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T2 Flashcards

1
Q

How is air inhaled and exhaled?

A

1) Air is drawn in due to lower pressure in the lungs, created by an increase in the thorax when the ribs move up and the diaphragm moves down.
2) The diaphragm muscles then relax with the intercostal muscles, volume decreases, pressure increases resulting in air being forced out through the trachea.

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2
Q

Explain the structure of the trachea.

A

It branches into two bronchi which carry air to and from the lungs.

Within the lungs, there is a tree-like system; bronchioles attached to alveoli.

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3
Q

What produces mucus and what’s its function.

A

It’s continuously produced by goblet cells in the walls or the airways.

It’s function is to trap dust, debris or microorganisms.

Thus, stopping pathogens.

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4
Q

How is the mucus removed?

A

Mucus is continuously removed by cilia that cover the epithelial cells lining the tube.

It’s normally moved to the back of the mouth cavity where it is either swallowed or coughed out.

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5
Q

What happens to the mucus that’s swallowed?

A

Stomach acid skills most microorganisms.

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6
Q

How does Cystic Fibrosis affect the mucus?

A

It makes it excessively sticky so the cilia cannot move it.

The thickened mucus builds up blocking airways.

Over-inflation in the lungs which damages elasticity.

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7
Q

What defence occurs with white blood cells and mucus?

A

White blood cells fight infections but they break down as they die.

This releases DNA contributing to the stickiness of the mucus.

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8
Q

What are the 3 properties of alveoli?

A

1) Large surface area - more gaseous exchange occurs.
2) Moist lining - for absorbing the oxygen more efficiently.
3) Thin lining - reducing the diffusion distance.

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9
Q

What is the equation for the rate of diffusion?

A

Thickness of the gaseous exchange surface

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10
Q

What is the structure of an amino acid.

A

It has a central carbon atom which bonds to an AMINE group, CARBOXYLIC ACID group, a HYDROGEN, and a RESIDUAL group.

        R
         |
A -- C -- CXA
         | 
        H

Each amino acid has a different R group.

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11
Q

What is a primary structure?

A

A sequence of amino acids joined together by peptide bonds forming a polypeptide chain.

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12
Q

How do two amino acids join?

A

By condensation reaction.

It forms a dipeptide, with a peptide bond forming between two subunits.

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13
Q

What is the secondary structure?

A

Chain of amino acids that may twist to form A-HELIX or fold back to form B-PLEATED sheets.

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14
Q

Explain the a-helix chain of amino acids.

A

There are hydrogen bonds between the slightly negative carboxylic acid and the slightly positive amine group.

Hydrogen bonds stabilise the shape.

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15
Q

Explain the folded B-pleated sheets of amino acids.

A

Maintains parallel chains by the hydrogen bonds.

Hydrogen bonds are weak but maintain stability.

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16
Q

Explain the tertiary and quaternary structure.

A

Polypeptide chain bend and fold further developing into a 3D shape.

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17
Q

Explain the R group in the tertiary and quaternary structure.

A

An R group is polar when there is an uneven sharing of electrons.

Polar R groups attract other polar molecules like water and are thus hydrophilic.

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18
Q

Why and how are ionic bonds formed between amino acids.

A

Some amino acids contain R groups that are ionised (charged) which allows ionic bonds to form.

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19
Q

Compare disulphide and ionic bonds to hydrogen bonds.

A

Disulphide bonds and ionic bonds are much stronger than the hydrogen bonds.

However, they’re sensitive to changes in pH.

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20
Q

What are globular proteins?

A

Compact spherical shape.

Coiled up so the hydrophilic parts are on the outside making them soluble.

E.g. Enzymes, antibodies and haemoglobin.

Their 3D shapes are critical to their roles in binding to other substances.

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21
Q

What are fibrous proteins?

A

Long polypeptide chains.

Held by hydrogen and disulphide bonds.

Cross linked for addition strength.

Insoluble proteins.

E.g. Keratin in hair and skin, Collagen in the skin, tendons, bones, cartilage.

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22
Q

What is the phospholipid bilayer?

A

Two fatty acids; a negatively charged phosphate group replaces the 3rd.

Head is polar. One end positive, rest negative.

Phosphate head is hydrophilic.

Tail is non-polar.

