Topic 2

Question 1

What 3 factors make the gas exchange system in lungs very efficient?

Answer 1

• Large surface areas of alveoli,
• numerous capillaries
• thin walls of capillaries and alveoli

Question 2

What are the properties of gas exchange surfaces in living organisms?

Answer 2

Large Surface area to volume ratio, thickness of gas exchange surfaces and difference in concentration gradient.

Question 3

What causes the molecules to form a bilayer?

Answer 3

The head contains the phosphate group and is hydrophilic so attracts water.

The tail is made of two fatty acids and is hydrophobic so repels water.

So the molecules automatically arrange themselves into a bilayer.

Question 4

Describe the structure of the fluid mosaic model? including the different molecules found within

Answer 4

Proteins are able to move around within the bilayer due to its ‘fluid’ nature.

Glycoproteins: Protein with a polysaccharide (carbohydrate) chain attached.

Glycolipids: Lipids with a polysaccharide chain attached

Question 5

What impact does cholesterol have on the bilayer?

Answer 5

It fits in between the phospholipids, forming bonds with them. Which makes the membrane more rigid.

Question 6

What is the differences between the two types of protein on a phospholipid bilayer?

Answer 6

Integral- fully embedded within the phospholipid Peripheral - loosely attached to the outside surface

Question 7

Give five ways substances move through cell membranes

Answer 7

Diffusion, osmosis, active transport, exocytosis and endocytosis

Question 8

When will diffusion always occur?

Answer 8

When there is a difference in concentration between two areas ie the concentration gradient

Question 9

How do non polar molecules travel through the bilayer?

Answer 9

Channel proteins

Question 10

How do gated channels work?

Answer 10

They are different shapes to allow only one type of ion or molecule and can also be open or closed in the presence of a signal

Question 11

What do carrier proteins do?

Answer 11

Ions/molecules bind to a specific site on a protein. The protein changes shape and they cross the membrane

Question 12

The more cholesterol the more ….. the membrane?

Answer 12

rigid

Question 13

What is meant by passive transport?

Answer 13

No metabolic energy is needed for transport

Question 14

How does bulk transport take place?

Answer 14

Exocytosis and endcytosis

Question 15

What does bulk transport use? e.g exocytosis and endocytosis

Answer 15

Vesicles either created or fused with cell surface membrane

Question 16

What is the basic structure of mononucleotides?

Answer 16

Deoxyribose or ribose linked to a phosphate and a base

Question 17

What is the structure of a strand of DNA/RNA?

Answer 17

Polynucleotides composed of mononucleotides linked through condensation reactions.

Question 18

What reaction holds together mononucleotides?

Answer 18

Condensation reaction

Question 19

What bond forms between the phosphate molecule and the (ribose sugar) deoxyribose/ribose? of two adjoining nucleotides?

Answer 19

Phosphodiester

Question 20

What bond holds together two complimentary bases in a DNA double helix?

Answer 20

Hydrogen bonds

Question 21

What happens in transcription ?

Answer 21

1. RNA polymerase attaches to the DNA and the hydrogen bonds between bases break and the DNA molecule unwinds.
2. The template strand is transcribed to make an mRNA molecule with the same DNA sequence as the DNA coding strand.
3. RNA nucleotides get into position and then phosphodiester bonds form to produce an mRNA molecule.
4. The mRNA molecule leaves through a pore in the nuclear envelope.

Question 22

Where does transcription take place?

Answer 22

nucleus

Question 23

What is the name of a codon for DNA?

Answer 23

Triplet

Question 24

What is the name of the triplet for tRNA?

Answer 24

Anti-codon

Question 25

What is the anti-codon for mRNA called?

Answer 25

Codon

Question 26

What is the nature of the genetic code?

Answer 26

1. 3 bases (**triplet**) code for one amino acid 2. The code is **non-overlapping** and each triplet code is adjacent 3. The code is **degenerate** a several triplets can code for the same amino acid.

Question 27

What is a gene?

Answer 27

A sequences of bases on a DNA that codes for a sequence of amino acids on a polypeptide chain

Question 28

What is the basic structure of an amino acid?

Answer 28

Amine group, residual and carboxcylic acid group

Question 29

What does an amine group look like?

Answer 29

A carbon bond in the centre with a nitorogen and two single bond hydrogens

Question 30

What does a carboxcylic acid group look like?

Answer 30

Carbon attached to a carbon with a double bond oxygen and single bond OH

Question 31

What bonds in an amino acid are attached to the central carbon?

Answer 31

N,H,C,R

Question 32

What are proteins made up of?

Answer 32

amino acid monomers

Question 33

What bonds form a protein?

Answer 33

Peptide bonds

Question 34

What reaction form the bonds in a protein?

Answer 34

Condensation

Question 35

What 5 bonds form a proteins 3 D structure?

Answer 35

Hydrogen bonds, covalent disulphide bonds, ionic bonds, hydrophilic and hydrophobic bonds

Question 36

Which is soluable; fibrous or globular?

Answer 36

Globular

Question 37

What is the structure of globular proteins?

