IB Biology Topic 6 (mark scheme)

Explain antibody production.

a. lymphocyte variety;

b. lymph node storage;

c. specific antigens;

d. cloning;

e. antibody secretion;

f. specific immune response;

g. plasma (memory) cells;

Explain why antibiotics are effective against bacterial diseases but not against viral diseases.

a. block metabolism;

b. viruses lack metabolism;

c. antibiotics don't affect eukaryotes;

Outline the role of the skin in temperature regulation.

heat causes:

vasodilation of arterioles;

blood nears surface, heat loss;

sweating

evaporation of sweat for cooling;

cold causes:

vasoconstriction of arterioles

less blood at surface, more heat;

less sweating;

receptors in skin transmit impulses to hypothalamus;

Explain the dietary advice that should be given to a patient who has developed type II diabetes.

regulate diet;

low fat;

complex carbs for gradual release of glucose into blood;

small meals;

don't skip meals, avoid glucose drops;

avoid abrupt changes in blood glucose;.

Describe how body temperature is maintained in humans.

37°C;

blood transmits heat;

hypothalamus has thermoreceptors;

hypothalamus monitors temperature;

dilation of skin arterioles warms skin;

constriction of skin arterioles retains heat;

sweat glands;

evaporation of sweat;

shivering;

example;

Outline the principle of immunity.

immunity results

limit epidemics;

diseases can be eradicated;

reduces mortality;

protects vulnerable

decrease symptoms

decreased health care costs;

Distinguish between type I and type II diabetes.

Type 1

early childhood

body does not produce sufficient insulin

destrucution of beta cells

requires insulin injections.

Type 2:

occurs in adulthood

body does not respond to insulin

caused by down regulation of insulin receptors.

controlled with monitored diet.

Explain the mechanisms involved in the ventilation of the lungs.

external intercostals contract;

internal intercostals relax;

rib cage up;

diaphragm contracts;

increase in volume of thoracic cavity;

reduces pressure;

air enters the lungs;

EXHALATION:

internal intercostal muscles contract;

diaphragm relaxes;

diaphragm upwards;

volume decrease;

pressure increase;

air leaves;

Explain how the structure of an artery allows it to carry out its function efficiently.

thick wall;

elastic fibrest;

narrow lumen for high pressure

thick outer layer of collagen for strength;

no valves since pressure prevents backflow

smooth inner lining to reduce friction;

Describe the need for a ventilation system in humans.

aerobic respiration

gas exchange between lungs and blood

concentration gradient of gases

Explain how nerve impulses are transmitted along and between neurons.

calcium ions released from sarcoplasmic reticulum;

make blocking molecules move;

cross-bridges between actin and myosin form;

ATP energy

for myosin to push actin;

ATP energy to release myosin from binding site;

action repeats along molecule;

Outline a mechanism used to transport products of digestion from the lumen of the ileum into the blood.

facilitated diffusion;

down concentration gradient;

protein channels used;

passive;

Outline the role of hormones in the menstrual cycle.

FSH grows follicile;

eggs mature;

follicle produces estrogen;

estrogen signals lining of uterus to thicken;

matures follicle;

high estrogen levels cause secretion of LH;

LH spike stimulates ovulation, releasing eggs;

LH makes follicles become corpus luteum;

LH makes corpus luteum secrete progesterone;

progesterone maintains uterus lining;

if no pregnancy, corpus luteum disintegrates;

drop in progesterone levels causes menstruation;

progesterone & estrogen inhibit FSH & LH release;

Explain the mechanism of ventilation in humans

air enters through trachea, bronchi and bronchioles;

INHALATION:

intercostal muscles contract;

ribs up;

diaphragm contracts

volume increase;

pressure decrease;

EXHALATION

internal intercostals contract;

ribs down;

diaphragm relaxes;

abdominal muscles contract to lift diaphragm;

volume decrease;

pressure increase;

Some blood proteins are involved in defence against infectious disease. Explain the roles of named types of blood proteins in different defence mechanisms.

