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SNAB A level Biology > Unit 2 > Flashcards

Unit 2 Flashcards

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1
Q

What do lungs allow gas exchange between?

A

They allow rapid gas exchange between the atmosphere and the blood

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2
Q

What is the job of the basement membrane and what is it made from?

A

It holds the cell in position and is made of protein fibres in a jelly like protein-carbohydrate matrix

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3
Q

Where are the ciliated epithelial cells found?

A

They line the airways

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4
Q

What do goblet cells produce and where is that released into?

A

They produce mucus which is released into the airway

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5
Q

What is the structure and function of cilia?

A

They are hair like structures that beat and move mucus up and out the lungs

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6
Q

What is the difference in mucus between people with and without cf?

A

People with cf have less water in their mucus so it’s sticker

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7
Q

What is the problem with stickier mucus in people with cf?

A

It is more difficult for the cilia to move which increases the chance of lung infection and makes gas exchange less efficient

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8
Q

Name 3 features of the alveoli

A
  • Large SA due to many alveoli
  • good blood supply
  • a short diffusion distance due to thin walls of the alveoli and capillaries
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9
Q

What is the equation for Fick’s law?

A

Rate of diffusion=SA X difference in conc/ thickness of surface

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10
Q

Fill the blank: Surface area is ——– to the rate of diffusion

A

Directly proportional

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11
Q

Is concentration gradient directly or inversely proportional to the rate of diffusion?

A

Directly proportional

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12
Q

True or false: thickness of the gas exchange surface is directly proportional to the rate of diffusion

A

False. Thickness of the gas exchange surface is inversely proportional to the rate of diffusion

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13
Q

How many different amino acids are there?

A

20

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14
Q

Draw an amino acid

A 
Amine group = -on the left
      N bonded to 2 H's
Hydrogen above the carbon
R group below the carbon
Carboxylic group = -on the right
       C bonded to OH double bond
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15
Q

Name the reaction that joins 2 amino acids

A

A condensation reaction

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16
Q

What does the cell surface membrane contain?

A
  • phospholipid bilayer
  • proteins
  • cholesterol
  • glycoproteins
  • glycolipids
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17
Q

Describe the primary structure of a protein

A

a chain of amino acids

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18
Q

Describe the secondary structure of a protein

A

alpha helix or beta pleated sheet

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19
Q

Describe the tertiary structure of a protein

A

The polypeptide chain folds to produce a 3D shape and is held together by ionic bonds

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20
Q

Describe the quaternary structure of a protein

A

when 4 a-heix come together, they form a globular protein

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21
Q

Compare and contrast globular and fibrous proteins

A
  • Globular proteins are in a compact spherical shape whereas fibrous proteins are long chains
  • Globular proteins are soluble whereas fibrous proteins are insoluble
  • Globular proteins are important in metabolic reactions whereas fibrous proteins are important in keratin in hair and collagen in skin
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22
Q

Give an example of a globular and fibrous protein

A

globular = Enzymes

fibrous =cartilage

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23
Q

How can the phospholipid bilayer be seen?

A

Using an electron microscope as it is about 7nm wide

24
Q

What are the 2 parts of the phospholipid bilayer?

A

The hydrophilic head and hydrophobic tail. The head is polar and the tail is non-polar

25
Q

What is the fluid mosaic model?

A

Some proteins are fixed upon the membrane of a cell but others can move around, creating fluidity

26
Q

What was the cell membrane thought of as up to 1972?

A

it was thought that the cell membrane was a 3 layer protein-lipid sandwich

27
Q

Evidence for the fluid mosaic model

A

In 1972, Singer and Nicholson came up with the fluid mosaic model, with evidence coming from the freeze fracture electron microscopy studies. The first model was created by Grendel and Gonter

28
Q

Describe how water is regulated in mucus with too much water (non CF lungs)

A
  1. Excess water detected by epithelial cells
  2. Na+ is actively pumped into tissue fluid through basal membrane
  3. Na+ channel opens and Na diffuses in which creates an electrical gradient
  4. Cl- diffuses through gaps from mucus into tissue fluid
  5. Osmosis due to increase in Na+ and Cl- moves water from mucus to tissue fluid
29
Q

Describe how water is regulated in mucus with not enough water (non CF lungs)

A
  1. Cl- transported to epithelial cells which causes conc. gradient
  2. Conc. gradient causes CFTR channel ( a gated protein channel) to open
  3. Build up of Cl- in mucus creates electrical gradient between mucus and tissue fluid
  4. Na+ diffuses through gaps from tissue fluid into mucus
  5. Higher salt conc in mucus means osmosis draws water out of cells into mucus
30
Q

Effect of CF on the digestive system

A
  • Problems with digestion and absorption of nutrients resulting in low body mass
  • People may need to take supplements that contain digestive enzymes
31
Q

Why may a CF sufferer may need to take digestive enzymes?

