Biological processes glossary Paper 1

Question 1

Changes which take place inside a beta cell to cause release of insulin in the presence of high blood glucose concentration:

Answer 1

The changes which take place inside a beta cell to cause release of insulin in the prescence of high blood glucose concentration:
-Glucose enters cells by transporter
-Glucose metabolised inside mitochondria, resulting in ATP production
-ATP binds to potassium channels and they close (ATP-sensitive potassium channels)
-Potential reduces and depolarisation causes, meaning voltage-gated calcium channels open and calcium ions enter cell -> causes secretory vesicles to release insulin by exocytosis

Question 1

Interactions of the neuronal and hormonal systems in the fight or flight response

Answer 1

Interactions of the neuronal and hormonal systems in the fight or flight response:
Hypothalamus communicates with sympathetic nervous system and adrenal-corticol system
-Sympathetic system uses neuronal pathways to initiate body reactions and adrenal-corticol system uses hormones in the blood stream
-Sympathetic -> activates adrenal medulla to release adrenaline and noradrenaline into bloodstream + impulses activate glands and smooth muscles.
-Adrenal-corticol system -> activated -> pituitary gland secretes hormone ACTH -> ACTH arrives at adrenal cortex and releases hormones into bloodstream

Question 2

Transcription of DNA

Answer 2

Transcription of DNA:
1). Free RNA nucleotides base pair with complementary bases exposed on the antisense strand when the DNA unzips (thyme replaced with uracil)
2). Phosphodiester bonds form by RNA polymerase and transcription ends at the end of the gene, and the mRNA formed detaches from DNA and leaves through a nuclear pore

Question 3

Translation of DNA

Answer 3

Translation of DNA:
3). mRNA binds to specific site of small subunit on the ribosome, which holds it in place whilst it is translated into an amino acid sequences
4). Anticodons on the tRNA binds to the complementary codons on the mRNA strand, and the amino acids are brought together to form the primary structure of the protein

Question 4

Process of DNA replication

Answer 4

DNA replication:
1). DNA helicase causes two strands of DNA to seperate
2). Once split, free nucleotides activated and attracted to their complementary nucleotides
3). Nucleotides lined up by DNA polymerase and remaining unpaired bases attracts to their complementary nucleotides
4). New DNA is formed, each molecule of DNA composed of one original strand and one newly formed strand

Question 5

Active transport across membranes

Answer 5

Active transport across membranes:
1). Molecule/ion binds to receptors in channel of carrier protein outside the cell
2). ATP binds to carrier protein inside the cell and is hydrolysed into ADP and inorganic phosphate
3). Binding of phosphate to carrier proteins causes protein to change shape, opening inside of cell
4), Molecule/ion released inside
5). Phosphate released and recombines with ADP to form ATP
6). Carrier protein returns to original shape

Question 6

Cell Cycle

Answer 6

Cell cycle:
-> Spindle assembly checkpoint
-> G1 phase: growth phase, cell synthesises various nutrients necessary for DNA replication and cell division
->G1 checkpoint = checks for cell size, nutrients, growth factors and DNA damage
-> S phase = DNA synthesis/replication
-> G2 phase = cell prepares for nuclear division by protein production and nutrients
-> G2 checkpoint = checks for cell size, DNA replication and DNA damage
-> Mitosis = Process of cell duplication, where on cell divides into two genetically identical daughter cells

Question 7

Mitosis

Answer 7

Mitosis:
1). Prophase => chromatin coils and condenses to form chromosomes and become visible, nuecleolus disappears and membrane breaks down, microtubules form spindle fibres
2). Metaphase => chromosomes moved to metaphase plate by spindles
3). Anaphase => Chromatids are separated/pulled to opposite poles by shortening of spindle fibres
4). Telophase => Chromatids reached poles and now called chromosomes , assembled at poles and nuclear envelope reforms

Question 8

Meiosis

Answer 8

Meiosis:
1). Prophase I => Chromosomes condense, nuclear envelope disintegrates and spindles form, homologous chromosomes pair up to form bivalents
2). Metaphase 1 => Homologous pairs align along metaphase plate, random arrangement, maternal or paternal chromosomes end up facing either pole (independent assortment) and results in genetic variation
3). Anapahse 1 => Homologous chromosomes pulled to opposite poles, sections of DNA on sister chromatids entangled during crossing over and rejoin which can exchange DNA (chiasmata = point at which the chromatids break and rejoin)
4). Telophase 1=> Chromosomes assemble at poles and membrane reforms and chromosome uncoil, undergo cytokinesis -> cell now haploid
5). Prophase II => Chromosomes (two chromatids) consense, become visible, envelope breaks down and spindles form
6). Metaphse II => individual chromosomes assemble on metaphase plate, independent assortment takes place
7). Anaphase II => Chromatids pulled apart to poles after division at centromeres
8). Telophase II => Chromatids assemble at poles, chromosomes uncoil and evenlope reforms, four daughter cells in total that are genetically different

Question 9

Ventilation in fish

Answer 9

Ventilation in fish:
1). Mouth opens and buccal cavity lowered, increasing its volume and pressure drops -> water moves into buccal cavity
2). Opercular valve shut and opercular cavity expands, lowering pressue. When buccal cavity rises up, pressure increases and water moves from buccal cavity over the gills.

