Division & Differentiation In Human Cells Flashcards
1
Q
What happens rather than each cell carrying out every function?
A
A DIVISION OF LABOUR in multicellular organism and cells become differentiated
2
Q
What is differentiation?
A
Differentiation is the process by which a cell develops more specialised functions by expressing the genes characteristic for that type of cell
3
Q
All the genes at the embryonic stage are either ______ or have the _____ to be ______
A
Switched on
Potential
Switched on
4
Q
How do specialised cells arise?
A
From the differentiation of unspecialised cells during embryonic development
5
Q
Once a cell becomes differentiated…
A
It only expresses the genes that code for specific proteins
Eg nerve cell - genes for neurotransmitters switched on/ genes for mucus production switched off
6
Q
What are somatic cells?
A
Body cells
Any differentiated cell (except reproductive cells)
7
Q
What does DNA do during mitosis and what does it produce?
A
DNA replicated and the cells divide during mitosis to produce two identical daughter cells with the full chromosome complement
8
Q
Where are germline cells found?
A
In sex organs
9
Q
What do germline cells do?
A
Lead to the formation of gametes
10
Q
What process do germline cells go through to produce haploid gametes?
A
Meiosis
11
Q
Describe the process of meiosis
A
- 1st division - separating homologous pairs
- 2nd division - separating chromatids
Genetic material is divided between 4 nuclei and each receives a single set of 23 chromosomes
12
Q
What are stem cells?
A
Stem cells are unspecialised (undifferentiated) cells that can:
- reproduce (self renew) themselves by repeated mitosis and cell division while remaining undifferentiated
- then differentiate into a diverse range of specialists cells when required to do so
13
Q
What is a blastocyst?
A
An early embryo consisting of a ball of embryonic stem cells
14
Q
All of the genes in an embryonic stem cell are _______
A
Switched on
15
Q
How many cell types are there in the body?
A
> 200
16
Q
How many cell types can embryonic stem cells differentiate into?
A
They are pluripotent which means they can turn into any cell type
17
Q
Where are tissue stem cells found? Include examples
A
Tissue stem cells are found in small numbers in the tissues and organs of adults and children including the brain, bone marrow, skeletal muscle, and skin
18
Q
What are tissue stem cells involved in?
A
The growth, repair, and renewal of the cells found in that tissue
19
Q
How many types of cells can tissue stem cells differentiate into?
A
A much more limited range of specialised cell types.
20
Q
Why can tissue stem cells only differentiate into a limited range of specialised cell types?
A
Because many of their genes are already switched off
21
Q
Cell types that tissue stem cells can differentiate into and their origin tissue
A
- Epithelial - cheek cells
- Connective - blood, bone, cartilage
- Muscle - Skeletal, cardiac or smooth
- Nerve - sensory or motor nerves
22
Q
What is a model organism?
A
One that is suitable for laboratory research because it’s biological characteristic are similar to those of a group of related (but often unavailable) organisms eg mice used for research into human conditions
23
Q
Stem cells can be used in research as model cells to investigate:
A
- The means by which certain diseases and disorders develop
* the responses of cells to new pharmaceutical drugs
24
Q
Therapeutic uses of stem cells?
A
- In the treatment of diseases eg leukaemia (bone marrow transplant) and heart disease
- In medicine, including skin grafts for burns and stem cells grafts for cornea repair
25
What does the regulation of stem cells ensure?
This ensures that the quality of the stem cells used and the safety of the procedures carried out are of the highest order and that abuses of the system are prevented
26
What is a cancer?
An uncontrolled growth of cells
27
Cancerous cells do not respond to ______ ______ that normally control cell division
Regulatory signals
28
Cancer cells ______ __________ to produce a mass of abnormal cells called a _____
Divide uncontrollably
Tumour
29
What is a tumour?
A mass of abnormal cells
30
When is a tumour described as benign?
If it remains as a discrete growth of abnormal cells in one place, within an otherwise normal tissue
31
When is a tumour said to be malignant?
If it invades nearby tissues.
Some of its cells can lose the surface molecules that keep them attached to the original cell group.
These can enter the circulatory system and spread through the body.
32
Where do most cancers originate from?
From a cell that has undergone a succession of mutations to the genes involved in the control of cell division
33
How is the risk of mutation increased?
By exposure to agents that cause genetic damage such as smoking, pollution and excessive exposure to of skin to ultraviolet radiation
34
Why is cancer particularly common in skin, lung and bowel tissue?
As theses cells have a high frequency of division so the mutation rate is higher than normal
35
What tissues are more likely to have cancerous mutations?
Skin
Lung
Bowel
36
What does a molecule of DNA consist of?
Two strands of repeating units called nucleotides
37
What is a nucleotide made up of?
- a deoxyribose sugar
- a phosphate group
- a base
38
What type of sugar is on a nucleotide?
Deoxyribose sugar
39
What type of bond forms between the phosphate group of one nucleotide and the carbon (3) of the deoxyribose sugar on another nucleotide forming a sugar phosphate backbone?
Strong peptide bond/ strong chemical bond
40
Name the nucleotide bases
Adenine
Guanine
Cytosine
Thymine
41
What nucleotide bases pair together?
