Genes and Health :) Flashcards
(108 cards)
1
Q
What is surface area to volume ratio?
A
Surface area / volume
2
Q
TBC
A
Living organisms have to exchange substances with their surroundings, such as taking in oxygen and nutrients and getting rid of waste materials such as carbon dioxide.
3
Q
Describe unicellular organisms SA:V ratio
A
In unicellular organisms, the whole cell surface membrane is the exchange surface, substances diffuse into or out of a cell down a concentration gradient from an area of high concentration to an area of low concentration.
4
Q
How is the concentration gradient maintained?
A
By the cells continuously using the substances absorbed and producing waste
5
Q
Why is sole diffusion harder in larger organism
A
The larger the organism, the more exchange has to take place to meet the organisms metabolic needs, larger multicellular organisms have difficulty absorbing substances because of the size of their surface area compared to their volume (SA:V Ratio)
6
Q
What is the general trend with an organisms size and SA:V Ratio
A
As an animal increases in size, its SA:V Ratio decreases
7
Q
Why can’t larger animals rely solely on diffusion?
A
If larger organisms relied only on their general body surface for exchange of substances, they couldn’t survive because the distance to the innermost tissues is too far for diffusion to supply oxygen quickly enough; exchange would be too slow
8
Q
What are the features of the gas exchange surface?
A
- Large surface area of the alveoli
The alveoli have large surface area for gas exchange between the air and the blood - Numerous capillaries around the alveoli
Gas exchange of oxygen and CO2 takes place in the alveoli, oxygen from the inhaled air diffuses through the walls of the alveoli (epithelial cells) adjacent to capillaries in to the red blood cells (haemoglobin), the oxygen is then carried away by the blood to body tissues. - Thin walls of alveoli and capillaries
The alveoli and capillaries have thin walls meaning a shorter distance between the alveolar air and blood in the capillaries.
9
Q
What is Fick’s law?
A
TBC
10
Q
Ficks law - Surface Area
A
The rate of diffusion is directly proportional to the surface area - as the surface area increases, the rate of diffusion also increases.
11
Q
Ficks law - Concentration gradient
A
The rate of diffusion is directly proportional to the difference in concentration across the gas exchange surface - the greater the concentration gradient, the faster the diffusion
12
Q
Ficks law - Thickness of the gas exchange surface
A
The rate of diffusion is inversely proportional to the thickness of the gas exchange surface, the thicker the surface, the slower the diffusion
13
Q
What is the calculation for rate of diffusion?
A
thickness of gas exchange surface
14
Q
How is the gas exchange surface efficient?
A
The large SA of the alveoli, the steep concentration gradient between the alveolar air and the blood, the thin walls of the alveoli and capillaries all combine to ensure the rapid diffusion across the gas exchange surface
15
Q
What is magnification?
A
Magnification is the degree to which the size of an ice is larger than the image its self
16
Q
What is resolution?
A
Resolution is the degree t which it is possible to distinguish between two objects that are very close together
17
Q
Calculation for magnification
A
Size of image
Magnification = ——————————
Actual size of object
18
Q
Calculation for actual size of an image
A
Image size
Actual size = ——————-
Magnification
19
Q
What makes up a protein?
A
Amino Acids
20
Q
What is an amino acid?
A
Amino acids are a basic unit that join in a condensation reaction to form a protein.
21
Q
Amino acids in plants
A
Plants can make all of the required amino acids themselves
22
Q
Amino acids in animals
A
Animals can only make some amino acids, they obtain the other amino acids though their diet and these amino acids are known as essential amino acids.
23
Q
What is the general structure of an amino acid?
A
In every amino acid, a central carbon atom is bonded to an amine group (-NH2), a carboxylic acid group (-COOH), a hydrogen (-H) and a residual group (-R).\
Each amino acid has a different R group
24
Q
What is the primary structure?
A
The primary structure is the sequence of amino acids in the polypeptide chain.
25
What happens when 2 amino acids join?
