TOPIC 2 MARK SCHEME SHIT Flashcards
Why is control strip important when testing for monoclonal antibodies? (2)
- Prevents false negative results
- Shows that the antibody has moved up the strip/not bound to any of the _________
Why are some viruses described as inactive? (2)
- No more cells infected
- because virus isn’t replicating
When mice are injected to make it produce a monoclonal antibody, what should the injection contain?
Regulator protein
Give two ways in which pathogens can cause disease
- Releases toxins
- Kills cells/tissues
How to prepare a tissue sample to be observed under a light microscope (4)
- Add drop of water to glass slide
- Obtain thin section of tissue and place on slide/float on drop of water
- Stain
- Lower cover slip using mounted needle
2 advantages of using a TEM to observe cells
- High resolution
- Can see INTERNAL STRUCTURE of organelles
Describe how the RER is involved in the production of enzymes (2)
- RER contains RIBOSOMES
- to make proteins
Name 4 structures in an eukaryotic cell that CANNOT be identified using an optical microscope
- Mitochondrion
- Ribosome
- Endoplasmic reticulum
- Lysosome
The events that take place during interphase and mitosis lead to the production of two genetically identical cells. Explain how (4)
- DNA replicated
- Specific/accurate/complementary base-pairing
- Two identical/sister chromatids
- Each chromatid moves to opposite poles/ends of cell
Describe and explain how cell fractionation and ultracentrifugation can be used to isolate mitochondria from a suspension of animal cells (6)
- Cell homogenisation to break open cells
- Filter to remove large debris/whole cells
- Use isotonic solution to prevent damage to organelles
- Keep cold to prevent/reduce damage by enzymes / use buffer to prevent protein/enzyme denaturation
- Centrifuge at lower speed to separate heavy organelles
- Re-spin supernatant at higher speed to get mitochondria in pellet/at bottom
Describe the principles and limitations of using a TEM to investigate cell structure (5)
- Electrons pass through/enter thin specimen
- Denser parts absorb more electrons
- So denser parts appear darker
- Electrons have shorter wavelength so give high resolution
- Can’t look at living material/must be in a vacuum
- Specimen must be very thin
- Artefacts present
- Long preparation time/complex staining method
- Only 2D image produced
Outline the role of organelles in the production, transport and release of proteins from eukaryotic cells (4) DO NOT INCLUDE DETAILS OF TRANSCRIPTION & TRANSLATION IN YOUR ANSWER
- DNA in nucleus is code for protein
- Ribosomes/RER produce protein
- Mitochondria produce ATP for protein synthesis
- Golgi apparatus package/modify
- Vesicles transport
- Vesicles fuse with cell-surface membrane
Contrast how an optical microscope and a transmission electron
microscope work and contrast the limitations of their use when studying cells. (6)
- TEM use electrons and optical use light;
- TEM allows a greater resolution;
- (So with TEM) smaller organelles / named cell structure can be observed
OR
greater detail in organelles / named cell structure can be observed; - TEM view only dead / dehydrated specimens and optical (can) view live specimens;
- TEM does not show colour and optical (can);
- TEM requires thinner specimens;
- TEM requires a more complex/time consuming preparation;
- TEM focuses using magnets and optical uses (glass) lenses;
Describe binary fission in bacteria (3)
- Replication of DNA
- Replication of plasmids
- Division of cytoplasm to produce daughter cells
Evaluation ?s: points AGAINST drug being effective
- No stats test
- Only shows short-term results (over N months)
- Only one/two people
- Unknown side effects
- No control group
Describe how vaccinations can lead to protection against a virus (6)
- Antigen on surface of virus binds to surface receptor on a specific B cell
- Activated B cell divides by mitosis
- This is stimulated by T cells
- B cells/plasma cells release antibodies
- Some B cells become memory cells
- Memory cells produce plasma/antibodies faster
