2. Genes and Health (1)

Question 1

Know the properties of gas exchange surfaces in living organisms

Answer 1

Higher SA:V = increased rate of diffusion
Thinner surfaces = shorter diffusion distance = increased rate of diffusion
Higher difference is concentration = steeper concentration gradient = increased rate of diffusion

Question 2

Fick’s law

Answer 2

Rate of gas exchange is directly proportional to = Surface area x difference in concentration /diffusion distance

Question 3

How is the mammalian lung adapted for rapid gaseous exchange

Answer 3

> Many Alveoli = many alveoli with high surface area to volume ratio = overall high surface area to volume ratio = increased rate of diffusion
Gas exchange within alveoli increases
High number/ coverage of capillaries - large blood supply = steeper concentration gradient = increased rate of diffusion
Capillaries and alveoli, right next to each other and one cell thick = short diffusion distance

Question 4

Name the structure and properties of cell membranes

Answer 4

> Cell membrane is made of a phospholipid bilayer. Phospholipids are molecules with polar (because of phosphate group), hydrophilic phosphate group head and a hydrophobic fatty acid tail.
Hydrophobic cores as fatty acid tails face inwards, with the polar phosphate heads facing outside of the cell but also inside of the cell.
Between this bilayer, there are channel proteins, other transmembrane proteins, and carrier proteins.

Question 5

What’s the role of cholesterol and glycoproteins in the cell membrane

Answer 5

• Cholesterol embedded within cell membrane for stability
• Glycoproteins on outside of cell membrane for cell recognition and cell adhesion

Question 6

What is the fluid mosaic model of the cell membrane

Answer 6

the cell membrane is fluid and can fuse with other cell membranes, can pinch off/ absorb vesicles

Question 7

Who proposed the fluid mosaic model and what is the evidence for it?

Answer 7

the fluid mosaic model proposed by Singer and Nicolson is supported by evidence showing the dynamic and fluid nature of membrane components and the flexible behavior of biomembranes.
i.e proteins diffusing at rates affected by the viscosity of the lipid bilayer

Question 8

Osmosis

Answer 8

the net movement of water from an area of high water potential (higher solvent/ water concentration) to an area of low water potential (higher solute/ lower water concentration) across a partially permeable membrane.

Question 9

Passive Transport

Answer 9

membrane transport that does not require energy to move substances across cell membranes

Question 10

Diffusion

Answer 10

net movement of a substance from an area of high concentration to an area of low concentration across a partially permeable membrane

Question 11

Facilitated diffusion

Answer 11

the transport of substances across a partially permeable membrane from an area of higher concentration to an area of lower concentration with help of a transport molecule. (hydrophilic substances are able to cross the cell membrane)

Question 12

Active transport

Answer 12

the movement of molecules across a partially permeable cell membrane from a region of low concentration to an area of high concentration/ against the concentration gradient

Question 13

ATP as a source of energy

Answer 13

energy is needed to move against the concentration gradient so ATP is used

Question 14

Endocytosis

Answer 14

cell membrane engulfs material forming a vesicle around the material

Question 15

Exocytosis

Answer 15

vesicles fusing with cell membrane and releasing their contents out of the cell

Question 16

Carrier proteins

Answer 16

have a binding site for a specific molecule/ chemical, when this chemical binds, the tertiary structure of the protein changes and the molecule is carried across the membrane into the cell where it is released.

Question 17

Channel proteins

Answer 17

protein with a central pore with a channel coated in hydrophilic amino acids, selective of what molecules can enter
Some are always open
Some only open after a certain trigger which could be a chemical binding to the protein channel

Question 18

Describe selective/ active transport dependent channel proteins

Answer 18

Channel proteins are selective of the chemical/ molecule that can pass through

Question 19

Active transport carrier proteins

Answer 19

transport molecules from a region of lower concentration to a region of higher concentration (against concentration gradient)

Question 20

How do active transport carrier protein

Answer 20

Energy provided by atp.
Molecules that wants to be transported binds to the receptor site on carrier protein. ATP molecule binds to carrier protein and is hydrolysed resulting in ADP and inorganic phosphate, this causes a change in shape, allowing the protein to transport the molecule to the other side of the membrane

Question 21

purine vs pyrimidine

Answer 21

Purine bases - 2 rings (A+G)
Pyrimidine - 1 ring (T + C)

Question 22

what is ribose

Answer 22

5 carbon sugar

Question 23

features of a mononucleotide

Answer 23

Phosphate group, ribose sugar, nitrogenous base

Question 24

What is a sugar phosphate backbone

Answer 24

DNA/ RNA polynucleotides consist of a sugar phosphate backbone. This occurs when you join two nucleotides in a condensation reaction, resulting in phosphodiester bonds between each nucleotide

Question 25

Complementary base pairs

Answer 25

Complementary base pairing A+T/U and C+G C+G have 3 hydrogen bonds, T+A have 2 hydrogen bonds

Question 26

How is double helix structure kept

Answer 26

Hydrogen bonds, collectively help keep double helix structure.

Question 27

polynucleotides

Answer 27

chain of mononucleotides linked

Question 28

Transcription

Answer 28

> DNA helicase unzips DNA molecule by breaking hydrogen bonds between nitrogenous bases > 2 strands of DNA, sense codon and antisense (template) DNA strand > Free nucleotides line up with complementary base pairs, forming hydrogen bonds. > RNA polymerase catalyses reaction between free nucleotides, forming a sugar phosphate backbone. mRNA strand is formed > mRNA strand exits the nucleus via nuclear pore in nuclear envelope.