Amino acids join in a condensation reaction to form a dipeptide held together by a peptide bond, this process can be repeated to form a polypeptide chain with many amino acids.
26
What molecule is released in a condensation reaction?
Water
27
What causes the polypeptide chain to change into a 3-D shape?
Interactions between the amino acids cause the chain to twist and fold into a 3-D shape
28
What is secondary structure?
A secondary structure occurs when the amino acids in the polypeptide chain begin to interact and this causes the chain to twist and fold into a 3-D shape
29
Describe what an alpha helix is and how it may occur
The chain of amino acids may twist to form and alpha helix (extended spring shape). Within the helix, hydrogen bonds form between the slightly positive carboxylic acid group and the slightly negative amine group of the different amino acids that lie above and below each other. This stabilises the shape.
30
Describe a beta pleated sheet and how it may occur
Amino acids may fold back on themselves or several lengths of the amino acid chain, may link together with hydrogen bonds holding the parallel chains in an arrangement known as a beta pleated sheet. Each hydrogen bond is weak but the cumulative effect of may hydrogen bonds makes the structure strong and stable.
31
What is tertiary structure?
The tertiary structure is when the polypeptide chain fold into its final 3-D shape. Chemical bonds and hydrophobic interactions between R groups maintain the final tertiary structure of a protein.
32
What are the types of bond found within the tertiary structure of a protein?
Hydrogen bonds
Ionic Bonds
Covalent disulphide bond
33
R Groups
An R group is polar when the sharing of electrons within it isn't quite even, Polar R groups attract other polar molecules, like water they are hydrophilic.
Non-polar R groups are hydrophobic, the R groups are arranged so they face the inside of the protein which excludes water from the centre of the molecule.
Chemical bonds may form between R groups that are close to each other in the folded structure, if two R groups are close together the a covalent disulphide bond may form.
Some amino acids contain R groups that are ionised and therefore ionic bonds may form between the positively charged and negatively charged R groups.
34
Which are stronger, disulphide and ionic bonds or hydrogen bonds?
Disulphide and ionic bonds
35
What are ionic and disulphide bonds very sensitive to?
Changes in PH
36
How do proteins gain the quaternary structure?
Only proteins with more than one polypeptide chain have a quaternary structure because single chain polypeptides stop at the tertiary structure.
37
What is the quaternary structure?
TBC
38
Tertiary structure - Ionic bonding
Ionic bonds are much stronger than hydrogen bonds but are very sensitive to changes in pH.
Some amino acids contain R groups that are ionised and therefore ionic bonds can form between positively charged and negatively charged R groups.
39
Tertiary structure - Covalent disulphide bond
Covalent disulphide bonds are much stronger than hydrogen bonds but are very sensitive to changes in pH.
If two cysteine R groups are close to each other then a covalent disulphide bond may form
40
Tertiary structure - Hydrogen bonds
hydrogen bonds are weak but the cumulative effect of many hydrogen bonds makes the structure stable.
41
What makes each amino acid unique?
The Residual group
42
What is the term given to describe amino acids and what does it mean?
Amino acids are amphoteric, this means that an amino acid can act as both an acid and a base.
43
What two groups can proteins be divided into?
Globular and Fibrous
44
Describe a globular protein
In a globular protein, the polypeptide chain is folded into a compact spherical shape. Their 3-D shape is critical to their roles in binding to other substances
45
Why are globular proteins soluble?
They are soluble because of the hydrophilic side chains which project from the side of the molecules - this means that they are important in metabolic reactions
46
Give examples of why the 3-D shape of a globular protein is essential to them binding to other substances.
Examples include transport proteins within membranes, and the oxygen transport pigments haemoglobin
47
Describe a fibrous protein
Fibrous proteins are long insoluble chains, not a folded up ball shape. A fibrous protein may contain several polypeptide chains that are cross-linked for additional strength
48
Give examples of fibrous proteins
fibrous proteins include collagen in the skin, tendons, cartilage, bones and blood vessel walls
49
How are the polypeptide chains cross linked in a fibrous protein?
