of the glycolytic pathway.
216
What happens in the pay off phase of glycolysis?
4 molecules of ATP are produced per molecule of glucose, during this phase an enzyme called dehydrogenase releases hydrogen ions from some of the compounds in this part of the pathway. These hydrogen ions are picked up by a carrier molecule called NAD+ which in turn becomes NADH.
217
What does ATP synthase do?
ATP synthase regenerates molecules of ATP
218
What is the net gain of ATP during glycolysis?
Because 4 ATP are produced in the energy investment phase and 2 ATP are used in energy pay-off phase, there is a net gain of 2 ATP.
219
Where does the citric acid cycle happen?
Matrix of mitochondrion
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What happens in the citric acid cycle?
If oxygen is present, puruvate is broken down into carbon dioxide and an acetylene group. The carbon dioxide or released. The acetyl group then combines with coenzyme A temporarily forming acetyl coenzyme A.
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What does coenzyme A join with in the citric acid cycle?
Coenzyme A joins with the acetyl group in the citric acid cycle to from citrate.
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What is citrate regenerated back to in the citric acid cycle?
Citrate is regenerated back to oxaloacetate on a series of enzyme-controlled steps during the citric acid cycle. During these steps, carbon dioxide is also released.
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What also happens during the citric acid cycle?
Also during the citric acid cycle, hydrogen ions and high energy electrons are removed from compounds by dehydrogenase enzymes.
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What happens to the hydrogen ions and hog energy electrons during the citric acid cycle?
These hydrogen ions and high energy electrons are then passed to the other coenzymes called NAD forming NADH. The coenzymes carry these hydrogen ions to the electric transport chain.
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Where does the electric transport chain happen?
Cristal of the mitochondrion
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What happens during the electron transport chain?
Folds are attached to the inner membrane of mitochondrion.