a. clotting factors are proteins that start clotting

b. fibrin is a protein that permits clotting

c. the protease thrombin converts fibrinogen to fibrin

d. fibrin forms a mesh that prevents the entry of pathogens

e. antibodies are proteins that lymphocytes make

f. each antibody corresponds to a specific antigen

g. antibodies create specific immunity

h. plasma cells male lots of antibodies

i. immunoglobulins are antibodies against pathogens

j. enzymes in phagocytic white blood cells digest pathogens

Outline the role of FSH and LH in the menstrual cycle.

a. FSH causes estrogen secretion by follicle cells;

b. at start of menstrual cycle;

c. develops endometrium;

d. FSH and LH peak and cause egg release;

e. causes follicle cells to secrete less estrogen and more progesterone;

f. progesterone maintains uterine lining.

g. LH changes follicle to corpus luteum;

h. secretion of LH and FSH regulated by negative feedback;

i. regulated by high estrogen and progesterone;

j. low progesterone causes menstruation;

State the source, substrate, products and optimal pH condition for lipase in the human digestive system.

source: pancreas

substrate: fats

product: glycerol and 3 fatty acids

optimal pH: 8

Outline the unconscious control of the heart rate.

heart contracts without nervous stimulation;

SA node is generates heart beat;

adrenalin speeds up heart rate;

autonomic and parasympathetic nervous system control;

sympathetic speeds up heart rate;

parasympathetic nerve slows heart rate to resting rate;

Explain the role of calcium ions in muscle contraction.

released when impulse reaches muscle;

released from sarcoplasmic reticulum;

exposes binding sites for myosin heads;

allows cross-bridges between myosin and actin to form;

Explain how the direction of blood flow in the heart is controlled.

valves open due to blood pressure differences;

prevent backflow;

atrioventricular valves between ventricles and atria;

semilunar valves between arteries and ventricles;

Outline what is meant by homeostasis.

stable internal environment;

within limits;

example;

variable levels monitored;

negative feedback mechanisms

Blood transports molecules throughout the body. State where the blood absorbs oxygen.

alveoli

Describe how pancreatic cells directly affect blood glucose levels.

α cells produce glucagon;

glucagon releases glucose;

glucagon raises blood glucose levels;

β cells produce insulin;

insulin stores glycogen in body cells;

insulin lowers blood glucose levels;

negative feedback mechanism;

Explain how the structure of veins is adapted to their function.

valves avoid backflow

thin walls give low pressure

wide lumen for slow blood

Plants store carbohydrate in the form of starch. Explain the reasons for starch being digested by the human digestive system.

starch is large;

intestine can't absorb it;

glucose from digested starch is absorbed;

glucose provides energy;

humans don't use starch;

glucose stored as glycogen;

blood can't move starch;

Research is being conducted into treatment for diabetes based on stem cells. Discuss the ethical issues involved in stem cell research.

cure diseases;

less cost than treating diseases;

specific example of ethical conflict (religious fanatics);

forced religion restricts research;

still in experimental stages;

example of risk;

death of early-stage embryos

use of stem cells from patients could overcome these objections;

Outline the control of the heartbeat by the nervous and endocrine systems.

myogenic muscle contraction;

contracts without stimulation;

pacemaker in right atrium;

pacemaker causes contraction;

nerves message to pacemaker;

to alter rate of pacemaker;

medulla controls heart rate;

adrenaline produced by adrenal gland;

adrenaline accelerates heart rate;

Discuss the cause, transmission and social implications of AIDS.

a. HIV;

b. penetrates (T) lymphocytes;

e. lymphocyte number reduced;

f. lower immunity;

g. other illnesses develop;

h. AIDS = final stage;

i. HIV transmitted through body fluids;

l. those without cell receptors are immune;

m. condoms protect

n. expensive treatment;

o. discrimination against victims;

q. economic consequences;

Explain the concept of homeostasis, using the control of blood sugar as an example.

