Things I forget

Question 1

What is the definition of risk?

Answer 1

the likelihood of harm arising from exposure to hazard

Question 2

give 2 examples of a control measure

Answer 2

• using appropriate handling technique
• protective clothing and equipment
• aseptic technique

Question 3

What is a linear dilution series?

Answer 3

they differ by an equal interval
ex:
0.1, 0.2, 0.3 and so on

Question 4

What is a log dilution series?

Answer 4

they differ by s constant proportion
ex:
10^-1, 10^-2, 10^-3 and so on

Question 5

How does affinity chromatography work?

Answer 5

• a solid matrix or gel column is created with specific molecules bound to the matrix or gel
• soluble, target proteins in a mixture, with a high affinity for these molecules become attached to them as the mixture washes down the column
• other non-target molecules with a weaker affinity are washed out

Question 6

What happens during electrophoresis?

Answer 6

charged macromolecules move through an electric field applied to a gel matrix

Question 7

How are proteins separated during electrophoresis?

Answer 7

native gels separate proteins by their shape, size and charge
native gels do not denature the molecule so that the separation is by shape, size and charge

Question 8

What is the isoelectric point?

Answer 8

the pH at which a soluble protein has no net charge and will precipitate out of solution

Question 9

Explain how proteins are separated using their isoelectric points in electrophoresis

Answer 9

• soluble proteins can be separated using an electric field and a pH gradient
• a protein stops migrating through the gel at its isoelectric point in the pH gradient because it has not net charge

Question 10

What are immunoassay techniques used for?

Answer 10

used to detect and identify specific proteins

Question 11

How do immunoassays work?

Answer 11

• use stocks of antibodies with the same specificity, known as monoclonal antibodies
• an antibody specific to the protein antigen is inked to a chemical ‘label’
• the ‘label’ is often a reporter enzyme producing a colour change, but chemiluminescence, fluorescence and other reporters can be used
• in some cases the asset uses a specific antigen ti detect the presence of antibodies

Question 12

What is western blotting?

Answer 12

• used after SDS-PAGE electrophoresis
• the separated proteins from the gel are transferred (blotted) onto a solid medium
• the proteins can be identified using specific antibodies that have reporter enzymes attached

Question 13

What do culture media do?

Answer 13

promote the growth of specific types of cells and microbes

Question 14

What are animal cells grown in?

Answer 14

medium containing growth factors from serum

Question 15

What is the proteome?

Answer 15

the proteome is the entire set of proteins expressed by a genome

Question 16

What are genes that do not code for proteins called?

Answer 16

non-coding RNA genes

Question 17

What are the receptors for hydrophobic signalling molecules?

Answer 17

Transcription factors

Question 18

What are transcription factors?

Answer 18

proteins that when bound to DNA can either stimulate or inhibit initiation of transcription

Question 19

What does the hormone receptor complex do?

Answer 19

Moves to the nucleus where it binds to specific sites on DNA and affects gene expression

Question 20

What DNA sites does the hormone receptor complex bind to and what effect does this have?

Answer 20

• Binds to specific DNA sequences called hormone response elements (HREs)

-Binding at these sites influences the rate of transcription, with each steroid hormone affecting the gene expression of many different genes

Question 21

How do transmembrane receptors act as signal transducers?

Answer 21

By converting the extracellular ligand-binding event into intracellular signals, which alters the behavior of the cell

Question 22

Describe what happens once insulin binds to its receptor

Answer 22

• Binding of insulin to its receptor causes a
  conformational change that triggers
  phosphorylation of the receptor.
• This starts a
  phosphorylation cascade inside the cell,
• Which eventually leads to GLUT4-containing
  vesicles being transported to the cell
  membrane.

Question 23

How is the resting membrane potential restored?

Answer 23

inactivation of the sodium channels and the opening of potassium channels

Question 24

Explain the steps of the travel of the action potential

Answer 24

1) Binding of a neurotransmitter triggers the opening of ligand-gated ion channels at the synapse

2) Ion movement occurs and there is depolarisation of the plasma membrane.

3) If sufficient ion movement occurs, and the membrane is depolarised beyond a threshold value, the opening of voltage-gated sodium channels is triggered and sodium ions enter the cell down their electrochemical gradient

4) this leads to a rapid and large change in the membrane potential

5) a short time after opening the sodium channels become inactivated

6) voltage-gated potassium channels then open to allow potassium ions to move out of the cell to restore the resting membrane potential

Question 25

What does restoration of the resting membrane potential allow?

Answer 25

• the inactive voltage-gated sodium channels to return to a conformation that allows them to open again in response to depolarisation of the membrane
• ion concentration gradients are re-established by the sodium potassium pump, which actively transports excess ions in and out of the cell

Question 26

What is the function of retinal?

Answer 26

absorbs a photon of light and rhodopsin changes conformation to photoexcited rhodopsin

Question 27

What is the role of photoexcited rhodopsin?

Answer 27

• Activates a G-proteins called transducin which activates the enzyme phosphodiesterase (PDE)
• One photo excited rhodopsin activates hundreds of molecules of G-protein.
• Each activated G-protein activates one molecule of PDE

Question 28

What does PDE do?

Answer 28

• It catalyses the hydrolysis of a molecule called cyclic GMP (cGMP)
• Each active PDE molecule breaks down thousands of cGMP molecules per second
• The reduction in cGMP concentration as a result of its hydrolysis affects the function of ion channels in the membrane of rod cells

Question 29

What does the reduction in cGMP concentration result in?

Answer 29

The closure of ion channels in the membrane of rod cells, which triggers nerve impulses in neurone in the retina

Question 30

What do cyclin proteins do and where do they come from?

Answer 30

• they are proteins that accumulate during cell growth
• involved in regulating the cell cycle

Question 31

How do cyclin proteins regulate the cell cycle?

Answer 31

• Cyclins combine with active cyclin-depndant kinases (CDKs)
• Active cyclin-CDK complexes phosphorylate proteins that regulate progression through the cycle
• If sufficient phosphorylation is reached. progression occurs

Question 32

What happens at the G1 checkpoint?

Answer 32

• Retinoblastoma protein (Rb) acts as a tumour supressor 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

Question 33

What happens at the G2 checkpoint?

Answer 33

• The success of DNA replication and and 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

Question 34

What is an example of an external death signal?

Answer 34

The production of death signal molecules from lymphocytes

Question 35

What is an example of an internal death signal?

Answer 35

DNA damage

Question 36

How do external death signals work?

Answer 36

External death signal molecules bind to a surface receptor protein and trigger a protein cascade within the cytoplasm

Question 37

What causes activation of p53 tumour-suppressor protein?

Answer 37

An internal death signal resulting from DNA damage

Question 38

What do both types of death signal result in?

Answer 38

activation of caspases (types of protease enzyme) that cause the destruction of the cell

Question 39

What is the role of apoptosis in development of an organsim?

Answer 39

to remove cells no longer required as development progresses or during metamorphosis