Topic 6

Question 1

Draw a labeled diagram of the human digestive system. 5 marks

Answer 1

Award one mark for every two of the following structures clearly drawn and labeled correctly. Connections between organs must be correct for full marks

mouth/ teeth/ tongue
esophagus
stomach
small intestine
large intestine/colon
anus
rectum
sphincters
salivary glands
liver
pancreas
gall bladder

Question 2

Describe the role of enzymes in the digestion of proteins, carbohydrates and lipids in humans. 6 marks

Answer 2

Award one mark per role. Examples of specific enzymes:

protease/trypsin/pepsin/chumotrypsin/other named protease digest proteins into polypeptides/ dipeptides/ amino acids/ peptides
lipase digest lipids into glycerol/ fatty acids
amylase digest polysaccharides into disaccharides/ monosaccharides
Enzymes must match products.
speed up/ catalyze reactions/ increased efficiency
lower the (activation) energy required for digestive reactions to occur
occurs at body temperature
require optimum pH
enzymes are specific
digestive enzymes carry out hydrolytic processes

Question 3

Explain how the structure of the villi in the small intestine are related to absorption of digested food. 3 marks

Answer 3

Award marks for a clearly drawn and correctly labelled diagram.

large surface area by microvilli / protrusion of exposed parts
epithelium only one layer thick
protein channels allow facilitated diffusion and active transport
mitochondria provide ATP
blood capillaries close to epithelium/ surface
absorption of glucose/ amino acids
lacteal / lymphatic vessel in center to absorb fats
tight junctions assist in controlling absorption

Question 4

Outline the events that occur within the heart, which cause blood to move around the body. 6 marks

Answer 4

blood is collected in the atria
blood is pumped from the atria to the ventricles
opened atrio-ventricular valves allow flow from the atria to the ventricles
closed semi-lunar valves prevent backflow from the arteries to the ventricles
blood is pumped out from the ventricles to the arteries
open semi-lunar valves allow flow from ventricles to arteries
closed atrio-ventricular valves prevent backflow to the atria
pressure generated by the heart causes blood to move around the body
pacemaker (SAN) initiates each heartbeat

Question 5

Explain the relationship between the structure and function of arteries, capillaries and veins. 9 marks

Answer 5

(3 marks maximum for information on arteries.)

carry blood away from the heart
have thick walls to withstand high pressure / prevent bursting
have muslce fibers to generate the pulse / help pump blood / even out blood flow
have elastic fibers to help generate pulse / allow artery wall to stretch / recoil
(3 marks maximum for information on capillaries.)
allow exchange of oxygen/carbon dioxide/ nutrients/waste products from tissues/cells
have a thin wall to allow (rapid) diffusion / movement in / out
have pores / porous walls to allow phagocytes / tissue fluid to leave
are narrow so can penetrate all parts of tissues / bigger total surface area
(3 marks maximum for information on veins.)
carry blood back to the heart / from the tissues
have thinner walls because the pressure is low / to allow them to be squeezed
have fewer muscle / elastic fibers because there is no pulse / because pressure is low
have valves to prevent backflow

Question 6

Blood is a liquid tissue containing glucose, urea, plasma proteins and other components. List the other components of blood. 5 marks

Answer 6

plasma/water;
dissolved gases / CO2 / O2;
erythrocytes / red blood cells;
leucocytes / white blood cells;
lymphocytes and phagocytes;
platelets;
hormones / named hormone(s);
amino acids / albumin / antibodies;
salts / minerals / ions other named solute in plasma apart from glucose, urea and plasma proteins;

Question 7

Describe the mechanism of ventilation in the human lung. 5 marks

Answer 7

consists of inhaling and exhaling air / exchanging stale air with fresh air (with the environment)
external intercostal muscles contract moving the rib cage up/out
diaphragm contracts
increaes volume of thorax / lowers lung pressure relative to air pressure / pulls air in
diaphragm relaxes
abdominal muscles contract
internal intercostal muscles contract moving the rib cage down/in
force air out / decreases volume of thorax / raise lung pressure relative to air pressure

Question 8

Describe the need for a ventilation system. 6 marks

Answer 8

(small) animals obtain oxygen (by diffusion) through skin / in humans (large) animals skin is ineffective for ventilation
humans are large / have a small ratio of surface area:volume
so need ventilation system to increase surface area
to maintain a concentration gradient in alveoli
as oxygen is used in respiration (and carbon dioxide is produced)
gaseous exchange occurs between air in alveoli and blood capillaries
alveoli have high ratio of surface area:volume (to facilitate ventilation)
to bring in fresh air (and remove stale air)

Question 9

Distinguish between ventilation and gas exchange in humans. 4 marks

Answer 9

ventiallation: 2 max

movement of air
movement in and out of the lungs
caused by muscles
an active process
involves mass flow / involves flow along air passages
gas exchange 2 max

movement of carbon dioxide and oxygen
(occurs when) oxygen moves from lungs / alveoli to red blood cells / carbon dioxide moves to lungs / alveoli from red blood cells
(occurs when) oxygen moves from red blood cells to tissues / carbon cioxide moves to red blood cells from tissues
a passive process / diffusion
takes place across a surface