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23
Q

What happens to the phospholipids when placed in water?

A

Form a layer on the surface with the tails directly out of the water.

Alternately, they form spherical clusters called micelles or a bilayer.

Bilayer is preferred as it’s the most stable.

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24
Q

What does the fluid mosaic model suggest?

A

Some proteins are fixed within the membrane but others can move.

Cell surface contains proteins, cholesterol, glycoproteins, glycolipids.

Some proteins span the membrane.

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25
Q

Where did the evidence for integral membrane proteins come from?

A

The freeze-fracture electron microscopy studies.

Frozen membrane sections were fractured along weak points between lipid layers covered in heavy metal.

Revealed a smooth mosaic-like surface (lipid tails) interspersed by larger particles (integral proteins).

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26
Q

Explain the experiment involving mouse and human cells?

A

It involved fusing mouse cells with human cells.

Mouse membrane was given green fluorescent and human protein was given red fluorescent.

After 40 mins, there was a complete intermixing of the proteins.

Greater ratio of phospholipids that contain unsaturated fatty acids to saturated, the more fluid the membrane will be.

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27
Q

What are 5 ways molecules move across membranes?

A

1) Diffusion
2) Osmosis
3) Active transport
4) Endocytosis
5) Extocytosis

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28
Q

What is facilitated diffusion?

A

Molecules cross the membrane with the aid of proteins.

Polar molecules and ions may diffuse through water-filled pores within channel proteins that span the membrane.

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29
Q

Within facilitated diffusion, what are gated channels?

A

Channels that open depending on a presence or absence of a signal.

E.g. Potential difference or hormone.

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30
Q

Within facilitated diffusion, what are carrier proteins?

A

Ions or molecules bind onto a specific site on the protein where the protein changes shape.

This means that it can cross the membrane.

Can occur in either direction; dependent on the concentration difference.

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31
Q

Within facilitated diffusion, what is passive transport?

A

Passive meaning no “metabolic” energy is needed for transport.

Driven by concentration gradient itself.

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32
Q

What is osmosis?

A

The net movement of molecules from a high concentration of water to a low concentration of water.

Through a partially permeable membrane.

Continue until sides are equally concentrated.

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33
Q

Explain active transport.

A

When substances move against the concentration (low to high concentration) and energy is required.

Specific carrier proteins are needed.

Energy supplied from ATP.

34
Q

What is exocytosis?

A

It is the release of substances, usually proteins, from the cell.

Vesicles (small membrane-bound sacs, containing the substance) fuse with the cell membrane and contents are released.

E.g. Insulin from pancreas as it’s released into the blood.

35
Q

What is endocytosis?

A

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.

E.g. Cholesterol taken up into the cells.

White blood cells ingesting bacteria.

36
Q

What happens when there’s excess water in the mucus?

A

1) Na+ are actively pumped across basal membrane.
2) Na+ diffuse through Na channels in apical membrane.
3) Cl- diffuse down electrical gradient.
4) Water is drawn out of the cells by osmosis due to high salt concentration in the tissue.
5) Water is drawn out of the mucus thus, becoming thick and sticky.

37
Q

What happens when there’s too little water in the mucus?

A

1) Cl- are pumped into cells across basal membrane.
2) Cl- diffuse through the open CFTR channels (cystic fibrosis transmembrane conductance regulator).
3) Na+ diffuse down electrical gradient into the mucus.
4) Elevated salt concentration in the mucus draws water out of the cell by osmosis.
5) Water is drawn into the cell by osmosis.

38
Q

How does have cystic fibrosis affect mucus?

A

1) CFTR channel is absent or not functional.
2) Na+ are permanently open.
3) Water is continuously removed from mucus by osmosis.

39
Q

What is the effect of CF on the digestive system?

A

Causes difficulty maintaining body mass due to problems with digestion of nutrients.

High metabolic rates.

Have to take food supplements that contain digestive enzymes.

40
Q

What’s the function of glands?

A

They secrete digestive enzymes into the lumen of the gut.

Acts as a catalyst speeding up the extracellular break down of food.

41
Q

What’s the effect of CF on the pancreas?

A

Pancreatic duct becomes blocked by sticky mucus, impairing the release of digestive enzymes.

Additional damage when pancreatic enzymes become trapped so they start damaging the pancreas.

