Unit 2- cells + transport =) Flashcards
(100 cards)
1
Q
What would the scientists have inserted into the plasmid along with the spider gene
to ensure that the spider gene was only expressed in the silk glands of the
silkworms?
A
Promoter.
2
Q
Suggest two reasons why it was important that the spider gene was expressed only
in the silk glands of the silkworms. (2)
A
- So that proteins can be harvested
- Fibres in others cells may cause harm
3
Q
Describe how the Golgi apparatus is involved in the secretion of enzymes. (1)
A
- modifies proteins
- packages into vesicles
- transport to cell surface
4
Q
A transmission electron microscope was used to produce the image in the figure
above.
Explain why. (2)
A
- High resolution;
- Can see internal structure of organelles.
5
Q
Describe and explain how centrifuging the culture allowed the scientists to obtain a
cell-free liquid. (3)
A
- Large / dense / heavy cells;
- Form pellet / move to bottom of tube (when centrifuged);
- Liquid / supernatant can be removed.
6
Q
Explain why the homogenate was filtered before spinning at low speed in the centrifuge. (2)
A
- Remove debris
- Which may contaminate pellet 1
7
Q
Explain why the scientists homogenised the tissue. (1)
A
Break open cells –> release cell contents
8
Q
Give one advantage of SEM over TEM.
A
- Specimen X have to be thin
- 3D
9
Q
Describe and explain the appearance of chromosomes in metaphase/ (2)
A
- DNA replicated
- each chromosome consists of 2 chromatids/ attached at centromere
10
Q
Suggest why a number of chromosomes has doubled in metaphase. (1)
A
DNA replicated but no cell division yet
11
Q
Cloning frogs by nuclear transfer: nuclei from brown embryos, placed into empty green eggs.
- What colour would the cloned offspring be? (1)
- Give 2 differences between the nuclei removed from the embryo cells and the nuclei discarded from the unfertilised egg cells. (2)
A
- brown- genes/ genetic info from NUCLEUS
- embryo- diploid vs egg- haploid
contain diff. alleles of colour gene
12
Q
Only 30% of cloned cells in nuclear transfer successfully developed into embryos.
Suggest a reason for this low success rate. (1)
A
Damage to nucleus during transfer.
13
Q
Explain how a gene codes for a protein. (2)
A
- base sequence
- determines sequence of a.a.
- by determining base sequence on mRNA
- 3 bases code for an a.a.
14
Q
What are homologous chromosomes? (2)
A
- pairs of chromosomes
- w/ same genes/ genes for same features
- in same sequence
15
Q
U. marinum cells (eukaryotic) ingest bacteria and digest them in the cytoplasm.
Describe the role of one named organelle in digesting these bacteria. (3)
A
- lysosomes
- fuse w/ vesicles
- releases hydrolytic enzymes (lysozymes)
16
Q
Suggest one explanation for the faster rate of plasmid replication in cells growing in a culture with a high amino acid concentration. (2)
A
- protein synthesis
- ↑ enzymes for DNA/ plasmid replication (eg. DNA polymerase)
// - a.a. used in respiration
- ↑ energy for DNA replication
17
Q
Name two structures present in eukaryotic cells that are not present in the cells of prokaryotes. (2)
A
- Nucleus/ mitochondria
- Linear DNA/ chromosomes
18
Q
Describe what is meant by a malignant tumour. (3)
A
- mass of undifferentiated cells
- uncontrolled cell division
- metastasis
19
Q
Suggest why death rate from malignant skin tumours increases with age. (1)
A
- cancer takes time to develop
- old ppl have ↓ effective immune systems
- ↑ time exposed to UV
20
Q
Explain why skin colour was a factor likely to affect the death rate. (2)
A
- dark skin (pigment) prevents burning
- ↓ cancer risk in dark skinned ppl
21
Q
Describe the roles played by
1. nucleus
2. ribosomes
3. golgi
in secreting a protein. (3)
A
- carries genetic code (DNA)
- binds a.a. –> protein synthesis
- modifies proteins –> glycoproteins
22
Q
Haemoglobin is a protein. Explain why a mature red blood cell cannot make haemoglobin. (2)
A
- x nucleus
- x code for protein/ x make RNA
// - x ribosomes
- proteins x synthesised
// - x mitochondria
- x ATP for protein synthesis
23
Q
Spectrin strengthens the membrane and is involved in maintaining the three-dimensional shape of the red blood cell.
