Biology 3

Front 1

Explain why the values for the pressure in the xylem are negative.

Back 1

(Inside xylem) lower than atmospheric pressure / (water is under) tension;

Front 2

Explain the difference in thickness between the pulmonary artery and the pulmonary
vein.

Back 2

there's higher blood pressure in the artery,so thicker muscle larger than pulmonary vein to sooths out blood flow. the atery wall is thicker because contains more collagen,elastic fires.

Front 3

The thickness of the aorta wall changes all the time during each cardiac cycle.
Explain why.

Back 3

the aorta wall streth under high pressure because ventricles contracts.
when ventricle relaxes, the pressure fall the arota recoil. hence change all the time during each cardiac cycle to maintain smooth flow.

Front 4

Describe how tissue fluid is formed and how it is returned to the circulatory system.

Back 4

capillaries are narrower than arteries thus create hydrostatic pressure.
then fluid force out of the capillaries to decrease hydrostatic pressure.
but large proteins are remain in capillaries.

When the blood reaches the venous end of the capillaries it has a lower hydrostatic pressure than the tissue fluid outside them (in the tissues), so tissue fluid is forced back into the capillaries. water re-enter the capillarary by osmosis because the water potential is lower in capillary.
but not all the tissue fluid will return to the capillary the rest move into the lymatic system.

Front 5

why using control group?

Back 5

To show the effect of independent variable, (allow to compare without independent variable)

Front 6

when evaluate the graph , conclusion

Back 6

state bad and good

Front 7

Give two ways in which a bacterium could become resistant to an antibiotic.

Back 7

1. Mutation;
2. Horizontal transmission / conjugation

Front 8

S. aureus lives inside people’s mouths. Some dentists believe that this bacterium can
get into the blood of people who have had teeth extracted and infect their heart valves.
The people chosen to be included in the survey were all of a similar age. Suggest why

Back 8

Age affects immune system / heart / teeth;

Front 9

take antibiotics but not finish the course

Back 9

1. Antibiotic reduces number of bacteria;
2. (Survivors have) resistant gene/allele;
3. (Resistant bacteria) reproduce/multiply;

Front 10

Use your knowledge of the cell cycle to explain why some cells had 8.4 units of DNA
and others had only 4.2 units.

Back 10

1. 8.4/cells with twice DNA content = replicated DNA / late interphase / prophase / metaphase / anaphase;
2. 4.2 = DNA not replicated / (early) interphase / telophase / cell just divided / finished mitosis;

Front 11

A scientist carried out breeding experiments with catfish from different populations.
Describe how the results could show that the catfish belong to the same species.

Back 11

produce the offspring that can fertile.

Front 12

Give ways in
which courtship increases the probability of successful mating.

Back 12

1. Attracts/recognises same species;
2. Attracts/recognises mate/opposite sex;
3. Indication of sexual maturity/ fertility / synchronises mating;
4. Stimulates release of gametes;
5. Form pair bond;

Front 13

Explain how mutation leads to the formation of non-functioning enzyme PAH.

Back 13

1. Change in amino acid/(sequence of) amino acids/primary structure;
2. Change in hydrogen/ionic/ disulphide bonds;
3. Alters tertiary structure/active site (of enzyme);
4. Substrate not complementary/cannot bind (to enzyme/active site) / no enzyme-substrate complexes form;

Front 14

One mutation causing phenylketonuria was originally only found in one population in
central Asia. It is now found in many different populations across Asia. Suggest how
the spread of this mutation may have occurred.

Back 14

Founder effect / colonies split off / migration / interbreeding;

Front 15

Frequent treatment with vancomycin can result in resistant strains of bacteria. Explain
how

Back 15

1. Mutation present/occurs;
2. Resistance gene/allele;
3. Resistant bacteria (survive and) reproduce;
4. Vertical (gene) transmission / Horizontal (gene) transmission / conjugation;

Front 16

Use your knowledge of gene transmission to explain how the gene was passed from
one species of bacterium to another.

Back 16

1. Horizontal (gene) transmission;
2. Via conjugation/pilus;
3. Plasmid/Gene/DNA replicated/copied;
4. Plasmid transferred (to S.aureus);

Front 17

Scientists can use protein structure to investigate the evolutionary relationships
between different species. Explain why.

Back 17

1. Amino acid sequences / primary structure;
2. Closer the (amino acid) sequence the closer the relationship;
3. (Protein structure) related to
(DNA) base/triplet sequence;

Front 18

Comparing the base sequence of genes provides more evolutionary information than
comparing the structure of proteins. Explain why.

Back 18

1. Reference to base triplets/triplet code / more bases than amino acids / longer base sequence than amino acid sequence;
2. Introns / non-coding DNA;
3. Degeneracy of code / more than one code for each amino acid;

Front 19

Root pressure moves water through the xylem. Describe what causes root pressure.

Back 19

Endodermis cells actively transport ions into the cell to lower the water potential this means more water is absorbed by osmosis.

Front 20

the cohesion tension theory-MASS FLOW

Back 20

transpiration causes lower pressure in the leaves, so water is suck up the stem to replace the lost of water.
the coloum of water in xylem vessel is therefore under tension. water molecules stick together by hydrogen bond.

Front 21

Explain how oxygen is loaded, transported and unloaded in the blood.

Back 21

haemoglobin carry oxygen in red blood cell. at high partial pressure like in the lungs,haemoglobin have high affinity for oxygen so it loads oxygen.
at tissue have a low partial pressure of oxygen as it has been used in respiration , haemoglobin have low affinity for oxygen so it unloads oxygen.

Unloading linked to higher carbon dioxide (concentration);

Front 22

how partial pressure of carbon dioxide affects oxygen unloading?

Back 22

pco2 affects oxygen unloading. haemoglobin gives up its oxygen more readily at high pco2.

Front 23

BOhr effect

Back 23

when cell respire they produce carbon dioxide, which rise the pco2. this increase the rate of oxygen unloading- this dissociation curve shift to the right . the saturation of blood with oxygen is lower for a given oxygen， meaning more oxygen is being released.

Front 24

Describe how the control group should have been treated

Back 24

Treated the same;
but without independent variable( state)

Front 25

Volunteers who drank the same concentration of caffeine solution often had different
concentrations of caffeine in their blood. Suggest one reason for the difference in
concentration of caffeine in the blood of volunteers.

Back 25

1. Absorb different amounts;
2. Broken down by enzymes/digested;
3. Different blood volumes;
4. Differences in metabolism;
5. Caffeine from a different source

Front 26

The investigation showed that caffeine reduces the blood flow to certain parts of the
brain. Suggest one way in which this could lead to a reduced risk of brain cancers.

Back 26

1. Less oxygen/glucose to (cancer) cells;
2. Less carcinogens;
3. Reduces spread of cancer (cells);

Front 27

How does carbon dioxide reduce haemoglobins affinity for oxygen?

Back 27

Dissolved carbon dioxide is acidic - the low pH causes haemoglobin to change shape.

Front 28

what bond join chains of beta glucose in cellulose

Back 28

hydrogen bond

Front 29

what bond join together monosaccharide

Back 29

glycosidic

Front 30

apoplast

Back 30

the cell wall are quite thick and open, so water simply diffusion down the water pentential gradient.
at the endodermis the water stop because the water proof casparian strip seals the apoplast pathway.at this point water has to cross the cell membrane by osmosis

Front 31

symplast

Back 31

water is absorb into root hair cells by osmosis. since the cells have a lower water potential in the cell than soil.
water diffuses through the cortex including endothemis to xylem down the water potential gradient.