Adenine bonds with Thymine
Cytosine bonds with Guanine
42
How are the two strands of nucleotides joined together?
Weak hydrogen bonds
43
Why is DNA described as being anti-parallel?
Because the 2 sugar phosphate backbones rum in opposite directions
44
Where is the 5’ end of a DNA molecule?
On a phosphate group
45
Where is the 3’ end of a DNA molecule?
On a deoxyribose sugar
46
Which end do DNA nucleotides add on to?
The 3’ end
47
Why is DNA a unique molecule?
Because it is able to direct its own replication and ensures an exact copy of genetic information is passed from cell to cell during growth and from generation to generation during reproduction
48
What does semi-conservative mean?
This means that each raw strand of DNA is composed of one original strand and one new strand
49
When does DNA replication begin?
When a starting point on DNA is recognised
50
Describe the formation of the leading DNA strand
1) The enzyme DNA Helicase unwinds - separates the two strands by breaking the weak hydrogen bond between base pairs (‘unzips’)
2) These template strands became stabilised and expresses the bases at a Y-shaped replication ark
3) A short sequence of nucleotides known as a primer bond at the ‘3’ end of the template flow strand
4) Once nucleotides have aligned with complementary base pairs, replication of leading strand begins. The enzyme DNA polymerase adds nucleotides to the ‘3’ end in one direction.
The leading strand is synthesised as a single strand (continuously) from the point of origin towards the opening replication ark
51
Describe the formation of the lagging DNA strand
DNA polymerase is only able to add nucleotides to the ‘3’ end of a growing strand.
The DNA parental template strand that has the 5’ end has to be replicated in fragments, each starting at the 3’ end of a primer
Each fragment must be primed to enable the DNA polymerase to bind individual nucleotides together
Once replication of a fragment is complete, its primer is replaced by DNA.
Finally, the enzyme ligase (which acts like a glue) joins the fragment together.
The strand formed is called the lagging strand and the formation is described as discontinuous.
52
Describe DNA replication
1 - The parental double helix unwinds forming replication forks
2 - The DNA molecule becomes stabilised as two template strands
3 - DNA polymerase promotes formation of the single leading strand on a 5’ to 3’ direction (DNA can only grow from the 3’ end)
4 - The DNA polymerase bonds a nucleotide to a primer
5 - DNA polymerase promotes the formation of a fragment of the lagging strand of replicating DNA
6 - Ligase joins fragments together on the lagging strand of replicating DNA
53
For DNA replication to occur, what must the nucleus contain?
* DNA ( to act as a template)
* Primers
* Free DNA nucleotides (A,C,G,T)
* Enzymes (DNA polymerase and ligase)
* ATP
54
What is a Polymerase Chain Reaction (PCR)?
Procedure used to amplify DNA using primers (short strands of DNA complementary to specific target sequences at the two ends of the region of DNA to be amplified
55
What can PCR be used for?
To help solve crimes, settle paternity suits and diagnose genetic disorders
56
Describe the stages of PCR
* Solution containing DNA template, primers, heat tolerant polymerase, and free nucleotides added to test tube
* DNA is heated (92-98 °C) to separate the strands - DENATURING
* Cooling (50-65 °C) allows primers to bind to target sequences - ANNEALING
* Heated between (70-80 °C) to allow heat tolerant DNA polymerase to add nucleotides to primers and replicate regions of DNA - EXTENDING
57
What does PCR allow for?
Allows DNA to be screened for the presence/ absence of a specific sequence characteristic to a genetic disease.
58
Medical applications of PCR?
* Eliminate the risk of disease onset by identifying mutations in the persons genome
* Confirm a diagnosis of a suspected genetic disorder
59
Describe how PCR is used to test for a mutant allele
Testing for the mutant allele can be done using blood cells.
DNA is amplified and probes are used to test for the presence of the mutant allele.
60
What can be used to confirm genetic relationships?
PCR and gel electrophoresis
61
Why must every band in a DNA profile (genetic fingerprint) match one of the mother or father?
As 50% of our DNA is inherited from each parent
62
Forensic applications of PCR?
DNA samples from crime scenes of victims and suspects are amplified, separated by gel electrophoresis and compared.
63
What is a cell’s genotype determined by?
The sequence of the DNA bases in its genes
64
What is phenotype determined by?
The proteins produced as the result of gene expression
65
How many bases code for an amino acid?
Three (triplet)
66
How many of the genes in a cell are expressed?
Only a fraction
67
What determines a proteins structure, shape and ability to carry out its function?
The sequence of amino acids
68
How many strands does mRNA have?
One (single stranded)
69
What is on an mRNA nucleotide?
* A ribose sugar
* A phosphate group
* A base
70
What are the mRNA bases?
Adenine
Guanine
Cytosine
Uracil
71
Sugar present in mRNA nucleotide?
Ribose
72
Sugar present in DNA nucleotide?
Deoxyribose
73
What is the function of mRNA?
Carries a copy of the DNA code from the nucleus to the ribosome
74
What is ribosomal DNA?
This RNA + proteins form the ribosome
75
What is transfer RNA?
3D shape
Folds due to complementary base pairing
Carries a specific amino acid to the ribosome
76
Definition of TRANSCRIPTION
Synthesis of mRNA from a section of DNA in the nucleus
77
What is the enzyme responsible for transcription?
