topic 2 Flashcards
1
Q
Prokaryote and
animal cell
comparison
A
- Bacterial cell is much smaller than a human cell;
- Bacterial cell has a cell wall but human cell does not;
- Bacterial cell lacks a nucleus but human cell has a nucleus;
- Bacterial cell lacks membrane-bound organelles but human cell has membrane-bound organelles;
- Bacterial ribosomes smaller than human ribosomes / bacteria have
70S ribosomes whereas humans have 80S ribosomes; - Bacterial DNA is circular but human DNA is linear;
- Bacterial DNA is ‘naked’ whereas human DNA is bound to histones / proteins
2
Q
Phospholipid arrangement in a
membrane
A
- Bilayer OR Water is present inside and outside a cell;
- Hydrophobic (fatty acid) tails point away/are repelled from water
OR
Hydrophilic (phosphate) heads point to/are in/are attracted to water;
3
Q
Hydrophobic
substances moving
across membranes
A
- Lipid soluble;
- (Diffuse through) phospholipid (bilayer);
4
Q
Role of organelles and
proteins
A
- 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;
5
Q
Describe how you
would use cell
fractionation
techniques to obtain a
sample of
mitochondria from
leaf tissue.
A
- Macerate / homogenise / blend / break tissues / cells (in solution);
- Centrifuge the supernatent;
- At different / increasing speeds until mitochondria fraction obtained/until 3 rd pellet is obtained;
6
Q
Explain the conditions
that would be
necessary for cell
fractionation.
A
- Ice-cold - Slows / stops enzyme activity to prevent digestion of
organelles / mitochondria; - Buffer - Maintains pH so that enzymes / proteins are not denatured;
Reject reference to cells - Same water potential - Prevents osmosis so no lysis / shrinkage of organelles / mitochondria;
7
Q
Explain how
ultracentrifugation
separates different
molecules.
A
- Spin (liquid / supernatant) at (very) high speed / high g;
Need context of high, not just ‘faster’, ‘higher’ in context of use of bench centrifuge - Molecules separate depending on (molecular) mass / size / density;
8
Q
Why is a detergent
used to lyse (breaking
open) cells and
organelles.
A
- Cell membranes made from phospholipid;
- (Detergent) dissolves membranes / phospholipid (bilayer);
Ignore breaks down
Reject hydrolysis
9
Q
TEM compared to
optical microscope
A
- 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
10
Q
TEM compared to
SEM
A
Higher resolution OR View internal structures
11
Q
Why must a sample
for a microscope be
thin?
A
- Need a single layer of cells / only a few cells thick / not too many layers / detail obscured by cells underneath;
- Light must be able to pass through;
12
Q
Making a temporary
mount (microscope
slide)
A
- Add drop of water to (glass) slide;
- Obtain thin section (of plant tissue) and place on slide / float on drop of water;
- Stain if necessary;
- Lower cover slip using mounted needle.
13
Q
Measuring dry mass
A
- Heat at 100°C / heat to temp to evaporate water;
Value which would not burn material - Weigh and heat until no further change in mass;
14
Q
Mitosis
A
(During prophase)
1. Chromosomes coil / condense / shorten / become visible;
2. (Chromosomes) appear as (two sister) chromatids joined at the centromere;
(During metaphase)
3. Chromosomes line up on the equator / centre of the cell;
4. (Chromosomes) attached to spindle fibres;
5. By their centromere;
(During anaphase)
6. The centromere splits / divides;
7. (Sister) chromatids / chromosomes are pulled to opposite poles /
ends of the cell / separate;
(During telophase)
8. Chromatids / chromosomes uncoil / unwind / become longer
15
Q
Mitosis - root tip
experiment
Why the tip?
Pressed down firmly
on the cover slip?
