Anything and Everything y2

Question 1

What are the reaction equations for aerobic respiration, anaerobic respiration in humans, and anaerobic respiration in yeasts?

Answer 1

• Aerobic respiration:
  C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Large amount of energy
• Anaerobic respiration in humans:
  C₆H₁₂O₆ → 3C₃H₆O₃ + Small amount of energy
• Anaerobic respiration in yeasts:
  C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ + Small amount of energy

Question 2

Explain, in terms of respiration, what happens in the muscles during and after exercise.

Answer 2

• Muscles contract vigorously, causing rate of aerobic respiration and oxygen consumption to increase
• Heart rate and breathing rate increase, enabling more oxygen to reach muscles
• When oxygen intake does not meet oxygen demand, oxygen debt occurs and anaerobic respiration takes over from aerobic respiration
• Lactic acid accumulates, leading to fatigue and muscle pain
• After exercise, lactic acid is oxidised in the liver to produce energy, converting remaining lactic acid back to glucose

Question 3

State the adaptations of the nasal cavity, trachea and bronchi

Answer 3

• Nasal cavity:
  Hair and mucus layer to trap dust and foreign particles
• Trachea:
  Supported by C-shaped rings of cartilage to ensure it is always open
• Walls of trachea and bronchi:
  Gland cells to secrete mucus layer, trapping dust and bacteria
  Ciliated epithelial cells to sweep trapped dust and bacteria into pharynx

Question 4

State the adaptations of the alveoli

Answer 4

• Numerous and small in size to increase SA:V ratio
• Well supplied with blood capillaries to maintain constant flow of blood and ensure steep diffusion gradient
• Coated with film of water to allow gases to dissolve and diffuse more efficiently
• One-cell thick wall to minimise diffusion distance

Question 5

State what happens during inspiration

Answer 5

• Diaphragm contracts and flattens
• Internal intercostal muscles relax, external intercotal muscles contract
• Rib cage moves upwards and outwards
• Thoracic volume increases
• Pressure in lungs decreases to below surrounding air
• Air is drawn in

Question 6

What are the chemicals found in smoke and their effects?

Answer 6

• Nicotine:
  Highly addictive
  Makes blood clot more easily
• Carbon monoxide:
  Binds to haemoglobin, decreasing ability of RBCs to transport oxygen
  Increases rate of fat deposits on artery walls leading to atherosclerosis
• Tar:
  Paralyses cilia lining in air passages, leading to less efficient gaseous exchange

Question 7

What is the composition of blood and their adaptations/functions?

Answer 7

• 55% Plasma:
  Mostly water
  Transports proteins, mineral salts, food substances, waste products and hormones
• 44% Red blood cells:
  No nucleus, biconcave shape to increase SA:V ratio
  Elastic to squeeze through blood capillaries
  Transports oxygen
• 1% White blood cells, platelets:
  Lymphocytes produce antibodies that bind to antigens on pathogens, causing clumping
  Phagocytes surround and engulf pathogens, destroying them
  Platelets begin process of blood clotting when damaged

Question 7

What are the symptoms and effects of chronic bronchitis and emphysema?

Answer 7

• Chronic bronchitis:
  Infection of the bronchi, inflaming epithelium of airways and causing excessive mucus, leading to breathing difficulties and coughing
• Emphysema:
  Breakdown of alveolar walls due to excessive coughing, reducing SA:V ratio leading to decreased rate of gaseous exchange

Question 8

Describe the mechanism of blood clotting

Answer 8

• Damaged platelets release thrombokinase
• Thrombokinase and Ca²⁺ ions convert inactive prothrombin to thrombin
• Active thrombin converts soluble fibrinogen to insoluble fibrin

Question 9

Describe the 3 ways that carbon dioxide is transported in the blood

Answer 9

• 70% diffuses into red blood cells and forms carbonic acid, which is catalysed by carbonic anhydrase. Carbonic acid dissociates to form hydrogen ions and bicarbonate ions, which diffuse back into plasma
• 23% dissolved in plasma directly
• 7% binds to haemoglobin in red blood cells

Question 10

State how blood is transported by the vena cava, pulmonary artery, pulmonary vein and aorta

Answer 10

• Vena cava transports deoxygenated blood from rest of body to heart
• Pulmonary artery transports deoxygenated blood from heart to lungs
• Pulmonary vein transports oxygenated blood from lungs to heart
• Aorta transports oxygenated blood from heart to rest of body

Coronary arteries are connected to aorta

Question 11

Describe the location of the 4 valves in the heart

Answer 11

• Tricuspid valve/Right atrioventricular valve is located between right atrium and right ventricle
• Bicuspid valve/Left atrioventricular valve is located between left atrium and left ventricle
• Pulmonary valve is located between right ventricle and pulmonary artery
• Aortic valve is located between left ventricle and aorta

Aortic and Pulmonary valves are also referred to as semilunar valves

Question 12

Describe and explain how to determine if two blood groups are compatible for donation

Answer 12

If the antigens on the donor’s red blood cells and the antibodies in the recipient’s plasma match, they are incompatible. If they are mixed, the antibodies in the recipient’s plasma will bind to their respective antigens on the donor’s red blood cells, causing agglutination.