RNA polymerase
78
Description of TRANSCRIPTION
- RNA polymerase moves along the promoter, unwinding the DNA and breaking the hydrogen bonds between bases
- Nucleotides are added
- mRNA gets a nucleotide sequence complementary to one of the two DNA strands
- The mRNA strand produces becomes separated from its DNA template and is called the primary transcript of mRNA
- This mRNA carries a copy of the DNA code from the nucleus to the ribosome
79
What is a codon?
A triplet of based of mRNA which codes for a specific amino acid
80
Where does RNA polymerase add nucleotides to on a growing mRNA molecule?
Only the 3’ end
81
When does an mRNA molecule elongate until?
Till a terminator sequence of nucleotides is reached on the DNA strand
82
How long is the region of DNA transcribed to mRNA normally?
About 8000 nucleotides long
83
How many nucleotides are needed to code for an average sized polypeptide chain?
About 1200 nucleotides
84
What are introns?
Non-coding regions of DNA interspersed between the coding regions
85
What are exons?
Coding regions of DNA
86
Describe splicing
The introns are removed and the exons are spliced together to form a mature transcript with a continuous sequence of nucleotides
87
Definition of TRANSLATION
The synthesis of protein as a polypeptide chain at the ribosome
88
Where is tRNA found?
In the cytoplasm
89
Why does tRNA have a complex folded structure?
Due to hydrogen bonding between its bases
90
What does tRNA fold to form?
A triplet anticodon site, complementary to a codon
91
What does the triplet anticodon site correspond to?
A specific amino acid carried at the tRNA’s attachment site
92
How do anticodon bond to codons?
By complementary base pairing
93
Where does tRNA pick up its specific amino acid from?
The cytoplasm’s amino acid pool
94
Where does translation start and end?
Starts at a start codon and ends at a stop codon
95
Example of a start codon?
AUG
/
Methionine
96
Example of a stop codon?
UGA
97
Describe translation
1) Each tRNA picks up a specific amino acid molecule from the cytoplasm’s amino acid pool at its site of attachment and takes it to a ribosome.
2) Anticodons bond to codons by complementary base pairing ( hydrogen bonds form between anticodon and codon)
3) The amino acid is then added to the growing end of a polypeptide chain. Amino acids are held together by strong peptide bonds.
4) Each tRNA then leaves the ribosome as the polypeptide is formed (to pick up another amino acid)
98
What kind of bonds form between anticodon and codon?
Hydrogen bonds
99
The same primary transcript has the potential to produce _______ _______ _____ ________ depending on which exons are retained
Different mature mRNA transcripts
100
How can one gene code for several different proteins?
Alternative segments of RNA may be treated as exons and introns and produce several different mRNA molecules with a different sequence of bases coding for a different polypeptide
101
Describe how amino acids become proteins
* Amino acids are linked by peptide bonds
* Polypeptide chains fold to form a 3D shape of a protein, held together by hydrogen bonds and other interactions between individual amino acids
* The sequence of amino acids determines the proteins final structure
* Proteins have a variety of shapes which determine their function
102
What can influence phenotype?
* The proteins hat are synthesised when the genes are expressed
* Environmental factors eg diet linked to growth
103
Example of an environmental factor which influences phenotype?
Diet linked to growth
104
Describe enzymes and their function
* Speed up chemical reactions
| * Folded in such a way as to expose an active site ready to combine with a specific substrate
105
Describe structural proteins and their function
• One of the components that make up the cell membrane and plays a vital structural role in living cells
106
Describe hormones and their functions
• Chemical messengers transported in blood to target tissues to exert a regulatory effect on growth and metabolism
107
Describe antibodies and their function
• Y-shapes proteins produced by white blood cells to defend the body against foreign antigens
108
What are the building blocks of proteins?
Amino acids
109
Site of protein synthesis?
Ribosome
110
What is a mutation?
A random change in the structure or composition of an organism’s DNA that can result in the gene expressing a faulty protein or no protein at all
111
What’s the chromosomal abnormality for Down Syndrome?
An extra chromosome (21)
112
What can mutations vary from?
A tiny change in the DNA sequence of a gene to a large scale alteration in chromosome structure or number
113
Frequency of mutations?
In the absence of outside influences gene mutations arise spontaneously and at random but only occur rarely
114
What can mutation rate be artificially increased by?
Mutagenic agents
115
Examples of mutagenic agents?
- certain chemicals (eg mustard gas)
| - various types of radiation (eg gamma rays, x-rays, UV light)
116
What do single gene mutations involve?
The alteration of a DNA nucleotide sequence in the genes
117
Single gene mutations lead to ____ __ ____ _____ for one or more amino acids becoming _____ altered
One or more codons
Altered
118
What are the 3 different types of single gene mutations?
A single nucleotide is:
* Substituted
* Inserted
* Deleted
119
How many types of single gene mutations are there?
3
SID
120
What is a substitution mutation?
In this type of mutation, one nucleotide is replaced by another
121
What can happen in a substitution mutation?