maintains internal environment;

example like temperature;

changes in blood sugar level trigger homeostasis;

controlled by nervous and endocrine systems;

high blood sugar stimulates insulin release;

insulin secreted by β cells in pancreas;

insulin lowers blood sugar;

by converting to glycogen;

low blood sugar stimulates glucagon release;

glucagon secreted by α cells in pancreas;

glycogen converted to glucose;

increases blood glucose level;

Outline the reasons for increasing rates of clinical obesity in some countries.

sedentary lifestyle;

processed food;

diet of fats

cheap food;

Outline how leptin controls appetite.

a. inhibits appetite

b. secreted by adipose

c. level is controlled by food intake

d. leptin targets hypothalamus

e. causes hypothalamus to inhibit appetite

f. blood leptin increases with adipose tissue

Outline the control mechanism for appetite in humans.

a. appetite control center makes person feel full;

b. function is both nervous and hormonal;

c. after eating responds to leptin;

d. centre responds to hormone;

e. centre responds to blood sugar levels

Which blood vessel directly supplies oxygen to the heart muscle?

A. Aorta

B. Coronary artery

C. Pulmonary artery

D. Pulmonary vein

B. Coronary artery

What is a long-term effect of HIV on the immune system?

A. Increase in leucocytes

B. Reduction in erythrocytes

C. Increase in antibody production

D. Reduction in active lymphocytes

D. Reduction in active lymphocytes

What is a consequence of AIDS?

A. Excess production of lymphocytes to help fight disease

B. Excess erythrocytes in capillaries

C. Loss of ability to produce antibodies

D. Loss of ability to produce antigens

C. Loss of ability to produce antibodies

Discuss the ethical issues surrounding IVF.

infertile couples get children;

decision to have children is clearly conscious;

genetic screening of embryos could decrease genetic diseases;

spare embryos used for stem cell research;

expensive

could lead to eugenics

religious fanaticism

Blood is a liquid tissue containing glucose, urea, plasma proteins and other components. List the other components of blood.

water;

dissolved gases;

red blood cells;

white blood cells;

lymphocytes and phagocytes;

platelets;

hormones;

amino acids;

salts

Explain why diabetes could be detected through the analysis of urine.

urine of diabetics has glucose;

urine of non-diabetics lacks glucose;

glomerular filtrate has glucose;

glucose (normally) reabsorbed into blood;

through wall in proximal convoluted tubules;

blood glucose concentration higher in diabetics;

reabsorption not completed;

glucose in pee is found with test strips;

type I diabetes is lack of insulin;

type II diabetes is immunity to insulin;

Outline the mechanism of the action of antibiotics.

inhibition of:

a. synthesis of walls;

b. protein synthesis;

c. nucleic acid synthesis;

What route does blood follow to supply oxygen to heart muscle?

A. pulmonary vein → left atrium → left ventricle → aorta → coronary artery

B. pulmonary vein → right atrium → right ventricle → aorta → coronary artery

C. pulmonary artery → left atrium → left ventricle → aorta → coronary artery

D. pulmonary artery → right atrium → right ventricle → aorta → coronary artery

A. pulmonary vein → left atrium → left ventricle → aorta → coronary artery

What stimulates the production of antibodies?

A. AIDS

B. Antibiotics

C. Anticodons

D. Antigens

D. Antigens

What change occurs to the pressure and volume of the lungs when the external intercostal muscles contract?

A. Both pressure and volume increase.

B. Pressure increases and volume decreases.

C. Pressure decreases and volume increases.

D. Both pressure and volume decrease.

C. Pressure decreases and volume increases.

In which process is "surface area" of key importance for humans?

A. Reabsorption of glucose in the proximal convoluted tubule

B. Release of surfactants by type I pneumocytes

C. Display of antibodies by red blood cells

D. Secretion of enzymes by villi of the small intestine

A. Reabsorption of glucose in the proximal convoluted tubule

Which conditions are correct for inspiration?

