Paper 2 Flashcards by Hannah Forster

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

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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

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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.

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How can steroid hormones rapidly enter cell?

They are hydrophobic.
Lipid soluble.
Diffuse through phospholipid bilayer

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How can transcriptional factors stimulate gene expression?

Binds to promotor
Stimulates RNA polymerase

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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.

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Why is most of the light that falls on leaves/chlorophyll not used in photosynthesis?

Light wrong wavelength.
Light is reflected.
Light misses chlorophyll.

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Products of LDR?

ATP and Reduced NADP

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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.

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Causes of genetic variation

Crossing over
Random fusion of gametes

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What would this suggest … Cw and Cr ? In terms of alleles

Codominance

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How do you ensure all water removed from a sample?

Weigh sample. Heat 80C. Weigh again. Repeat until no change in mass

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Where is a sex-link mutation located?

Non homologous section of X chromosome

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How many chromosomes in human 46 , 23 pairs

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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.

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Name 6 gene mutations which could arise during DNA replication .

Additional, deletion, substitution, inversion, duplication and translocation

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Gene mutations occur…

Spontaneously

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Mutation rate increased by …

Mutagenic agent

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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