Question 10

Inspiration in animals

Answer 10

Inspiration (inhaling):
1). External intercostal muscles contract, pulling the rib cage up and out as diaphragm also contracts
2). Increases the volume of the lungs, which decrease the air pressure inside them
3). As pressure in lungs is less than that of atmospheric pressure, air is drawn in

Question 11

Expiration in animals

Answer 11

Expiration in animals (exhaling):
1). External intercostal muscles relax so ribs move down and in, diaphragm also relax so moves back up
2). Decreases the volume and increases the air pressure inside the lungs
3). Air pressure in lungs higher than atmospheric pressure, air is forced out, elastic recoil of alveoli also causes this movement of air out of the lungs

Question 12

Cardiac cycle

Answer 12

Cardiac cycle:
1). Wave of excitation begins in SAN, causing the atria to contact. Layer of non-conducting tissue prevents excitation passing directly into ventricles.
2).AVN picks up the excitation, imposes a delay before stimulating bundle of His (conducting tissue made up of purkyne fibres)
3). Bundle of His conducts excitation to apex of the heart, triggering contracting at the ventricles starting at apex

Question 13

Transport of Carbon Dioxide

Answer 13

★Transport of CO2★
-Carbon dioxide diffuses into bloodstream from respiring tissues – 5% of this remains dissolved in the plasma
-95% of carbon dioxide diffuses into red blood cells (erythrocytes)
-10-20% of this binds to haemoglobin forming carbaminohaemoglobin
-Remaining % gets converted to carbonic acid by carbonic anhydrase
-Carbonic acid dissociates into hydrogen ions and hydrogen carbonate ions
-Hydrogen carbonate ions move out of the red blood cells and are replaced by chloride ions –Known as the chloride shift
-The hydrogen ions are picked up by haemoglobin creating haemoglobinic acid – acts as a buffer – this is the molecular basis of the bohr shift

Question 14

Formation of tissue fluid and lymph

Answer 14

★Formation of tissue fluid and lymph★
1). Start of capillary bed – hydrostatic pressure > oncotic pressure
2). Fluid forced out into spaces around cells – from capillaries – forming the tissue fluid
3). Fluid leaves – reducing hydrostatic pressure
4). Venule end of capillaries – oncotic pressure greater than hydrostatic pressure
5). Due to fluid loss from capillaries and high oncotic pressure – some water re-enters capillaries at venule end by osmosis

Question 15

Basis of cohesion-tension theory

Answer 15

Basis of cohesion-tension theory:
☆ 1). Transpiration - water evaporated off plant
☆ 2). Water loss creates tension (formation of H bonds between water molecules and sides of the xylem vessel elements), water pulled upwards by tension
☆ 3). Cohesion - water forms H bonds with each other - continuous pull upwards of water to replace water lost in transpiration
☆ 4). Water being pulled up decreases water potential at roots and so water diffuses in roots via osmosis

Question 16

Movement of water in the transpiration stream

Answer 16

★ Movement of water in the transpiration stream: ★
☆ -Water evaporates from the leaves which decreases the water potential of the air space inside the mesophyll
☆ -Water moves into air spaces from adjacent cells
☆ -Water moves out of the xylem into the cells in the leaves
☆ -Water hydrogen bonds to itself (cohesion) and bond to walls of the xylem vessel walls (tension) resulting in capillary action

Question 17

Process of translocation

Answer 17

Process of translocation:
☆ 1). Sucrose enters phloem by active loading (companion cells using ATP to transport hydrogen ions into surrounding tissue) -> creates diffusion gradient meaning H ions diffuse back into companion cells
☆ 2) Facilitated diffusion allows H ions to bring sucrose into companion cells causing conc of sucrose to increase
☆ 3). Sucrose diffuses out companion cells down gradient into plasmodesmata
☆ 4). Water potential reduced as sucrose enters sieve tube elements, water moves in by osmosis and hydrostatic pressure increases (mass flow)
☆ 5). Water moves down sieve tube from high to low hydrostastic pressure (mass flow)
☆ 6). Sucrose removed by diffusion or active transport into surrounding cells, increasing water potential and water leaves by osmosis back into xylem, reducing sink pressure (mass flow)

