Unit 1 - Human Cells Flashcards
1
Q
How many pairs of chromosomes do human diploid cells contain?
A
23
2
Q
What are stem cells used for?
A
Growth and Repair
3
Q
Where are stem cells found?
A
Embryos
Adult Tissue
4
Q
What are therapeutic uses of stem cells?
A
Skin Grafts
Cornea Repairs
Repair of damaged/diseased organs
5
Q
What are somatic cells?
A
Body cells
6
Q
How do somatic cells divide?
A
Mitosis
7
Q
What are germline cells?
A
Sex cells (gametes)
8
Q
How do germline cells divide?
A
Mitosis
Meiosis
9
Q
Give examples of germline cells?
A
Sperm
Ova
10
Q
What is cellular differentiation?
A
The process by which a cell expresses certain genes to produce proteins characteristic for that type of cell
11
Q
Why is cell differentiation important?
A
Allows cells to carry out specialised functions
12
Q
What does pluripotent mean and where can these cells be found?
A
- Pluripotent means that all the genes in a cell have the ability to be activated
- Found in embryonic cells
13
Q
What does multipotent means and where are these cells found?
A
- Can only differentiate into certain cells based upon where the cells are formed from
- Found in adult tissue - skin and bone marrow
14
Q
Give the research based use of stem cells
A
Investigate how certain diseases/disorders develop and the response of cells to new pharmaceutical drugs
15
Q
How do cancer cells form?
A
Don’t respond to regulatory signals, causing them to excessively divide forming abnormal masses
16
Q
How do cancer cells spread to secondary locations?
A
Masses breach into systems such as the blood vessels and if the cells fail to attach to each other they can travel to secondary locations and start a secondary tumour there
17
Q
What does benign mean?
A
localised abnormal cells (often not harmful)
18
Q
What does Malignant mean?
A
Ability to spread (harmful)
19
Q
What is DNA made of?
A
Repeating nucleotide bases joined by strong hydrogen bonds with a double helix structure
20
Q
What are the four bases in DNA and how do they pair?
A
Adenine + Thymine
Cytosine + Guanine
21
Q
How do the strands of nucleotides run?
A
Antiparallel (like traffic)
22
Q
How should DNA be read?
A
From 5’ end to 3’ end
23
Q
What are the requirements for DNA replication to take place?
A
- DNA
- Primers
- Free DNA nucleotides
- Enzymes (DNA polymerase and ligase)
- ATP energy
24
Q
What are the main stages of DNA replication?
A
Breaking
Attaching
Adding
Joining
25
What happens during the breaking stage of DNA replication?
DNA unwinds and the hydrogen bonds between the bases break, forming a replication fork
26
What breaks the hydrogen bonds between bases in DNA?
Helicase
27
What happens during the attaching stage of DNA replication?
Primers attach themselves to the target sequence at the 3' end
28
What happens during the addition stage of DNA replication?
DNA polymerase adds free nucleotides to the template strands of DNA from the 3' end to the 5' end
29
Why is there a leading strand and a lagging strand of DNA during DNA replication?
```
Leading strand (running 3' to 5') can have nucleotides added continuously
Lagging strand (running 5' to 3') has to be added in fragments as the strand is running the opposite way to how it is read
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30
What happens during the joining stage of DNA replication?
Hydrogen bonds form between the template bases and the added bases, joining the two strands
31
What does ligase do in DNA replication?
Joins the fragments on the lagging strand to make it complete
32
Why would DNA be artificially amplified in a lab?
- Paternity testing
- Screening/Diagnosis of Genetic Disorders
- Forensics/Criminology
33
How is DNA artificially amplified?
Through a polymerase chain reaction (PCR)
34
What are the five stages of PCR?
- DNA is heated to 90 degrees to separate the strands
- DNA is cooled to 50-60 degrees to allow primers to bind to DNA
- DNA is heated to 70-80 degrees for heat tolerant DNA polymerase to replicate the region of DNA
- Two strands are produced
- Process restarts
35
Why is DNA replication referred to as semi conservative?
One template makes two strands
36
What does helicase do in DNA replication?
Unzips the strands of DNA by breaking the hydrogen bonds between bases
37
What does primase do in DNA replication?
Makes primer made of RNA. Tells DNA polymerase where to start adding nucleotides
38
What does DNA polymerase do during DNA replication?
Build new strands of DNA with free nucleotide bases
| Goes in 5' to 3' direction
39
What are the stages of Protein Synthesis?
Transcription and Translation
40
Where does transcription take place?