Question 13

State the features/adaptations of the 3 main types of blood vessels

Answer 13

• Arteries:
  High pressure, small lumen relative to diameter
  Thick muscular walls to prevent rupture, can contract and relax to cause vasoconstriction/vasodilation
  Elastic fibres that can stretch and spring
• Veins:
  Low pressure, large lumen relative to diameter
  Valves to prevent backflow of blood
• Blood capillaries:
  Largest lumen relative to diameter
  One-cell thick epithelium to reduce diffusion distance
  Extensive network to increase total cross-sectional area leading to more efficient transport of subtances between cells

Question 14

Describe exactly what happens during the 3 stages of the cardiac cycle

Answer 14

• Atrial systole and ventricular diastole (~0.1s):
  Atria contracts, forcing blood in atrium to enter ventricles
  Pressure in atria increase
• Atrial diastole and ventricular systole (~0.3s):
  Atria relax and ventricles contract, forcing in ventricles to enter aorta/pulmonary artery
  Pressure in ventricles increase, pressure in atria decrease
  Blood hits atrioventricular valves and backflow is prevented, causing “lub” sound
  Wall of aorta stretches due to influx of blood
• Atrial diastole and ventricular diastole (~0.4s):
  Ventricles relax
  Pressure in ventricles decrease
  Blood hits semilunar valves and backflow is prevented, causing “dub” sound
  Walls of aorta spring back, causing slight bump in left ventricular pressure (dicrotic notch)

Question 15

Define a gene, allele, genotype and phenotype

Answer 15

• Gene:
  A section of DNA at a specific location on a chromosome that contains information that defines a trait
• Allele:
  A specific variant of a gene
• Genotype:
  The genetic makeup of an organism
• Phenotype:
  The observable traits of an organism

Question 16

Define codominance and incomplete dominance, discontinuous variation and continuous variation

Answer 16

• Codominance:
  When the effects of two alleles are mixed in a heterozygous environment
• Incomplete dominance:
  When the effects of two alleles are equally expressed in a heterozygous environment
• Discontinuous variation:
  A trait with a few, clear-cut phenotypes that are controlled by one/a few genes, and not affected by the environment
• Continuous variation:
  A trait with a range of phenotypes that are controlled by many genes with additive effect, and can be affected by the environment

Question 17

Define a calyx, corolla, stamen, androecium, carpel, gynoecium and inflorescence

Answer 17

• Corolla: Collective noun for petals
• Calyx: Collective noun for sepals
• Stamen: Anther and filament, male reproductive parts of flower
• Androecium: Collective noun for stamen
• Carpel: Stigma, style and ovary, female reproductive parts of flower
• Gynoecium: Collective noun for carpel
• Inflorescence: Cluster of flowers, common in wind-pollinated plants

Question 18

State the functions of petals, sepals, anther, filament, stigma and style

Answer 18

• Petal: Brightly coloured to attract insects, providing a landing platform (insect-pollinated flowers)
• Sepal: Protects flower in bud stage
• Anther: Produces pollen grains
• Filament: Keeps anther upright in a position suitable to disperse pollen grains
• Stigma: Swollen structure, receives pollen grains and secretes sugary fluid to stimulate their germination
• Style: Connects stigma to ovary, holds stigma upright

Question 19

State the differences between self-pollinated and cross-pollinated plants

Answer 19

• Self pollinated:
  Between same or different flowers on the same plant
  Bisexual (both male and female parts)
  Anther and stigma mature at same time
  Stigma typically situated directly below anthers
• Cross pollinated:
  Between different plants
  Can be dioecious (each flower one gender) or monoecious (each flower two genders)
  Anther and stigma mature at different times
  Stigma typically situated away from anthers

Question 20

State the difference between insect-pollinated and wind-pollinated flowers

Answer 20

• Insect pollinated:
  Brightly coloured, large petals
  Sweet, fragrant scent
  Sticky stigma
• Wind pollinated:
  Dull coloured, small petals
  Long and pendulous anthers
  Large, feathery stigma