Question 18

Pacnian corpuscle as a transducer

Answer 18

★Pacinian corpuscle – sensory receptor ★
1). In its normal/resting state, stretch mediated sodium ion channels are closed – maintains the resting potential
2). Pressure is applied, the membrane changes shape and stretches
3). Stretching causes sodium ion channels to widen and open, sodium ions open to diffuse in
4). Influx of sodium ions causes the membrane to become depolarised
5). A generator potential is reached and this creates an action potential

Question 19

Generation of an action potential

Answer 19

Generation of an action potential:
1. Polarisation – Neurone resting potential – some K+ channels open but voltage gated NA+ channels closed -> energy from stimulus triggers some ion channels to open, membrane permeable to sodium – diffuses into axon
2. Depolarisation – Change in charge causes more sodium channels to open (positive feedback), voltage gated NA+ channels close and voltage gated K+ channels open – sodium can no longer enter axon – more permeable to potassium
3). Repolarisation – potassium diffuse out axon, reducing charge so inside of axon more negative than outside
4). Hyperpolarisation – potassium diffuses out axon, inside axon less negative than normal resting state, voltage gated potassioum channels close and sodium potassium pump causes sodium to move out and potassium to move in, returning axon to its resting potential

Question 20

Action at a synapse

Answer 20

★ Action of a synapse ★
1). Action potential arrives at end of presynaptic neurone, calcium ion channels open and calcium ions enter the synaptic knob
2). Influx of calcium ions causes vesicles of acetylcholine to fuse with the presynaptic membrane
3). Acetycholine released and diffuses across the synaptic cleft
4). Acetycholine binds to receptor sites on the soidum ion channels of the postsynaptic neurone
5). Sodium ion channels open and ions diffuses into postsynaptic
6). Aciton potential generates
7). Acetycholinesterase hydrolyses acetycholine into ethanoic acid and choline and diffuses back into presynaptic neurone – preventing the continuous generationof action potential

Question 21

Sliding Filament model - Muscle Contraction

Answer 21

Sliding Filament model - Muscle Contraction:
-Action potential reaches the neuromuscular junction
-Vesicles of acetycholine are released into the synaptic cleft
-Neurotransmitter diffuses across the synaptic cleft and binds to the sarcolemma
-Wave of depolarisation spreads down the T tubules, opening sodium channels
-Acetycholinesterase causes acetycholine to break down, preventing overstimulation of the muscle
-Calcium ions are released from the sarcoplasmic reticulum
-Calcium ions bind to troponin, changing its shape
-Tropomyosin is displaced from myosin binding sites
-Myosin heads bind to the binding sites on the actin forming cross bridges
-Power stroke – myosin heads sweep the actin along, causing the sarcomere to shorten in length
-ATP binds to the myosin head, causing it to detach from the actin
-ATP is hydrolysed to ADP and inorganic phosphate
-Myosin heads return to their original position
-Cycle continues as long as muscle remains stimulated, rapidly forming and breaking actin/myosin cross bridges and further shortening the sarcomere length
-ATP is regenerated by either aerobic respiration, anaerobic respiration or creatine phosphate

Question 22

Secretion of insulin in the Pancreas

Answer 22

★ Insulin Secretion ★
☆ 1). Normal levels -> potassium channels of beta cells open
☆ 2). Concentration rises + glucose enters via transporter
☆ 3). Glucose metabolised in mitochondria and ATP released
☆ 4). ATP binds to potassium channels and they close
☆ 5). Potential reduces + depolarisation occurs
☆ 6). Depolarisation occurs -> voltage-gated calcium channels open and ions enter causing secretory vesicles to release by exocytosis

Question 23

Adrenaline secretion - medulla oblongata

Answer 23

★ Medulla oblongata + adrenaline secretion ★
☆1). Releases adrenaline when sympathetic nervous system simulated -> fuses with receptor and activates enzyme inside the membrane
☆2). The activated enzymes converts ATP -> cyclic AMP -> which acts as a second messenger that activates other enzymes

Question 24

Chemoreceptors action on increasing heart rate

Answer 24

★ Chemoreceptors action on increasing heart rate ★
☆ increased mobile activity -> more carbon dioxide produced by tissues due to increased respiration -> blood pH lowered -> centre in medulla oblongata that increases heart rate increases impulse frequency to SAN via sympathetic nervous system -> SAN increases heart rate -> increased blood flow removes carbon dioxide faster -> carbon dioxide levels return to normal ☆