Nucleus
41
What is DNA short for?
Deoxyribose nucleic acid
42
What happens during transcription?
RNA polymerase unwinds double helix structure
mRNA makes a complementary copy of the DNA sequence on the strand
Splicing occurs
43
What does mRNA have instead of Thymine?
Uracil
44
How does splicing work?
Introns (none coding bits of genes) are removed from the primary transcript and the mature transcript is left as exons (coding regions of genes)
45
How does mRNA know where to find the required genes?
Start and stop codons
46
Where does translation occur?
In the ribosome
47
What occurs during translation?
Mature mRNA travels to a ribosome in the cytoplasm
tRNA (transport) reads the mature mRNA and adds amino acids to a chain
The amino acids fold to make a protein
48
What is a ribosome made from?
Ribosomal Ribose Nucleic Acid
49
How does tRNA read the mRNA?
In triplets - codons
50
What holds amino acids together?
Peptide bonds
51
What are the types of proteins?
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Enzymes
Antibodies
Hormones
Structural
Receptors
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52
What is a mutation?
A random change to genetic material
53
What can mutations cause in terms of proteins?
Can result in an altered protein or no protein synthesised at all
54
What are the two classifications of mutations?
Single gene mutations
| Chromosomal mutations
55
What classification of mutation is more dangerous and why?
Chromosomal - alters an entire gene rather than just one nucleotide
56
What increases the rate of mutation?
Radiation
High temperatures
Chemicals
57
What are the two types of single gene mutation and they're sub groups?
Substitution - Missense, Nonsense, Splice Site
| Frameshift - Insertion, Deletion
58
What happens in a missense substitution and what is the result?
One base is swapped for another ( eg T is swapped for G)
Alters a single codon
Results in either a non functioning protein or had little effect
59
What is a codon?
A set of three bases which make an amino acid
60
What happens in a nonsense substitution and what is the result?
Premature STOP codon
Shorter polypeptide
Results in smaller protein
61
What happens in a splice site substitution and what is the result?
Introns are kept and/or exons are removed
Alters the mature transcript
Results in an entirely different protein
62
What happens in a single gene Insertion mutation?
An extra base is added to region of DNA
Alters all following codons/amino acids
Results in a drastically altered protein
63
What happens in a single gene deletion mutation?
A base is deleted from the DNA
Alters all following codons/amino acids
Results in a drastically altered protein.
64
What happens in a duplication mutation?
A section of a chromosome is added from its homologous partner
(One section is copied onto daughter chromosome and is duplicated)
(e.g. original strand -> ATCCGAGCTTA
mutated strand -> ATCCGAGT CGAGT TA)
65
When can mutations occur?
During DNA replication and meiosis
66
What happens during a inversion mutation?
A section on the chromosome is inverse
(A section reads the wrong way around)
(e.g. original strand -> ATC CGAGCT TA
mutated strand -> ATC TCGAGC TA)
67
What happens during a translocation mutation?
A section of a chromosome is added to the chromosome, not form its homologous partner
(The chromosome gets a bit of DNA from the wrong template)
(e.g. original strand 1 -> ATC CGAGCT TA
original strand 2 -> CG TAT GACTA
mutated strand 1 -> ATC TAT TA
mutated strand 2 -> CG CGAGCT GACTA)
68
What happens during a chromosomal deletion mutation?
A section of a chromosome is removed
| e.g. ATC CGAGC TTA -> ATCTTA
69
What is bioinformatics?
The study and comparison of the human genome and data sequencing
70
Give an example of a disease caused by a missense mutation
Sickle cell disease
Phenylketonuria (PKU) - protein that metabolises phenylamine isn't synthesized. Phenylamine converts into phenylpyruvate which damages metal grow
71
What is a genome?
The entire hereditary information of an individual, encoded in DNA
72
What is a genome made up of?
Genes and other DNA sequences that do not code for proteins
| DNA
73
What is genomic sequencing?
Determining the sequence of nucleotide bases to find out an individuals genes and genome
74
How is genomic sequencing achieved?
Through the use of computer programmes and statistical analysis
75
What is pharmacogenetics?
The study of how an individuals genetic make up affects their responses to drugs
76
What are the uses of pharmacogenetics?
Predict the likelihood of an individual developing diseases
| Prescribe effective drugs and dosages
77
What is personalised medicine?
Using a persons genome to select the most effective drugs and dosage from them
78
What are the two types of metabolic pathways?
Anabolic
| Catabolic
79
What happens in an anabolic pathway?
