11.1 Antibody Production and Vaccination Antigens in blood transfusion

● Antigen: toxic or foreign substance which can trigger an immune response ● Antibody: blood protein produced in response to a specific antigen

Antigens in blood transfusion

● Blood groups are based on the presence of certain types of antigens on the surface of haemoglobins

● Agglutination (foreign response) and hemolysis (haemoglobins destroyed and accumulate in the vessels) can occur if wrong blood type is given

Specific immune response

● Specific Immune response: producing antibodies in response to pathogens ● Process (①~③ on the right)

1. Macrophage (type of WBC) engulfs pathogen, displays antigen 2. Helper T cells/lymphocyte (WBC) binds to the antigen using receptor

protein → T cell activates 3. T cells bind to B cells/lymphocyte (WBC) with same receptor protein

→ B cell activated Plasma Cells

● Plasma cells are mature B cells which can produce specific antibodies during an immune response

● Has large rough endoplasmic reticulums to transport proteins (antibodies) Clonal selection and memory cell formation

● Process (④~⑥ on the right) 1. (After B cell activated) B cell divides to produce memory cells (cells

which can respond to the same pathogen when exposed)... 2. ...and also to produce antibody-secreting plasma cells (differentiated

B cells) 3. Plasma cells produce more clones and produces specific antibodies

Antibody functions

● Opsonisation: makes pathogens more recognisable for phagocytes ● Neutralisation of viruses and bacteria: prevents viruses from attaching to host

cells ● Neutralisation of toxins: binds to toxins to prevent them from affecting cells ● Activation of complement: causes pathogens to rupture by forming a pore in the membrane ● Agglutination: antibodies can stick together pathogens for easier phagocytosis

Immunity

● Immunity to a disease is due to the presence of antibodies which recognises the antigens causing the disease ● Immune system releases memory cells and antibodies in response to a challenge

Role of vaccines towards immunity

● Vaccines contain weakened pathogens or antigens that can trigger primary immune response but not cause the disease ● Secondary immune response occurs if the same pathogen enters by infection (stronger response)

Ethics behind Jenner’s vaccine experiments ● After hearing that milkmaids don’t get smallpox after being exposed to cowpox, Edward Jenner tested this by

infecting a young boy with cowpox and exposing him to smallpox later → boy had ability to resist smallpox ● Ethical problems

○ Jenner didn’t do preliminary investigation ○ Smallpox can be fatal

Eradication of smallpox

● Factors contributing to the eradication: ○ Only humans can get smallpox ○ Symptoms are obvious (fast vaccination) ○ Immunity to smallpox is long term (no reinfection)

Vaccines and epidemiology

● Epidemiology: study of disease distribution and causes within population (predicting outbreaks) Zoonosis

● Zoonosis: diseases that can cross a species barrier Histamines

● White cells can produce histamines (widens small blood vessels to allow flow of immune components) ● Histamines cause allergic symptoms (e.g. itching, mucus secretion)

Production of monoclonal antibodies using hybridoma cells

1. Animal (often mouse) is injected with an antigen → produces plasma cells

2. Plasma cell collected from spleen 3. Plasma cells are fused with myeloma (tumour) cells for division

(fused cells: hybridoma cells) 4. Hybridoma cells are screened to select only the one which

produces the specific antibodies 5. Hybridoma cells produce monoclonal antibodies (highly specific

antibodies) Pregnancy tests employ monoclonal antibodies

● Pregnancy test kits use monoclonal antibodies to detect hCG in urine, a type of hormone produced by the developing embryo and the placenta.

● Point C is the test site and point D is the control site

11.2 Movement Function of bones and exoskeletons in muscle movement

● Bones and exoskeletons facilitate movement by acting as levers (changing size and direction of forces)

● Components of the lever ○ Effort force (➨) ○ Fulcrum (pivot) [▲] ○ Resultant force (■)

● Position of the components on the lever determine its class Skeletal muscles are antagonistic muscles

● Skeletal muscles are antagonistic (when one contracts, the other relaxes) ● Triceps and Biceps are antagonistic

Antagonistic muscles in insects

● Hindleg of grasshoppers are specialised for jumping ● Femur and tibia are close together when preparing to

jump (flexing) → extensor relaxed, flexor contracts ● Tibia extends, grasshopper jumps → extensor

contracts, flexor relaxes

Human elbows are synovial joints ● Cartilage: covers bones, prevents friction, and absorbs shock (prevents

fracture) ● Synovial fluid: lubricates the joint (fills up space between bones), prevents

frictions ● Joint capsule: prevents dislocation of joints by sealing the joint and

holding it to the synovial fluid Joint movement

● Knee joints → both hinge joints and pivotal joints (pivotal hinge joint) ○ Flexion (bending) ○ Extension (straightening)