Some people have red blood cells that do not contain spectrin. These red blood cells are
spherical in shape. They also burst more quickly when put in distilled water.
Explain why more oxygen is taken up by normal red blood cells than by these
spherical cells. (1)
A
- ↑ s.a. : vol/
- ↓ distance to centre
24
Q
Describe the structure of an amino acid molecule and explain how amino acids link together. (6)
A
- Carbon with 4 groups attached
- amine & carboxyl
- R-group/ side chain + H atom
- R-group differs in diff. a.a.
- a.a. joined by condensation
*** - peptide bond formed between NH2 and COOH;
- H from amine + OH from carboxyl
- removal of molecule of water;
25
Describe the path of a molecule of oxygen from the air in the alveolus to the plasma
membrane of a rbc. (1)
- EPITHELIUM of alveolus
- capillary wall
- plasma mem
26
Describe and explain how you would expect the height to breadth ratio of an
epithelial cell from a lung alveolus to differ from the height to breadth ratio of a
milk-producing cell. (2)
- lower
- ↑ s.a. / thin
- for diffusion
27
Testing cancer drugs with mice:
Suggest and explain 2 factors which should be considered when deciding the number of mice to be used in this investigation. (2)
- large no.- RELIABLE
- too many- x ethical ∵ likely leads to death
- too many- expensive/ hard to keep in a lab
28
The scientists measured the volume of tumours.
Explain the advantage of using volume rather than length to measure the growth of tumours. (1)
- diff. shapes ∵ x grow uniformly
29
The scientists concluded that taxol was effective in reducing the growth rate of the tumours over the 50 days of treatment.
Use suitable calculations to support this conclusion.
(Comparing effects of 2 different drugs using volume of tumour over time under treatment)
- rate of growth for each
- ratio of vol at end
- percentage decrease for each
30
In cells, taxol disrupts spindle activity. Use this information to explain the results in the group that has been treated with taxol. (3)
- spindle x attach to chromosomes in metaphase
- chromatids x pulled apart by spindle in anaphase
- slower cell division
31
What information does standard deviation give? (1)
Degree of variation around the mean
32
Suggest why the development of a monopolar mitotic spindle would prevent successful mitosis. (2)
- chromatids x pulled apart by spindle in anaphase
- all go to one pole of cell
- one daughter cell would have no chromosomes
- the other would be diploid
33
More cancer cells could be destroyed if the drug was given more frequently.
Suggest why it was not given more frequently. (2)
- too many healthy cells killed
- ∴ takes time to replace cells
- may have side effect/ lead to death
34
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. (4)
- **DNA in nucleus codes for proteins**
- production by ribosomes on RER
- MITOCHONDRIA- **ATP** for protein synth.
- modified by golgi (by adding carbs--> glycoproteins)
- transported by vesicles--> fuse w/ cell mem.
35
Suggest why the chloroplasts are, but the nucleus is not visible in a microscopic image. (1)
- outside of plane of section
// - x stained
36
Name an organelle found in both a chloroplast and a prokaryotic cell. (1)
70S ribosomes
37
Name two structures present in plant cells that are not present in animal cells. (1)
1. cell wall
2. chloroplasts
3. vacuole
4. starch grains
38
DNA and RNA can be found in bacteria.
Give two ways in which the nucleotides in DNA are different from the nucleotides in RNA. (2)
1. Thymine vs Uracil
2. Deoxyribose vs Ribose
39
No organelles are visible in the cytoplasm of this red blood cell.
Suggest why. (1)
Cytoplasm occupied by haemoglobin
40
Before the cell was examined using the electron microscope, it was stained. This stain caused parts of the structure of the cell-surface membrane to appear as two dark lines.
