1
Q
What characteristics do native gels separate proteins by?
A
Shape, size and charge
2
Q
What characteristics does SDS-PAGE separate proteins by?
A
Size
3
Q
How can proteins be separated?
A
Using their isoelectric points
4
Q
What happens if a solution is buffered to a specific pH with regards to proteins?
A
Only the proteins that have an isoelectric point of that pH will precipitate
5
Q
What techniques are used to identify and detect specific proteins?
A
Immunoassay techniques
6
Q
What can aseptic techniques do when culturing micro-organisms or cells?
A
Eliminates unwanted microbial contaminants
7
Q
How can a microbial culture start?
A
Using an inoculum of microbial cells on an agar medium, or in a broth with suitable nutrients
8
Q
What are animal cells grown in?
A
In medium containing growth factors from serum
9
Q
What is the difference between primary and tumour cell lines in culture?
A
Primary: can divide a limited number of times
Tumour: can divide unlimited times
10
Q
What is required to identify and count viable cells in a culture?
A
Vital staining
11
Q
What is the proteome?
A
The entire set of proteins expressed by a genome
12
Q
Why is the proteome larger than the number of genes in an organisms?
A
because more than one protein can be produced from a single gene as a result of alternative RNA splicing
13
Q
What is endoplasmic reticulum and what is its function?
A
An organelle that forms a network of membrane tubules continuous with the nuclear membrane.
The site of synthesis of proteins and lipids
14
Q
What is the Golgi apparatus and what is its function?
A
A series of flattened membrane discs.
Is the site of post translational modification.
15
Q
What are lysosomes and what is their function?
A
To digest proteins, lipids, nucleic acids and carbohydrates.
16
Q
What is the function of a vesicle?
A
An organelle which transports materials between membrane compartments.
17
Q
Where specifically are lipids synthesised?
A
Smooth ER
18
Q
Where does the synthesis of all proteins begin?
A
Cytosolic ribosomes
19
Q
What are the different R groups for proteins?
A
Basic (+ charged), acidic (-charged), polar and hydrophobic
20
Q
What is the primary structure of a protein?
A
The sequence in which the amino acids are synthesised into the
polypeptide
21
Q
What does hydrogen bonding along the backbone of a protein strand result in?
A
Regions of secondary structure
22
Q
What are the types of secondary structures for a protein?
A
Alpha helices, parallel or anti-parallel beta-pleated sheets, or turns
23
Q
How is the tertiary structure of a protein formed?
A
By the polypeptide folding
24
Q
What circumstances must be present for a protein to have a quaternary structure?
A
When proteins have two or more connected polypeptide subunits
25
What is a prosthetic group?
A non-protein unit tightly bound to a protein and necessary for its
function
26
How is the tertiary structure of a protein stabilised?
By many different interactions between the R groups of the amino acids; including disulphide bridges and hydrogen bonds.
27
What is a ligand?
A substance that can bind to a protein
28
What happens when a ligand binds to a protein-binding site?
The conformation of the protein changes - this causes a functional change
29
What is an allosteric enzyme?
An enzyme whose activity is regulated by altering its conformation.
30
Many allosteric proteins ... because they consist of multiple subunits
have a quaternary structure
31
What is a modulator?
Something that regulates the activity of the enzyme when they bind to the allosteric site.
32
What happens when a modulator binds to an enzyme?
The conformation of the enzyme changes altering the affinity of the active site for the substrate
33
What is a common form of post-translational modification?
The addition or removal of phosphate that can cause a reversible conformational change in proteins
34
What catalyses the transfer of a phosphate group to other proteins?
Protein kinases
35
What catalyses the reverse reaction?
Protein phosphotases
36
What are the effects of phosphorylation?
Can bring about conformational changes, which can affect a protein’s activity.
37
The head region of a phospholipid is ... and the tail is ...
Charged / hydrophilic
Uncharged / non-polar / hydrophobic
38
What are integral proteins?
Proteins found within the membrane.
39
What is meant by a transmembrane integral protein?
A protein that spans the entire width of the membrane.
40
What are peripheral proteins?
Proteins are found on the surface of the membrane.
41
Why must most molecules get help from proteins to pass through the phospholipid bilayer?
As the phospholipid bilayer acts as a barrier to ions and most uncharged polar molecules.
42
What is facilitated diffusion?
Passive transport of substances across the membrane through specific transmembrane proteins.
43
What proteins are used facilitated diffusion?
Channel proteins
Transporter proteins
44
What are channel proteins?
Multi-subunit, transmembrane proteins with the subunits arranged to form water-filled pores.
45
What does it mean if a channel protein is gated?
It changes conformation to allow or prevent diffusion.
46
What can the stimulus for a channel gated protein be?
chemical (ligand-gated)
electrical (voltage-gated)
47
What do transporter proteins do?
Bind to the specific substance and undergo a conformational change to transfer the solute across the membrane.
48
What do protein pumps do?
Transfer substances across the membrane against their concentration gradient.
