Essay P3 Topics Flashcards
Mitosis (5)
1) Interphase:
- DNA replicates by Semi-conservative replication.
2) Prophase:
- Nuclear membrane begins to breakdown.
- Centrioles move to poles of the cell.
- Chromatin supercoils and condense into chromosomes.
3) Metaphase:
- Spindle fibres form.
- Spindle fibres attach to the centromere of chromosomes.
- Chromosomes align at the equator
4) Anaphase:
- Spindle fibres shorten.
- Centromere splits.
- Sister chromatids are separated.
- Chromatids are pulled to opposite poles of the cell.
5) Telophase:
- Nuclear membrane begins to reform.
- Chromosomes unwind.
Meiosis (5)
- Homologous chromosomes pair up
- Maternal and paternal chromosomes are arranged in any order
- Independent segregation
- Crossing over, Bivalent, Chaismata
- Equal proportions of chromatids are swapped between chromosomes
- Produces new combinations of alleles
- Chromatids separated at meiosis II/later
Phagocytosis (5)
- Pathogen is engulfed by the phagocyte
- Engulfed pathogen enters the cytoplasm of the phagocyte in a vesicle
- Lysosomes fuse with vesicle, releasing hydrolytic enzymes
- Lysosome enzymes break down the pathogen
- Waste materials are ejected from the cell by exocytosis
Vaccines (5)
- Vaccine contains antigen from pathogen
- Macrophage presents antigen on its surface
- T (helper) cell with complementary receptor protein binds to antigen
- T cell stimulates B cell
- With complementary antibody on its surface
- B cell divides to form clone secreting / producing same antibody
- B cell secretes large amounts of antibody
Starch digestion (5)
- Salivary/pancreatic amylase
- Starch -> Maltose
- Maltose -> Glucose
- Maltase
- Hydrolysis
- Glycosidic bonds
Protein digestion (5)
- Hydrolysis of peptide bonds
- Endopeptidases act in the middle of the polypeptide chain / produces shorter polypeptides / increases number of ends
- Exopeptidases act at the end of the polypeptide chain
- Dipeptidases act between two amino acids
Co-Transport (5)
- Facilitated diffusion of amino acid (into cell when higher concentration in lumen)
- Co-transport
- Sodium ions actively transported from cell to blood/capillary
- Creating sodium ion concentration gradient
- Facilitated diffusion of amino acid into blood/capillary
Lipid absorption (5)
- Micelles include bile salts and fatty acids
- Micelles make the fatty acids more soluble in water
- Bring fatty acids to the cells lining the ileum
- Maintain higher concentration of fatty acids to cells lining the ileum
- Fatty acids absorbed by diffusion
Transpiration (5)
- Evaporation/transpiration from leaves
- Creates cohesion/H-bonding between water molecules
- Adhesion / water molecules bind to xylem
- Creates continuous column of water
Translocation / transport of carbohydrates (5)
- Sucrose actively transported into phloem (cell); OR Sucrose is co-transported/moved with H+ into phloem (cell);
- (By) companion/transfer cells;
- Lowers water potential (in phloem) and water enters (from xylem) by osmosis;
- ((Produces) high(er) (hydrostatic) pressure; OR (Produces hydrostatic) pressure gradient;
- Mass flow to respiring cells OR Mass flow to storage tissue/organ;
- Unloaded/removed (from phloem) by active transport;
Transcription (5)
- Hydrogen bonds break
- Only one DNA strand acts as a template
- Free RNA nucleotides align by complementary base pairing
- In RNA, Uracil base pairs with Adenine on DNA
- RNA polymerase joins adjacent nucleotides
- By phosphodiester bonds
- Pre-mRNA is spliced / introns are removed to form mRNA
Translation (5)
- mRNA attaches to ribosome
- tRNA anticodons bind to complementary mRNA codons
- tRNA brings a specific amino acid
- Amino acids join by peptide bonds
- Amino acids join with the use of ATP
- tRNA is released after amino acid is joined to polypeptide
- The ribosome moves along the mRNA to form the polypeptide
Light Dependent Reaction (5)
- Chlorophyll absorbs light energy + excites electrons
- electrons removed (oxidation of chlorophyll) via photoionisation
- electrons move along carriers/ETC releasing energy (by a series of REDOX reactions)
- Energy released by electrons used to form proton gradient
- H+ ions move through ATP synthase
- providing energy to join ADP and Pi to from ATP
- Photolysis of water produces 2 protons, 2 electrons and 1/2 oxygen
- NADP reduced by electrons and protons / hydrogen
Light Independent Reaction / Calvin cycle (5)
- Carbon dioxide combines with RuBP
- Produces two GP molecules using enzyme Rubisco
- GP reduced to triose phosphate
- Using reduced NADP
- Using energy from ATP
- Triose phosphate converted to useful organic substances (glucose, amino acids etc.)