● Hip joints → ball and socket joint ○ Flexion ○ Extension ○ Rotation ○ Adduction/abduction (in/out of midline)

Structure of muscle fibres

● Skeletal/striated muscles are muscles used to move the body which are attached to bones

● Striated muscles are composed of bundles of muscle cells called muscle fibres

● Myofibrils: contractile units inside muscle fibres ● Sarcolemma: plasma membrane which surrounds

each muscle fibre ● Sarcoplasmic reticulum: wraps around myofibrils

to convey signals to contract ● Mitochondria for ATP production

Myofibrils

● Myofibrils: long parallel structures making up the muscle fibres

● Light and dark pattern caused by layout of thick myosin filament and thin actin filament

● Actin filaments attached to Z-line/disk at one end ● Myosin filaments surrounded by 6 actin filaments

(forms cross-bridge) during muscle contraction

Drawing the sarcomere ● Length of actin and myosin

filaments should be indicated (short of long) to indicate extent of contraction

● Draw myosin with heads Skeletal muscle contraction mechanism

● Thick myosin filaments pull thin actin filaments towards centre of sarcomere → muscle contraction ● Process of contraction

1. Myosin filaments have heads/projections that can bind to actin filaments (cross-bridge) 2. ATP is used to exert force for pulling actin

● Many cross bridges form because of multiple heads on myosin and binding sites on actin Skeletal muscle contraction process

1. Tropomyosin blocks the binding sites on actin when muscle are relaxed

2. Motor neuron sends signals to contract 3. Sarcoplasmic reticulum releases calcium ions 4. Calcium ions bind to troponin 5. Troponin moves tropomyosin, exposing binding sites 6. Myosin heads bind to actin 7. (process repeated)

ATP in skeletal muscle contraction

● To repeat the above process, ATP is used. ● Process

1. ATP binds to myosin heads and detaches it from actin binding site (cross-bridge broken)

2. ATP is hydrolysed into ADP + P, allowing myosin head to to change the angle (ADP + P binds to head)

3. Heads attach to the next binding site away from the centre of sarcomere (P released)

4. ADP released, heads pull the actin filament towards centre of sarcomere (power stroke)

Use of fluorescence to study contraction

● Visible or invisible light which can be detected by light microscopes as a result of exposure to radiation of different wave length

11.3 The Kidney and Osmoregulation

Different responses to changes in osmolarity in the environment ● Osmolarity: solute concentration of a solution ● Animals are either osmoregulators or osmoconformers

○ Osmoregulators ■ Organisms which maintains a constant internal solute concentration ■ ⅓ of the concentration of seawater and 10 times that of fresh water ■ E.g. terrestrial animals

○ Osmoconformers ■ Organisms which maintains the same internal solute concentration as the concentration of solutes in

its surrounding ■ E.g. most marine animals

Malpighian tubule system in insects

● Malpighian tubule: system which carries out osmoregulation and removal of nitrogenous wastes in insects ● Hemolymph are the circulating fluid in insects (blood)

● Process 1. Cells lining the tubules actively transport ions and uric acid from the hemolymph

(blood) into the lumen of the tubules 2. Water enters the lumen from the hemolymph through osmosis 3. Tubules contents move into the hindgut, where most of the water and salts are

reabsorbed 4. Nitrogenous waste remains, excreted with feces

Drawing the human kidney

● Cortex: selective reabsorption of blood contents ● Medulla: Reabsorbs water ● Pelvis: where urine is discharged ● Ureter: carries urine to bladder ● (Renal vein should be wider than renal arteries) ● (Cortex ⅕ thickness in relation to kidney)

Renal artery and renal vein

● Kidneys remove substances from the blood which are unnecessary or are harmful

Renal artery Renal vein -Unfiltered blood -More ingested toxins -More excretory waste -More water -More salt -More oxygen and glucose, less CO2 (metabolism by kidney)

-Filtered blood -Less ingested toxins -Less excretory waste -Less water -Less salt -Less oxygen and glucose, more CO2 (metabolism by kidney)

● Substances filtered (excess or undesired) are removed by the ureter into the bladder Bowman’s capsule ultrastructure

● Ultrafiltration (separation of particles differing in size) occurs in the glomerulus (inside Bowman’s capsule)