Question 24

Movement of filtrate through the kidneys

Answer 24

★ Movement of filtrate through the kidneys ★
1. Ultrafiltration takes place at the glomerulus – the thicker afforent arteriole brings in the molecules, applying high amounts of pressure. The molecules (amino acids, glucose, ions, hormones, vitamins, water, urea) passes through the basement membrane (1st filter), the endothelium gaps (2nd filter) then the podocytes->pedicels on the wall of the Bowmans capsule to filter out the rbc, wbc and plasma proteins (which leaves through the efferent arteriole)
2. The filtrates are selectively reabsorbed in the proxal convoluted tubule (PCT), where 100% of glucose, hormones, vitamins and some sodium ions are moved back in the blood by active transport, followed by some water by osmosis and some diffusion by chloride ions.
3. Filtrate moves to the loop of henle, where in the descending limb, water is moving into blood by osmosis due to the concentration gradient caused by the movement of ions. Loop of Henle is hypertonic at the bottom due to the high salt conc, but in the ascending limb ions are moved out by diffusion and so filtrate becomes isotonic.
4. Further ion reabsorption occurs at the distal convoluted tubule (DCT) as well as some water, but the reabsorption depends on the needs of the person.
5. The collecting duct is affected by prescence of ADH (osmoregulation) and brings the urine to the ureter -> bladder -> urethra to be excreted

Question 25

Processes occuring in the liver/hepatocytes

Answer 25

Processes occurring the liver/hepatocytes:
-Deamination (removal of amine group of amino acid -> ammonia -> urea) (orthicine cycle)
-Detoxification (removal of toxins ie ethanol into ethanoate to be used in cellular respiration, or hydrogen peroxide into oxygen and water by catalase)
-Bile production (bile secreted into the bile duct to be stored in gallbladder)
-Glucose to glycogen conversion (responsive to insulin)

Question 26

Pregnancy tests

Answer 26

Pregnancy Tests:
1. Wick is soacked in urine (highest levels of Hcg)
2. Test contains mobile monoclonal anitbodies with coloured attached beads -> binds to hcg if present – forming a complex that colours the beads
3. Urine carried to window of test – where there are immobolised monoclonal antibodies arranged in pattern so a positive sign (+) appears when bindings to hcg-antibody complex
4. Urine carried along to second window where there are immbolised antibodies that attach to the mobile antibodies regardless of hcg being present
pregnant = two lines, not pregnant = one line (due to the second window)

Question 27

Haemodialysis

Answer 27

★ Haemodialysis: ★
-Blood leaves body from artery and flows into dialysis machine, flowing between partially permeable membranes (mimicking the basement membrane of the Bowman’s Capsule)
-Dialysis fluid is on other side of the membrane – this contains the normal plasma levels of glucose to ensure no net movement of glucose out of the blood as well as mineral ions which diffuses into the fluid only when in excess in order to restore the electrolyte balance
-Dialysis fluid contains no urea so maintain steep concentration gradient from blood to fluid so urea leaves the blood
-Blood and dialysis fluid moves in opposite directions to maintain a countercurrent exchange system and maximise the exchange taking place
-No active transportation occurs here, only diffusion

Question 28

Peritoneal dialysis

Answer 28

Peritoneal dialysis:
-Done inside of the body, making use of natural dialysis membraned formed from the abdominal lining – done at home
-Dialysis fluid enters abdomen by a catheter and left for several across so urea and excess mineral ions pass out capillaries into tissue fluid then into the dialysis fluid which is drained and discarded.

Question 29

Action of ADH in the kidneys

Answer 29

Action of ADH in the kidneys:
1). Water potential in the blood drops (due to dehydration)
2). Change in water potential is detected by the hypothalamus
3). Pituitary gland releases ADH
4). ADH acts on distal convoluted tubule and collecting duct by putting aquaporins in their walls
5). This causes more water to get reabsorbed into the blood from the filtrate (which becomes urine)
6). This increases the water potential of the blood – this is an example of negative feedback

Question 30

The orthicine cycle -> productino of urea from ammonia

Answer 30

★Orthicine cycle – production of urea from ammonia★
1- Ammonia + ornithine + carbon dioxide -> citrulline and water
2- Citruline and ammonia -> arginine and water
3- Arginine + water -> Urea and ornithine

Question 31

Non-cyclic phosphorylation

Answer 31

★Non-cyclic phosphorylation/Chemiosmosis★
1).Light/Proton hits photosystem 2 – excites pair of electrons -> leaves the chlorophyll molecule
2). Electrons passed along electron transport chain – energy is used to synthesise ATP
3). These electrons (along with H+ protons made at PS2 by photolysis of water) causes formation of reduced NADP from NADP at photosystem 1

Question 32

Calvin Cycle/Light Independant stage of photosynthesis

Answer 32

Calvin Cycle/Light Independant stage of photosynthesis:
1). carbon fixation -> carbon dioxide (1carbon molecule) added to rubisco, forming two molecules of GP (6total carbons)
2). Reduction -> ATP and NADPH generated -> 2 molecules of TP formed (total 3 carbons)
3). 1 carbon released when RuBP formed -> that carbon is used to generate hexose sugar (glucose)
-> Cycle repeated 6 times to form one molecule of glucose