The change may be minor (one different amino acid) and the organism may be slightly affected or not at all, unless the different amino acid occurs at a crucial position in the protein then a major defect can arise
122
How many types of substitution mutations are there?
3
123
What are the 3 types of substitution mutations?
* Nonsense mutations
* Missense mutations
* Splice-site mutations
124
What is a nonsense mutation?
As a result of a substitution, a codon that used to code for an amino acid is exchanged for one that acts as a stop codon.
Protein synthesis is stopped prematurely resulting in the formation of a shorter polypeptide chain that is unable to function
125
Example of a nonsense mutation?
DMD - Duchenne Muscular Dystrophy
126
What is a missense mutation?
Following a substitution, the altered codon codes for an amino acid but not the original amino acid.
This can produce non-functional protein OR may have little effect on the protein
127
Example of a missense mutation?
Sickle cell, phenylketonuria
128
What is splicing controlled by?
Specific nucleotide sequences + splice sites on those parts of introns that are next to exons
129
What is a splice site mutation?
If a substitution mutation occurs at one of these splice sites, the codon for an intron-exon splice may be affected
Some introns are retained and/o some exons are not included in the mature transcript, producing an abnormally functioning protein
130
Example of a splice site mutation?
Beta (b) thalassemia
131
What do nucleotide insertions and deletions both result in?
Frame-shift mutations
132
What is a nucleotide insertion mutation?
Extra nucleotide is inserted into sequence of bases
133
What is a nucleotide deletion mutation?
A nucleotide is deleted from sequence of bases
134
Why do nucleotide insertions and deletions lead to a major change?
As it causes all of the codons and all of the amino acids after the mutation to be changed
This leads to a very different and generally non-functional protein product
135
Example of a nucleotide insertion mutation?
Tay-Sachs syndrome
136
Example of a nucleotide deletion mutation?
Cystic Fibrosis
137
What makes Chromosome Structure Mutations lethal?
The substantial changes in chromosome structure (eg loss of several functional genes)
138
How can the structure of a chromosome be altered?
As a result of a breakage of one or more chromosomes
139
What are the 4 types of chromosome structure mutations?
* Deletion
* Inversion
* Duplication
* Translocation
140
What happens in a chromosome deletion mutation? What does it result in?
A deletion occurs when a chromosome breaks in two places and the segment in between becomes detached.
The two end then join up, giving a shorter chromosome which lacks certain genes.
141
Example of a chromosome deletion mutation?
Cri du chat syndrome - deletion of a section of chromosome 5
142
What is a chromosome inversion mutation?
This mutation results in a set of genes being reversed
eg
GHI —> IHG
143
Example of chromosome inversion mutation?
Haemophilia - a disease that inhibits the ability of blood to clot
144
What happens in a chromosome duplication mutation?
A section of chromosome (deleted from the matching partner) becomes attached to its homologous partner resulting in a set of genes being repeated
145
Example of a chromosome duplication mutation?
The duplication of certain genes is a common cause of cancer
146
What is a chromosome translocation mutation?
Translocation involves a section of one chromosome breaking off and becoming attached to another chromosome that is not its homologous partner
Can bring about a major change in an individuals phenotype
147
Example of a chromosomal translocation mutation
Familial Down’s Syndrome
Most common type of mutation associated with cancer eg Chronic Myeloid Leukemia (CML)
148
What is a genome?
The genome of an organism is its entire hereditary information encoded in DNA
149
What is a genome made up of?
Genes and other DNA sequences that do not code for proteins
150
What is human genomics?
The study of the human genome
151
What does human genomics involve?
It involves determining the sequence of the nucleotide base molecules all the way along the DNA (genomic sequencing) and then relating this genetic information to their information
152
What does SNP stand for?
Single nucleotide polymorphisms
153
What is a single nucleotide polymorphism?
SNPs (snips) are single nucleotide substitution point mutations and cause an alteration to the genome
154
How much of all human genetic variations do SNPs make up?
Around 90%
155
What does people affected by certain diseases always inheriting a group of SNPs that unaffected people do not suggest?
The gene for the disease is located near the group of SNPs
156
What can we analyse if we know the location of SNPs?
Nearby genes
157
Describe the process of sequencing DNA to find the genome
* A portion of DNA with an unknown base sequence is chosen + many copies of the strand are synthesised
* Modified nucleotides are incorporated into DNA strand halting synthesis
* If carries out on a large enough scale, synthesis of complementary strand will have been stopped at every possible nucleotide position along the DNA template
* The fragments of various lengths are separated by electrophoresis (shortest fragments travel the furthest distance)
* Detection of the four dyes is linked to a computer which displays the sequence of bases in the DNA sample as a series of peaks
158
How long did it take for the human genome to be unravelled?
13 years
159
How many nucleotide bases make up the human genome?
3 billion
160
Thanks to genome sequencing how many disease causing genes do we know exist?
300 disease causing genes
161
Thanks to genome sequencing how many genes do we know each express several different forms of the protein they encode?
4000 genes
162
What is bioinformatics?
A fusion of biology, computer technology and statistical analysis which allows for quick mapping and analysis of DNA sequences on a large scale
163
What does bioinformatics allow for?
Quick mapping and analysis of DNA sequences on a large scale
164
What is bioinformatics often used for?