49
What do protein pumps consist of?
A transporter protein coupled to an energy source
50
What chemical reaction is ATPases involved in?
To hydrolysis of ATP
51
What are examples of extracellular signalling molecules?
Steroid hormones, peptide hormones, and neurotransmitters
52
Hydrophobic signals can diffuse directly through the phospholipid bilayers of membranes.
T or F?
True
53
Why can hydrophobic signals diffuse directly through the phospholipid bilayers of membranes?
Because the tails of the phospholipids in the plasma membrane are also hydrophobic and allow the molecules to pass across.
54
What are examples of hydrophobic signals?
Thyroxine
Steroid hormones
55
Where is thyroxine produced and what does it do?
Thyroid
Regulates the rate of metabolism
56
What are examples of hydrophobic signalling molecules?
Steroid hormones: testosterone and oestrogen.
57
Pathway of steroids
58
What are transcription factors and what can they do?
Proteins that when bound to DNA can either stimulate or inhibit initiation of transcription
59
What are hydrophilic signals?
Molecules that bind to transmembrane receptors and do not enter the cytosol.
60
Why do hydrophilic signals not enter the cytosol?
Because they are not capable of passing across the hydrophobic plasma membrane.
61
What is meant by the membrane potential?
The electrical potential difference (voltage) across a cells plasma membrane
62
What is meant by the resting membrane potential?
A state where there is no net flow of ions across the membrane.
63
What is an action potential?
A wave of electrical excitation along a neuron’s plasma membrane.
64
What are the two types of photoreceptors in an animals retina?
Cones and rods
65
How are the photoreceptors in an eye produced?
Retinal is combined with a membrane protein, opsin
66
What is the retinal-opsin complex called in rod cells?
Rhodopsin
67
What are the steps involved in a retinas response to light?
1a) Retinal absorbs a photon of light and becomes photoexcited rhodopsin
1b) Photoexcited rhodopsin activates G-protein (Transducin)
2. G-proteins activate phosphodiesterase (PDE)
3a)PDE catalyses hydrolysis of cGMP
3b) Concentration of cGMP decreases
4a) Ion channels close – membrane potential increases
4b) Nerve impulse is triggered in neurons in the retina
68
What is the function of a cytoskeleton?
Gives mechanical support and shape to cells
69
What do cytoskeletons consist of?
Different protein structures including microtubules
70
What is the function of microtubules?
Control the movement of membrane-bound organelles and chromosomes
71
What does the cells cycle involve?
Interphase and mitotic (M) phase
72
What does the mitotic phase of a cell cycle involve?
Mitosis and cytokinesis
73
What type of bonding holds the secondary structure of a protein together?
Hydrogen
74
What do the two ends of spindle fibres attach to during mitosis?
Centrosome and centromere
75
What are the order of events in the transmission of a nerve impulse?
- Vesicles containing the neurotransmitter fuse with the membrane.
- The neurotransmitter diffuses across the synaptic cleft.
- The neurotransmitter binds to its receptor.
- Ligand‑gated ion channels open.
- Voltage‑gated sodium channels open and sodium ions diffuse into the cell causing local depolarisation.
76
What type of bonding holds the secondary structure of a protein together?
Hydrogen
77
What does the use of centrifuge separate substances by?
Density
78
What characteristics does an amino acid have with an acidic r-group?
r-group = carboxylic acid group
- charged
hydrophilic
79
What characteristics does an amino acid have with a basic r-group?
r-group = amine group
+ charged
hydrophilic
80
What characteristics does an amino acid with a polar r-group have?
r-group = different functional groups
slightly charged
hydrophilic
81
What characteristics does an amino acid with a hydrophobic r-group have?
r-group = CH3 / long chains of CH / rings of CH
no charge
hydrophobic
non-polar
82
In gel electrophoresis, proteins migrate to the ... end of the electrode from the ... .
positive
negative
83
Why might signalling molecules have different effects on different target cell types?
Due to differences in the intracellular signalling molecules and pathways that are involved.
84
What are chiasmata?
The points of contact between non-sister chromatids of homologous chromosomes, the site of crossing over and factors contributing to genetic variation in meiosis.
84
How are hydrophilic signalling molecules able to activate intracellular signalling molecules?
By binding to a receptor on the surface of the membrane, resulting in a phosphorylation cascade
85
What characteristic does native gel electrophoresis have?
Does not denature proteins
86
What characteristic does SDS-PAGE electrophoresis have?
Does denature the proteins
87
What is western-blotting?
A technique used after SDS-PAGE electrophoresis, using specific antibodies
88
What is the name of the transporter protein responsible for transporting sodium ions and glucose at the same time and in the same direction?
Glucose symport
89
What happens when there is an increase in temperature on haemoglobin
and oxygen delivery to cells?
Affinity for haemoglobin decreases and oxygen delivery increases
90
What is the mechanism of glucose symport?
- Sodium-potassium pump pumps Na+ out of cell which generates lower concentration of Na+ within cell
- Glucose Symporter transports Na+ down its concentration gradient alongside glucose
91
What is meant by the electrochemical gradient?