Muscles contracted: external intercostal

Pressure in thorax: decreases

Explain the structures and functions of arteries and veins.

a. three layer walls

b. high pressure in arteries

c. arteries exit heart

d. lumen of artery is small for high pressure

e. arteries have thick walls

f. elastic fibres recoil at heart contraction

g. elastic fibres maintain pressure between heartbeats

h. veins carry blood to heart

i. large lumen of veins for less resistance

j. valves in veins prevent backflow

Explain the propagation of electrical impulses along a neuron including the role of myelin.

Neurotransmitter binds receptor site

action potential

resting potential is negative

sodium enters

depolarization

currents cause action potential

K ions leave

myelin insulates neuron

causes node jumping

Glands are organs that secrete and release particular chemical substances. Melatonin is an important hormone secreted in the pineal gland in the brain. Describe its role in mammals.

a. circadian rhythm

b. light detected by retina

c. high production in dark

d. affects jet lag

Explain how hormones are used to control the human menstrual cycle.

pituitary hormone FSH

develops folliciles

folliciles produce estrogen

estrogen repairs uterus lining

estrogen secretes LH

LH causes ovluation

LH develops corpus luteum

which secretes progesterone

progesterone thickens lining

and inhibits LH secretion

low progesterone causes menstruation

Describe the action of the heart in pumping blood.

a. atria collect blood;

b. sinoatrial node impulses muscle to contract;

c. atria contract to push blood to ventricles;

d. atrioventricular (AV) valves are open;

e. semilunar valves are closed;

f. ventricles contract;

g. AV valves close to stop backflow;

h. blood pushed through semilunar valves to

pulmonary artery and aorta;

i. ventricles relax, semilunar valves close to stop backflow;

Explain the processes that control changes in ventilation rate during exercise.

a. exercise increases respiration;

b. CO2 concentration increases;

c. blood more acidic;

d. breathing centers impulse diaphragm and intercostal muscles;

e. increase contraction rate;

f. increase in ventilation rate increases oxygen uptake;

Outline the symptoms of type II diabetes.

a. glucose in urine;

b. high blood glucose;

c. excess thirst;

d. constant hunger;

e. weight loss;

f. tiredness;

Explain the relationship between structure and function of arteries, capillaries and veins.

a. thick walls withstand high pressure;

b. collagen fibres strengthen wall;

c. muscle layer maintains pressure;

d. narrow lumen maintains high pressure;

e. smooth endothelium reduces friction;

Describe the relationship between the structure and function of blood vessels.

arteries carry blood under high pressure;

thicker elastic wall

muscles control pressure

veins blood under lower pressure

have thin walls with less elastic fiber

valves prevent backflow

capillary walls are one cell thin

allow diffusion across wall

porous

Outline the control of the heartbeat.

a. myogenic;

b. pacemaker

c. stimulates atria to contract;

d. vesicle contraction;

e. (autonomic) nerves alter pace;

f. adrenaline increases pace;

g. acetylcholine reduces pace;

h. adrenal glands release adrenaline;

i. carried by blood to heart;

j. to increase pace;

Explain how the units used to measure lung function are useful in showing if a person suffers from asthma.

a. asthma constricts airways;

b. units measure efficiency of exhalation;

Outline the hormonal control of birth.

at end of pregnancy, progesterone levels decrease

allows oxytocin secretion;

oxytocin from pituitary

stimulates uterus contraction

cervix widens

oxytocin increases contraction rate/intensity;

positive feedback;

Membranes of pre-synaptic and post-synaptic neurons play an important role in transmission of nerve impulses. Explain the principles of synaptic transmission.

synaptic gap opens

depolarization

opens calcium cannels

calcium ion influx

synaptic vesicles fuse with pre-synaptic membrane

vesicles release neurotransmitter

diffuses into cleft

binds to receptors on post-synaptic membrane

opens channels for sodium to enter

starts action potential

breaks down neurotransmitter

Explain how the small intestine moves, digests and absorbs food.

a. contraction of muscle moves food

b. peristalsis mixes food and enzymes

c. enzymes digest macromolecules into monomers

d. pancreatic enzymes chemically digest food in small intestine

e. amylase digests starch

f. bile in small intestine causes good pH for enzymes

g. some final digestion into monomers is associated with epithelial cells

h. mucosa layer in surface of small intestine has villi

i. microvilli increase surface area for better absorption

j. villi absorb digestion products

k. glucose enters blood

l. active transport

Nerves connecting the brain and heart contain neurons that control heart rate. Explain how a nerve message passes from one neuron to another neuron.