Ensuring accuracy
A
Where dividing cells are found / mitosis occurs
Single / thin layer of cells / spread out cells so light passes through
1. Examine large number of fields of view / many cells;
2. To ensure representative sample;
OR
3. Repeat count;
4. To ensure figures are correct;
OR
5. Method to deal with part cells shown at edge /count only whole cells;
6. To standardise counting
16
Q
Cytokinesis
A
The division of the cytoplasm
17
Q
Explain how bacterial
cells divide
A
- Binary fission;
- Replication of (circular) DNA;
- Replication of plasmids
- Division of cytoplasm to produce 2 daughter cells;
- Each with single copy of (circular) DNA;
18
Q
Transport across
membranes (parts of membrane)
A
- Phospholipid (bilayer) allows movement/diffusion of nonpolar/lipid-soluble substances;
- Phospholipid (bilayer) prevents movement/diffusion of polar/charged/lipid-insoluble substances OR (Membrane) proteins allow
polar/charged substances to cross the membrane/bilayer; - Carrierproteins 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;
19
Q
Facilitated diffusion
A
- Carrier / channel protein;
- (Protein) specific / complementary to substance;
- Substance moves down concentration gradient
20
Q
Diffusion and osmosis
similarities
A
- (Movement) down a gradient / from high concentration to low concentration;
- Passive / not active processes;
OR
Do not use energy from respiration / from ATP / from metabolism;
21
Q
Co-transport of
glucose
A
- Sodium ions actively transported from ileum cell to blood;
- Maintains / forms diffusion gradient for sodium to enter cells from gut (and with it, glucose);
- Glucose enters by facilitated diffusion with sodium ions;
22
Q
ATP hydrolase and
active transport
A
- (ATP to ADP + Pi ) Releases energy;
- (energy) allows ions to be moved against a concentration gradient
OR
(energy) allows active transport of ions;
23
Q
Osmosis - tissue in
more concentrated
solution
A
- Water potential of solution is less than / more negative than that of potato tissue;
Allow Ψ as equivalent to water potential - Tissue loses water by osmosis.
24
Q
Membrane
adaptations for
absorption
A
- Membrane folded so increased / large surface area;
OR
Membrane has increased / large surface area for (fast) diffusion / facilitated diffusion / active transport / co-transport; - Large number of protein channels / carriers (in
membrane) for facilitated diffusion; - Large number of protein carriers (in membrane) for active
transport; - Large number of protein (channels / carriers in membrane) for co-transport
25
What is a monoclonal
antibody?
(Antibodies with the) same tertiary structure;
OR
(Antibody produced from) identical/cloned plasma cells/B cells/B lymphocytes;
26
Cells that stimulate an
immune response
1. (Cells from) other organisms/transplants;
2. Abnormal/cancer/tumour (cells);
3. (Cells) infected by virus
4. Pathogens
27
What is an antigen?
1. Protein;
2. Found on a cell surface membrane/pathogen surface
3. (that) stimulates an immune response / production of antibody;
28
What is an antibody?
1. A protein / immunoglobulin specific to an antigen;
2. Produced by B cells
OR
Secreted by plasma cells
29
Antibody specificity
1. Each protein has a different tertiary structure;
2. (Each) antibody has a specific antigen / binding / variable region / site;
3. So, (each antibody) forms different antigen-antibody complex
OR
(each antibody) only binds to complementary (protein);
30
Phagocytosis
1. Phagocyte engulfs to form vacuole / vesicle / phagosome;
2. Lysosome fuses and empties contents into vacuole / vesicle / phagosome;
3. (Releasing) enzymes that digest / hydrolyse bacteria;
31
Role of the disulphide
bridge in antibody
structure
Joins two (different) polypeptides;
32
Production of
antibodies
1. Helper T cell / TH cell binds to the antigen (on the antigen-presenting cell / phagocyte);
2. This helper T / TH cell stimulates a specific B cell;
3. B cell clones
OR
B cell divides by mitosis;
4. (Forms) plasma cells that release antibodies;
33
Vaccination
1. Antigen on surface of pathogen binds to surface receptor on a (specific / single) B cell.
2. (Activated) B cell divides by mitosis;
3. (Division) stimulated by T cells;
4. B cells release antibodies;
5. (Some) B cells become memory cells;
6. Memory cells produce antibodies faster
34
Active v passive
immunity
1. Active involves memory cells, passive does not;
2. Active involves production of antibody by plasma cells / memory cells;
3. Passive involves antibody introduced into body from outside / named source;
4. Active long term, because antibody produced in response to antigen;
5. Passive short term, because antibody (given) is broken down;
6. Active (can) take time to develop / work, passive fast acting
35
ELISA test
1. (First) antibody binds/attaches /complementary (in shape) to antigen;
2. (Second) antibody with enzyme attached is added;
3. (Second) antibody attaches to antigen;
Accept (second) antibody attaches to (first) antibody (indirect ELISA test).
4. (Substrate/solution added) and colour changes;
Only award if enzyme mentioned
36
viral replication
1. virus attaches to surface of host cell
2. virus injects viral DNA/RNA into host cell
3. viral DNA/RNA replicates and produces new viral proteins
4. new viral particles are formed
5. host cell bursts, releasing viral particles
37
mitotic index equation
number of cells in mitosis / total number of cells