The chains are staggered to prevent any weak points along the length of a molecule, to ensure it has tremendous strength.
50
Describe the cell membrane
The cell membrane is a phospholipid bilayer (7nm wide)
51
What is a phospholipid?
A phospholipid is a molecule with a hydrophilic head and a hydrophobic tail.
52
Why is the head of a phospholipid hydrophilic?
The phosphate head of the molecule is polar because one end is slightly positive and one end is slightly negative. This makes the phosphate head attract other polar molecules like water and is therefore HYDROPHILIC
53
Why are the tails of a phospholipid hydrophobic?
The tails are non polar and therefore hydrophobic because they don't attract water molecules
54
Why do water and fats not mix?
When phospholipids are added to water, they become arranged so that there is no contact between the tails and the water, they may form a layer on the surface with the hydrophobic tails directing out of the water.
They may also become arranged into a spherical clusters called micelles or even form a bilayer.
55
Which of the above arrangements is favoured by phospholipids?
Bilayer because the fatty acid tails are too bulky to fit into the interior of a micelle.
56
What arrangement do phospholipids take in the cell surface membrane?
cells are filled with an aqueous cytoplasm and are surrounded with aqueous tissue fluid, the cell surface membranes adopt the shape of a bilayer, in this arrangement the fatty acid, hydrophobic tails have no contact with the water on either side of the membrane, whist the phospholipid heads remain in contact with the aqueous environment.
57
What else does the cell surface membrane contain?
Proteins, cholesterol, glycoproteins (protein molecules with polysaccharides attached) and glycolipids (lipid molecules with polysaccharides attached).
Some proteins span the membrane, some are found only within the layer and others only within the outer layer.
58
Where are membrane proteins hydrophobic areas placed?
Within the membrane bilayer
59
What is the fluid mosaic model?
It is thought that some of the proteins are fixed within the membrane but others are not and can move around in the fluid phospholipid bilayer.
60
Who proposed the fluid mosaic model?
Jonathan Singer and Garth Nicholson (1972)
61
Previous theories - Protein lipid sandwich
- Based of evidence from electron micrographs in which the dark outer layers were thought to be the proteins and the lighter region within w.as thought to be the lipid
62
Negatives of protein lipid sandwich
Doesn't allow the hydrophilic phosphate heads to come in contact with the water or does it allow any non-polar amino acids on the outside of the membrane proteins to be kept away from the water
63
How was the theory refined?
Interpretation of the electron micrograph changed to support the new model of the membrane structure, the phosphate heads are more electron dense and show up as the dark edges to the membrane with the lipid tails being the lighter inner part.
64
How did the experiments show that there were two types of proteins? How does it support the fluid mosaic model?
Showed that there were two types of protein, those that could be dissociated from the membrane quite easily by increasing the ionic strength of the solution and those that could only be removed by more drastic action such as adding detergents.
This supports the fluid mosaic model where some peripheral proteins are loosely attached on the outside surface of the membrane whilst integral proteins are fully embedded within the phospholipids.
65
How fluid will the membrane be?
The greater the ratio of phospholipids that contain unsaturated fatty acids to those containing saturated fatty acids, the more fluid the membrane will be. The kinks in the hydrocarbon tails of the unsaturated phospholipids prevent them from packing closely together, so motor movement is possible. Cholesterol sits between the phospholipids and maintains the fluidity of the membrane by effecting the movement of the phospholipids.
66
Types of protein found within the membranes
Channel proteins
Carrier proteins
enzymes
67
what are the 5 ways that substances can pas through cell membranes?
```
Diffusion
Osmosis
Active transport
Exocytosis
Endocytosis
```
68
What is diffusion?
Diffusion is the net movement of molecules or ions from a region of higher concentration to a region of lower concentration. Particles are always moving and net movement is the sum of all of the movement. When there is a high concentration in an area, there is an increased possibility that the particles will move to an area of lower concentration.