Synthesis of small molecules into large molecules with the aid of energy
80
What happens in a catabolic pathway?
Large molecules are degraded (broken down) into smaller molecules, releasing energy
81
Come up with a way to remember what happens in each metabolic pathway
Cats knock over vases and break them, so CATabolic pathways involve the breaking (degradation) of molecules
82
What controls metabolic pathways?
Enzymes
83
What is an induced fit?
How the active site of an enzyme changes shape to better fit the substrate
84
What causes substrates to be attracted to and released from the active site of an enzyme?
Substrates have a high affinity (attraction) for the active site and the subsequent molecules have a low affinity, allowing them to be released
85
What affects the rate of an enzyme controlled reaction?
Concentration of a substrate
Concentration of an end product
Inhibitition
86
What are the three types of enzyme inhibition?
Competitive
Non-Competitive
Feedback
87
What happens during competitive inhibition?
A competitive inhibitor binds to the active site of the enzyme, preventing substrates from binding
88
Can competitive inhibition be reversed, and if so, how?
Yes
| Increasing the concentration of the substrate
89
Where do competitive inhibitors bind?
The active site of an enzyme
90
What happens during non-competitive inhibition?
A non-competitive inhibitor binds away from the active site
| This changes the shape of the active site, preventing substrates from binding
91
Can non-competitive inhibition be reversed, and if so, how?
No
92
Where do non-competitive inhibitors bind?
Away from the active site at the ALLOSTERIC SITE
93
What happens in feedback inhibition?
The end product binds to the allosteric site of the first enzyme in the chain
This prevents the first substrate from binding
This prevents the further synthesis/degradation of and substrate
94
What drives the sequence of reactions/direction in a metabolic pathway?
Presence of substrates
| Removal of products
95
What is cellular respiration?
The process by which energy is released and used for cellular processes
96
Give an example of a cellular process that would require glucose?
Protein synthesis
Muscle contraction
Active transport
DNA replication
97
What are the three stages of respiration?
Glycolysis
The Citric Acid Cycle (Kreb's Cycles)
Electron Transport Chain (Cytochrome system)
98
What happens during glycolosis?
Glucose is converted into pyruvate
99
Where does glycolysis occur?
In the cytoplasm
100
During glycolysis, how is glucose converted into pyruvate?
Two ATP are used to break down glucose
Coenzyme NAD removes Hydrogen ions from the broken down glucose, making it NADH2.
4 ATP is released
Pyruvate is the product
101
Why is glycolysis referred to as energy investment and payoff?
2 ATP have to be inputted to break down the glucose - energy investment
4 ATP are released as a result of the degradation of glucose
Net gain of 2 ATP
102
What are the requirements for glycolysis?
ATP
| - does NOT require oxygen
103
Where does the citric acid cycle take place?
In the matrix of the mitochondria
104
What are the requirements for the citric acid cycle to occur?
Oxygen
105
What controls the citric acid cycle?
Enzymes
106
What does Acetyl CoA mean?
Acetyl is being carries by co enzyme A (into kreb's cycle)
107
What combines with Acetyl CoA to make Citrate?
Oxaloacetate
108
What happens when acetyl coA when it enters the citric acid cycle?
It combines with oxaloacetate to form citrate
109
What happens during the Citric Acid Cycle? Include the number of carbons (it'll help to remember it)
1. Pyruvate (3C) loses a CO2 and becomes Acetyl CoA (2C)
2. Acetyl CoA combines with Oxaloacetate (4C) in the matrix of the mitochondria to form Citrate (6C)
3. Citrate loses a CO2 to become intermediate 1 (5C). NAD removes a H ion and becomes NADH
4. Intermediate 1 loses a CO2 to become intermediate 2 (4C). NAD removed a H ion and becomes NADH. ATP is generated
5. Intermediate 2 becomes Intermediate 3 (4C). NAD removes a H ion and becomes NADH
6. Intermediate 3 converts into Oxaloacetate. NAD removes a H ion and becomes NADH
7. Oxaloacetate restarts the cycle
110
If asked to write an essay on the citric acid cycle, what would you say, simplified? (Max 5 marks)
1) Pyruvate is converted to Acetyl and is carried by coenzyme A to the citric acid cycle
2) Acetyl combines with Oxaloacetate to form Citrate
3) A series of enzyme controlled reactions break down citrate, releasing carbon dioxide
4) Dehydrogenase enzymes remove hydrogen during the cycle and pass hydrogen ions and electrons to NAD
5) A small amount of ATP is created
111
What do dehydrogenase enzymes do?