Question 29

Translation

Answer 29

> mRNA travels to ribosome on rER in cytoplasm and attaches to tRNA > Each Anti Codons with amino acid attach to a complementary Codons (group of 3 bases) on mrna strip. > First trna anticodon carries the start codon on the mRNA (AUG) > Second anticodon carrying the second amino acid arrives > Peptide bond forms between the amino acids as they are released > Ribosome continues reading mRNA strand in a 5’ 3’ direction until stop codon reached

Question 30

Understand the roles of the DNA template (antisense) strand in transcription, codons on messenger RNA and anticodons on transfer RNA.

Answer 30

Antisense strand - the coding strand Codons group of 3 bases Anticodons carry amino acids needed in starting polypeptide chain

Question 31

Understand the nature of the genetic code

Answer 31

triplet code, non-overlapping and degenerate

Question 32

Triplet code

Answer 32

3 bases are in a codon and therefore code for one amino acid

Question 33

Non-overlapping

Answer 33

each base in a codon is only read once in a sequence

Question 34

Degenerate

Answer 34

multiple bases/ codon combinations code for one amino acid

Question 35

gene

Answer 35

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

Question 36

proteins

Answer 36

also known as polypeptides are molecules made from chains of of amino acid monomers linked by peptide bonds that are formed in condensation reactions.

Question 37

Displayed formula of amino acid

Answer 37

https://biologynotesonline.com/wp-content/uploads/2024/03/Amino-Acid-Formula.jpg

Question 38

Peptide bond

Answer 38

Formed in a condensation reaction https://cdn.savemyexams.com/uploads/2020/12/Dipeptide-formation.png

Question 39

Primary structure

Answer 39

the sequence of amino acids/ the polypeptide chain

Question 40

secondary structure

Answer 40

sequence begins to fold into alpha helix or beta pleated sheets depending on the hydrogen bonds created between different amino acids in the primary sequence.

Question 41

The hydrogen bonds in amino acids are formed between what?

Answer 41

The amine group and carboxyl group hydrogen bonds.

Question 42

Tertiary structure

Answer 42

further folding determined by interactions between r groups on the amino acids.

Question 43

Types of bonds between r groups that influence tertiary structure

Answer 43

Hydrogen bonds, Ionic bonds, Disulphide bonds (a.k.a. disulphide bridges) in the case of the serine amino acid

Question 44

Quaternary structure

Answer 44

A protein consisting of one or more polypeptide chain

Question 45

Features of globular proteins

Answer 45

Soluble in water with hydrophilic amino acids on their surface. Hydrophobic amino acids folded within centre of the protein Complex tertiary/ quaternary structures. Usually found in the use as hormones, antibodies, carrier proteins

Question 46

Example of a globular protein

Answer 46

Haemoglobin - found in red blood cells - its role: bind reversibly to oxygen in the lungs. Is released in the body. Four beta polypeptide subunits - oxygen binds to the haem Fe2+ group and oxygen is released when required

Question 47

features of fibrous proteins

Answer 47

Long parallel polypeptides, Very little tertiary/quaternary structure Occasional cross-linkages which form microfibres for tensile strength Insoluble - large portion of amino acids with hydrophobic amino acids Used for structural purposes - such as collagen.

Question 48

Example of a fibrous protein

Answer 48

Collagen - found in skin Triple helix structure consisting of polypeptide chains, where every third amino acid is glycine which is one of the smallest amino acids meaning that it can wind tightly around itself Hydrogen bonds found between polypeptide chains, multiple joined together called microfibrils and fibrils.

Question 49

Enzymes are...?

Answer 49

Biological catalysts that increase the rate of reaction by lowering the activation energy of the reactions they catalyse

Question 50

Lock and key theory

Answer 50

The active site of an enzyme is structured to fit a specifically shaped substrate. Once the substrate binds to the active site, the enzyme will facilitate the reaction and release products of the reaction

Question 51

Induced fit theory

Answer 51

a substrate binds to an active site and both tertiary/ quaternary structure change shape slightly, creating an ideal fit for catalysis.

Question 52

Enzyme concentration as a limiting factor

Answer 52

However, increasing the enzyme concentration beyond a certain point has no effect on the rate of reaction as there are more active sites than substrates so substrate concentration becomes the liming factor.

Question 53

Substrate concentration as a limiting factor

Answer 53

Beyond a certain point the rate of reaction no longer increases as enzyme concentration becomes the liming factor

Question 54

pH affecting the rate of enzyme-controlled reactions

Answer 54

Enzymes work within a narrow range of a specific pH value, values above or below this alter the bonds within its structure, hence the shape of its active site.

Question 55

Temperature affecting the rate of enzyme-controlled reactions

Answer 55

Rate of reaction increases up to the optimum temperature which is the temperature enzymes work best at. Rate of reaction decreases beyond the optimum temperature because enzymes denature.

Question 56

How does enzyme concentration increase the rate of reaction?

Answer 56

The rate of reaction increases as enzyme concentration increases as there are more active sites for substrates to bind to.

Question 57

How does substrate concentration increase the rate of reaction.

Answer 57

As concentration of substrate increases, rate of reaction increases as more enzyme-substrate complexes are formed

Question 58

Extracellular vs Intracellular enzymes

Answer 58

Extracellular enzymes (can oftentime be secreted from cells) - enzymes functioning and catalysing reactions outside of the cell Intracellular enzymes - enzymes functioning within the cell