69
When will diffusion occur?
When there is a difference in concentration between two areas.
70
When will diffusion stop?
Diffusion won't stop until its reached equilibrium, when all of the particles of a substance are evenly spread throughout the whole volume.
71
Diffusion - small uncharged particles
Small uncharged particles can diffuse directly across the cell membrane, passing between lipid molecules as they move down the concentration gradient.
72
Give examples of molecules that can diffuse this way
Small molecules including oxygen and carbon dioxide
73
What is facilitated diffusion?
Hydrophilic (polar) molecules and ions that are generally lager than CO2 cannot simply diffuse through the bilayer. They are also insoluble in pis because the hydrophobic tails of the phospholipids provide an impenetrable barrier. They cross the membrane with the aid of proteins (FACILITATED DIFFUSION).
74
Different types of channel proteins
there are different channel proteins for transporting different molecules. Each type of channel protein has a specific shape that permits the passage of only one type of ion or molecule.
75
What are gated channels?
Some channels can be opened or closed depending on the presence or absence of a signal, which would be a specific molecule like a hormone or a potential difference across the membrane (GATED MEMBRANES)
76
What are carrier proteins?
The ion/molecule binds onto a specific site on the protein, the protein changed shape and as a result the ion or molecule crosses the membrane. The movement can occur in either direction, with the net movement being dependent on the concentration difference across a membrane. Molecules move from a high to low concentration due to more frequent binding to carrier proteins on the side of the membrane where the concentration is higher.
77
What can diffusion also be called and why?
Passive transprit because no metabolic energy is needed for the transport, the process is driven by the concentration gradient.
78
What is osmosis?
The net movement of water molecules from a solution with a lower concentration of solute to a solution with a higher concentration of solute through a partially permeable membrane.
79
Examples of osmosis
Lower concentration of solute molecules, higher concentration of free water molecules
Higher concentration of solute molecules, lower concentration of free water molecules.
80
What causes osmosis?
The random movement of water molecules
81
When will osmosis continue to?
Until the solutions on either side are equal or isotonic
82
What is active transport?
Sometimes substances need to move against the concentration gradient to get across a membrane then energy is required.
83
How is the energy for active transport supplied?
The energy is supplied by the energy transfer molecule ATP, which is formed during respiration, the breakdown of energy storage molecules.
84
How does active transport work?
The substance that needs to be transported across a membrane binds to the specific carrier protein. One phosphate group is removed from ATP by hydrolysis and ADP forms and one removed, the phosphate group becomes hydrated and a lot of energy is released as bonds from between the water and phosphate. This energy from the ATP changes the shape of the carrier protein, causing the substance to be released on the other side of the membrane and moving it against the concentration gradient.
85
What causes endocytosis and exocytosis?
When large molecules or particles or very large quantities of particles have to be transported across cell surface membranes.
86
What is exocytosis?
The RELEASE of substances (usually proteins or polysaccharides) from the cell.
87
What are vesicles?
Vesicles are small membrane bound sacs containing the substance.
88
How does exocytosis occur?
Vesicles fuse with the cell membrane and the contents are released
89
Give an example of exocytosis
Insulin is released into the blood by exocytosis
90
What is endocytosis?
Substances are taken into the cell by the creation of a vesicle from the cell surface membrane, part of the cell membrane engulfs the solid or liquid material to be transported.
91
Give an example of exocytosis
Cholesterol is taken into cells this way
92
Diffusion summary
- Down a concentration gradient, until equilibrium reached
- Hydrophobic (lipid soluble) or small uncharged molecules
- Through phospholipid bilayer
- Passive, no energy required
93
Facilitated diffusion summary
- Down a concentration gradient, until equilibrium reached
- Hydrophilic molecules or ions
- Through channel proteins or via carrier proteins that change shape
- Passive, no energy required
94
Osmosis summary
- Type of diffusion involving water molecules
- From high to low concentration until equilibrium
- Through phospholipid bilayer
- Passive, no energy required
95
Active transport summary
- Against concentration gradient, low to high concentration
- Through carrier proteins that change shape
- Requires energy supplied by ATP
96
Exocytosis summary
- Used for bulk transport of substances out of the cell
| - Vesicles fuse with the cell surface membrane, relaxing their contents
97
Endocytosis summary
- Used for bulk transport of substances into the cell
| - Vesicles are created from the cell surface membrane, bringing their contents into the cell
98
What do the cells that line the airways produce?
