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Biology - Topic 2 Genes and Health > 2.2 - Why is CF Mucus so Sticky? > Flashcards

2.2 - Why is CF Mucus so Sticky? Flashcards

1
Q

Why is CF mucus sticky?

A

It has reduced water content due to abnormal salt and water transport across cell surface membranes, caused by a faulty transport protein channel in the membrane.

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2
Q

What are some functions of proteins?

A
  • Antibodies
  • Enzymes
  • Hormones
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3
Q

What are the basic units making up proteins?

A

Amino acids

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4
Q

What are the amino acids called that animals must obtain through their diets?

A

Essential amino acids

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5
Q

What is the common structure of an amino acid?

A

A central carbon atom is bonded to an amine group (-NH2), a carboxylic acid group (-COOH), a hydrogen group (-H) and a residual group (-R).

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6
Q

What defines an amino acid?

A

Each amino acid has a different R group

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7
Q

Define primary structure in proteins

A

Two amino acids join in condensation to form a dipeptide, held together by a peptide bond. This is repeated to form polypeptide chains. This sequence is known as the primary structure.

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8
Q

What causes further structures beyond primary to form?

A

Interactions between amino acids in the chain cause it to twist and fold into a 3-D shape.

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9
Q

What is an a-helix?

A

The chain of amino acids can twist to form a helix. Hydrogen bonds form between the slightly negative C=O of the carboxylic acid and the slightly positive -NH of the amine group which lie above and below each other, holding the structure together.

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10
Q

How long can an a-helix be?

A

Around 35 amino acids

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11
Q

What is a B-pleated sheet?

A

The chain can fold back on itself and several lengths of the chain (up to around 15 acids) may link together with hydrogen bonds to hold the parallel chains together in a pleated arrangement

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12
Q

Why is a B-pleated sheet strong even though hydrogen bonds are quite weak?

A

The cumulative effects of many bonds makes the structure quite stable

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13
Q

In an a-helix, how often is there a bond?

A

Every 4 amino acids

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14
Q

What determines a tertiary structure?

A

Chemical bonds and hydrophobic interactions between R-groups

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15
Q

When is an R-group polar?

A

When the sharing of electrons is not quite even

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16
Q

What to polar R-groups do to the structure?

A

They attract other polar molecules such as water and are hydrophilic.

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17
Q

What property do non polar R-groups have?

A

They are hydrophobic

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18
Q

How is a protein arranged in the tertiary structure?

A

Non-polar and hydrophobic R-groups are forced inwards and exclude water from the centre of the molecule. R-groups also form between nearby amino acids.

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19
Q

What is an example of an R-group bond?

A

A disulphide bond between two cysteine (SH) R-groups

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20
Q

How do ionic bonds form in proteins?

A

Between positively and negatively charged R-groups

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21
Q

What are disulphide and ionic bonds sensitive to?

A

Changes in pH

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22
Q

What is a quaternary structure?

A

Some proteins are made up of several polypeptide chains held together. For example, haemoglobin is made up of four.

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23
Q

What are conjugated proteins?

A

Proteins that have another chemical group associated with their chains.

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24
Q

What are the two different types of protein?

