AS Exam Questions Flashcards
(27 cards)
Describe the primary structure of all proteins.
Sequence order of amino acids joined by peptide bonds.
Genetic code.
Define universal, non-overlapping and degenerate.
Universal- same triplet always codes for the same amino acid.
Non-overlapping- each base is only part of one triplet.
Degenerate- more than one triplet codes for each amino acid.
Describe how the appearance of the area containing DNA in a TEM image of a eukaryotic cell would differ from a Streptococcus bacterium.
- Nucleus
- Nucleolus
- Mitochondria
Describe one difference between the structure of DNA in a prokaryotic cell and in a eukaryotic cell.
In prokaryotes it is circular not linear.
Streptococcus bacteria can infect the lungs when air is breathed in and cause lung disease.
Describe the mechanism of breathing that causes air to enter the lungs.
-Diaphragm muscles contract and diaphragm flattens.
-External intercostal muscles contract and ribcage pulled out.
-Causes volume increase and pressure decrease in thoracic cavity.
Suggest how Streptococcus bacteria with a thicker capsule are more likely to survive and so cause lung disease.
Thicker capsule so phagocytes less likely to bind to murein in cell wall. Reduced phagocytosis so more bacterial growth.
Describe 2 differences between the structure of the triglyceride and a phospholipid.
- Triglyceride has 3 fatty acids rather than 2.
- Triglyceride has no phosphate group.
Explain why phospholipids can form a bilayer but triglycerides cannot.
-Phospholipid both hydrophobic and hydrophillic
- Triglycerides are only hydrophobic.
- Hydrophillic / phosphate group attracts water to either side of bilayer.
Suggest why the fluidity of the membrane was higher after 4 months.
- Fatty acid A is saturated.
- At 4 months less fatty acid A and more fatty acid B
- Increase in fluidity caused by increased unsaturated fatty acids.
- Double bonds cause bends in fatty acid tail.
State one role of a helper T cell.
Stimulating B cells.
The rate of translation is increased in T cells activated by antigens.
Describe the role of tRNA in translation.
- Anticodon on tRNA binds to complementary codon on mRNA.
- tRNA brings specific amino acid to ribosome.
How do you work out surface area?
Multiply the length times the width- for 2D shapes.
Find the area of all the different faces and add them together for the total surface area- for 3D shapes
After collecting data, the student noticed that shape C, block 2 was damaged.
Suggest what the student could have done when they saw shape C, block 2 was damaged.
Repeat with an undamaged shape C block.
State a few variables that students can control sometimes in experiments in order to get valid results.
Temperature, concentration of the liquid used, type of agar
Describe how gas exchange occurs in a single-celled organisms and explain why this method cannot be used by large, multicellular organisms.
-Diffusion across the cell surface membrane.
-Large organisms have smaller surface area to volume ratio.
-Rate of diffusion too slow.
The human papilloma virus contains a double-stranded DNA genome.
Which components are found in a human papilloma virus?
Capsid and attachment protein
Name 2 enzymes that are involved in replicating the DNA of the human papilloma virus and describe their roles in the replication process.
Name of enzyme 1- DNA Helicase
Role- Breaks hydrogen bonds to unwind DNA
Name of enzyme 2- DNA polymerase
Role- Condensation reactions to join adjacent nucleotides.
Human papilloma virus infects cells that are no longer dividing. The human papilloma virus genome contains genes that code for proteins that cause human cells to restart their cell cycles.
Human papilloma virus infection can cause cancer.
Explain why.
Uncontrolled cell cycle
Human papilloma virus (HPV) is transmitted through sexual contact. More than 95% of cervical cancers (only in females) are due to HPV infection.
A vaccine is available that is over 80% effective at preventing HPV infection, if given before person is exposed to HPV.
Evaluate whether 10 to 12 year old boys should be given the HPV vaccine.
FOR
- Needs to be given early (age 10-12) before exposure to HPV.
- Will reduce transmission to girls when older.
AGAINST
- Cervical cancer only affects females. May be side effects from vaccine.
What are the definitions of species richness and index of diversity?
Species richness- number of species in an ecosystem.
Index of diversity- the relationship between the number of species in a community and the number of individuals in each species.
In recent years, knowledge of prokaryotic biodiversity in the soil has increased.
Explain why.
- DNA/genome sequencing now used.
- Now can analyse every prokaryote species in community.
- Rather than just recording measurable characteristics.
A student prepared a plant root to observe cells undergoing mitosis. He put the root in a small bottle of hydrochloric acid in a 40 degree water bath.
Why did he put the plant root in acid?
To separate cells/ cell walls.
State 2 precautions required when working with hydrochloric acid.
- Eye protection
- Wear gloves