Glycolysis (5)
- Phosphorylation of glucose using ATP
- Phosphorylated glucose is unstable, so splits into 2 triose phosphate molecules
- Oxidation of triose phosphate to pyruvate
- Net gain of ATP
- NAD reduced
Link / Krebs / ETC - Mitochondrion (5)
LINK:
- Occurs in the mitochondrial matrix
- Pyruvate oxidised and decarboxylated into acetate
- Produces reduced NAD and CO2
- Acetate combines with coenzyme A to produce Acetyl coA
KREBS + ETC:
- substrate level production of ATP / in KC
- production of reduced NAD / FAD
- electrons fed into ETC / used in oxidative phosphorylation
- electrons pass along carries / through ETC / through series of REDOX reactions
- Energy released
- Protons move into intermembrane space through ATP synthase
- ADP + Pi -> ATP
Effect of IAA on root and shoot growth (5)
SHOOTS:
- IAA is synthesised in shoot tips
- IAA diffuses into growing region
- Light causes movement of IAA from light side to shaded side
- Proportionally more IAA on shaded side
- Stimulates cell elongation
- Causes directional growth as there is greater cell elongation on shaded side
- Shaded side grows faster and causes shoot to bend towards the light
ROOTS:
- IAA is synthesised in root tips
- IAA diffuses into growing region
- IAA moves towards shaded side
- Inhibits cell elongation
- Uneven growth (more cell elongation on side with less IAA)
- Causes directional growth away from light and towards gravity
Sequence of events leading to release of NT and its binding to post synaptic neurone / synaptic transmission (5)
- Depolarisation of presynaptic membrane
- Ca2+ channels open and calcium ions enter
- Calcium ions cause synaptic vesicles to fuse with presynaptic membrane and release ACh/NT
- ACh/NT diffuses across synaptic cleft
- ACh binds to receptors on the postsynaptic membrane
- Sodium ions enter postsynaptic neurone leading to depolarisation
Role of oestrogen in transcribing target gene (5)
- Oestrogen diffuses through the phospholipid bilayer as it’s lipid soluble
- Diffuses through nuclear envelope
- Binds to ERa repceptor
- ERa receptor changes shape/ 3’ structure
- Causes release of transcription factor
- Transcription factor binds to promoter region of DNA
- Stimulates RNA polymerase to bind to DNA and initiate transcription of gene
- Produces mRNA
Muscle contraction / Sliding filament theory / Shortening of sarcomeres (5)
- Ca2+ released from sarcoplasmic reticulum
- Ca2+ bind to troponin and cause tropomyosin to move
- Exposes myosin head binding sites on actin
- Actinomyosin cross-bridge forms
- Myosin head pulls actin a short distance over myosin (POWER STROKE)
- ADP + Pi are released from the myosin head
- A new ATP molecule binds to myosin head and breaks cross-bridge
- ATP is hydrolysed to ADP + Pi by ATP hydrolase (activated by Ca2+) - energy released returns myosin head to its original position
(Ca2+ actively transported into sarcoplasmic reticulum)
Semi conservative DNA replication (5)
- DNA strands separate / H-bonds break
- Each strand acts as a template
- Free DNA nucleotides align by complementary base pairing (A-T and C-G)
- DNA polymerase joins adjacent nucleotides on developing strand by condensation reactions, and forms phosphodiester bonds
- Each new DNA molecule has 1 old strand and 1 new strand
Role of receptors + nerves in the control of HR (5) (to increase HR)
- Chemoreceptors detect rise in CO2/acidity
OR Baro-receptors detect rise in blood pressure - Send impulses to medulla oblongata
- More impulses to SAN
- Via sympathetic nerve (for chemoreceptors)
- Via parasympathetic nerve (for baro-receptors)
Action of ADH in kidney (5)
- ADH bind to target cell membrane receptor proteins on cells lining DCT and CD
- Permeability of cells to water is increased
- More water absorbed from DCT/CD into blood
- by osmosis
- Smaller volume of urine produced
- Urine becomes more concentrated
How insulin reduces blood glucose concentration (5)
- Insulin binds to complementary receptors on target cells membrane
- Stimulates uptake of glucose by glucose channel proteins
- Activates liver + muscle enzymes that convert glucose to glycogen
How the movement of substances across cell membranes is affected by membrane structure. (5)
· Phospholipid (bilayer) allows movement/diffusion of non-polar/lipid-soluble substances;
· Phospholipid (bilayer) prevents movement/diffusion of polar/ charged/lipid-insoluble substances OR (Membrane) proteins allow polar/charged substances to cross the membrane/bilayer;
· Carrier proteins allow active transport; · Channel/carrier proteins allow facilitated diffusion/co-transport;
· Shape/charge of channel / carrier determines which substances move;
· Number of channels/carriers determines how much movement;
· Membrane surface area determines how much diffusion/movement;
· Cholesterol affects fluidity/rigidity/permeability;
Describe how substances can cross a cell surface membrane. (5)
1 (Simple / facilitated) diffusion from high to low concentration / down concentration gradient;
2 Small / non-polar / lipid-soluble molecules pass via phospholipids / bilayer; OR Large / polar / water-soluble molecules go through proteins;
3 Water moves by osmosis / from high water potential to low water potential / from less to more negative water potential;
4 Active transport is movement from low to high concentration / against concentration gradient;
5 Active transport / facilitated diffusion involves proteins / carriers;
6 Active transport requires energy / ATP;
7 Ref. to Na+ / glucose co-transport;
Explain how water enters xylem from the endodermis in the root and is then transported to the leaves. (6)
(In the root)
- Active transport by endodermis;
- (Of) ions/salts into xylem;
- Lower water potential in xylem / water enters xylem by osmosis /down a water potential gradient;
(Xylem to leaf)
- Evaporation / transpiration (from leaves);
- (Creates) cohesion / tension / H-bonding between water molecules / negative pressure;
- Adhesion / water molecules bind to xylem;
- (Creates continuous) column of water