● Ultrafiltration 1. Blood enters from afferent arteriole 2. Fenestrations: passes fluids but not blood cells 3. Basement membrane: prevents plasma proteins from being

filtered out 4. Podocytes: prevents small molecules from being filtered 5. Unfiltered particles enter efferent arteriole 6. Filtered particles (glomerular filtrate) are removed out from

proximal convoluted tubule Role of proximal convoluted tubule

● Proximal convoluted tubule actively reabsorbs useful substances from the glomerular filtrate ● All glucose, amino acids, and 80% of the water, sodium, and other mineral ions are absorbed ● Adaptations

○ Microvilli for increasing surface area ○ Many mitochondria (ATP for active transport)

Nephron

● Nephron: functional units in kidney made of glomerulus and various tubules Ultrafiltration Capillaries Tubules

-Afferent arteriole: brings unfiltered blood -Glomerulus: site of ultrafiltration -Bowman’s capsule: collects fluid filtered from blood -Efferent arteriole: transports filtered blood (narrow for high pressure)

-Vasa recta: carries blood into medulla and back to cortex -Peritubular capillaries: absorbs fluid from convoluted tubules -Venule: carries blood to renal vein

-Proximal convoluted tubule: actively reabsorbs useful substances from filtrate -Loop of Henle: carries filtrate into medulla and back to cortex -Distal convoluted tubule: reabsorbs useful substances (less capable) -Collecting duct: carries filtrate to renal pelvis (to urine)

Loop of Henle function

● Descending loop of Henle: permeable to water but not to sodium ions → increased solute concentration ● Ascending loop of Henle: permeable to sodium ions but not to water → allow osmosis of water from descending loop ● Filtrates more sodium than water (dilute) ● Generate high concentration of solutes in medulla compared to filtrate in nephron → aid reabsorption of water (by

medulla) in the collecting duct Some animals have long loops of Henle

● Longer loop of Henle → more water reabsorption by the medulla ● Common in animals adapted to dry habitats

Function of ADH

● ADH: hormone which balances the water concentration of the blood by changing the permeability of the collecting duct

● If the individual is dehydrates, ADH makes the collecting duct more permeable to water (allows individuals to excrete less water)

Animals vary in terms of the type of nitrogenous waste they produce

● Different organisms are adapted to excrete nitrogenous waste in different forms (ammonia, urea, or uric acid) ○ Ammonia is toxic ○ Conversion of ammonia into uric acid or urea requires extra energy ○ Uric acid doesn’t require water to excrete ○ Uric acid doesn’t dissolve in eggs when released by developing fetus (less toxic)

● Excretion of nitrogenous waste in different organisms ○ Most marine animals release waste directly as ammonia (can be diluted) ○ Terrestrial organisms (including marine mammals) use energy to convert ammonia into less toxic urea or

uric acid ○ Amphibians release ammonia in larval stage and release urea after metamorphosis (less energy) ○ Birds and insects convert ammonia into uric acid (no water = less weight to carry)

Dehydration and overhydration consequences

Dehydration Overhydration -Metabolic waste cannot be removed (urine requires water) → increased tissue exposure to metabolic waste -Less water in blood → low blood pressure -Unable to sweat → body temperature cannot be controlled

-Dilution of blood solutes → body fluid becomes hypotonic (low solute) → swelling of cells due to osmosis

Kidney failure treatment

Hemodialysis Kidney transplant -Uses dialysis machine (artificial kidney) -Common when kidney is unable to filter out products properly -Risk of infection

-Kidney from donor is transplanted to recipient -Greater independence for recipient -Recipient’s body may reject organ

Urinalysis

● Urinalysis: detects blood cells, glucose, proteins, and drugs in urine ● Indications

○ Blood cells: cancer, infections, diseases ○ Glucose: diabetes ○ Large number of proteins: kidney disease ○ Drugs: drug usage

11.4 Sexual Reproduction

Similarities between oogenesis and spermatogenesis ● Oogenesis: production of egg cells in the ovaries ● Spermatogenesis: production of sperm cells in the testes (inside seminiferous tubules) ● Similarities

○ Ultimately produces haploid cells through meiosis ○ Undergoes mitosis to produce diploid cells

Stages of gametogenesis

● Oogenesis 1. (During fetal development) germinal cells undergo mitosis to produce 2 diploid oogonia (2n) and grows

larger (stops at prophase) 2. (At puberty) oogonium (2n) undergoes mitosis to produce 2 diploid primary oocytes (2n) [becomes

contained in primary follicles] 3. Primary oocytes (2n) undergoes meiosis I to produce a secondary oocytes (n) and a polar body (n)

a. Polar body (n) degenerates (unequal division) b. Secondary oocytes (n) continues into meiosis II (stops at prophase II)

4. Secondary oocyte (n) completes meiosis II in secondary follicle, forms ovum (egg) and a polar body (n) a. Polar body (n) degenerates b. Ovum (egg) remains inside mature follicle

