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A-level Biology (Edexcel Salters) > Topic 2 > Flashcards

Topic 2 Flashcards

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1
Q

How is air drawn to the lungs?

A

Air travels down the trachea due to low pressure in the lungs

  • created by increase in volume of thorax
  • as ribs move up
  • and as diaphragm moves down
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2
Q

What happens when the diapragm muscles and those between the ribs relax?

A
  • Volume of thorax decreases
  • pressure rises
  • air is forced out through the trachea
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3
Q

Describe the strcture of the trachea.

A

It’s divided into two bronchi which carry air to and from lungs

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4
Q

Describe the structure of the lungs.

A
  • Tree-like system of tubes
  • Ending in narrow tubes, bronchioles
  • These are attached to tiny ballon-like alveoli
    • sites of gas exchange
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5
Q

Where is mucus produced?

A

Produced continously from goblet cells in the walls of the airways

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6
Q

How is mucus removed?

A

Continously removed by the wave-like beating of cilia that cover epithelial cells lining the tubes of the gas exchange system

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7
Q

How does sticky mucus effect our health?

A
  • Increases chance of lung infection
  • Makes gas exchange less efficient
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8
Q

Where can epithelial cells be found?

A
  • On the outer surface of many animals including mammals
  • Line cavities and tubes within animals
  • Cover surfaces of internal organs
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9
Q

What does the epithelium sit on?

A

The basement membrane

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10
Q

What is the basement membrane made up of?

A

Protein fibres in a jelly-like protein-carbohydrate matrix

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11
Q

What is the job of the basement membrane?

A

Anchors the epithelium onto the connective tissue below

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12
Q

Name the surfaces of the epithelium.

A

Surface that faces the basement membrane - basal membrane

Surface that faces away - apical membrane

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13
Q

What type of epithelium is in the walls of the alveoli and capillaries?

A

Squamous (pavement) epithelium

  • Very thin, flattened cells
  • Fit like paving
  • Apical membrane faces lumen
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14
Q

What type of epithelium is in the small intestine?

A

Columnar epthelium

  • Column-shaped cells
  • extend out from basement membrane
  • Free surface facing the lumen is covered in microvilli
    • increase surface area for absorbtion
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15
Q

What type of epithelium is in the trachea, bronchi and bronchioles?

A

Ciliated epithelial cells

  • Cilia on the apical surface
  • Cilia beat in coordinated way to move substances along
  • Appear stratified (composed of several layers) but actually each cell is in contact with basement membrane
  • Appears stratified as some cells have nucleus at their base whereas others have them in their centre
  • Therefore epithelium is known as pseudostratified
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16
Q

What are microorganisms that cause illness called?

A

Pathogens

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17
Q

How are pathogens killed?

A

Pathogens get trapped in mucus which is moved by the cilia into back of the mouth cavity

  • Either coughed out or swalled, reducing risk of infection
  • If swallowed the stomach acid kills most microorganisms
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18
Q

What effect does CF have on the mucus?

A
  • Mucus is sticky so can’t move
  • Production still continues
  • layers of thickended mucus build up
  • Low levels of oxygen in mucus
    • due to oxygen diffusing slowly or epithilial cells use up more oxygen in CF patients
    • harmful bacteria can thrive in anaerobic conditions
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19
Q

How do white blood cells make mucus even stickier?

A

White blood cells fight infections wihtin mucus but as they die they break down and release DNA that makes mucus even more sticky

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20
Q

How does oxygen croos the walls of the alveoli into the blood?

A

Diffusion

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21
Q

What’s special about the surface membrane’s in unicelluar organisms?

A

All of the surface area is the exchange surface.

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22
Q

How is a concentration gradient maintained?

A

Cells continously using the substances absorbed and producing waste

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23
Q

What are the main features of a gas exchange surface?

A
  • Large surface area of alveoli
  • Numerous capillaries around the alveoli
  • Thin walls of alveoli and capillaries
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24
Q

What three properties is the rate of diffusion dependant on?

A
  • Surface area
    • directly proportional
  • Concentration gradient
    • directly proportional to the difference in concentration across the gas exchange surface
  • Thickness of gas exchange surface
    • inversely proportional
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25
Q

What is Fick’s law?

A
26
Q

Why is there less water in mucus with people with CF?

A

Due to abnormal salt and water transportation across cell surface membranes

  • Caused by a faulty transport protein channel in membrane
27
Q

How many amino acids does a protein contain?

A

Between 50 and 200 amino acids

28
Q

How many amino acids commonly occur in proteins?

A

20 different amino acids

  • Plants can make all
  • Animals can only make some (essiential amino acids)
29
Q

What is the structure of an amino acid?

A
30
Q

What is a peptide bond?

A

A bond that forms between two subunits of amino acids when they join in a condenastion reaction to form a dipeptide

31
Q

What is the primary structure of a protein?

A

The sequence of amino acids in the polypeptide chain

32
Q

What is the secondary structure of a protein?