Suggest an explanation for the appearance of the cell-surface membrane as two dark lines. (3)
- cell surface membrane = phospholipid bilayer
- stain binds to phosphate
- inside and outside of membrane
41
Describe binary fission in bacteria. (3)
- replication of DNA
- replication of plasmids
- cytoplasm divides
42
Suggest and explain how two environmental variables could be changed to increase the growth rate of bacterial cells. (4)
1. ↑ temp--> ↑ enzyme activity (↑ ke)
2. ↑ glucose conc. --> ↑ respiration
3. ↑ O2--> ↑ respiration
4. ↑ phosphate conc. --> ↑ ATP/ DNA/ RNA
5. ↑ nucleotide conc. --> ↑ DNA synthesis
43
Describe the role of the spindle fibres and the behaviour of the chromosomes during prophase. (2)
- chromosomes condense
- centromeres attach to spindle fibres
44
Suggest and explain why ABZ could be used as a treatment for cancer even though it affects some healthy cells. (1)
Cancer cells divide ↑ + ↑ rapidly + uncontrollably
vs healthy cells divide less + ↑ slowly
45
The epithelial cells of the small intestine have large numbers of mitochondria.
Explain how this is an adaptation for the function of the organelle. (3)
- ↑ respiration in cells
- ↑ energy released from A.T.
- for absorption of digested food
46
Describe two ways in which both types of tumour may cause harm to the body. (2)
1. May cause blockages.
2. May put pressure on organs.
47
What is the link between sunbathing and skin cancer? (2)
1. Sun's radiation contains UV light
2. UV light leads to mutation of genes which control cell division.
48
Explain how the doctor could have recognised which cells were in interphase when looking at the tissue samples. (1)
- x visible chromosomes
- nucleus can be seen
49
1. The scientists used a control group in the drug trial. Explain why. (1)
2. Suggest how the control group would have been treated. (2)
1. see effect of drug
2. placebo; otherwise treated the same
50
The action of the carrier protein is linked to a
membrane-bound ATP hydrolase enzyme.
Explain the function of this ATP hydrolase. (2)
- releases energy
- so **ions** can be transported against conc gradient by A.T.
51
The movement of Na+ out of the cell allows the absorption of glucose into the cell lining the ileum.
Explain how. (2)
- **maintains conc. gradient of Na+**
- moves **into** cell **bringing glucose** w/ it in **co-transport**
52
Suggest how the increase in temperature of the water caused the release of the red pigment from cells of the beatroot. (2)
- **damage** to cell-surface mem
- **proteins denature**
- ↑ **fluidity** of phospholipid bilayer
53
In mammals, in the early stages of pregnancy, a developing embryo exchanges substances with its mother via cells in the lining of the uterus. At this stage, there is a high concentration of glycogen in cells lining the uterus.
Suggest and explain two ways the **cell-surface membranes** of the cells lining the uterus may be **adapted to allow rapid transport of nutrients**. (2)
1. **folded mem**- ↑ s.a.
2. **large no.** of **protein channels + carriers** for **facilitated diffusion / co-transport**
3. large no. of **carrier proteins** for **A.T.**
54
NHE3 actively transports one sodium ion into the cell in exchange for one proton (hydrogen ion) out of the cell.
Use your knowledge of transport across cell membranes to suggest how NHE3 does this. (3)
- **co-transport**
- Na+ and proton **bind** to protein
- **hydrolysis of ATP**
- protein **changes shape** to transport them across the mem
55
High absorption of salt from the diet can result in a higher than normal concentration of salt in the blood plasma entering capillaries. This can lead to a build-up of tissue fluid.
Explain how. (2)
- ↑ salt ↓ ψ of **tissue fluid**
- ↓ water reabsorbed into capillary by **osmosis**
56
Compare and contrast the processes by which water and inorganic ions enter cells. (3)
S:
1. both move **down conc. gradient**
2. both move through **protein channels** in mem
D: **ions** moved **against gradient by A.T.**
57
The scientists measured the absorption of each sample of blood plasma using a **colorimeter**. They used a **calibration curve** to find the concentration of protein in samples of blood plasma.