Pass the H ions onto the NAD
112
Where does the electron transport chain take place?
The Inner Membrane of the Mitochondria
113
What stage of cellular respiration has the highest yield of ATP?
Electron Transport Chain
114
What are the requirements for Electron Transport Chain?
Hydrogen ions and enzymes collected in previous stages
115
What are the key stages of Electron Transport Chain?
1) NADH arrives at the inner membrane of the mitochondria and deposits the hydrogen ions and electrons
2) Energy from the electrons is used to force the hydrogen ions across the membrane via the protein channels.
3) With a large accumulation of H ions on the other side of the membrane, the travel back across the membrane through the protein ATP Synthase
4) As the hydrogen ions come through, ATP Synthase spins, generating large quantities of ATP
5) Hydrogen ions and electrons combine with oxygen to form water
116
What does ATP Synthase do?
Synthesises (makes) ATP
117
What happens to the electrons and hydrogen ions at the end of cellular respiration?
Combine with oxygen to form water that
118
What is the final acceptor of hydrogen?
Oxygen
119
Quick summary of cellular respiration.
| Glycolysis : how much ATP is made, where does it occur, what is required, and what is the product?
ATP = 2
Occurs in the Cytoplasm
Requires glucose
Product is Pyruvate
120
Quick summary of cellular respiration.
| Citric Acid Cycle : how much ATP is made, where does it occur, what is required, and what is the product?
ATP = Some
Occurs in the Matrix of the Mitochondria
Requires Oxygen, Pyruvate/Acetyl
Product is Carbon Dioxide
121
Quick summary of cellular respiration.
| Electron Transport Chain : how much ATP is made, where does it occur, what is required, and what is the product?
ATP = Lots
Occurs in the Inner Membrane of the Mitochondria
Requires Electrons, Hydrogen Ions, Oxygen
Products are ATP and Water
122
When does lactate form?
When there is no oxygen available during cellular respiration, the pyruvate converts into lactate
123
Where is lactate stored?
In the liver
124
What does lactate do in the liver?
Fermentation
125
What allows the body to move?
Skeletal muscles
126
What are the two classifications of muscle fibres?
Fast Twitch and Slow twitch
127
What type of skeletal fibres do humans usually have?
Both fast and slow twitch fibres
128
What is myoglobin, where is it found, and what does it do?
Protein
Found in muscle tissue
Stores oxygen necessary for respiration
129
What are the characteristics of slow twitch fibres?
(Hint : there's 7)
```
(Hint 2)
Contract length
What is it good for?
Where does ATP come from?
How many mitochondria?
Blood supply?
Storage Fuel?
Myoglobin count?
```
```
Contract slowly
Good for endurance
ATP provided by aerobic respiration
Many mitochondria
Large blood supply
Storage fuel
Large quantity of myoglobin
```
130
What are the characteristics of fast twitch fibres?
(Hint : there's 7)
```
(Hint 2)
Contract length
What is it good for?
Where does ATP come from?
How many mitochondria?
Blood supply?
Storage Fuel?
Myoglobin count?
```
```
Fast contractions, short periods
Good for bursts of energy
Glycolysis provides ATP
Few mitochondria
Low blood supply
Storage fuel is glycogen
No myoglobin
```
131
What type of muscle fibre would an athlete have more of?
Depends on sport
132
What activities would fast twitch muscle fibres be beneficial to?
Sprinting
| Weights
133
What activities would slow twitch muscle fibres be beneficial to?
Long distance running
| Football
134
How do you calculate a percentage increase/decrease?
biggest no - smallest no / original no x 100
135
How do you calculate a percentage of a quantity?
%/100 x no. given
136
How do you calculate the percentage of each other?
no1/no2 x 100
137
For cell division, what power should be used to work out the number of cells?
2 to the power of (however many divisions there have been)
| e.g. four divisions = 2^4
138
* Essay questions from Unit 1 can include :
- cell differentiation
- DNA Structure
- DNA Replication
- Gene Expression -> Transcription & Translation
- Effects of mutations -> chromosomal or single gene
- Effects of competitive and non competitive inhibition
- Cellular Respiration -> Glycolysis, Citric Acid Cycle &/or Electron Transport Chain
- Skeletal Muscle Fibres -> fast and slow twitch
139
A fragment of DNA contained 144 nucleotide base pairs.
| What is the total number of deoxyribose sugars in this fragment?
288
140
Benign – localised abnormal cells (often not harmful)Malignant – Ability to spread (harmful)