A

The pancreatic duct become blocked by sticky mucus, impairing digestive enzymes so less nutrients is absorbed. This causes malabsorption syndrome

32
Q

Effect of CF on reproductive system

A
  • Females have reduced chance of pregnancy as mucus plug blocks the cervix
  • Males often lack the sperm duct (vas deferens) so sperm cannot leave the testes
33
Q

What monomers make up DNA?

A

Nucleotides

34
Q

Describe the structure of a DNA nucleotide

A

The pentose sugar ‘deoxyribose’ at the centre, with phosphate at the top and an organic base to the right

35
Q

Name the 4 organic bases

A
  • Adenine
  • Cytosine
  • Guanine
  • Thymine
36
Q

What is the difference between mRNA and DNA?

A

RNA is a single stranded polynucleotide made of ribonucleic acid and contains ribose rather than deoxyribose. It also contains thymine rather than uracil

37
Q

Describe DNA Replication

A
  • hydrogen bonds break between the bases and DNA unzips
  • DNA nucleotides pair up with comp bases. DNA polymerase links adjacent nucleotides
  • two identical daughter stands are created
38
Q

How do we know DNA replication is semi conservative?

A

Watson and Crick used DNA from E Coli grown in the Heavy isotope of Nitrogen, N15.

The nucleotides in bacteria at the start contained heavy nitrogen, making the DNA heavier than normal. The bacteria was then put in the medium isotope of N. The DNA replicated once and was centrifuged

39
Q

What type of bond holds together nucleotides?

A

Phosphodiester

40
Q

Describe the positioning of each part of a nucleotide

A

The sugars and phosphates form the sugar-phosphate backbone on the outside and the bases point inwards horizontally, being held together by hydrogen bonds; the 2 nucleotides run antiparallel

41
Q

Describe transcription

A
  1. RNA polymerase attached to the DNA, the hydrogen bonds break and the DNA unwinds
  2. The template strand is transcribed to make mRNA which has the same base sequence as DNA
  3. The complimentary base RNA nucleotides align themselves and phosphodiester bonds form to produce mRNA
  4. When transcription is complete, the mRNA leaves through a nuclear pore and the DNA ‘zips up’.
42
Q

Describe translation

A
  1. mRNA attaches to the small subunit of a ribosome
  2. Free amino acids become attached to the correct tRNA molecules
  3. The first codon will always be AUG and the next codon is facing the binding site; this attracts the tRNA- amino acid complex with the complimentary anticodon
  4. The ribosome holds the mRNA, tRNA and amino acids in place long enough for a peptide bond to form between the two aminos
43
Q

What does non-overlapping mean?

A

Each triplet code is adjacent

44
Q

What is a triplet codon?

A

The code carried b the DNA contains 3 bases

45
Q

What are the 4 types of genetic testing ?

A
  • Amniocentesis
  • Chronic villus sampling
  • Non invasive prenatal diagnosis
  • pre implantation genetic diagnosis
46
Q

What is amniocentesis and when should it occur?

A

Involves inserting a needle into the amniotic fluid to collect cells

This should occur between 15 and 17 weeks

1% risk of miscarriage

47
Q

What is Chorionic villus sampling and when should it occur?

A

A sample of cells is removed either through the vagina or wall of abdomen

Between 8 and 12 weeks

1-2% risk of miscarriage

48
Q

What is non-invasive prenatal diagnosis and when should it occur?

A

Analyses DNA fragments in the mother’s blood and can detect chromosomal conditions

Occurs between 7-9 weeks

No risk of miscarriage

49
Q

What is pre implantation genetic diagnosis and when should it occur?

A

A cell of the baby is removed and is screened to look for any conditions. The couple will have to undergo IVF for this to happen

Occurs when the baby has around 8 cells

Very low success rate

50
Q

Summarise Diffusion

A

Down a conc grad, from high to low conc

Hydrophobic (lipid soluble) it small uncharged molecules

Through phospholipid bi-layer

No energy required

51
Q

Summarise facilitated diffusion

A

Down a conc grad from high to low conc

Hydrophilic molecules or ions

Through channel proteins or via carrier proteins

No energy required

52
Q

Summarise osmosis

A

Low to high conc

Movement of water

Through Phospholipid bi-layer

No energy required

53
Q

Summarise active transport

A

Against a conc grad, from low to high conc

Through Carrier proteins that change shape

Require energy, supplied by ATP

54
Q

Summarise exocytosis

A

Used for bulk transport out of a cell

Vesicles fuse with the cell membrane releasing their contents

55
Q

Summarise endocytosis

A

Used for bulk transport into the cell

Vesicles are create from the cell surface membrane, bringing their contents into the cell

SNAB A level Biology (8 decks)

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