Answer 37

Compact spherical shape and soluable due to hydrophilic side chains

Question 38

What is the structure of fibrous proteins?

Answer 38

They remain as long chains and are insoluble

Question 39

Why do proteins primary structure have such an effect on 3 D structure?

Answer 39

Chemical bonds and hydrophobic interactions between r groups maintain the tertiary structure

Question 40

What type of proteins are enzymes?

Answer 40

globular proteins

Question 41

What is the site on the enzyme where the catalytic reaction takes place called?

Answer 41

Active site

Question 42

What is the role of enzymes?

Answer 42

Biological catalyst that reduces activation energy

Question 43

What are intracellular enzymes?

Answer 43

They catalyse reactions inside cells

Question 44

What are extracellular enzymes?

Answer 44

They are produced by cells catalysing reactions outside of cells eg tissue fluid or blood

Question 45

What does DNA polymerase do in DNA replication?

Answer 45

Links adjacent nucleotides

Question 46

What bonds form between adjacent nucleotide

Answer 46

Phosphodiester bonds

Question 47

What bonds form between the complimentary bases

Answer 47

Hydrogen bonds

Question 48

Why do we think that DNA replication is semi-conservative?

Answer 48

Meilson and Stahl found that each DNA strand contained one new strand and one parent strand

Question 49

Why might errors in replication lead to DNA replications?

Answer 49

If it plays a role in protein synthesis it may cause a genetic disorder

Question 50

What is the most common way of cystic fibrosis occuring?

Answer 50

The deletion of 3 nucleotides - so missing one amino acid resulting in misfolding of the protein

Question 51

What is an allele?

Answer 51

A different form of a gene that codes for a different version of a characteristic

Question 52

What is a genotype?

Answer 52

A description of a pair of alleles present for a characteristic

Question 53

What is a gene?

Answer 53

A section of DNA that codes for a train or characteristic

Question 54

What is a phenotype?

Answer 54

Physical expression of the alleles

Question 55

What does dominant mean?

Answer 55

An allele that will always be expressed when present

Question 56

What does incomplete dominance mean?

Answer 56

A cross between organisms with two different phenotypes produces offspring with a third phenotype that is blending parental traits eg red and white = pink

Question 57

What does homozygote mean?

Answer 57

HH or hh - two of the same

Question 58

What does heterozygote mean?

Answer 58

Two different e.g Hh

Question 59

what would they be?

Answer 59

Ff

Question 60

How does cf impact the gaseous system?

Answer 60

Cillia cannot move mucus Due to transport of sodium and chloride ions not being effective If sodium and chloride ions cannot flood Water cannot follow through osmosis

Question 61

How does CF mutation affect pancreas in patients?

Answer 61

pancreatic duct is blocked by sticky mucus Impair the release of digestive enzymes Lowering the concentration of enzymes within the small intestine Reducing the rate of digestion so nutrients not full absorbed

Question 62

How does the CF mutation impact the reproductive system in females?

Answer 62

Mucus develops in the cervix stopping sperm from reaching the egg

Question 63

How does the CF mutation impact the reproductive system in males?

Answer 63

The sperm duct wont be there or is blocked

Question 64

WHat are the 3 uses of genetic screening?

Answer 64

confirm a diagnosis identify carriers testing embryos

Question 65

What are the implications of prenatal screening

Answer 65

abortion is an option

Question 66

What are the 4 ethics frameworks

Answer 66

Right and duties max amount of good in world making decisions by self leading a virtuous life

Question 67

What is ficks law equation?

Answer 67

Rate of diffusion= (surface area x difference in concentration) / thickness of the gas exchange surface

Question 68

How does the structure of the mammalian lung adapt it for rapid gaseous exchange?

Answer 68

1. Large surface area of the alveoli 2. Numerous capillaries around the alveoli 3. Thin walls of the alveoli and capillaries meaning a short distance between the alveolar air and blood in the capillaries.

Question 69

What is meant by osmosis?

Answer 69

The movement of free water molecules through a partially permeable membrane

Question 70

What did scientists before the 1970s believe cell membranes were composed of? and why?

Answer 70

Scientists believed that cell membranes were composed of a phospholipid layer between two continuous layers of proteins. Because the electron microscope showed three layers in a cell membrane.

Question 71

What did improved electron microscope techniques and new methods for analysing proteins show?

Answer 71

That there is a bilayer of phospholipids and that proteins were randomly distributed not in a continuous layer.

Question 72

What are the 2 sets of complementary base pairs?

Answer 72

A and T C and G

Question 73

How many hydrogen bonds can A and T form?

Answer 73

Two hydrogen bonds

Question 74

How many hydrogen bonds can C and G form?

Answer 74

3 hydrogen bonds

Question 75

What are the key features of how DNA double helix is formed?

Answer 75

* The two nucleotide strands run in opposite directions and are anti-parallel * A and G have two ring structures and C and T have one ring * A and T have two hydrogen bonds and C and G have 3 * A and T, and C and G are complementary base pairs.