Mucus
99
In people who don't have CF
The water content is continually regulated to maintain constant viscosity of the mucus. It must be runny enough to be moved by the beating cilia but not too runny so that it floods the airways.
100
How is the water content regulated?
The regulation of the water content is achieved by the transport of sodium ions and chloride ions across the epithelial cells, water then follows the ions by osmosis.
101
Regulating water content in unaffected lungs - EXCESS WATER IN THE MUCUS
If the mucus layer is too runny (excess water) then the excess water is detected by epithelial cell membranes that line the airways. Carrier proteins in the basal membranes of the epithelial cells pump sodium ions out of the cell into the tissue fluid. The concentration of sodium ions in the cells falls and there is a higher concentration of sodium cells in the atmosphere creates a concentration gradient across the apical membrane. Sodium ions then diffuse from an area of higher concentration to an area of lower concentration into the epithelial cell by facilitated diffusion through epithelial sodium ion channels (ENaC's).
The tissue fluid now contains more positively charged ions than the mucus - this creates an electrical gradient between the tissue fluid and the mucus. This causes negative chloride ions to diffuse out of the mucus and into the tissue fluid via the gas between the epithelial cells.
This increases the salt concentration in the tissue fluid (Sodium Chloride), this draws water out of the epithelial cells by osmosis across the basal membrane. The water loss increases the overall solute concentration within the ell and water is drawn out of the mucus by osmosis across the apical membrane into the epithelial cell,
102
Regulating water content in unaffected lungs - Too little water in the mucus
When there is too little water in mucus, chloride ions are transported across the basal membrane into the epithelial cell. This creates a concentration gradient across the apical membrane with the concentration of chloride ions being higher inside the cells rather than outside. The chloride ion imbalance causes the cystic fibrosis transmembrane conductance regulator (CFTR) protein channels to open (Gated protein channel), Chloride ions diffuse out of the cell through the CFTR channels down the concentration gradient into the mucus. The build up of negatively charged chloride ions in the mucus create an electrical gradient between the mucus and tissue fluid. When the CFTR channels are open, the sodium ion channels close. Sodium ions diffuse out of the tissue fluid and move down the concentration gradient between the cells into the mucus. The movement of sodium and chloride ions into the mucus draws water out of the epithelial cells by osmosis until the solutions are isotonic. The movement of water prevents the mucus from becoming too viscous.
103
Give an example of when there is too little water in the mucus
After a period of rapid breathing during exercise
104
what thing may be missing/inactive in people with Cystic Fibrosis?
The CFTR protein
105
Why can people with CF not regulate the water content of their mucus?
When there is too little water in the mucus and it is sticky, chloride ions cannot be secreted across apical membrane. Unusually the sodium ion channels (ENaCs) aren't blocked and are constantly open, allowing more sodium ions than usual to go into the epithelial cells. The raised levels of sodium ions draws the chloride ions out of the mucus into the cells which makes it more viscous - this makes it harder for the beating cilia to move the mucus.
106
Consequences of the viscous mucus
As a result of highly viscous mucus, the mucus isn't cleared up and out of the lungs and this build up reduces the effective ventilation of the alveoli. The mucus becomes frequently infected with bacteria because its moist and warm.
107
Consequences of bacteria invasion
The bacteria infect the mucus and the phagocyte (WBC) that clear pathogens are over produced in response, when these phagocytes break down, their DNA makes the mucus stickier still = Downward Spiral
108
amino acids are amphoteric, what does this mean?
Their molecules contain both acidic and basic groups