Describe how the scientists could obtain data to produce a calibration curve and how they would use the calibration curve to find the concentratiom of protein in a smaple of blood plasma. (3)
- produce known concentrations of protein
- measure **absorbance** of each concentration w/ the colorimeter
- plot a **graph** of absorbance on the y-axis against conc. on x-axis + draw a **curve**
- find protein conc. w/ absorbance of sample from curve
58
Explain why a potato cylinder placed in distilled waterincreased in length. (2)
- ψ ↑ **-ve** inside potato
- water *enters* by osmosis--> **cells** become turgid
59
Explain why the potato cylinder placed in the 1.0 mol/dm3 sucrose solution showed no further decrease in length after 40 minutes. (2)
- ψ reached equilibrium (isotonic)
- x further osmosis (**net movement** of water)
//
- **all water** has **moved out**- x water remaining in potato
- **cell wall prevents further shrinkage**
59
Explain why the structure of a membrane is described as *fluid-mosaic*. (2)
- **fluid**- molecules can move
- **mosaic**- *proteins floating among phospholipids*
60
Describe 2 functions of the cell surface membrane. (2)
1. **selectively permeable**- impermeable barrier to water-soluble substances, ✔ non-polar substances
2. **maintains conc. gradient** on both sides
3. mem **self-sealing**, ✔ **fuse** w/ other mem + form **vesicles**
60
Give one function of a glycoprotein in a cell membrane. (1)
- **cell recognition**
- binding to hormones
61
Explain how the doctor could have recognised which cells were in interphase when looking at the tissue samples. (1)
**x visible chromosomes**
62
Describe 2 ways in which both types of tumour may cause harm to the body. (2)
1. may **damage** the organ concerned
2. may cause **blockages**/ obstructions
3. may damage/ **exert pressure on other organs**
63
Explain the link between sunbathing and skin cancer. (2)
- UV radiation from sun's radiation
- causes mutation of **genes controlling division**
64
Suggest why fair-skinned people are at a greater risk of skin cancer than dark-skinned people when sunbathing. (1)
- fair skin- little **melanin** (dark pigment)
- which **protects against UV radiation**
65
Suggest why people with a family history of cancer are at a greater risk of cancer than those with no family history of cancer. (1)
cancer has **genetic component** (gene may be inherited)
66
The rate of cell division is important in investigations into cancer.
Suggest why. (2)
- ↑ rate of **cell division**--> **faster growth**
- measure rate of cell division --> **effectiveness** of treatment
| 'cell division'- use word from q
67
Scientists have investigated the effects of a cancer drug, bromelain, on cancer growth in humans.
Suggest why they gave bromelain in addition to, rather than instead of, the usual treatment. (2)
- unethical to **replace conventional treatment**
- ∵ life of patient at risk
68
Give 2 functions of proteins in plasma membranes. (2)
1. **enzymes**
2. **cell recognition**
3. receptors
4. carriers/ channels
69
Explain how the shape of a red blood cell allows it to take up a large amount of oxygen in a short time. (2)
1. **large s.a. : vol** --> diffusion
2. **flat**- short diffusion pathway --> O2 ✔ **reach all haemoglobin**
70
No cells are seen, slide appears a uniform pale red colour when detergent is added to a sample of blood.
Detergent dissolves lipids.
Explain why. (2)
1. phospholipid bilayer **broken down**
2. **allows haemoglobin to leak out**
71
Name an organelle in a plant cell that is not surrounded by 2 membranes.
Golgi
72
Give one way in which the student could ensure the first three beetroot cylinders were kept at 25C throughout her experiment. (1)
- measure temp at **regular intervals**
- **AND** add ↑ tap water if temp increased above 25C - vice versa (correct when temp fluctuates)
73
How does ethanol damage beetroot cells? (1)
Ethanol **dissolves phospholipid bilayer**
74
Explain why molecules of oxygen and carbon dioxide are able to diffuse across membranes. (2)
- **lipid** in mem = **non-polar**
- O2 + CO2 = small & non-polar
- can **diffuse** through molecules in bilayer
- **down conc. gradient**
75
The student produced the sucrose solutions with different concentrations from a concentrated sucrose solution.
Name the method she would have used to produce these sucrose solutions. (1)
Dilution series
76
The addition of a respiratory inhibitor stops the absoprtion of amino acids.
Explain why. (3)
- x ATP produced --> x a.t.
- Na+ x moved
- x conc. gradient for Na+ so x a.a. can be moved into cell tgt
77
A student is observing the lower epidermis of a leaf using an optical microscope.
