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Biology Edexcel A Alevel > Topic 2 > Flashcards

Topic 2 Flashcards

1
Q

What 3 factors make the gas exchange system in lungs very efficient?

A
  • Large surface areas of alveoli,
  • numerous capillaries
  • thin walls of capillaries and alveoli
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2
Q

What are the properties of gas exchange surfaces in living organisms?

A

Large Surface area to volume ratio, thickness of gas exchange surfaces and difference in concentration gradient.

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3
Q

What causes the molecules to form a bilayer?

A

The head contains the phosphate group and is hydrophilic so attracts water.

The tail is made of two fatty acids and is hydrophobic so repels water.

So the molecules automatically arrange themselves into a bilayer.

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4
Q

Describe the structure of the fluid mosaic model? including the different molecules found within

A

Proteins are able to move around within the bilayer due to its ‘fluid’ nature.

Glycoproteins: Protein with a polysaccharide (carbohydrate) chain attached.

Glycolipids: Lipids with a polysaccharide chain attached

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5
Q

What impact does cholesterol have on the bilayer?

A

It fits in between the phospholipids, forming bonds with them. Which makes the membrane more rigid.

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6
Q

What is the differences between the two types of protein on a phospholipid bilayer?

A

Integral- fully embedded within the phospholipid Peripheral - loosely attached to the outside surface

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7
Q

Give five ways substances move through cell membranes

A

Diffusion, osmosis, active transport, exocytosis and endocytosis

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8
Q

When will diffusion always occur?

A

When there is a difference in concentration between two areas ie the concentration gradient

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9
Q

How do non polar molecules travel through the bilayer?

A

Channel proteins

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10
Q

How do gated channels work?

A

They are different shapes to allow only one type of ion or molecule and can also be open or closed in the presence of a signal

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11
Q

What do carrier proteins do?

A

Ions/molecules bind to a specific site on a protein. The protein changes shape and they cross the membrane

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12
Q

The more cholesterol the more ….. the membrane?

A

rigid

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13
Q

What is meant by passive transport?

A

No metabolic energy is needed for transport

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14
Q

How does bulk transport take place?

A

Exocytosis and endcytosis

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15
Q

What does bulk transport use? e.g exocytosis and endocytosis

A

Vesicles either created or fused with cell surface membrane

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16
Q

What is the basic structure of mononucleotides?

A

Deoxyribose or ribose linked to a phosphate and a base

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17
Q

What is the structure of a strand of DNA/RNA?

A

Polynucleotides composed of mononucleotides linked through condensation reactions.

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18
Q

What reaction holds together mononucleotides?

A

Condensation reaction

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19
Q

What bond forms between the phosphate molecule and the (ribose sugar) deoxyribose/ribose? of two adjoining nucleotides?

A

Phosphodiester

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20
Q

What bond holds together two complimentary bases in a DNA double helix?

A

Hydrogen bonds

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21
Q

What happens in transcription ?

A
  1. RNA polymerase attaches to the DNA and the hydrogen bonds between bases break and the DNA molecule unwinds.
  2. The template strand is transcribed to make an mRNA molecule with the same DNA sequence as the DNA coding strand.
  3. RNA nucleotides get into position and then phosphodiester bonds form to produce an mRNA molecule.
  4. The mRNA molecule leaves through a pore in the nuclear envelope.
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22
Q

Where does transcription take place?

A

nucleus

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23
Q

What is the name of a codon for DNA?

A

Triplet

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24
Q

What is the name of the triplet for tRNA?

A

Anti-codon

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25
Q

What is the anti-codon for mRNA called?

A

Codon

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26
Q

What is the nature of the genetic code?

A
  1. 3 bases (triplet) code for one amino acid
  2. The code is non-overlapping and each triplet code is adjacent
  3. The code is degenerate a several triplets can code for the same amino acid.
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27
Q

What is a gene?

A

A sequences of bases on a DNA that codes for a sequence of amino acids on a polypeptide chain

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28
Q

What is the basic structure of an amino acid?

A

Amine group, residual and carboxcylic acid group

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29
Q

What does an amine group look like?

A

A carbon bond in the centre with a nitorogen and two single bond hydrogens

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30
Q

What does a carboxcylic acid group look like?

A

Carbon attached to a carbon with a double bond oxygen and single bond OH

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31
Q

What bonds in an amino acid are attached to the central carbon?

A

N,H,C,R

32
Q

What are proteins made up of?

A

amino acid monomers

33
Q

What bonds form a protein?

A

Peptide bonds

34
Q

What reaction form the bonds in a protein?

A

Condensation

35
Q

What 5 bonds form a proteins 3 D structure?

A

Hydrogen bonds, covalent disulphide bonds, ionic bonds, hydrophilic and hydrophobic bonds

36
Q

Which is soluable; fibrous or globular?