A

Interactions between the amino acids in the polypeptide chain cause the chain to change shape into either α-helices or β-pleated sheets

33
Q

Describe a α-helix

A
  • extended spring
  • hydrogen bonds form between the slightly negetive C=O of the carboxylic acid and the slightly postive -NH of the amine group of different amino acids
  • stablises the shape
  • sections of α-helix can be up to 35 amino acids long
34
Q

Describe β-pleated sheets

A
  • amino acid chains fold back on themsleves
  • about 15 amino acids in length
  • may link together with hydrogen bonds holding parallel chains in arrangement
  • Hydrogen bonds are weeak but overall the H-bonds make the structure quite stable
35
Q

What is the tertiary structure of a protein?

A

Polypeptide chains often bend and folds further to produce a precise 3D shape

  • chemical bonds and hydrophobic interactions between R groups maintain the tertiary structure
36
Q

What makes an R group polar?

A

When the sharing of electrons within it isn’t even

37
Q

What makes R groups hydrophillic?

A

As they are polar they attract other polar molecules such as water.

38
Q

What makes an R group hydrophobic?

A

If it isn’t polar.

  • arranged so they face inside the protein, excluding water from the centre of the protein
39
Q

How does a covalent disulphide bond form?

A

If two cysteine R groups are close to each a covalne disulphide bond will form as they contain a -SH side group.

40
Q

Whats the strongest type of bond?

A

Disulphide and ionic bonds are stronger than hydrogen bonds.

However they are sensitive to changes in pH

41
Q

What is a quaternary structure?

A

Proteins that have more than one polypeptide chains.

Single chain proteins stop at the tertiary level.

42
Q

What is a conjugated protein?

A

Proteins that have another chemical group associated with their polypeptide chain(s).

43
Q

What are the two distinct shapes of proteins?

A

Globular and Fibrous

44
Q

Describe a globular protein.

A
  • Polypeptide chain is folded into a compact spherical shape.
  • Soluble due to hydrophillic side chains
    • important in metabollic reactions
  • 3D shape is crucial to their roles in binding to other substances
  • Examples: enzymes, haemoglobin, myglobin
45
Q

Describe a fibrous protein.

A
  • Long chains
  • Several polypeptide chains can be linked for additional strength
  • Insoluble
  • Important structural molecules
  • Examples: Keratin, collagen
46
Q

What is the phospholipid bilayer?

A

The surface membrane of epithelial cells are made up of tow layers of phospholipids

47
Q

Why is the phosphate head hydrophillic?

A

The phosphate head is polar

  • One end is slightly positive
  • The rest is slightly negetive
48
Q

Why is the fatty acid tail hydrophobic?

A

Its non-polar

49
Q

How do phospholipids arrange themselves in water?

A
  • Form spherical clusters called micelles or form a bilayer
  • Hydrophillic tails point inwards
  • A lipid bilayer will close on itself so no en are exposed with hydrocarbon chains
50
Q

What are glycoproteins and glycolipids?

A

Glycoproteins- protein molecules with polysccharides attached.

Glycolipids - lipid molecules with polysccharides attached.

51
Q

What makes the fluid mosaic model more fluid?

A

The greater the ratio of phospholipids that contain unsaturated fatty acids to those containing saturated fatty acids.

  • The kinks in the hydrocarbon tails prevent them form packing closely together
    • therefore more movement is possible
  • Cholesterol sits between the phospholipids and maintains fluidity of membrane
52
Q

What is the importance of glycolipids and glycoproteins?

A

Helps cell-to-cell recognition anf as receptors

53
Q

How do molecules and ions move across membranes?

A
  • Diffusion
  • Osmosis
  • Active transport
  • Exocytosis
  • Endocytosis
54
Q

What is diffusion?

A
  • Down a concentration gradient, form high to low until equilibrium is reached
  • hydrophobic or small uncharged molecule
  • through phospholipid bilayer
  • passive, no energy required
55
Q

What is facilitated diffusion?

A
  • Dow a concentration gradient, form high to low until equilibrium is reached
  • hydrophillic molecules or ions
  • through channel proteins or via carrier proteins that change shape
  • passive, no energy required
56
Q

What is osmosis?

A
  • type of osmosis involving movement of free water molecules
  • from high concentrations to low until equilibrium is reached
  • through phosphlipid bilayer
  • passive, no energy required
57
Q

What is active transport?

A
  • Against a concentration gradient, from low to high
  • through carrier proteins that change shape
  • requires energy supplied by ATP
58
Q

What is exocytosis?

A
  • used for bulk transport of substances out of the cell
  • vesuscles fusee with the cell surface membrane, releasing their contents
59
Q

What is endocytosis?

A
  • used for bulk transport of substances into the cell
  • vesicles are created from the cell surface membrane, bringing their contents into the cell
60
Q

What does viscosity mean?

A

‘stickiness’

A-level Biology (Edexcel Salters) (7 decks)

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