To search for specific sequences such as known genes or promotors
165
What is a complete sequencing of a person’s DNA bases called?
Personal genome sequence (personal genomics)
166
What is pharmacogenetics?
The study of the effects (therapeutic, neutral, or adverse) of pharmaceutical drugs in the genetically diverse members of the human population
167
What would the benefits of personalised medicine be?
It may be possible to select the most effective drugs and dosage to treat their disease as indicated by a person’s gene sequence.
Thus increasing drug efficiency and reducing side effects
168
What fraction of drugs varies in effect depending on differences in a person’s DNA profile (SNPs) and example?
1 in 10 drugs (eg warfarin)
169
What is cell metabolism?
The term used to describe all of the integrated, enzyme-controlled reactions which take place within a living cell
170
What are the 2 types of metabolic pathways?
* Catabolic pathways
| * Anabolic pathways
171
What is a Catabolic pathway?
Break down complex molecules into simple building blocks usually releasing energy
172
What is an anabolic pathway?
Synthesise complex molecules from simple molecules usually requiring energy
173
Anabolic and catabolic relationships _____ on each other to _____
Depend
Function
174
Example of anabolic and carbolic pathways relying on each other
Aerobic respiration (catabolic) releases energy required for protein synthesis (anabolic)
175
What is the importance of enzymes?
Without enzymes chemical pathways would proceed too slowly for life to exist
176
What’s a metabolic pathway?
Integrated and controlled pathways, regulated by enzymes that catalyse specific reactions
177
Why do pathways contain both reversible and irreversible stages?
to keep the process highly controlled
178
Reversible and irreversible steps of respiration?
IRREVERSIBLE- glucose - intermediate 1 - maintains low concentration of glucose inside cell, promoting diffusion of glucose into cell
REVERSIBLE - intermediate 1 - intermediate 2. If more int.2 than cell requires then some can be converted back into int.1 and used in alternative pathway (eg build up glycogen)
179
What do alternative metabolic routes allow?
Allows steps to be bypassed
180
Describe the alternative route for respiration
Glucose bypasses the steps controlled by enzymes A,B, and C via an intermediate called sorbitol and returns to glycolysis later in the pathway.
This is used when the cell has a plentiful supply of sugar.
181
What is the energy required to break chemical bonds in reactant molecules called?
Activation energy
182
What is the transition state?
When the bonds of a molecule in the reacting have absorbed enough energy to make them unstable so they can break
183
What is a catalyst?
A substance that:
* lowers the activation energy required for a chemical reaction to proceed
* speeds up the rate of a chemical reaction
* takes part in the reaction but remains unchanged at the end of it
184
What are enzymes?
Biological catalysts
185
What are metabolic pathways controlled by?
The presence or absence of particular enzymes
186
What is the affinity of a substrate?
It’s chemical attraction to the active site
187
The active site is _____ and _____
Flexible and dynamic
188
When a substrate binds to an enzyme, the ____ of the active site _____ ___ _____ to better fit the substrate
Shape
Changes very lightly
189
What is induced fit?
When a substrate binds to an enzyme, the shape of the active site changes very slightly to better fit the substrate
190
What does induced fit ensure?
This ensures that the active site is in very close contact with the substrate and increases the chance of a reaction taking place
191
When the reaction involves two or more substances, what does the shape of the active site determine?
The orientation of reactants to ensure they are held together in such a way that the reaction can take place
192
The substrate molecules have a __ _____ for the active site
High affinity
193
The products have a __ _____ for the active site allowing them to ____ the active site
Low affinity
Leave
194
Factors affecting enzyme action?
* Temperature
* pH
* Substrate concentration
195
Why is the reaction rate low at low concentrations of substrate?
There are too few substrate molecules for enzymes to bind to
196
What does an increase in substrate concentration have on reaction rate?
Causes an increase in reaction rate until the reaction rate remains constant as all the active sites are occupied.
The rate is constant until more enzymes are added
197
Some metabolic reactions are _____ and the presence of a _____ or the _____ of a product will drive a sequence of reactions in a particular ______
Reversible
Substrate
Removal
Direction
198
If metabolite Y were to increase and X were to decrease, enzyme 2 could go into _____ and convert Y back into X until a _____ was _____
Reverse
Balance
Restored
199
If the appropriate enzyme is present the metabolic pathway _____ ; if an enzyme is absent the pathway ____
Proceeds
Halts
200
Why are some metabolic pathways only required to operate under certain circumstances?
To prevent waste of resources
201
Genes coding for enzymes controlling each of the stages in a metabolic pathway are ‘_____ ___’ or ‘___’ as required
Switched on or off
202
When is the only time E.coli can make use of glucose?
If it’s released from galactose
203
When is the enzyme B-galactosidase switched on ?
When lactose is present
204
What special gene does E.coli carry?
A genes which codes for the enzyme B-galactosidase which is switched on when lactose is present
205
Describe what happens when lactose is present in a cell
1 - lactose (inducer) enters the cell
2 - transcription and translation to form a repressor protein molecule
3 - some lactose combined with repressor
4 - repressor unable to combine with operator
5 - operator free
6 - successful transcription and translation to form B-galactosidase
7 - enzyme digests lactose until supply runs out then repressor combines with operator and switches the gene off
206
What is the system called that controls the coding of the enzyme B-galactosidase in E.coli cells?