a. nerve impulse reaches end of presynaptic neuron;

b. calcium channels open;

c. calcium diffuses into presynaptic neuron;

d. vesicles of neurotransmitter fuse with presynaptic membrane;

e. (neurotransmitter) released (by exocytosis) into synaptic cleft;

f. (neurotransmitter) diffuses across synapse;

g. (neurotransmitter) attaches to receptors on postsynaptic neuron;

h. receptors open sodium channels;

i. depolarization;

j. causes a new action potential;

k. (neurotransmitter) on postsynaptic membrane is broken down;

l. (neurotransmitter) is reabsorbed into the presynaptic neuron;

What initiates an action potential along a neuron?

A. Potassium and sodium ions diffuse out of a neuron.

B. Potassium and sodium ions diffuse into a neuron.

C. Neurotransmitters cause depolarization of membrane.

D. Acetylcholinesterase breaks down acetylcholine.

C. Neurotransmitters cause depolarization of membrane

LH causes the rupture of a follicle and release of an egg cell. What is this process called?

A. Conception

B. Fertilization

C. Menstruation

D. Ovulation

D. Ovulation

What will be happening in a person after eight hours of sleep?

A. β cells in the pancreas will be producing insulin.

B. Glucose will be converted into glucagon.

C. α cells in the pancreas will be producing glucagon.

D. Glycogen is being produced and stored in the liver and muscle cells.

C. α cells in the pancreas will be producing glucagon.

Is the blood in the aorta, left ventricle and pulmonary artery oxygenated or deoxygenated?

Aorta: oxygenated

left ventricle: oxygenated

pulmonary artery: deoxygenated

A process occurs in which the inside of a neuron develops a net positive charge compared with the outside. What is the name of this process?

A. Resting potential

B. Repolarization

C. Depolarization

D. Hyperpolarization

C. Depolarization

Between which structures do sensory neurons carry nerve impulses?

A. From receptors to muscles

B. From effectors to the central nervous system (CNS)

C. From the central nervous system (CNS) to receptors

D. From receptors to the central nervous system (CNS)

D. From receptors to the central nervous system (CNS)

Describe the importance of hydrolysis in digestion.

digestion definition

makes food soluble

food absorbed into blood

move from blood to cells

small molecules join

enzymes involved

requires water

polysaccharides to monosaccharides

protein to amino acids

fats to fatty acids and glycerol

Describe three features of alveoli that adapt them to gas exchange.

high capillary density

large surface area

thin walls

moist layer

Explain the need for a ventilation system and the mechanism of ventilation of the lungs in humans.

respiration needs oxygen;

gas exchange depends on ventilation;

alveoli provide surface area for gas exchange;

ventilation system maintains a high concentration of oxygen in the alveoli;

bloodstream links alveoli to cells;

inhalation by contraction of diaphragm;

and external intercostals;

decrease pressure, pulling air into lungs;

exhalation by relaxation of the diaphragm;

occurs with relaxation of external intercostals;

decrease volume/increase pressure in the thorax,

air leaves;

Outline how the human body prevents blood glucose concentration from rising excessively.

glucose monitored by pancreas;

insulin secreted in response to high blood glucose

insulin makes cells absorb glucose

respiration uses glucose

glucose converted to glycogen;

by liver

glucose converted to fat

negative feedback

Why are antibiotics effective against bacteria?

A. They can produce specific antibodies.

B. They can engulf foreign matter.

C. They can block specific metabolic pathways.

D. They can act as a vaccine.

C. They can block specific metabolic pathways.

What is an effect of the HIV virus on the immune system?