Question 21

Describe the process of double fertilisation

Answer 21

• Pollen grain lands on stigma, which secretes sugary fluid, causing pollen grain to germinate
• Pollen tube nucleus secretes enzymes to digest stigma and style, forming pollen tube
• Pollen tube travels down style into ovary, and enteres ovule through micropyle
• Generative nucleus undergoes mitosis to form 2 haploid male gametes
• One male gamete fuses with haploid ovum to form diploid zygote, other male gamete fuses with 2 haploid polar nuclei to form triploid endosperm

Ensures that plants do not waste energy by forming endosperm for ovules that are not fertilised

Question 22

Describe the effects of puberty on males and females

Answer 22

• Male:
  Larynx enlarges, voice deepens
  Increased growth of pubic hair, facial hair and armpit hair
  Penis and testes enlarge and mature, testes start producing sperm
  Increased levels of GnRH, testosterone
• Female:
  Breasts and uterus enlarge
  Increased growth of pubic hair
  Sex organs mature, beginning of ovarian cycle and menstruation
  Increased levels of GnRH, oestrogen, progesterone

Question 23

Describe the functions of the parts of the male reproductive system

Answer 23

• Testes: Produces sperm and secretes testosterone and other sex hormones
• Scrotum: Sac of skin that supports the testes, maintaining optimal temperature of 33-34°C for sperm growth
• Epididymis: Coiled duct next to each testis, storing inactive sperm
• Sperm duct : Conducts sperm from testes or epididymis to penis
• Seminal vesicle: Temporarily stores sperm before it is released into urethra
• Cowper’s gland and Prostate gland: Releases fluids containing nutrients and enzymes that activate sperm

Question 24

Describe the functions of the parts of the female reproductive system

Answer 24

• Ovary: Stores diploid primary follicles and produces ovum, secreted oestrogen and progesterone
• Fimbria: Ciliated structure between ovaries and fallopian tube that sweep ovum into fallopian tube
• Fallopian tube: Conducts ovum from ovary to uterus, acts as site of fertilisation
• Endometrium: Outer muscular layer of uterus, acts as site of implantation of embryo

Question 25

Describe the phases of the ovarian cycle

Answer 25

• Follicular phase:
  GnRH stimulates secretion of FSH, stimulating development of primary follicle into Graafian follicle
  Mature haploid ovum develops in Graafian follicle
  Graafian follicle secretes oestrogen, repairing endometrium and stimulating release of LH
• Ovulation phase:
  Spike in LH causes rupture of Graafian follicle, releasing ovum into fallopian tube and producing corpus luteum
  Start of fertile period
• Luteal phase:
  Corpus luteum secretes oestrogen and progesterone, thickening endometrium to allow implantation of embryo
  Oestrogen and progesterone have negative feedback on pituitary gland, decreasing secretion of FSH and LH
  If fertilisation unsuccessful, corpus luteum breaks down, decreasing secretion of oestrogen and progesterone

Question 26

Describe the phases of the menstrual cycle

Answer 26

• Menstrual phase (Day 1-5):
  Decrease in levels of oestrogen and progesterone leads to shedding of endometrium, degenerated ovum and blood, which are removed through the vagina
  Rise in GnRH stimulates secretion of FSH, stimulating start of ovarian cycle
• Proliferative phase (Day 6-13):
  High levels of FSH stimulate secretion of oestrogen, stimulating repair and growth of endometrium
  High levels of oestrogen stimulate secretion of GnRH, which stimulates secretion of LH
• Ovulation (Day 14):
  Spike in LH stimulates rupture of Graafian follicle and release of ovum into fallopian tube
  Ovum remains viable for 1-3 days (fertile period)
• Secretory phase (Day 15-28):
  High levels of oestrogen and progesterone thicken and maintain thickness of endometrium, and have negative feedback on GnRH, surpressing secretion of FSH and LH
  Preparation of implantation of embryo in endometrium
  If fertilisation does not occur, corpus luteum degenerates, causing drop in levels of oestrogen and progesterone

Question 27

State the functions/adaptations of the placenta and amniotic sac

Answer 27

• Placenta:
  Maternal blood bathes whole surface of chorionic villi to increase SA:V ratio
  Chorionic villi have highly folded structure to increase SA:V ratio
  Continuous flow of maternal blood in maternal blood pools and foetal blood in foetal blood capillaries to maintain steep diffusion gradient
• Amniotic sac:
  Contains amniotic fluid, which supports and cushions foetus to prevent bodily injury
  Maintains foetal body temperature
  Lubricates vagina during birth

Question 28

State the corrective mechanisms of the body when there is high external temperature.

Answer 28

• Arterioles vasodilate, shunt vessels vasoconstrict to increase flow of blood to capillaries at skin surface
• Sweat glands increase sweat production to increase heat lost as latent heat of vaporatisation during evaporation
• Hair erector muscles relax to allow hair to lie flat
• Rate of metabolic activities and respiration decreases to decrease heat produced