A combination of the concentration
gradient and the membrane potential
92
What is the use of a standard curve?
The determine unknown concentrations.
93
What is meant by monoclonal antibodies?
Antibodies with the same specificity
94
How can rod cells function in low light intensities?
Due to having a high degree of amplification
95
What is the process surrounding sodium-potassium pumps?
- The pump has high affinity for sodium ions inside the cell - binding occurs.
- Pump hydrolyses ATP and phosphate attaches to it. Phosphorylation by ATP causes the conformation of the protein to change.
- The affinity for sodium ions decreases resulting and are released outside the cell.
- The pump has high affinity for potassium ions outside the cell - binding occurs.
- Dephosphorylation occurs which causes the conformation of the protein to change.
- Potassium ions are taken into the cell and the affinity returns to the start.
96
What happens in the interphase of the cell cycle?
G1: The initial growth phase. Protein synthesis occurs and new organelles are formed.
Synthesis (S): Replication of nuclear DNA.
G2: Second phase of growth prior to mitosis. By the end of this phase the centrosome has been duplicated.
97
What happen in the M phase of the cell cycle?
Mitosis: The accurate separation and distribution (segregation) of replicated chromosomes and the formation of daughter nuclei.
Cytokinesis: The division of the cytoplasm into two separate daughter cells.
98
Why must the cell cycle be monitored?
To ensure that events occur in the correct sequence and do not take place unless the previous ones have been completed.
99
What features should an effective cell cycle control system possess?
Systems should be adjustable to cope with different environmental conditions and suit different types of cells.
The system should be able to respond to internal and external feedback.
100
What are the three checkpoints within the cell cycle?
G1, G2, M
101
What are cyclins?
Proteins that are involved in regulating the cell cycle.
102
How do cyclin proteins regulate the cell cycle?
Cyclins combine with and activate cyclin-dependent kinases (CDKs).
Active cyclin-CDK complexes phosphorylate proteins that regulate progression through the cycle.
If sufficient phosphorylation is reached, progression occurs.
103
What happens at the G1 checkpoint in the cell cycle?
At the G1 checkpoint, retinoblastoma protein (Rb) acts as a tumour suppressor by inhibiting the transcription of genes that code for proteins needed for DNA replication
Phosphorylation by G1 cyclin-CDK inhibits the retinoblastoma protein (Rb).
This allows transcription of the genes that code for proteins needed for DNA replication. Cells progress from G1 to S phase.
104
What happens in the cell cycle when there is an absence in mitogens?
Cells enter a non-dividing state (G0 phase)
Cells can remain in this state or re-enter the cell cycle when they receive appropriate signals.
105
What are examples of cells that can proliferate continuously?
Tumour and stem
106
What are examples of cells that exist in a terminally differentiated G0 state?
Red blood cells, neurons and skeletal muscles
107
What happens at the G2 checkpoint in the cell cycle?
At the G2 checkpoint, the success of DNA replication and any damage to DNA is assessed
DNA damage triggers the activation of several proteins including p53 that can stimulate DNA repair, arrest the cell cycle or cause cell death.
108
What is the purpose of the M checkpoint?
Ensures that each daughter cell receives the same chromosome complement as its parent when anaphase occurs.
109
What happens at the M phase checkpoint in the cell cycle?
Progression is halted until the chromosomes are aligned correctly on the metaphase plate and attached to the spindle microtubules.
110
What controls the cell cycle?
The activity of CDKs
111
What are the different ways p53 can affect a cell?
- Stimulates DNA repair
- Promotes transcription of genes that induce cell cycle arrest
- Promotes transcription of genes that induce apoptosis
112
An uncontrolled...
- decrease
- increase
...in the rate of the cell cycle may result in...
- degenerative diseases
- tumour formation
113
What is the proto-oncogene
A gene involved in the control of cell growth or division, which can mutate to form a tumour promoting oncogene.
114
What is apoptosis?
Controlled cell death
115
When may cells initiate apoptosis?
In the absence of growth factors
116
Why do multicellular organisms need to regulate the death of their cells?
To allow body structures to grow and develop correctly.
117
Why do multicellular organisms need to regulate the death of their cells?
To regulate the size of cell populations
118
Why do multicellular organisms need to regulate the death of their cells?
- To kill cells that have been infected by pathogens.
- To prevent the survival of cells with damaged DNA (these have the potential to become cancerous)
- To eliminate white blood cells that would produce an immune response to the body’s own cells.
119
What is necrosis?
Uncontrolled cell death
120
What are the steps involved in apoptosis?
- Activation of procaspase proteins
- Caspase activation cascade
- Caspases are proteinases: they cleave key cell proteins
- Caspase activity results in the controlled destruction of the cell
121
What is involved in the initiation of apoptosis?
- Adaptor proteins cause initiator procaspases to cluster together.
- Clustering induces a conformational change that activates the procaspases.
122
Biology
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