A. Reduction of the number of phagocytes

B. Reduction of the number of lymphocytes

C. Increase in the ability to form antibodies

D. Decrease in the ability to produce antigens

B. Reduction of the number of lymphocytes

What happens to the external and internal intercostal muscles and diaphragm when inhaling?

esternal intercostals: contract

internal intercostals: relax

diaphragm: contracts

Explain the importance of enzymes to human digestion.

food must be small enough;

chemical breakdown necessary;

enzymes required;

increase digestion rate;

biological catalysts;

digestion at body temperature;

sequential process (e.g. from protein to peptide to amino acid);

specific location with specific conditions for each reaction (e.g. stomach high acidity);

most enzymes work extracellularly;

different enzymes have different optimal pHs;

amylases digest carbohydrate to monosaccharides;

proteases digest proteins to amino acids;

lipases digest fats to fatty acids and glycerol;

Explain the principles of synaptic transmission.

myogenic contraction;

without stimulation;

pacemaker in right atrium

pacemaker causes contraction

nerves message pacemaker

to alter pacemaker rate

medulla controls heart rate

adrenaline produced by adrenal gland

adrenaline accelerates heart rate

Describe the digestion of food in the human digestive system.

chewing food makes smaller particles

saliva digests starch

stomach digests proteins

stomach acids give optimum pH

stomach muscles contract

enzymes in small intestine complete digestion

alkaline condition of small intestine provides optimum pH

bile salts emulsify fats

All motor neurons use acetylcholine to activate skeletal muscle. Explain the effect of neonicotinoid pesticides in insect synapses in the central nervous system.

pesticides akin to nicotine

Bind to nicotinic receptors

binding is irreversible

blocks acetylcholine binding

causes paralysis

Outline the exchange of materials between capillaries and tissues.

a. molecules move by diffusion

b. nutrients enter tissues

c. gas exchange

d. excess water move from cells into blood

e. gland tissues release hormones into the bloodstream

Explain how circulation of the blood to the lungs and to other systems is separated in humans and what the advantages of this separation are.

a. pulmonary and systemic circulations

b. heart has separate pumps for lungs and other systems

c. deoxygenated blood pumped to the lungs and oxygenated to the body

d. each side of heart has atrium and ventricle

e. left ventricle pumps blood to the systems, right ventricle pumps blood to lungs

f. left atrium receives blood from the lungs, right atrium receives blood from tissues

g. left ventricle pumps blood via the aorta, right ventricle pumps blood via the pulmonary artery

h. left atrium receives blood via the pulmonary vein, right atrium receives blood via the vena cava

i. lungs require lower pressure blood

j. high pressure required to pump blood to tissues

k. blood has to be pumped again after returning from lungs

l. all tissues receive blood with high oxygen

If schizophrenia is caused by an overabundance of the neurotransmitters dopamine and serotonin in the synapses of some areas of the brain, which drug action could work in treating the symptoms?

A. Release of cholinesterase into the synaptic cleft

B. Increased re-uptake of dopamine and serotonin by presynaptic neurons

C. Increased permeability of the presynaptic neuron to sodium

D. Blockage of dopamine and serotonin receptors on presynaptic neurons

B. Increased re-uptake of dopamine and serotonin by presynaptic neurons

State the tissue that produces leptin in humans.

adipose

Which hormone shows the greatest fall in blood concentration just before menstruation?

A. FSH (follicle stimulating hormone)

B. LH (luteinizing hormone)

C. Progesterone

D. Estrogen

C. Progesterone

Outline how nerve impulses are transmitted along a nerve fibre.

a. Na+ diffuse into neuron;

b. depolarization;

c. depolarization wave;

d. K+ leaves;

e. repolarization;

f. active transport of K+ and Na+ restores resting potential;

Bacteria are prokaryotes that sometimes act as pathogens. Describe how the body can defend itself against pathogens.

a. skin=barrier;

b. sebaceous glands secrete fatty acids to acidify skin surface

c. acid prevents pathogen growth;

d. lysozyme in mucus kills bacteria;

e. pathogens caught in sticky mucus and removed from body;

f. inflammatory response

g. phagocytes identify pathogens as foreign;

h. ingest pathogens;

i. specific lymphocytes recognize specific antigens;

j. lymphocytes clone themselves;

k. lymphocytes produce antibodies;

l. antigen-antibody complex formed, destroys pathogen

Active skeletal muscle requires a good supply of oxygen. Outline the mechanism of ventilation in the lungs.