A

Globular and fibrous

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25
What is a globular protein?
It is folded into a compact spherical shape
26
Why are globular proteins soluble?
They have hydrophilic side chains that project from the outside.
27
What are globular proteins important for?
They are important in metabolic reactions and forming enzyme-substrate complexes and catalysing reactions in cells.
28
What are three examples of globular proteins?
- Transport proteins in membranes - Haemoglobin and Myoglobin - Antibodies
29
What are fibrous proteins?
They do not form a ball but remain as long chains.
30
What gives chains in fibrous proteins their strength?
Crosslinks
31
Are fibrous proteins soluble?
No
32
What are examples of fibrous proteins?
- Keratin in hair and skin | - Collagen in skin, tendons, bones etc
33
What is the formation of a cell membrane?
Phospholipid bilayer
34
What is the difference between a triglyceride and the bilayer?
In the bilayer there are only two fatty acids and the third is replaced with a negatively charged phosphate group
35
What is the main property of the hydrophilic head?
It is polar and attracts other polar molecules like water
36
What is the main property of the hydrophobic tails?
They are non-polar and hydrophobic
37
Why is the formation of bilayers important?
They form natural compartments used for and within cells.
38
What does the cell membrane consist of?
- Phospholipid bilayer - Proteins - Cholesterol - Glycoproteins - Glycolipids
39
What are glycoproteins and glycolipids?
Proteins and fats with polysaccharidea attached.
40
What is it thought about proteins in the membrane?
Some are fixed within the membrane and some are free to move around in the bilayer.
41
What was the commonly accepted model prior to the fluid mosaic?
Protein lipid sandwich model
42
What was the main problem with the sandwich model?
It didn't allow hydrophilic heads to be in contact with water or hydrophobic parts of proteins to be kept away from it
43
Why do the phosphate heads show up as darker on the electron micrograph?
They are more electron dense.
44
What are the two types of protein called?
Peripheral proteins and integral proteins
45
How were peripheral and integral proteins proved to be?
Some could be easily removed and had to be attached to the outside surface and some needed more drastic action (adding detergents) and must be embedded within the bilayer.
46
How was it shown that some proteins spanned both layers?
Some proteins had hydrophilic regions at both ends, and hydrophobic segments in the middle
47
How did freeze fracture work?
Frozen segments were fractured between the layers and coated in heavy metal. This revealed a smooth mosaic-like figure interspersed with proteins
48
What happened when scientists fused human and mouse cells?
The proteins diffused and mixed after a while, showing the structure was fluid.
49
What impacts the fluidity of the bilayer?
More unsaturated fatty acids means more disruption to the structure and more fluidity.
50
What component maintains fluidity in the bilayer?
Cholesterol sits between the layers and maintains fluidity by affecting movement of phospholipids.
51
What are some functions of proteins in the membrane?
- Enzymes | - Carrier and channel proteins
52
What is the role of glycoproteins and glycolipids?
Receptors and cell-to-cell recognition
53
What are the five methods of molecules and ions moving across a membrane?
- Diffusion - Osmosis - Active transport - Exocytosis - Endocytosis
54
What is diffusion?
The net movement of molecules or ions from a region of their higher concentration to a region of their lower concentration
55
When does diffusion occur?
When there is a concentration gradient
56
When does diffusion end?
When equilibrium is reached.
57
What particles diffuse easily across membranes?
Small uncharged particles move between the lipid molecules. Even though CO2 is polar its size enables rapid diffusion
58
Why is facilitated diffusion needed?
Hydrophilic and large ions cannot just move through the bilayer
59
What is facilitated diffusion?
Proteins help large, polar molecules move across the membrane. This can be through water-filled pores within channel proteins.
60
What is special about channel proteins?
They each have an individual shape permitting the passage of only one type of ion or molecule
61
How can channel proteins open and close?
Depending on the presence or absence of a signal, such as a hormone or change in potential difference
62
What are channel proteins called that open and close?
Gated channels
63
What is a carrier protein?
Aids in facilitated diffusion by binding to a molecule, changing shape and therefore the molecule ending up inside the cell. This occurs in both directions
64
What is osmosis?
The net movement of water molecules from an area of high concentration to an area of low concentration through a partially permeable membrane.
65
When is active transport used?
When something must be transported against the concentration gradient
66
Where is the energy supplied from for active transport?
ATP
67
What kind of protein is responsible for active transport?
Carrier proteins
68
How does active transport work?
The substance to be transported binds to the protein. one phosphate group is removed from ATP and ADP forms. A small amount of energy is required for this. Once removed, the phosphate group is hydrated and these bonds forming releases energy. This changes the shape of the protein to move the substance.
69
What is transported by endocytosis and exocytosis?
Large molecules or large quantities of a particular molecule
70
What is exocytosis?
The release of substance from the cell
71
How does exocytosis work?
Vesicles (small membrane-bound sacs containing the substance) fuse with the membrane and release the substance.
72
Name an example of exocytosis
This is how insulin is released into the body
73
How does endocytosis occur?
A vesicle is created from the membrane. The material is engulfed.
74
How are receptors used in endocytosis?
In some cases the substance binds to a receptor to be grouped before endocytosis occurs.
75
What is the process for cells when mucus has too much water?
- Sodium ions actively pumped through basal membrane - Sodium diffuses through sodium channels in apical membrane - Negative Cl- diffuses down electrical gradient - Water drawn out of cells due to high ion content - Water drawn out of mucus
76
What is the process for cells when the mucus doesn't have enough water?
- Cl- ions pumped into cell across basal membrane - Cl diffuses through CFTR channels - Na diffuses down gradient - Water drawn out of cell by osmosis - Water drawn into cell from beneath by osmosis
77
What is the process for sticky mucus in a CF cell?
- CFTR channel absent or doesn't function - Sodium channel permanently open - Water constantly removed from mucus

Biology - Topic 2 Genes and Health (7 decks)

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