LAC Operon System
207
Describe what happens when no lactose is present in an E.coli cell
1 - transcription and translation to form a repressor protein molecule
2 - repressor combines with operator
3 - structural gene switched off
4 - no B-galactosidase produced
5 - bacterium conserves it’s resources
208
Some metabolic pathways operate continuously so the genes that code for their enzymes are ___ _____ __
Always switched on
209
Control of metabolic pathways which operate continuously is brought about by regulating the action of their enzymes with?
* competitive inhibitors
* non-competitive inhibitors
* feedback inhibition by an end product
210
What’s an inhibitor?
A substance which decreases the activity of an enzyme
211
How do competitive inhibitors prevent the substrate from binding to the active site?
They’re of a similar shape to the substrate so bind to the active site
212
How can a decrease in the rate of reaction due to competitive inhibitors be reversed?
By increasing the substrate concentration
213
Where do non competitive inhibitors bind to?
A non active site (allosteric site)
214
How do non competitive inhibitors work?
They bind to an allosteric site.
This changes the shape of the enzyme indirectly changing the shape of the active site and preventing the substrate from binding
215
Describe the effect of no inhibitor on the rate of reaction
Increase in substrate concentration causes an increase in reaction rate until all active sites are occupied
216
Describe the effect of a competitive inhibitor on the rate of reaction
Increase in substrate concentration causes gradual increase in reaction rate as substance and inhibitor compete for active sites
217
Describe the effect of a non competitive inhibitor on the rate of reaction
Increase in reaction rate which quickly levels off as active sites become denatured
218
What is inhibition by an end product?
The final product of the pathway acts an inhibitor for the first enzyme
When there is a large concentration of an end product it down regulated the pathway
219
Describe feedback inhibition by an end product
As the concentration of metabolite Z build up, some of it binds to enzyme 1 and slows down the conversion of metabolite W to X to regulate the pathway.
As the concentration of Z drops, fewer molecules of enzyme 1 are affected
This controls the pathway and wasteful conversion and accumulation of intermediates are avoided
220
The region of a DNA molecule which codes for a protein is called a ____
Gene
221
Name 2 substances which are necessary for DNA replication
ATP
DNA polymerase
222
Name a cellular process for which DNA replication is essential
Mitosis
223
State the importance of DNA replication to cells
It ensures an exact copy of genetic information is passed from cell to cell during growth and from generation to generation during reproduction
224
Name the component of a nucleotide which would be found at the 3’ end of a DNA strand
Deoxyribose sugar
225
State the role of DNA ligase in the replication of DNA
DNA ligase bonds fragments of replicated DNA into the lagging strand of DNA
226
Name the type of bond which links the primer to the DNA strand
Weak hydrogen bond
227
Name the chemical group found at the 5’ end of a DNA strand
Phosphate
228
State the function of PCR
Procedure used to amplify DNA using primers - used to help solve crimes, settle paternity suits and diagnose genetic disorders
229
Where does the process of cellular respiration begin? What happens?
In the cytoplasm of a living cell with a molecule of glucose being broken down to form two pyruvate molecules
230
Glycolysis consists of a series of ____-______ steps
Enzyme controlled
231
What is the first half of the glycolysis pathway called?
Energy investment phase
232
How many ATP are needed to start the process of glycolysis off?
2 ATP
233
What is the 2nd half of the glycolysis pathway called?
Energy payoff phase
234
How many ATP IN TOTAL are produced in glycolysis?
4 ATP
235
What is the ATP net gain of glycolysis?
2 ATP
236
Where does glycolysis take place?
Cytoplasm
237
ATP is required for p_______ of glucose and i_____ during energy investment phase of glycolysis
* phosphorylation
| * intermediate
238
What’s phosphorylation? (Glycolysis)
Occurs when a phosphate group is added to another molecule
| ATP-ADP
239
In glycolysis, hydrogen ions are released from glucose by __________ _____
Dehydrogenase enzymes
240
What carries hydrogen ions from glycolysis to the final stage of cellular respiration?
Carried by NAD
| Forms NADH
241
In glycolysis, one molecule of glucose is broken down into p_____
Pyruvate
242
In aerobic conditions pyruvate is broken down to an a_____ group and combines with c_______ A to form _____ ______ _ (AcoA)
* acetyl
* coenzyme
* acetyl coenzyme A
243
In the energy payoff phase of glycolysis what releases hydrogen ions from the substrate?
An enzyme called hydrogenase
244
If ____ is present, aerobic respiration proceeds in ________
Oxygen
Mitochondria
245
What is the inner membrane of the mitochondria folded into?
Many extensions (Cristae)
246
What’s the purpose of the cristae of the mitochondria’s inner membrane?
