Year 1 Flashcards
Carbohydrate digestion
- salivary amylase hydrolyses starch into maltose by breaking glycosidic bonds
- amylase is denatured in the stomach so no carb digestion there
- pancreatic amylase is released to hydrolyse excess / leftover starch
- membrane bound maltase in the ileum hydrolyses maltose to a-glucose by breaking glycosidic bonds
- glucose absorbed in cotransport
protein digestion
- hydrolysis of peptide bonds
- endopeptidases (in stomach) work in middle of polypeptide chains, making shorter chains and more ends
- exopeptidases (in stomach) work on the ends of polypeptides and hydrolyse them into dipeptides
- membrane bound dipeptidases (in ileum) work on dipeptides and hydrolyse them into a single amino acid
Cardiac cycle - left side
Blood arrives at the left atrium from the pulmonary vein filling the atrium increasing the pressure.
• The atrial muscle contracts increasing the pressure in the atrium until it is greater than the ventricle - this forces the blood through the atrioventricular valve into the left ventricle.
• The increase in pressure of the ventricle closes the atrioventricular valve,
• Then the left ventricle muscle contracts increasing the pressure until it is greater than in the aorta, this forces the blood through the semilunar valve.
• The pressure in the aorta increases causing the semilunar valve to close preventing back flow.
Cardiac cycle - right side
• Blood arrives at the right atrium from the vena cava filling the atrium increasing the pressure.
• The atrial muscle contracts increasing the pressure in the atrium until it is greater than the ventricle - this forces the blood through the atrioventricular valve into the right ventricle.
• The increase in pressure of the ventricle closes the atrioventricular valve, preventing back flow of blood.
• Then the right ventricle muscle contracts increasing the pressure until it is greater than in the pulmonary artery, this forces the blood through the semilunar valve.
• The pressure in the right pulmonary artery increases causing the semilunar valve to close preventing back flow.
Mitosis
• DNA is replicated in S-phase of interphase
• Prophase - Chromosomes condense and become visible, nuclear membrane dissolves
• Metaphase - Chromosomes line up at the middle of the cell
• Anaphase - Sister chromatids are pulled to the opposite poles of the cell
• Telophase - Chromosomes decondense and the nuclear envelope starts to reform around the two nuclei
• Cytokinesis - The cytoplasm and surface membrane splits forming two new cells that are genetically identical
Meiosis
• DNA is replicated in interphase before meiosis begins
• In the first division there is a separation of homologous chromosomes, halving the chromosome number
• In the second division there is separation of the sister chromatids
• This produced four genetically different daughter cells
Genetic variation
• Mutations can occur changing the base sequence leading to the formation of new alleles
• In the first division of meiosis there is crossing over where homologous chromosomes swap DNA producing new combinations of alleles
• In meiosis homologous chromosomes may be independently segregated, separating into different daughter cells producing new combinations of alleles
• During fertilisation there is random fusion of gametes this produces new combinations of alleles
Transpiration
• Water evaporates from the leaves/transpiration
• Due to heat/kinetic energy from sunlight
• Water diffuses out of the stomata from a high water potential to low
• The diffusion of water causes a negative hydrostatic pressure in the xylem
• This is due to water potential gradient
• Cohesion tension forms a continuous column of water that is pulled through the xylem in a transpiration stream
• Water’s adhesive properties aid the movement through the xylem
• Transpiration stream lowers water potential in the root cells
• Water is absorbed through the root hair cells by osmosis from a higher water potential to low.
Factors affecting transpiration
• Humidity - increases or decreases the water potential gradient
• Light intensity/stomata opening/no of stomata - more light more photosynthesise, stomata open in the day close at night
• Temperature - increases kinetic energy, more diffusion
• Wind movement - increases or decreases the water potential gradient
Translocation
• Sucrose (and other solutes) are actively transported into phloem (or co-transported with
H+) by companion cells
• This lowers the water potential in the phloem and water moves in by osmosis
• This creates high hydrostatic pressure leading to mass flow to respiring cells/storage organs
• Solutes/sucrose is unloaded from the phloem by active transport
Protein structure
• Proteins have a primary structure that is formed by a sequence of many amino acids that are joined by peptide bonds in a condensation reaction
• The primary structure folds into a secondary structure of either alpha helix or beta pleated sheets and these are held together by hydrogen bonds
• The secondary structure further folds into a tertiary 3D structure that is held together by hydrogen bonds, ionic bonds and disulphide bonds
• Some proteins e.g. antibodies may form a quaternary structure of more than one polypeptide chain(some of these may have prosthetic groups e.g. haem)
DNA structure
• DNA is made of a polymer of nucleotides/polynucleotide
• It is two molecules that are antiparallel to each other coiled into a double helix.
• Each nucleotide is made of deoxyribose, a phosphate group and a nitrogenous base that can either be adenine, cytosine, thymine or guanine
• The adjacent nucleotides are joined to each other between the sugar and phosphate groups in a condensation reaction forming a phosphodiester bond
• Complementary base pairing holds the two strands together due to hydrogen bonds forming between A - T and C - G.
Chromosome structure
• Chromosomes are wrapped around histone proteins forming a nucleosome
• Replicated chromosomes are formed of two sister chromatids attached at the centre by a centromere
Prokaryote vs Eukaryote
• Prokaryote DNA is short Eukaryote DNA is long
• Prokaryote DNS is circular Eukaryote DNA is linear
• Prokaryote DNA has no introns Eukaryote DNA has introns
• Prokaryote DNA is free floating Eukaryote DNA is in in the nucleus (and mitochondria and chloroplasts)
Splicing
• Eukaryotic DNA forms pre-mRNA when transcribed
• Pre-mRNA contains introns (non-coding DNA) this must be spliced out
• Pre-mRNA is spliced and introns are removed
• Mature mRNA is transcribed
