Topic 2: Genes and health Flashcards
What are the properties of a gas exchange surface?
The process of gas exchange occurs by diffusion meaning gas exchange is determined by
- surface area to volume ratio (as overall size of the organism increases the surface area becomes smaller
- thickness of surface
- concentration gradient
How are mammals adapted to rapid gas exchange?
- many alveoli provides a large surface area
- alveoli and capillaries have cell walls that are only 1 cell thick providing a short diffusion distance.
- extensive capillary network maintain a high concentration gradient.
- loads of capillaries also creat a large surface area.
Ficks law
Rate of diffusion = surface area x concentration gradient / thickness of surface
Structure of a cell membrane
There are four main components of a cell membrane
Phospholipid bilayer > this contains phospholipids which have a hydrophilic (polar) head which point outwards and a hydrophobic tail (non-polar) that face inwards.
Cholesterol > regulates the membrane fluidity, allowing the membrane to maintain structure as well as being flexible and able to change shapes.
Proteins > there are two types intrinsic proteins which are found in the outer layer and extrinsic which extend through the membrane. There job is to transport materials in and out of the cell and communicate with other cells.
Glycolipids > lipids with carbon hydrate attached, aid in cell to cell communication (recognition) and can act as cell markers. They can also bind with substances on the cell surface.
Glycoproteins > proteins with carbohydrates attached again aid in cell to cell communication, cell markers and can bind with substances at the cell surface (hormones).
Why is the cell membrane described as as fluid mosaic model?
The scattered pattern produced by the components whiting the phospholipid bilayer looks like a mosaic. The movement of the components around the bilayer makes it fluid.
Is the cell membrane permeable?
The membrane is partially permeable. Small, non-polar molecules can pass through gaps between the phospholipids whereas large polar molecules must pass through the channel and carrier proteins.
What is osmosis?
The movement of water molecule from an area of high water concentration to an area of low water concentration (down the concentration gradient) through a partially permeable membrane.
Passive diffusion
The movement of particles from an area of high concentration to an area of low concentration. (Down the concentration gradient)
e.g. The movement of small, non polar molecules through the phospholipid bilayer form
Facilitated diffusion
The movement of large, polar molecules through carrier through carrier and channel proteins form an area of high concentration to an area of low concentration.
Channel proteins
Proteins that extent though the membrane which allow charge substances to diffuse through the cell membrane. They can close and open allowing them to control the exchange of any ions.
Carrier proteins
Channel proteins change shape to allow molecules of pass through. Molecules bind to the carrier protein which then changes shape opening on the other side of the membrane. Happens down a concentration gradient.
What is active transport?
The movement if molecules through a cell membrane from a regions of lower concentration to a region of higher concentration, against the concentration gradient. It requires carrier proteins and ATP energy.
What is exocytosis?
The movement of large polar molecules contained within vesicles which fuse with the cell membrane and release their contents out of the cell.
Require a source of energy.
What is endocytosis?
When a molecule is two large to travel through proteins the cell can surround the substance with a section of the cell surface membrane. It then engulfs the substance and seals it of inside the cell creating a temporary vesicles.
Requires a source of energy
What’s the structure of a mononucleotide in DNA?
DNA nucleotide ps are made up of a deoxyribose sugar, a phosphate group and one of four nitrogenous bases (adenine, cytosine, guanine or thymine).
What’s the structure of a RNA mononucleotide?
The components of a RNA nucleotide are a ribose sugar, a phosphate group and one of the four bases.
How do mononucleotides from polynucleotides?
Separate nucleotides are joined by a condensation reaction forming a phosphodiester bond between the phosphate group of one nucleotide and the pentose sugar of the next. Forming polynucleotides such as DNA and RNA.
How is the sugar-phosphate backbone created?
Made up of a chain of alternating nucleotides held together by phosphodiester bonds making a sugar-phosphate backbone. Through condensation reaction.
What is the structure of a DNA molecule?
A double helix molecule comprised of two strands - which run in opposite directions) of polynucleotides which are he,d together by hydrogen bonds between complementary base pairs (G and C, A and T). Backbone comprised of deoxyribose sugar and phosphate group.
What so the structure of RNA?
This is a single strand of polynucleotides in which T bases are replaced by U. The backbone is comprised of ribose sugar and a phosphate group.
What is the process of transcription?
Transcriptions if the first step of protein synthesis and occurs in the nucleus
1. DNA helicase unzips the two stands of the double helix, by braking the hydrogen bind between the strands, exposing the template (antisense) strand.
2. Free-floating RNA nucleotides bind to the template strand forming a complementary mRNA strand. (T bases replaced by U bases)
3. Hydrogens bonds form between complementary base pairings. (A and U and G and C)
4. RNA polymerase cause phosphodiester binds to form between the adjacent nucleotides in a condensation reaction.
5.. When the mRNA molecule is complete, the hydrogen bonds are broken and the mRNA strand leaves through the nuclear pores in the nuclear envelope.
The process of translation?
The second part of protein synthesis which occurs in the cytoplasm of the cell.
1. After leaving the nuclear, the mRNA molecule binds to a ribosome.
2. Free tRNA molecules bind wiht their specific amino acid in the cytoplasm and brings them to the mRNA molecule on the ribosome.
3. The triplet anticodons on each tRN A pairs with a complementary triplet (a Condon) on the mRNA molecule.
4. The amino acid form peptide binds with adjacent amino acid in a condensation reaction growing the polypeptide chain and each tRNA detaches.
5. Translation stops when a STOP condon is reached.
What is the nature of the the genetic code?
The genetic code is
Universal > the same codons code for the same amino acids in all organisms.
Degenerate > some codons code for the same amino acid.
Non overlapping > each base is only read one, each codon is transcribed separately.
Definition of a gene
A a sequence of bases on a DNA molecule that codes for a sequence of amino acids in a polypeptide chains.
Definition of a genome
The collection of all the genes in an organism.
What is the basic structure of an amino acid?
Amino acids are the monomers of a polypeptides and has a general structure of
H H O
\ I //
N - C - C
/ I \
H R OH
- amine group (NH2)
- carboxylic acid (COOH)
- R group (where each amino acid differs)
How do amino acids join to make a polypeptide chain?
Amino acids join together by a condensation reaction forming polypeptide bonds. It can be broken by a hydrolysis reaction (gaining water).
What is the primary structure of a polypeptide chain?
The sequence of amino acids in a polypeptide chain. It determines the its 3D shape and therefore its properties.
What is the secondary structure of a polypeptide chain?
The 2D arrangement of amino acids in a polypeptide chain. It controlled by the formation of hydrogen binds between partially charged R groups. It can either be an alpha-helix or beta-pleated sheet.
What is a tertiary structure of a polypeptide chain?
The 3D folding of the secondary structure of polypeptides and is controlled by chemical bonding - hydrogen, disulphide, ionic and weak hydrophobic interactions.
What is the quaternary of a polypeptide chain?
When more than one polypeptide chain work together as a functional molecule.
What is the structure of a globular protein?
A polypeptide chain held in a 3D spherical structure by bonds (disulphide, ionic and hydrogen). There non polar hydrophobic R groups are orientated towards the centre of the proteins and the polar hydrophilic R grounds oriented themselves on the outside of the protein creating the spherical shape.
E.g. Haemoglobin