Describe how she could use an eyepiece graticule to determine the mean diameter of stomata. (3)
- eyepiece graticule- measure each stoma
- calibrated **against** stage micrometer
- **take a number of measurements** --> calculate mean
78
Give two structures found in all prokaryotic cells and in all eukaryotic cells. (2)
1. cell mem
2. **ribosomes**
3. cytoplasm
4. DNA
79
Describe how a sample of chloroplasts could be isolated from leaves. (4)
1. **homogenise** (break open cells) + filter
2. in cold, isotonic, buffered solution
3. **centrifuge** at low speed--> remove nuclei (1st pellet)
4. centrifuge at a higher speed --> cholorplasts = 2nd pellet
80
Name and describe five ways substances can move across the cell-surface membrane into a cell. (5)
1. diffusion- non-polar substances down conc gradient
2. osmosis- of H2O down Ψ gradient
3. a.t.- against conc gradient through carrier protein using ATP
4. co-transport- 2 **diff.** substances using carrier protein
5. f. diffusion- down conc gradient through channel proteins
81
Explain the arrangement of phospholipids in a cell-surface membrane. (2)
- bilayer
- hydrophilic phosphate heads **attracted to water** vs hydrophobic fatty acid tails **repelled from water**
82
Describe how lactose is formed and where in the cell it would be attached to a polypeptide to form a glycoprotein. (4)
1. glucose + galactose
2. joined in condensation
3. joined by **glycosidic bond**
4. attached to polypeptide in Golgi apparatus
83
Describe the mechanism for the absorption of amino acids in the ileum. (4)
- **facilitated diffusion** of a.a. into cell
- co-transport
- Na+ ions actively transported from cell **to blood**
- creates a Na+ ion conc gradient
- **facilitated diffusion into blood**
84
Give 2 types of molecule from which a ribosome is made. (2)
1. rRNA
2. protein
85
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. (1)
**shorter** wavelength **between e-**
86
Name 2 structures found in **all** bacteria that are **not** found in plant cells. (2)
1. circular DNA
2. **murein** cell wall
3. 70S ribosomes
87
Name 2 features of HIV particles that are not found in bacteria.
Do not include attachment protein. (2)
1. capsid
2. reverse transcriptase
3. **RNA genome**
4. envelope
88
What is a tumour? (2)
1. **mass of cells**
2. uncontrolled mitosis
89
Describe how you would determine a reliable mitotic index (MI) from tissue observed with an optical microscope.
Do not include details of how you would prepare the tissue observed with an optical microscope. (3)
1. count cells in mitosis in **field of view**
2. divide this by total no. of cells in fov
3. **repeat many times**/ select fov at random
90
The student used a sterilised pipette to transfer *E. coli* into each culture.
Suggest why the number of *E. coli* cells per mm3 in each culture after 24 hours might have been lower if the student had not used a sterilised pipette.
Explain your answer. (2)
- **unknown microorganisms** introduced
- which use food/ bacteria produce toxins
91
Describe the role of a centromere in mitosis. (2)
- **holds chromatids tgt**
- attaches to spindle fibres
- divides in anaphase so chromatids can be separated
92
Homologous chromosomes carry the same genes but they are not genetically identical.
Explain why. (1)
carry **diff. alleles**
93
Multi-locus typing (MLST) is a method used by scientists to establish how closely related different bacterial strains are. This method involves comparing several genes which are known to differ between different strains.
Suggest how scientists use MLST to identify how closely related different strains are. (2)
- compare **DNA** base seq.
- **↑ no. of differences when compared, ↓ closely related the strains**
94
To produce a mitotic index for cells during embryogenesis, scientists calculate the proportion of cells that are undergoing mitosis from a sample of cells.
Give two things that the scientists should do to ensure their mitotic index is reproducible. (2)
1. use **consistent method** when counting cells at edge of field of view
2. **large sample**
3. repeat
95
Give two features of all prokaryotic cells that are not features of eukaryotic cells. (1)
1. x mem-bound organelles
2. circular DNA free in cytoplasm
3. DNA x ass. w/ histones
96
Scientists observed these APs (antimicrobial channel proteins) on prokaryotes using a transmission electron
microscope. They stained the APs using a monoclonal antibody with gold attached to it.
Suggest how these techniques allowed observation of APs on prokaryotes. (3)
- antibody binds to AP
- ∵ 3' struc is **complementary**
- gold interacts w/ e- in TEM (deflected)
- **TEM used ∵ high res**
97
Field of view of cells in mitosis-
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. (2)
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;
98
The dark stain used on the chromosomes binds more to some areas of the chromosomes than others, giving the chromosomes a striped appearance.
Suggest one way the structure of the chromosome could differ along its length to result in the stain binding more in some areas. (1)
- diff base **seq**/
- diff histones
