cell exam questions Flashcards

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1
Q

What is a tumour?

A

Abnormal cells/tissue;
Uncontrolled mitosis/cell division;

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2
Q

Describe how you would determine a reliable mitotic index from tissue observed with an optical microscope.
Don’t include details of how you would prepare the tissue observed with an optical
microscope.

A
  1. Count cells in mitosis in field of view;
  2. Divide this by total number of cells in field of view;
  3. Repeat many/at least 5 times
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3
Q

Describe viral replication.

A
  1. Attachment proteins attach to receptors;
  2. (Viral) nucleic acid enters cell;
  3. Nucleic acid replicated in cell
  4. Cell produces (viral) protein/capsid/enzymes;
  5. Virus assembled and released (from cell);
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4
Q

A student prepared a stained squash of cells from the root tips of garlic to calculate a mitotic index.
2. placed the root tips into a Petri dish containing 5 cm3 of hydrochloric acid for 12 minutes
(a) Suggest why the student soaked the root tips in hydrochloric acid in step 2.

A

To break down links between cells/cell walls

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5
Q

Pressing the coverslip downwards enabled the student to observe the stages of mitosis clearly. Explain why.

A

Allowing the stain to pass/diffuse into the cells
OR
Allowing the cells to be (more easily) squashed;

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6
Q

Other students in the class followed the same method, but calculated different mitotic
indices.
Apart from student errors, suggest two explanations why.

A

(Garlic roots) are a different age
OR
(Garlic) grown in different conditions;

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7
Q

Describe how HIV is replicated.

A
  1. Attachment proteins attach to receptors on helper T cell/ lymphocyte;
  2. Nucleic acid/RNA enters cell;
  3. Reverse transcriptase converts RNA to DNA;
  4. Viral protein/capsid/enzymes produced;
  5. Virus (particles) assembled and released (from cell);
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8
Q

(a) A student prepared a stained squash of cells from the tip of an onion root and observed it using an optical microscope. During the preparation of the slide, he:
Explain why the student:
1. used only the first 5 mm from the tip of an onion root.

A

Where dividing cells are found / mitosis occurs;

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9
Q
  1. pressed down firmly on the cover slip.
A

Single / thin layer of cells / spread out cells so light passes through (making cells /
nuclei visible);

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10
Q

Tick (✓) the name given to the division of cytoplasm during the cell cycle.
A Binary fission
B Cytokinesis
C Phagocytosis
D Segregation

A

b

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11
Q

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.

A
  1. Examine large number of fields of view / many cells;
  2. To ensure representative sample;
  3. Repeat count;
  4. To ensure figures are correct;
  5. Method to deal with part cells shown at edge /count only whole cells;
  6. To standardise counting;
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12
Q

A scientist treated growing tips of onion roots with a chemical that stops roots growing.
After 24 hours, he prepared a stained squash of these root tips. Figure 2 is a drawing showing the chromosomes in a single cell observed in the squash of one of these root tips in anaphase. This cell was typical of other cells in anaphase in these root tips. Use all of this information to suggest how the chemical stops the growth of roots.

A
  1. Stops anaphase / cell division / mitosis;
  2. (By) stopping / disrupting / spindle fibres forming / attaching / pulling;
  3. Preventing separation of (sister) chromatids;
  4. (So) no new cells added (to root tip);
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13
Q

A student investigated mitosis in the tissue from an onion root tip.(a) The student prepared a temporary mount of the onion tissue on a glass slide. She covered the tissue with a cover slip. She was then given the following instruction. “Push down hard on the cover slip, but do not push the cover slip sideways.” Explain why she was given this instruction.

A
  1. Push hard – spread / squash tissue;
  2. Not push sideways – avoid rolling cells together / breaking chromosomes
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14
Q

The figure above is different from an image of this bacterium obtained using a transmission electron microscope. Describe and explain one difference between these images.
Description
Explanation

A
  1. 3D with SEM, but 2D with TEM
    OR Only surface visible with SEM, but internal structures visible with TEM;
  2. (Because) electrons deflected/bounce off (using SEM)
    Accept Resolution is lower (with SEM)
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15
Q

The resolution of an image obtained using an electron microscope is higher than the
resolution of an image obtained using an optical microscope.
Explain why.

A

Shorter wavelength between electrons;

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16
Q

A student determined the size of a cell structure from a photograph obtained using a
microscope. he used a ruler and a calculator and gave the answer in μm. Describe how the student determined the size of the structure.

A
  1. Measure (length of structure) and divide by magnification;
    Accept correct equation making reference to a measurement
  2. Correct conversion from measured length to μm, either
    × 10 000 from cm
17
Q

(e) Name two structures found in all bacteria that are not found in plant cells.

A
  1. Circular DNA (molecule in cytoplasm);
  2. Murein cell wall
18
Q

(f) Name two features of HIV particles that are not found in bacteria.
Do not include attachment protein in your answer.

A
  1. Capsid;
  2. Reverse transcriptase;
  3. RNA genome;
  4. Envelope;
19
Q

The detail shown in the diagram above would not be seen using an optical microscope. Explain why.

