Paper 2 Flashcards
Iris changes the size of the pupil. Suggest how interaction of circular and radial muscles cause pupils to contract.
Contraction of circular, relaxing of radial
Explain how fovea enables x to see prey in detail
High density of cone cells.
Each cone cell is connected to a singular bipolar neurone.
So separate impulses are sent to the brain.
High visual acuity
What enables night vision?
High density of rod cells.
High visual sensitivity.
Multiple rod cells connected to single bipolar neurone.
Spacial summation used to overcome threshold.
How can steroid hormones rapidly enter cell?
They are hydrophobic.
Lipid soluble.
Diffuse through phospholipid bilayer
How can transcriptional factors stimulate gene expression?
Binds to promotor
Stimulates RNA polymerase
What property of water makes it good for experiments involving temperature changes?
Water has high specific heat capacity, meaning lots of energy required to change overall temp.
Why is most of the light that falls on leaves/chlorophyll not used in photosynthesis?
Light wrong wavelength.
Light is reflected.
Light misses chlorophyll.
Products of LDR?
ATP and Reduced NADP
Explain banding pattern on sarcomere
Darkest region - A band - myosin and actin overlap. H zone in between dark band, here just myosin. Very light zones are just actin - I band.
Causes of genetic variation
Crossing over
Random fusion of gametes
What would this suggest … Cw and Cr ? In terms of alleles
Codominance
How do you ensure all water removed from a sample?
Weigh sample. Heat 80C. Weigh again. Repeat until no change in mass
Where is a sex-link mutation located?
Non homologous section of X chromosome
How many chromosomes in human 46 , 23 pairs
During hibernation HR and metabolic rate decrease. Suggest how these are linked.
Lower metabolism. So less OC2 in blood. So less detected by chemoreceptors. So fewer impulses sent to medulla oblongata.
Fewer impulses along sympathetic pathway to SAN.
Name 6 gene mutations which could arise during DNA replication .
Additional, deletion, substitution, inversion, duplication and translocation
Gene mutations occur…
Spontaneously
Mutation rate increased by …
Mutagenic agent
Why don’t all mutations result in a change to the AA sequence?
Degenerate nature of the genetic code, multiple triplets code for an amino acid
What is the result of a frame shift mutation?
Changes all base triplets downstream of the mutation
Which cells can divide to produce any cell?
Totipotent
How do totipotent cells specialise?
During development they only translate part of their DNA, resulting in specialisation
When do totipotent cells occur
For limited time in mammalian embryos
How does oestrogen affect transcription?
Oestrogen binds to specific transcriptional factor in cytoplasm. Forming oestrogen oestrogen complex.
This complex now moves from cytoplasm into nucleus.
Complex binds to promoter of the gene, activating or repressing transcription.
What part of gene expression does interfering RNAi affect?
Affect translation not transcription
Describe structure of RNAi
Double stranded
What does siRNA stand for?
Short interfering RNA - animals only
What does miRNA stand for?
Micro RNA - plants and animals
How does siRNA WORK?
- double stranded siRNA associated with proteins in cytoplasm and unwinds to two single strands.
- one strand chose the other defeated.
- the single strand siRNA binds to target mRNA (complementary base sequence)
- the proteins associated with siRNA cut the mRNA into small fragments so it can no longer be translated.
- process the degrades these strands
How does miRNA work?
No fully complementary
Folded strand separates, then double then single strands
MiRNA binds to mRNA and prevents ribosomes from binding
mRNA is then moved to processing where it is stored or degraded
What is the epigenome?
The tags on the histone proteins which are associated with DNA - tags can be changed easily.
Are tags inherited?
Tags are removed in gametes, sometimes they can remain allowing changes to gene expression due to environmental factors to be inherited.
What is it called when you add a methyl group CH3 do DNA?
Methylation
How does increased methylation of DNA affect expression?
Alters DNA structure by preventing transcriptional factors and enzymes from binding
What is acetylation?
Adding or removing acetyl group COCH3
What happens during anaerobic and not aerobic?
Reduction of pyruvate
Describe how to carry out chromatography for separating out photosynthetic pigments.
Draw line on chromatography paper.
Using pencil.
Add chlorophyll solution to the line.
Add solvent below line.
Remove before solvent reaches end.
Mark position where solvent reaches.
When investigating seeds, why might the soil be sterilized.
To kill/remove pathogens.
Kills/removes any remaining seeds.
Name the type of reaction between two genes.
Epistatic
How is colour vision possible?
Cone cells -> colour
Each type of photoreceptor has a different pigment. Each pigement absorbs at a different range.
Why do rod cells have a high sensitivity to light?
Several photoreceptors connected to one neurone and spatial summation
Rate of carbon dioxide production is slower with maltose than glucose, why?
Maltose contains glucose as disaccharide.
So slower as the glycosidic bond would first need hydrolysed.
Reasons for conserving rainforest?
-Acts as Carbon sink to soak up carbon dioxide in the atmosphere.
-provides many habitats and supports biodiversity.
Give 3 reasons for low efficiency of the energy transfer from secondary to tertiary consumers.
Energy lost through respiration.
Energy lost through faeciea/urine.
Not all organism eaten.
Suggest two reasons why bacteria may be able to grow in antibiotics.
Mutation
The conc was too weak to kill all
Other resistant bacteria.
An inc in muscle activity causes an inc in HR. Explain how.
Inc CO2 detected by chemoreceptors.
Send more impulses to medulla.
More impulses along sympathetic nervous system.
to SAN
