Aqa A level Biology: Common AO1 Questions
Describe how tissue fluid is formed and how it is returned to the circulatory system. - Correct
Answers-Formation
1. High blood / hydrostatic pressure /
pressure filtration;
2. Forces water / fluid out;
3. Large proteins remain in capillary;
Return
4. Low water potential in capillary /
blood;
5. Due to (plasma) proteins;
6. Water enters capillary / blood;
7. (By) osmosis;
8. Correct reference to lymph;
Describe how carbon dioxide in the air outside a leaf reaches mesophyll cells inside the leaf. -
Correct Answers-1. (Carbon dioxide enters) via stomata;
2. (Stomata opened by) guard cells;
3. Diffuses through air spaces;
4. Down diffusion gradient;
Explain how water enters xylem from the endodermis in the root and is then transported to the
leaves - Correct Answers-In the root
Casparian strip blocks apoplast pathway
Active transport by endodermis
If ions/salts into xylem
Lower water potential in xylem/water enters xylem by osmosis
Xylem to leaf
Transpiration from leaves
Creates cohesion hydrogen bonding between water molecules
Adhesion, water molecules bind to xylem
Creates continuous water column
Root pressure moves water through the xylem. Describe what causes root pressure. - Correct
Answers-1. Active transport by endodermis;
2. ions/salts into xylem;
3. Lowers water potential (in xylem);
, 4. (Water enters) by osmosis;
Explain how oxygen is loaded, transported and unloaded in the blood. - Correct Answers-1.
Haemoglobin carries oxygen /
has a high affinity for oxygen /
oxyhaemoglobin;
2. In red blood cells;
3. Loading/uptake/association in
lungs;
4. at high p.O2;
5. Unloads/ dissociates / releases to
respiring cells/tissues;
6. at low p.O2;
7. Unloading linked to higher carbon
dioxide (concentration);
Explain how a change in the DNA base sequence for a protein may result in a change in the
structure of the protein. - Correct Answers-Change in amino acid/s /primary
structure;
Change in hydrogen/ionic/ disulfide
bonds;
Alters tertiary structure;
Describe how gene transmission and selection have increased the difficulty of treating bacterial
infections with antibiotics. - Correct Answers-1. (Antibiotic) resistant gene/allele;
2. Vertical (gene) transmission;
3. Resistant bacteria (survive and)
reproduce / population of resistant
bacteria increases;
4. Increase in frequency of
(resistant) allele/gene (in future
generations);
5. Horizontal (gene) transmission;
6. Plasmid;
7. Conjugation / pilus (tube);
8. (Horizontal transmission/
conjugation) can occur between
bacteria of different species;
Farmers clear tropical forest and grow crops instead. Explain how this causes the diversity of
Describe how tissue fluid is formed and how it is returned to the circulatory system. - Correct
Answers-Formation
1. High blood / hydrostatic pressure /
pressure filtration;
2. Forces water / fluid out;
3. Large proteins remain in capillary;
Return
4. Low water potential in capillary /
blood;
5. Due to (plasma) proteins;
6. Water enters capillary / blood;
7. (By) osmosis;
8. Correct reference to lymph;
Describe how carbon dioxide in the air outside a leaf reaches mesophyll cells inside the leaf. -
Correct Answers-1. (Carbon dioxide enters) via stomata;
2. (Stomata opened by) guard cells;
3. Diffuses through air spaces;
4. Down diffusion gradient;
Explain how water enters xylem from the endodermis in the root and is then transported to the
leaves - Correct Answers-In the root
Casparian strip blocks apoplast pathway
Active transport by endodermis
If ions/salts into xylem
Lower water potential in xylem/water enters xylem by osmosis
Xylem to leaf
Transpiration from leaves
Creates cohesion hydrogen bonding between water molecules
Adhesion, water molecules bind to xylem
Creates continuous water column
Root pressure moves water through the xylem. Describe what causes root pressure. - Correct
Answers-1. Active transport by endodermis;
2. ions/salts into xylem;
3. Lowers water potential (in xylem);
, 4. (Water enters) by osmosis;
Explain how oxygen is loaded, transported and unloaded in the blood. - Correct Answers-1.
Haemoglobin carries oxygen /
has a high affinity for oxygen /
oxyhaemoglobin;
2. In red blood cells;
3. Loading/uptake/association in
lungs;
4. at high p.O2;
5. Unloads/ dissociates / releases to
respiring cells/tissues;
6. at low p.O2;
7. Unloading linked to higher carbon
dioxide (concentration);
Explain how a change in the DNA base sequence for a protein may result in a change in the
structure of the protein. - Correct Answers-Change in amino acid/s /primary
structure;
Change in hydrogen/ionic/ disulfide
bonds;
Alters tertiary structure;
Describe how gene transmission and selection have increased the difficulty of treating bacterial
infections with antibiotics. - Correct Answers-1. (Antibiotic) resistant gene/allele;
2. Vertical (gene) transmission;
3. Resistant bacteria (survive and)
reproduce / population of resistant
bacteria increases;
4. Increase in frequency of
(resistant) allele/gene (in future
generations);
5. Horizontal (gene) transmission;
6. Plasmid;
7. Conjugation / pilus (tube);
8. (Horizontal transmission/
conjugation) can occur between
bacteria of different species;
Farmers clear tropical forest and grow crops instead. Explain how this causes the diversity of