42
Q

Explain the properties of enzymes?

A

They act as biological catalysts.
- speed up chemical reactions.

Have a precise 3D shape.

Active site will have a particular shape.

43
Q

Explain the Lock-and-key theory.

A

A molecule with a complementary shape can fit into the active site.

These substrates from temporary bonds with the amino acids of the active site producing an enzyme-substrate complex.

They believed that each enzyme will only catalyse one specific reaction as one specific shape of substrate will fit.

44
Q

Explain Induced Fit theory.

A

They found out that the active site is often more flexible.

When a substrate enters the active site, enzyme molecule changes shape slightly to fit around the substrate more closely.

Slight change of the shape of the active site enables substrates to react.

45
Q

What is the activation energy?

A

The energy needed to break bonds and start the reaction.

In cells, enzymes reduce the amount of energy needed to bring about a reaction. This allows reactions to occur without raising the temperature of he cells.

46
Q

How do enzymes reduce the activation energy?

A

1) Random movement causes the enzyme and substrate to collide and the substrate entered the active site.
2) Enzyme-substrate complex forms. Charged groups attract, distorting the substrate and aiding bond breakage or forming.
3) Products are released from the active site leaving the enzyme unchanged and ready to accept another substrate molecule.

47
Q

Explain what is meant by enzyme concentration.

A

More enzymes mean higher rate of reaction until it plateaus.

So the amount of substrate is limited do adding more enzymes will be ineffective.

48
Q

What effect does CF have on a female reproductive system?

A

Females have a lower chance of becoming pregnant because a mucus plug develops in the cervix.

This stops the sperm from reaching the egg.

49
Q

What effect does CF have on a male reproductive system?

A

Males lack van deferens (sperm duct) on both sides.

This stops sperm from leaving the testes.

50
Q

Define the term gene.

A

It is a sequence of bases on a DNA molecule that codes for a sequence of amino acids in a polypeptide chain.

51
Q

Define Genome.

A

All the genes in an individual (or species).

Human Genome - all the genes of humans.

52
Q

Define DNA (Deoxyribose Nucleic Acid).

A

It is a polypeptide chain - A long chain polymer made up of many units called nucleotides.

Contains genetic information.

53
Q

Explain what is meant by the term Mononucleotide.

A

Contains 3 molecules linked together by condensation reactions.

Deoxyribose, Phosphate group, Organic base.

Four possible bases; A T C G

54
Q

What is the bond called that forms between 2 nucleotides?

A

Phosphodiester bond.

55
Q

What is the structure of DNA?

A

2 polynucleotides strands twisted around each other.

This forms a double helix.

Sugars and phosphates form 2 sugar-phosphate backbones.

Bases are held by hydrogen bonds.

56
Q

What is the process of semi-conservative replication?

A

1) Unwinds; where 2 single strands split. DNA helicase breaks hydrogen bonds.
2) Free DNA nucleotides line up and hydrogen bonds form between complimentary bases.
3) Enzyme DNA polymerase links adjacent nucleotides with phosphodiester bonds in condensation reactions.
4) Each DNA molecule has old and new strand.

57
Q

Explain the difference between DNA and RNA.

A

RNA is a single stranded polynucleotide.

RNA is made up of Ribonucleic Acid.

It’s sugar is Ribose.

Uracil replaces Thymine.

Can appear double stranded but it’s just folded back on itself.

58
Q

What is messenger RNA (mRNA)?

A

Made in the nucleus during transcription.

Carries genetic code from the DNA in the nucleus to the cytoplasm where it’s used to make proteins during translation.

59
Q

Define a codon.

A

3 adjacent bases.

60
Q

What is transfer RNA (tRNA)?

A

Found in the cytoplasm.

Amino acid binding site.

Sequence of 3 bases at the other end is called an anticodon.

Carries amino acids to the ribosomes to make protein during translation.

61
Q

Explain the process of Protein synthesis; Transcription.

mRNA copy is made.

Occurs in the nucleus.

A

1) RNA polymerase breaks hydrogen bonds between DNA double-helix.
2) One strand used as a template to make mRNA copy.
3) RNA polymerase lines up free RNA mononucleotides along the template strand. Complementary base pairing - uracil replaces thymine in RNA.
4) Joined together by RNA polymerase; forming an mRNA molecule.
5) DNA winds back up in a double helix.
6) When RNA reaches stop codon, it stops making mRNA.
7) mRNA moves out of the nucleus through nuclear pore and attaches to ribosome.