Increases the surface area for ATP production
247
In the citric acid cycle the acetyl group of acetyl coenzyme A combines with ___________ to form _____ and enter the citric acid cycle
* oxaloacetate
| * citrate
248
The citric acid cycle consists of several enzyme-mediated stages, which occur in the ____ _____ of the mitochondria and result finally in the regeneration of __________
* central matrix
| * oxaloacetate
249
In the citric acid cycle, __________ enzymes remove H+ ions from the respiratory substrate along with associated ____ _____ ______
Dehydrogenase
High energy electrons
250
In the citric acid cycle, ___ is produced in one of the steps and ____ ____ is released in two of the steps
* ATP
| * Carbon dioxide
251
A ____ of ____ ____ are attached to the inner membrane of the mitochondria
Series of carrier proteins
252
What is the electron transport chain?
Electrons are passed along the electron transport chain releasing energy as they flow along the chain of electron acceptors
253
What’s the energy from the electron transport chain used for?
Used to pump H+ ions across the inner membrane
254
What drives the synthesis of ATP?
The return flow of H+ ions back through membrane protein ATP synthase
255
How many ATP does the electron transport chain produce?
36 ATP
256
How many ATP does cellular respiration produce?
38
257
Describe the 2nd part of respiration (electron transport chain)
* NADH releases hydrogen and electrons
* flow of High energy electrons - electron transport chain
* energy from electrons used to pump H+ across membrane
* return flow of H+ makes part of the ATP synthase rotate
* ADP + Pi ——> ATP
* Finally hydrogen ions and electrons combine with oxygen to form water
258
What does ATP stand for?
Adenosine Triphosphate
259
What is cellular respiration?
* series of metabolic pathways
* brings about release of energy from a foodstuff
* the regeneration of the high energy compound adenosine triphosphate (ATP)
260
What is a molecule of ATP composed of?
* Adenosine
| * 3 inorganic phosphate (Pi) groups
261
When is the energy stored in an ATP molecule released?
When the bond attaching the terminal phosphate is broken by enzyme action
262
What’s the enzyme controlled process that requires energy to regenerate ATP from ADP + Pi called?
Phosphorylation
263
The break down of ATP ____ energy and the build up of ATP ______ energy
* releases
| * requires
264
What does phosphorylation from ATP do to a reactant in a metabolic pathway?
Adds energy - makes note reactive
265
Often a step in a pathway can proceed only if a reactant becomes ____ and energised
Phosphorylated
266
ATP acts as the ____ between catabolic energy releasing reactions (respiration) and anabolic energy consuming reactions (active transport)
Link
267
What is the transfer of energy via ATP?
It is the means by which chemical energy is transferred from one cell type of reaction to another in a living cell
268
ATP is ______ at the same time it is used up
Manufactured
269
What’s the quantity of ATP in the human body?
Remains constant at 50g
270
What’s the rate at which the human body uses up and regenerates ATP?
400g/h
271
Under what conditions will pyruvate be converted to lactate (fermentation)?
During vigorous exercise, when the muscle cells do not get sufficient oxygen to support the electron transport chain
272
What happens to the H+ from NADH produced during glycolysis in fermentation?
Transferred to pyruvate to produce lactate
273
Explain the importance of NADH in aerobic respiration
Generates the NAD needed to maintain ATP production through glycolic
H+ from NADH transferred to pyruvate to produce lactate
274
What does the accumulation of lactate cause?
Muscle fatigue
275
When is the oxygen debt of fermentation repaid?
During recovery time when exercise stops
276
What does the oxygen debt being repaid in fermentation allow for?
Allows respiration to provide the energy required to convert lactate back to pyruvate and glucose in the liver
277
How much ATP does lactate metabolism (fermentation) produce?
2 ATP
278
How much ATP does aerobic respiration produce?
38 ATP (2 in glycolysis and 36 in ETC)
279
What are the 2 types of skeletal muscle fibres?
* slow twitch muscle fibres
| * fast twitch muscle fibres
280
Describe the contractions of slow twitch muscle fibres
* Contract relatively slowly
* can sustain contractions for longer
* good for endurance activities
281
Examples of slow twitch muscle fibre activities
* Long distance running
* cycling
* cross country skiing
282
Energy source of slow twitch muscle fibres
Rely on Aerobic respiration to generate ATP
283
Relative no.pf mitochondria of slow twitch muscle fibres
Many
284
Blood supply of slow twitch muscle fibres
Large
285
What protein do slow twitch muscle fibres have a high concentration of?
Oxygen storing protein myoglobin
286
What is myoglobin?
* oxygen storing protein
* stronger affinity for oxygen than haemoglobin
* able to extract oxygen from blood for use by muscle cells, particularly slow twitch muscle fibres
287
What’s the major storage fuel of slow twitch muscle fibres?
Fats
288
Describe the contraction of fast twitch muscle fibres
* contract relatively quickly
* over short periods
* good for bursts of activity
289
Example of fast twitch muscle fibre activities
Power activities
- sprinting
- weight lifting
290
Energy source of fast twitch muscle fibres
Rely on glycolysis to generate ATP requirements
291
Relative no.of mitochondria in fast twitch muscle fibres
Fewer
292
Blood supply of fast twitch muscle fibres?
Lower
293
Why do fast twitch muscle fibres have fewer mitochondria and a lower blood supply than slow twitch muscle fibres?
They rely on glycolysis for energy and so produce less ATP
294
Major storage fuel of fast twitch muscle fibres?
