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A Level Biology (Edexcel Salters) > Genes and Health > Flashcards

Flashcards in Genes and Health Deck (44)
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1
Q

How are the lungs adapted for gas exchange?

A

Alveoli have a large surface area.

They are surrounded by a number of capillaries which leads to a short diffusion path due to the thinness of walls.

There is a steep concentration gradient between the alveoli and the blood.

2
Q

Describe Fick’s Law.

A

Increased surface area and a greater concentration gradient increase rate of diffusion.
Thicker surface areas reduce rate of diffusion.

Rate of diffusion is directly proportional to surface area x concentration difference divided by the thickness of the surface.

3
Q

Describe primary structure of a protein.

A

Two amino acids joined as a dipeptide, via a condensation reaction, with a peptide bond.

4
Q

Describe secondary structure of a protein.

A

Chain coils into alpha helices caused by hydrogen bonds or folds into beta pleated sheets.

5
Q

Describe tertiary structure of a protein.

A

Hydrophobic or hydrophilic R groups.

Disulphide, ionic or hydrogen bonds formed.

6
Q

Describe globular and fibrous proteins.

A

Globular proteins are compact and spherical. They are soluble.

Fibrous proteins are long chains that are strong and cross-linked. They are insoluble.

7
Q

Describe the phospholipid bilayer.

A

Phosphate heads are polar and hydrophilic. Fatty acid tails are non-polar and hydrophobic.

8
Q

Define diffusion.

A

Net movement from an area of high concentration to an area of low concentration.

9
Q

Define facilitated diffusion.

A

Polar molecules and ions cross membranes using proteins or channel proteins.

Channel proteins use a signal. Gated channels use a change in potential difference.

Some proteins are carrier proteins where molecules bind to a site, causing the protein to change shape and carry the molecule across the layer.

10
Q

Define osmosis.

A

Net movement of water molecules from an area of low concentration to an area of high concentration through a partially permeable membrane. Continues until isotonic.

11
Q

Define active transport.

A

Movement from an area of low concentration to an area of high concentration using energy supplied by adenosine triphosphate.

12
Q

Define exocytosis.

A

Release of a substance using vesicles.

13
Q

Define endocytosis.

A

Taking in a molecule using vesicles.

14
Q

Describe what happens where there is extra water in the mucus.

A

Sodium is transported across the basal membrane and diffuses through sodium channels. Chlorine diffuses down an electrical gradient. Water is drawn out of cells due to the high salt concentration and then drawn out of the mucus.

15
Q

Describe what happens hen there is too little water in the mucus.

A

Chlorine is transported across the basal membrane and diffuses through an open CFTR channel. Sodium diffuses down an electrical gradient. Water is drawn out of the cell and into the mucus.

16
Q

Describe what happens in cystic fibrosis sufferers.

A

CFTR channel is absent or dysfunctional. Sodium channel is permanently open. Water is constantly being removed.

17
Q

Describe the effect of cystic fibrosis on the digestive system.

A

Difficult to maintain body mass, high basal metabolic rate, requires 120-140% of daily calorie intake.
Pancreatic duct blocked with mucus, prevents release of digestive enzymes, food is not digested properly, resulting in malabsorption syndrome.

18
Q

Describe the effect of cystic fibrosis on the reproductive system.

A

Females are less likely to become pregnant due to a mucus plug in the cervix.

Males may have a mucus plug in the cast deferens or may lack the vas deferens.

19
Q

Describe the effect of cystic fibrosis on sweat.

A

It is unusually salty.

20
Q

What is the formula for calculating BMI.

A

Weight divided by height2.

21
Q

Describe DNA.

A

Made up of a phosphate, deoxyribose sugar and a nitrogenous base of adenine, thymine, guanine or cytosine. This is a nucleotide, with phosphodiester bonds, formed by a condensation reaction.

22
Q

Describe RNA.

A

Made up of a phosphate, a ribose sugar and a nitrogenous base of adenine, uracil, guanine and cytosine.

23
Q

Describe transcription.

A

DNA helicase unzips hydrogen bonds in the double helix. RNA polymerase base pairs free complementary nucleotides, forming the coding strand, which produces a single strand of RNA.

24
Q

Describe translation.

A

mRNA leaves the nucleus to the ribosomes. Triplets of based form codons which are matched with complementary anticodons on tRNA. Amino acids attached to tRNA forms peptide bonds and primary structure.
Translation is caused by a start and a stop codon.
The code is non overlapping and degenerate.

25
Q

What are the different types of mutations?

A

Substitution, insertion, deletion, frame shift.

26
Q

Describe replication.

A

Helicase unzips DNA by breaking the hydrogen bonds. Primase lays primers from 5’ to 3’ on the leading strand. DNA polymerase builds a new strand, ligase glues the fragments together. Single stranded binding fragments stop DNA from recoiling. Primase lays primers from 3’ to 5’ on the lagging strand.

27
Q

Describe Stahl and Meselson’s experiment.

A

DNA is grown in heavy Nitrogen (15). Moved to 14N. New nucleotides were light, original were heavy. Divided and replicated once.

28
Q

Define molecular phylogeny.

A

Tests DNA to look for similarities in order to determine sequences.

29
Q

Describe amniocentesis.

A

15-17 weeks.
Inserts a needle into amniotic fluid.
1% risk of miscarriage.

30
Q

Describe chorionic villus sampling.

A

8-12 weeks.
Removal of placental tissue through the abdomen or vagina.
1-2% risk of a miscarriage.

31
Q

Describe non-invasive prenatal diagnosis.

A

7-9 weeks.

Analyses blood plasma.

32
Q

Describe pre-implantation genetic diagnosis.

A

IVF created embryos of which cells are tested.

33
Q

What are the ethical frameworks?

A

Human rights and duties
Utilitarianism
Informed consent
Living a virtuous life.

34
Q

What are the treatments for cystic fibrosis?

A
Bronchodilators, antibiotics, DNAase enzymes, steroids.
Change in diet.
Enzyme supplements.
Physiotherapy.
Transplants
Gene therapy.
35
Q

Describe gene therapy.

A

Desired gene inserted into a vector. Modified DNA put into a human cell. Produces a functional protein.

36
Q

Define intracellular reactions.

A

Enzyme reactions that occur inside cells.

37
Q

Define extracellular reactions.

A

Enzyme reactions that occur outside of the cell.

38
Q

Define catabolic.

A

Breaking down.

39
Q

Define anabolic.

A

Building up.

40
Q

Define gene.

A

A sequence of bases that codes for a characteristic.

41
Q

What happens in sickle cell anaemia?

A

There is a substitution mutation where adenine replaces thymine, resulting in the non-polar amino acid valine rather than the polar amino acid glutamic acid. This causes haemoglobin to be less soluble. The red blood cells are sickle shaped and carry less oxygen.

42
Q

What happens in cystic fibrosis?

A

There are a number of different mutations. The most common is the DF508, which is the deletion of three nucleotides, resulting in a misformed protein.

43
Q

Define allele.

A

Alternative forms of a gene found at the same locus on a chromosome.

44
Q

Define monohybrid inheritance.

A

A characteristic is only controlled by one gene.