62
Q

Explain the process of Protein Synthesis; Translation.

Amino acids are joined together making polypeptide chain.

Happens in the ribosome.

A

1) mRNA attaches to ribosome and tRNA molecules carry amino acids to ribosomes.
2) tRNA molecule, with anticodon complimentary to start codon on mRNA, attaches itself to mRNA by complimentary base pairing.
3) 2nd tRNA molecule attaches itself to the next codon on mRNA.
4) 2 amino acids attached to tRNA are joined by a peptide bond.
5) Ribosomes move along to the next codon.
6) 3rd tRNA molecule binds to the codon on the mRNA. It’s amino acids bind to the first two and the second tRNA molecule moves away.
7) Process continues, produces a chain of linked amino acids. Until stop codon.
8) Polypeptide moves away.

63
Q

What is the nature of the genetic code?

A

DNA is three base or TRIPLET CODE.

Each adjacent group of 3 bases codes for an amino acid.

Code is non-overlapping.

Several triplets can code for same amino acid so the code is described as DEGENERATE.

64
Q

Explain what is meant by the term degenerate.

A

It is changes to the base sequences of DNA.

65
Q

What errors can be caused by mutation?

A 
Substitution 
Deletion
Insertion
Duplication
Inversion
66
Q

Define Genes.

A

A sequence of bases on a DNA molecule that cores for a protein, which results in a characteristic.

E.g. The gene for eye colour.

67
Q

Define allele.

A

A different version of a gene.

Different versions have slightly different base sequences.

68
Q

Define genotype.

A

The alleles a person has.

69
Q

Define phenotype.

A

The characteristic displayed by an organism.

70
Q

Define dominant allele.

A

An allele whose characteristic is expressed if present in the phenotype.

71
Q

Define recessive allele.

A

An allele whose characteristic is expressed only when no dominant is present.

72
Q

Explain what is meant by the term Carrier.

A

If a recessive allele can cause a disease but is not expressed due to the presence of a dominant allele.

73
Q

Define homozygote.

A

If the alleles present are the same allele.

E.g. BB or bb

74
Q

Define heterozygote.

A

If the alleles present are different.

E.g. Bb

75
Q

What are the 3 main uses of genetic screening?

A

1) Identifying carriers.
2) Preimplantation Genetic Diagnosis (PGD).
3) Prenatal testing.

76
Q

Explain identifying carriers in genetic screening.

A

Offered to people with a history of genetic disorders.

Raises Social and ethical issues:

  • Emotional stress
  • Isn’t 100% accurate
  • Abnormalities, increasing stress.
77
Q

Explain PGD in genetic screening.

A

Carried out on embryos produced by in-vitro fertilisation (IVF).

Screens them before being implanted into the woman.

Reduces the chances of a baby with a genetic disorder - avoids abortion.

However; it can lead to designer babies.

78
Q

What is prenatal testing and what are the 2 types of tests?

A

Involves screening unborn babies for genetic disorders.

Offer to pregnant woman with a history of genetic disorders.

1) Amniocentesis.
2) Chronic Villus Sampling (CVS).

79
Q

Explain Amniocentesis.

A

Carried out after 15-20 weeks.

Very fine needle inserts abs obtaining amniotic fluid.

Contains DNA.

1% charge of miscarriage.

Fast test = 3 - 4 days.

Thorough test = 2 - 3 weeks.

80
Q

Explain CVS (Chronic Villus Sampling).

A

Carried out after 11-14 weeks.

Less traumatic as an earlier decision can be made.

Sample taken via fine needle from chorionic villi (part of foetus that connects to its mother).

1-2% chance of miscarriage.

Few days for results.

Thorough results after 2 - 3 weeks.

81
Q

What are the benefits of prenatal screening?

A

Allows for informed decisions.

Helps prepare for future care.

Option to have an abortion.

82
Q

What are the negatives of prenatal screening?

A

Increases chance of miscarriage.

Possible false results.

Unethical to abort due to genetic disorder.

Biology (9 decks)

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