TOPIC 2 EXAM QUESTIONS Flashcards
Eukaryotic cells produce and release proteins.
Outline the role of organelles in the production, transport and release of
proteins from eukaryotic cells.
Do not include details of transcription and translation in your answer.
- DNA in nucleus is code (for protein);
- Ribosomes/rough endoplasmic reticulum produce (protein);
Accept rER for ‘rough endoplasmic reticulum’ - Mitochondria produce ATP (for protein synthesis);
- Golgi apparatus package/modify;
OR
Carbohydrate added/glycoprotein produced by Golgi apparatus;
Accept body for ‘apparatus’ - Vesicles transport
OR
Rough endoplasmic reticulum transports;
- (Vesicles) fuse with cell(-surface) membrane;
Accept exocytosis at cell membrane
Describe how you could make a temporary mount of a piece of plant tissue
to observe the position of starch grains in the cells when using an optical
(light) microscope
- Add drop of water to (glass) slide;
- Obtain thin section (of plant tissue) and place on slide / float on
drop of water; - Stain with / add iodine in potassium iodide.
- Allow any appropriate method that avoids
trapping air bubbles - Lower cover slip using mounted needle.
Describe binary fission in bacteria.
- Replication of (circular) DNA;
Accept nucleoid
Reject chromosome
Reject mitosis - Replication of plasmids;
- Division of cytoplasm (to produce daughter cells);
Ignore genetically identical
Describe and explain what the student should have done when counting
cells to make sure that the mitotic index he obtained for this root tip was
accurate.
- Examine large number of fields of view / many cells;
Mark as pairs only
Accept large number / 20 or more for many - To ensure representative sample;
Accept typical / reliable
OR - Repeat count;
- To ensure figures are correct;
OR - Method to deal with part cells shown at edge /count
only whole cells; - To standardise counting;
Name and describe five ways substances can move across the
cell-surface membrane into a cell.
- (Simple) diffusion of small/non-polar molecules down a
concentration gradient;
If no reference to ‘small/ non-polar’ for 1.
accept this idea from ‘large/charged’ given in
description of 2. - Facilitated diffusion down a concentration gradient via
protein carrier/channel;
Reject if active rather than passive - Osmosis of water down a water potential gradient;
- Active transport against a concentration gradient via
protein carrier using ATP; - Co-transport of 2 different substances using a carrier protein;
The movement of substances across cell membranes is affected by
membrane structure. Describe how.
- Phospholipid (bilayer) allows movement/diffusion of nonpolar/lipid-soluble substances;
- and 2. Accept correct named examples
- and 2. Ignore water
Accept phospholipid (bilayer) allows movement/diffusion
of O2/CO2
Accept water-insoluble - Phospholipid (bilayer) prevents movement/diffusion of polar/
charged/lipid-insoluble substances
OR
(Membrane) proteins allow polar/charged substances to cross
the membrane/bilayer;
Accept water-soluble - Carrier proteins allow active transport;
- Channel/carrier proteins allow facilitated diffusion/co-transport;
Accept aquaporins allow osmosis - 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; - and 7. Accept correct reference to faster/slower/rate for
‘how much movement’
Accept microvilli / Golgi (apparatus) / ER / rER
Accept surface area to volume for ‘surface area’ - Cholesterol affects fluidity/rigidity/permeability;
Compare and contrast the processes by which water and inorganic ions
enter cells.
- Comparison: both move down concentration gradient;
- Comparison: both move through (protein) channels in membrane;
Accept aquaporins (for water) and ion channels - Contrast: ions can move against a concentration gradient by active
transport
Contrast the processes of facilitated diffusion and active transport.
- Facilitated diffusion involves channel or carrier proteins whereas
active transport only involves carrier proteins; - Facilitated diffusion does not 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.
Describe how HIV is replicated.
- 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 the role of antibodies in producing a positive result in an ELISA
test.
- (First) antibody binds/attaches /complementary (in shape) to antigen;
- (Second) antibody with enzyme attached is added;
- (Second) antibody attaches to antigen;
Accept (second) antibody attaches to (first) antibody
(indirect ELISA test). - (Substrate/solution added) and colour changes;
When a person is bitten by a venomous snake, the snake injects a toxin
into the person. Antivenom is injected as treatment. Antivenom contains
antibodies against the snake toxin. This treatment is an example of passive
immunity.
Explain how the treatment with antivenom works and why it is essential to
use passive immunity, rather than active immunity.
- (Antivenom/Passive immunity) antibodies bind to the
toxin/venom/antigen and (causes) its destruction;
For ‘bind’ accept ‘attach’, ignore ‘attack’.
For ‘destruction of toxin’ accept agglutination or
phagocytosis.
Ignore reference to antibodies ‘neutralising
toxin/stopping damage’
Reject reference to ‘killing’ toxin/venom. - Active immunity would be too slow/slower;
Accept ‘passive immunity is faster’, not simply
‘passive immunity is fast’.
Describe the difference between active and passive immunity.
- Active involves memory cells, passive does not;
- Active involves production of antibody by plasma cells /
memory cells; - Passive involves antibody introduced into body from outside /
named source; - Active long term, because antibody produced in response to
antigen; - Passive short term, because antibody (given) is broken down;
- Active (can) take time to develop / work, passive fast acting.
Clostridium difficile is a bacterial species that causes disease in humans.
Antibiotic-resistant strains of C. difficile have become a common cause of infection
acquired when in hospital.
Explain how the use of antibiotics has led to antibiotic-resistant strains of bacteria
becoming a common cause of infection acquired when in hospital
- (Some bacteria have) alleles
for resistance; - (Exposure to) antibiotics is the
selection pressure
OR
Non-resistant bacteria die
OR
Resistant bacteria
survive/reproduce; - More antibiotics used in
hospital (compared with
elsewhere)
OR
Patients have weakened
immune systems
OR
(So) high frequency of
resistance allele (in bacterial
population);
Give two features of all prokaryotic cells that are not features of eukaryotic cells
No membrane-bound organelles/correct
example
OR
(Single,) circular/loop DNA (in cytoplasm)
OR
DNA free in cytoplasm
OR
DNA not associated with proteins/histones
OR
Murein/peptidoglycan (in) cell wall;
Describe viral replication.
- Attachment proteins attach to receptors;
- (Viral) nucleic acid enters cell;
- Nucleic acid replicated in cell
OR
Reverse transcriptase makes DNA from RNA; - Cell produces (viral) protein/capsid/enzymes;
- Virus assembled and released (from cell)