A

Globular

37
Q

What is the structure of globular proteins?

A

Compact spherical shape and soluable due to hydrophilic side chains

38
Q

What is the structure of fibrous proteins?

A

They remain as long chains and are insoluble

39
Q

Why do proteins primary structure have such an effect on 3 D structure?

A

Chemical bonds and hydrophobic interactions between r groups maintain the tertiary structure

40
Q

What type of proteins are enzymes?

A

globular proteins

41
Q

What is the site on the enzyme where the catalytic reaction takes place called?

A

Active site

42
Q

What is the role of enzymes?

A

Biological catalyst that reduces activation energy

43
Q

What are intracellular enzymes?

A

They catalyse reactions inside cells

44
Q

What are extracellular enzymes?

A

They are produced by cells catalysing reactions outside of cells eg tissue fluid or blood

45
Q

What does DNA polymerase do in DNA replication?

A

Links adjacent nucleotides

46
Q

What bonds form between adjacent nucleotide

A

Phosphodiester bonds

47
Q

What bonds form between the complimentary bases

A

Hydrogen bonds

48
Q

Why do we think that DNA replication is semi-conservative?

A

Meilson and Stahl found that each DNA strand contained one new strand and one parent strand

49
Q

Why might errors in replication lead to DNA replications?

A

If it plays a role in protein synthesis it may cause a genetic disorder

50
Q

What is the most common way of cystic fibrosis occuring?

A

The deletion of 3 nucleotides - so missing one amino acid resulting in misfolding of the protein

51
Q

What is an allele?

A

A different form of a gene that codes for a different version of a characteristic

52
Q

What is a genotype?

A

A description of a pair of alleles present for a characteristic

53
Q

What is a gene?

A

A section of DNA that codes for a train or characteristic

54
Q

What is a phenotype?

A

Physical expression of the alleles

55
Q

What does dominant mean?

A

An allele that will always be expressed when present

56
Q

What does incomplete dominance mean?

A

A cross between organisms with two different phenotypes produces offspring with a third phenotype that is blending parental traits eg red and white = pink

57
Q

What does homozygote mean?

A

HH or hh - two of the same

58
Q

What does heterozygote mean?

A

Two different e.g Hh

59
Q

what would they be?

A

Ff

60
Q

How does cf impact the gaseous system?

A

Cillia cannot move mucus Due to transport of sodium and chloride ions not being effective If sodium and chloride ions cannot flood Water cannot follow through osmosis

61
Q

How does CF mutation affect pancreas in patients?

A

pancreatic duct is blocked by sticky mucus Impair the release of digestive enzymes Lowering the concentration of enzymes within the small intestine Reducing the rate of digestion so nutrients not full absorbed

62
Q

How does the CF mutation impact the reproductive system in females?

A

Mucus develops in the cervix stopping sperm from reaching the egg

63
Q

How does the CF mutation impact the reproductive system in males?

A

The sperm duct wont be there or is blocked

64
Q

WHat are the 3 uses of genetic screening?

A

confirm a diagnosis identify carriers testing embryos

65
Q

What are the implications of prenatal screening

A

abortion is an option

66
Q

What are the 4 ethics frameworks

A

Right and duties max amount of good in world making decisions by self leading a virtuous life

67
Q

What is ficks law equation?

A

Rate of diffusion= (surface area x difference in concentration) / thickness of the gas exchange surface

68
Q

How does the structure of the mammalian lung adapt it for rapid gaseous exchange?

A
  1. Large surface area of the alveoli
  2. Numerous capillaries around the alveoli
  3. Thin walls of the alveoli and capillaries meaning a short distance between the alveolar air and blood in the capillaries.
69
Q

What is meant by osmosis?

A

The movement of free water molecules through a partially permeable membrane

70
Q

What did scientists before the 1970s believe cell membranes were composed of? and why?

A

Scientists believed that cell membranes were composed of a phospholipid layer between two continuous layers of proteins. Because the electron microscope showed three layers in a cell membrane.

71
Q

What did improved electron microscope techniques and new methods for analysing proteins show?

A

That there is a bilayer of phospholipids and that proteins were randomly distributed not in a continuous layer.

72
Q

What are the 2 sets of complementary base pairs?

A

A and T

C and G

73
Q

How many hydrogen bonds can A and T form?

A

Two hydrogen bonds

74
Q

How many hydrogen bonds can C and G form?

A

3 hydrogen bonds

75
Q

What are the key features of how DNA double helix is formed?

A
  • The two nucleotide strands run in opposite directions and are anti-parallel
  • A and G have two ring structures and C and T have one ring
  • A and T have two hydrogen bonds and C and G have 3
  • A and T, and C and G are complementary base pairs.

Biology Edexcel A Alevel (15 decks)

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