A
  1. Light has long(er) wavelength;
  2. (So) low(er) resolution;
20
Q

Name an organelle found in both a chloroplast and a prokaryotic cell.

A

(d) (70S) Ribosome;

21
Q

A biologist separated cell components to investigate organelle activity. She prepared a suspension of the organelles in a solution that prevented damage to the organelles.
Describe three properties of this solution and explain how each property prevented
damage to the organelles.
Property 1 /2 /3
Explanation

A
  1. (Ice) cold to prevent/reduce enzyme activity;
  2. Buffered to prevent denaturing of enzyme/protein;
  3. Same water potential/ Ψ to prevent lysis/bursting (of organelle);
    Accept: isotonic for same water potential.
22
Q

Some scientists support the theory that mitochondria are organelles that evolved from prokaryotic cells. Give one piece of evidence that supports the theory that mitochondria evolved from prokaryotic cells.

A

Circular DNA / smaller/70S ribosomes / no introns / no histones/proteins associated with DNA;

23
Q

A scientist examined the structure of mustard plant leaves. He viewed temporary mounts of leaf tissues with an optical microscope. The figure below shows a drawing of typical results.
(a) Describe how temporary mounts are made.

A
  1. Thin slice/ section
  2. Put on slide in water / solution / stain;
  3. Add cover slip
24
Q

Describe and explain how cell fractionation and ultracentrifugation can be used to isolate mitochondria from a suspension of animal cells.

A
  1. Cell homogenisation to break open cells
  2. Filter to remove debris / whole cells;
  3. Use isotonic solution to prevent damage to mitochondria / organelles;
  4. Keep cold to prevent / reduce damage by enzymes / use buffer to prevent protein / enzyme denaturation;
  5. Centrifuge (at lower speed) to separate nuclei / heavy organelles;
  6. Re-spin (after nuclei / pellet removed) at higher speed to get mitochondria in pellet / at bottom.
25
Q

Advantage of mitochondria

A

Able to respire aerobically;
So make (more) ATP/ release (more) energy;

26
Q

Describe the molecular structure of glycogen.

A

polymer/polysaccharide; (made of) α-glucose;
joined by 1,4 links;
glycosidic;
(chain is) branched;
1,6 links where branches attach

27
Q

Name the type of chemical reaction that takes place during the formation of glycogen.

A

hydrolyse, filtrate / juice / bond / non-reducing sugar;
with acid, then neutralise / add alkali
boil / heat with Benedict’s + test filtrate / repeat original procedure;

28
Q

This procedure does not test for non-reducing sugars, such as sucrose.
How should the procedure be altered to determine the concentration of non-reducing
sugar in the fruit juice?

A
29
Q

State one way, visible in the diagram above, in which the structure of fructose is: similar to glucose; different from glucose.

A
  • same number, carbon / oxygen / hydrogen (atoms) / OH (groups); A hexose same formula;
  • 5-membered ring / glucose has 6-membered ring;
30
Q

A student was carrying out tests to determine which biological molecules were present in a food sample. Describe a test that the student could carry out to discover whether this sample contained a lipid.

A

add / mix with, alcohol / ethanol / propanone / (suitable) organic solvent; then, add to / add / mix with, water;

31
Q

State what would be seen if a lipid was present.

A

emulsion / milky colour / cloudy

32
Q

Describe how the structure of a phospholipid differs from that of a triglyceride.

A

phospholipids have
1 less fatty acid / 2 fatty acid not 3; A hydrocarbon 1 less ester bond / 2 ester bonds not 3;
phosphate;
hydrophilic / polar, end / head;

33
Q

Describe how you would test a liquid sample for the presence of lipid and how you
would recognise a positive result.

A

Mix / shake sample) with ethanol, then water;
Sequence is important
2. White / milky (emulsion);

34
Q

Some seeds contain lipids. Describe how you could use the emulsion test to show that a seed contains lipids.

A
  1. Crush / grind;
  2. With ethanol / alcohol;
  3. Then add water / then add to water;
  4. Forms emulsion / goes white / cloudy;
35
Q

Explain why triglycerides are not considered to be polymers.

A

not made of monomers / many repeating units;

36
Q

a) Name the two scientists who proposed models of the chemical structure of DNA

A

Watson and Crick

37
Q

A scientist replicated DNA in a test tube. To do this, he mixed an enzyme with identical single-stranded DNA fragments and a solution containing DNA nucleotides. Name the enzyme used in this DNA replication.

A

DNA polymerase;

38
Q

Use your knowledge of semi-conservative replication of DNA to suggest:
1. the role of the single-stranded DNA fragments ____________________________
2. the role of the DNA nucleotides.

A
  1. Determines order of nucleotides/bases;
  2. Forms complementary pairs / A – T, G - C
39
Q

Nucleic acids, such as DNA, are polymers, made up of many repeating monomer units. Name the monomer from which nucleic acids are made.

A

nucleotide