2. Genes and Health (1) Flashcards
Topics 2.1- 2.10 dna/rna, protein synthesis, cell membranes, diffusion
Know the properties of gas exchange surfaces in living organisms
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
Fick’s law
Rate of gas exchange is directly proportional to = Surface area x difference in concentration /diffusion distance
How is the mammalian lung adapted for rapid gaseous exchange
> 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
Name the structure and properties of cell membranes
> 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.
What’s the role of cholesterol and glycoproteins in the cell membrane
- Cholesterol embedded within cell membrane for stability
- Glycoproteins on outside of cell membrane for cell recognition and cell adhesion
What is the fluid mosaic model of the cell membrane
the cell membrane is fluid and can fuse with other cell membranes, can pinch off/ absorb vesicles
Who proposed the fluid mosaic model and what is the evidence for it?
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
Osmosis
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.
Passive Transport
membrane transport that does not require energy to move substances across cell membranes
Diffusion
net movement of a substance from an area of high concentration to an area of low concentration across a partially permeable membrane
Facilitated diffusion
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)
Active transport
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
ATP as a source of energy
energy is needed to move against the concentration gradient so ATP is used
Endocytosis
cell membrane engulfs material forming a vesicle around the material
Exocytosis
vesicles fusing with cell membrane and releasing their contents out of the cell
Carrier proteins
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.
Channel proteins
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
Describe selective/ active transport dependent channel proteins
Channel proteins are selective of the chemical/ molecule that can pass through
Active transport carrier proteins
transport molecules from a region of lower concentration to a region of higher concentration (against concentration gradient)
How do active transport carrier protein
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
purine vs pyrimidine
Purine bases - 2 rings (A+G)
Pyrimidine - 1 ring (T + C)
what is ribose
5 carbon sugar
features of a mononucleotide
Phosphate group, ribose sugar, nitrogenous base
What is a sugar phosphate backbone
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
Complementary base pairs
Complementary base pairing
A+T/U and C+G
C+G have 3 hydrogen bonds,
T+A have 2 hydrogen bonds
How is double helix structure kept
Hydrogen bonds, collectively help keep double helix structure.
polynucleotides
chain of mononucleotides linked
Transcription
> 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.
Translation
> 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
Understand the roles of the DNA template (antisense) strand in transcription, codons on messenger RNA and anticodons on transfer RNA.
Antisense strand - the coding strand
Codons group of 3 bases
Anticodons carry amino acids needed in starting polypeptide chain
Understand the nature of the genetic code
triplet code, non-overlapping and degenerate
Triplet code
3 bases are in a codon and therefore code for one amino acid
Non-overlapping
each base in a codon is only read once in a sequence
Degenerate
multiple bases/ codon combinations code for one amino acid
gene
a sequence of bases on a DNA molecule that codes for a sequence of amino acids in a polypeptide chain.