5. Ovum (egg) is ovulated and the follicle forms corpus luteum, which produces estrogen and progesterone (develops uterus lining) and degenerates

● Spermatogenesis 1. Outer layer cells (germinal epithelial cells) undergo

mitosis to produce 2 diploid spermatogonia (2n) 2. Spermatogonium (2n) grows larger into primary

spermatocytes (2n) 3. Primary spermatocytes (2n) undergoes meiosis I to

produce 2 secondary spermatocytes (n) 4. Secondary spermatocytes (n) undergoes meiosis II to

produce 2 spermatids (n) 5. Spermatids (n) associates with sertoli cells to differentiate

into spermatozoa (sperm) 6. Spermatozoa (sperm) detaches from Sertoli cells

Diagrams of seminiferous tubule and the ovary

Diagrams of sperm and egg

Differences in the outcome of spermatogenesis and oogenesis

Oogenesis Spermatogenesis -Each meiotic division results in 1 functioning haploid cell -Each meiotic division results in 4 functioning haploid

cells -Volume of cytoplasm increases (takes in volume from polar body)

-Volume of cytoplasm decreases

-Continues until menopause after puberty -Continues until death after puberty -Only few hundred eggs produced -Millions of sperms are present at a time

Preventing polyspermy during fertilisation

● Fertilisation process 1. Acrosome reaction: sperm binds to jelly coat, releases enzymes from the acrosome → digests jelly coat 2. Penetration of membrane: protein on the tip of sperm binds to egg membrane, fuses together → releases

sperm nuclei 3. Cortical reaction: egg is activated and releases cortical granules (exocytosis) containing enzymes which

digest binding proteins and harden the jelly coat Internal and external fertilisation

Internal fertilisation External fertilisation -Common in terrestrial animals -Prevents gametes from drying out -Assures fertilisation (closer together) -Embryo can be protected inside female

-Common in aquatic animals -Risks predation, susceptibility to environmental variation (e.g. temperature, pH)

Implantation of the blastocyst

● Blastocyst: hollow ball of dividing cells undergoing mitosis (early form of embryo) ● Implantation (blastocyst sinking into the endometrium) process

1. (7 days) Blastocyst reaches uterus, gel coat breaks down 2. Blastocyst sinks into the endometrium (implantation) 3. Blastocyst grows finger-like projections to penetrate uterus lining to obtain nutrients for growth 4. (8 weeks) blastocyst grows bone tissues → becomes fetus

Role of hCG in early pregnancy

● Embryo produces hCG at early stage of pregnancy ● hCG stimulates corpus luteum (ovary) to secrete progesterone and estrogen

→ stimulate development of uterus Materials exchange by the placenta

● Placental villus increase during pregnancy to allow greater exchange of materials

● Blood flows in the intervillous space to allow for greater exchange of materials (between villi and intervillous space)

● Placental barrier thin to allow for quicker diffusion of nutrients ● Placental barrier is selectively permeable to regulate diffusion of nutrients ● Umbilical arteries carry deoxygenated blood (along with waste products) ● Umbilical vein carry oxygenated blood (along with hormones and nutrients)

Release of hormones by the placenta ● Placenta takes over role of secreting estrogen and progesterone (corpus luteum unneeded) after 9 weeks → stimulate

development of uterus ● Can lead to miscarriage if switchover fails

Role of hormones in parturition (birth)

● Progesterone produced by the placenta inhibits production of oxytocin (which stimulates contraction of muscle fibres in the myometrium) and prevents contraction of myometrium

● Hormones produced at the end of pregnancy stops secretion of progesterone → oxytocin is produced ● Oxytocin contracts the myometrium, causing it to produce more oxytocin → gradual increase in contraction → birth

Gestation times, mass and growth, and development strategies

● Gestation time: length of time in which the fetus develops inside the womb ● Longer gestation period allows the newborn to be more independent (mobile, has hair, open eyes) → precocial ● Shorter gestation period leads to less developed newborn → altricial

Hormone functions in females summary

Hormone Produced by Function FSH (follicle stimulating hormone)

-Pituitary gland -Stimulates production of mature follicle around egg

hCG (human chorionic gonadotropin)

-Embryo -Stimulates corpus luteum (ovary) to secrete progesterone and estrogen

Progesterone -Corpus luteum -Placenta

-Stimulates development of uterus wall -Prevents contraction of uterus wall (myometrium)

Estrogen -Corpus luteum -Placenta

-Development of secondary female sexual characteristics

Oxytocin -Pituitary gland -Stimulates contraction of uterus wall (myometrium)