INHALATION:

external intercostals contract, rib cage up;

diaphragm contracts, flattens

volume increases, pressure decreases

air enters

EXHALATION:

internal intercostals contract, ribs down;

diaphragm relaxes, domed shape

decrease in volume, increase in pressure

air exits

abdominal muscles force exhalation

Explain the changes in ventilation rate during exercise.

a. increased cell respiration decreases pH (in blood);

b. detected by medulla;

c. signal sent to respiratory muscles to contract at faster rate;

d. more oxygen needed for aerobic (cell) respiration;

Explain how the structure of capillaries relates to their functions.

capillaries' walls one cell thick for better diffusion;

narrow lumen to fit between cells;

small diameter for greater surface area for molecular exchange;

pores between cells of walls so plasma pass;

pores between cells of the walls allow phagocytes to enter tissues;

one red blood cell at a time;

Outline the digestion, absorption and assimilation of proteins in humans.

large molecules (proteins) must be digested into small molecules;

protease digests proteins;

pepsin works in the stomach;

polypeptides are digested by trypsin into amino acids;

trypsin acts in the small intestine;

amino acids absorbed by diffusion;

absorption occurs in the villus of the small intestine;

into capillaries;

blood carries amino acids;

amino acids diffuse into cells;

cells build proteins with amino acids;

assimilation, amino acids join cell;

protein synthesis in ribosomes;

Hemophilia is a disorder where the ability to control blood clotting or coagulation is impaired. Describe the process of blood clotting.

clotting factors released from platelets;

prothrombin converts to thrombin;

thrombin catalyses conversion of fibrinogen into fibrin;

fibrin captures blood cells;

Describe how the hormone leptin helps to prevent obesity.

Hormone produced by adipose

targets hypothalamus

inhibits hunger

more leptin with more adipose

obese people can be resistant

Explain the roles of specific hormones in the menstrual cycle, including positive and negative feedback mechanisms.

a. anterior pituitary secretes FSH which develops folliciles

b. follicles secrete estrogen

c. estrogen stimulates FSH receptors on follicle cells

d. increased estrogen has positive feedback on pituitary

e. estrogen stimulates LH secretion

f. estrogen promotes development of endometrium

g. increased LH levels cause ovulation

h. LH has negative feedback on follicle cells

i. follicle cells produce more progesterone

j. progesterone thickens the uterus lining

k. high progesterone results in negative feedback on pituitary

l. progesterone levels drop and allow FSH secretion

m. falling progesterone leads to menstruation

A supply of oxygen is needed for aerobic respiration in mitochondria. Describe the features of alveoli in human lungs that adapt them for efficient absorption of oxygen.

a. large surface area from alveoli number;

b. single layer of cells in wall;

c. dense capillary network;

d. short distance for gases to diffuse;

e. moist lining inside of alveolus;

f. moisture allows gases to dissolve;

g. diffusion of oxygen down concentration gradient;

Outline how leucocytes defend the body against pathogens.

a. leucocytes recognize pathogens;

b. engulf pathogens by phagocytosis;

c. migrate to tissues;

d. each pathogen has specific antigens;

e. leukocytes produce antibodies by reacting to specific antigens;

f. antibody joins to antigen destroying them;

g. lymphocyte clones itself;

h. increasing the total number of antibodies;

Explain the mechanism of ventilation in the lungs in order to promote gas exchange for cell respiration.

a. inhalation;

b. external intercostal muscles contract;

c. ribs up;

d. diaphragm ontracts;

e. volume increases;

f. pressure decreases, air enters;

g. exhalation;

h. internal intercostals contract;

i. abdominal wall muscles contract, raise diaphragm;

j. decreasing volume;

k. increasing pressure, air leaves;

l. a concentration gradient between air sacs and blood maintained;