Glycogen
295
Example of muscle with mostly slow twitch muscle fibres
Muscles in the back which are responsible for posture
296
Example of muscle with mostly fast twitch muscle fibres
Muscles that move eyeballs
297
Sources of embryonic stem cells?
* IVF
| * Embryos
298
Potential ethical issue with use of embryonic stem cells
Results in destruction of human embryo
299
Define the term multi-potent
Capable of differentiating into a limited range of specialised cell types
300
Define the term pluripotent
Capable of differentiating into all of the cell types found in the human body
301
Two properties of cancer cells
* do not respond to regulatory signals
| * divide uncontrollably to produce rumours
302
Describe the formation of a secondary tumour
* some of a malignant tumour’s cells lose the surface molecules that keep them attached to the original cell group
* these can enter the circulatory system and spread through the body
* now tissues are invaded and a secondary tumour forms
303
Two properties of stem cells?
* can reproduce (self renew) themselves by repeated mitosis and cell division while remaining undifferentiated
* can then differentiate into a diverse range of specialised cells when required to do so
304
Tissue stem cells found in bone marrow will develop into?
* red blood cells
* platelets
* phagocytes
* lymphocytes
305
Two locations of tissue stem cells?
* bone marrow
| * skin
306
Name of the repeating units that make up a molecule of DNA?
Nucleotides
307
The arrangement of the DNA strands is described as?
Antiparallel
308
Explain why the leading strand of DNA is copied continuously
* DNA polymerase can only add nucleotides to the 3’ end of a growing strand
* the leading strand is replicated in a 3’ to 5’ direction so it can be synthesised as a single strand
309
Name 5 substances that are required in order for DNA replication to take place
1) DNA (to act as a template)
2) Primers
3) Free DNA nucleotides (A,C,G,T)
4) Enzymes (DNA polymerase and ligase)
5) ATP
310
Explain why the ‘lagging’ stand has to be copied in fragments
* lagging strand goes in a 5’ to 3’ direction
* DNA polymerase can only add DNA nucleotides in a 3’ to 5’ direction so the lagging strand has to be replicated in fragments, each starting at the 3’ end of a primer
311
At what end of a DNA strand does DNA polymerase add new nucleotides?
3’
312
The small section of DNA needed by DNA polymerase to start replication is called?
A primer
313
Function of DNA polymerase in DNA replication
Bonds complementary nucleotides to the 3’ end of the DNA strand
314
Function of ligase in DNA replication?
Bonds fragments of replicated DNA together on the lagging strand of DNA
315
List 3 used of DNA amplified through PCR
* help solve crimes
* settle paternity suits
* diagnose genetic disorders
316
Site of translation
Ribosome
317
A ribosome is formed from?
* Ribosomal RNA
| * proteins
318
Differences between DNA and RNA
DNA
———-
• 1 nucleotide strand present in one molecule
* uracil = complementary base partner of adenine
* ribose = sugar present in a nucleotide
———-
RNA
———
• 2 nucleotide strands present in one molecule
* thymine = complementary base partner of adenine
* deoxyribose = sugar present in a nucleotide
319
Site of transcription?
Nucleus
320
Enzyme responsible for transcription?
RNA polymerase
321
The 3D shape of a protein is held together by which type of bonds?
* peptide bonds
| * hydrogen bonds
322
Give 4 different functions of proteins
* enzymes
* hormones
* structural proteins
* antibodies
323
What is a cell’s phenotype determined by?
The proteins that are synthesised when the genes are expressed
324
What does the shape of a protein determine?
The proteins function
325
What’s a cell’s genotype determined by?
The sequence of the DNA bases
326
Name 3 single gene mutations
* substitution
* insertion
* deletion
327
What type of mutation for insertion and deletion single gene mutations produce?
Frame shift mutations
328
Computer programs can be used to identify base sequences by looking for...?
* sequences that are similar/close to known genes
| * sequences that are different to known genes
329
Explain 2 ways that information about an individual genome could be used in personalised medicine
1) It may be possible to select the most effective drugs and dosage to treat their disease as indicated by a person’s gene sequence. Thus increasing drug efficiency and reducing side effects.
2) In the future people may be able to be forewarned of the possibility of disease in later life
330
Explain why mutations in germline cells are potentially more serious than mutations in somatic cells
Mutations in germline cells can be passed to offspring (while mutations in somatic cells cannot)
331
Describe what happens in the energy investment and energy payoff stages of glycolysis
INVESTMENT - ATP molecules are broken down/ used up - phosphorylation of phosphate to glucose/intermediates occur
PAY OFF - ATP molecules are produced
332
What’s Preimplantation Genetic Diagnosis (PGD)?
During IVF treatment, it is possible to detect single gene disorders in fertilised eggs before they are implanted into the mothers womb
333
State one way in which stem cells are used in research
To study diseases/drug testing
334
Explain why embryonic stem cells can differentiate into all cell types?
All genes are switched on
335
Describe the DENATURING star of PCR
DNA is heated (92-98°C) to separate the strands
336
Describe the ANNEALING stage of PCR
Cooling (50-65°C) allows primers to bind to target sequences
337
Describe the EXTENDING stage of PCR
Heated between (70-80°C) to allow heat tolerant DNA polymerase to add nucleotides to primers and replicate regions of DNA