Describe how a vaccine leads to the production of antibodies against a disease-causing organism (5)
- Vaccine contains antigen from pathogen
- Macrophage presents antigen on its surface
- T cell with complementary receptor protein binds to antigen
- T cell stimulates B cell
- with complementary antibody on its surface
- B cell secretes large amounts of antibody
- B cell divides to form clone which all produce the same antibody
Describe difference between active and passive immunity (5)
- Active involves memory cells, passive doesn’t
- Active involves production of antibody by plasma/memory cells
- Passive involves antibody being introduced into body from outside
- Active long term b/c antibody produced in response to antigen
- Passive short term b/c antibody is broken down
- Active takes time to develop, passive fast acting
What is evidence that an image has been viewed with an optical/light microscope? Explain your answer (1)
- Need LIGHT to see colour
- Can’t see colour with an electron microscope
- No organelles are visible
The movement of substances across cell membranes is affected by membrane structure. Describe how. (5)
- Phospholipid bilayer allows movement/diffusion of non-polar/lipid-soluble substances
- Phospholipid bilayer prevents movement/diffusion of polar/charged/lipid-insoluble substances
- Carrier proteins allow active transport
- Channel/carrier proteins allow facilitated diffusion/co-transport
- Shape/charge of channel/carrier determines which substances move
- Number of channels/carriers determines how much movement
- Membrane surface area determines how much diffusion/movement
- Cholesterol affects fluidity/rigidity/permeability
Describe HIV replication (4)
- Attachment proteins attach to receptors on helper T cell/lymphocyte;
- Nucleic acid/RNA enters cell;
- Reverse transcriptase converts RNA to DNA;
- Viral protein/capsid/enzymes produced;
- Virus (particles) assembled and released (from cell);
Describe how a phagocyte destroys a pathogen present in the blood (3)
- Engulfs;
- Forming vesicle/phagosome and fuses with lysosome;
- Enzymes digest/hydrolyse;
Describe how presentation of a virus antigen leads to the secretion of an antibody against this virus antigen (3)
- Helper T cell / TH cell binds to the antigen (on the antigenpresenting cell / phagocyte);
- This helper T / TH cell stimulates a specific B cell;
- B cell clones/divides by mitosis;
- (Forms) plasma cells that release antibodies;
Organelles involved in protein production/secretion (4)
- Golgi: package/process proteins
- RER/ribosomes: make polypeptide/protein/forming peptide bonds
- Mitochondria: release energy/make ATP
- Vesicles: secretion/transport of protein
Contrast the processes of facilitated diffusion and active transport (3)
- Facilitated diffusion involves channel or carrier proteins whereas active transport only involves carrier proteins
- Facilitated diffusion doesn’t use ATP/is passive whereas active transport uses ATP
- Facilitated diffusion takes place down a concentration gradient whereas active transport can occur against a concentration gradient
Compare & contrast DNA in eukaryotic cells with DNA in prokaryotic cells (5)
- Nucleotide structure is identical
- Nucleotides joined by phosphodiester bonds
- DNA in mitochondria/chloroplasts same/similar to DNA in prokaryotes
- Eukaryotic DNA is longER
- Eukaryotic DNA contains introns, prokaryotic DNA doesn’t
- Eukaryotic DNA is linear, prokaryotic DNA is circular
- Eukaryotic DNA is associated with/bound to histones, prokaryotic DNA is not
Describe the role of antibodies in producing a positive result in an ELISA test (4)
- (First) antibody binds/attaches/complementary to antigen
- (Second) antibody with enzyme attached is added
- (Second) antibody attaches to (first) antibody
- (Substrate/solution added and) colour changes
Give 3 ways in which DNA in chloroplast is different from DNA in nucleus (3)
- DNA shorter in chloroplasts
- Fewer genes in chloroplasts
- DNA circular in chloroplasts
- Not associated w/ histones
Give the two types of molecule from which a ribosome is made (1)
rRNA and protein
