1. (a) Label A to F
A-mouth, B-oesophagus,
C-stomach, D-pancreas, E-small intestine,
F-large
intestine
(b)
Part
|
Enzyme
|
Digestive process
|
A
mouth
|
Salivary amylase
|
Starch + water à maltose
|
C
stomach
|
Pepsin
Rennin
|
Protein + water à polypeptides
Rennin
coagulates milk by converting the soluble milk protein, caseinogens, into the
insoluble casein.
|
E
Small intestine
|
Pancreatic juice:
Pancreatic amylase
Trypsin
Lipase
Intestinal juice:
Erepsin
Maltase
Sucrase
Lactase
|
Starch +
water à maltose
Polypeptides
+ water à
peptides
Lipid
droplets + water à
glycerol +fatty acids
Peptides
+ water àamino
acids
Maltose
+ wateràglucose
Sucrose
+ wateràglucose
+ fructose
Lactose
+ wateràglucose
+ galactose
|
2. Figure below shows the digestion of
cellulose by a ruminant such as a cow.
(a) Label the following parts
Rumen Reticulum Omasum Abomasum
(b) Complete the table below:
Part
|
Processes involved
|
Rumen
|
Cellulose is broken down by the cellulose
produced by bacteria. Part of the
breakdown products are absorbed by the bacteria, the rest by the cow.
|
Reticulum
|
Cellulose undergoes further
hydrolysis. The cud is regurgitated
into the mouth to be chewed making the cellulose softer and easier to be
broken down.
|
Omasum
|
Food is broken down
into smaller pieces by peristalsis.
Water is removed from the cud.
|
Abomasum
|
Gastric juice containing digestive enzymes
completes the digestion of proteins and other food substances.
|
3. What is meant by assimilation?
A process whereby
nutrients are used to form complex compounds or structural components in the
cells.
4. Using the above figure, describe how
body cells use glucose, amino acids and lipids.
Most of the glucose is converted
into glycogen and stored in the liver.
When the blood sugar level falls and the body needs energy, the stored
glycogen is converted back to glucose.
When the glucose molecules reach the cells, they are oxidized to release
energy during cellular respiration. When
the glycogen stored in the liver is full, excess glucose is converted into
lipids by the liver.
Amino acids which enter the cells
are used for the synthesis of new protoplasm and the repair of damaged
tissues. They are also important
building blocks in the synthesis of enzymes and hormones. Excess amino acids cannot be stored in the
body and are broken down in the liver by a process called deamination.
Lipids such as fats represent the
major energy store of the body. Excess lipids are stored in the adipose
tissue. Phospholipids and cholesterol
are major components of plasma membranes.
5. Identifying the macronutrients, the
functions and effects of deficiency.
Macronutrient
|
Functions
|
Effects of
deficiency
|
Phosphorus
|
Synthesis
of nucleic acids, adenosine triphosphates (ATP) and phospholipids of plasma
membranes.
|
Poor root growth and formation of dull,
dark green leaves. Red or purple spots
on old leaves.
|
Potassium
|
Protein synthesis, carbohydrate metabolism
and as a cofactor for many enzymes.
Maintains turgidity in plants.
|
Reduced
protein synthesis, yellow-edged leaves and premature death of plants.
|
Calcium
|
A
major constituent of the middle lamella of cell walls. Formation of spindle fibres during cell
division.
|
Stunted growth, leaves become distorted and
cupped, areas between leaf veins become yellow.
|
Magnesium
|
The
main structural component of chlorophyll.
Activates many plant enzymes.
Involved in carbohydrate metabolism.
|
Yellowing in the regions between the veins
of mature leaves. Red spots on leaf
surfaces, leaves become cupped.
|
Sulphur
|
A component of certain amino acids, a
constituent of vitamin B and some coenzymes.
|
General
yellowing of the affected leaves or the entire plants.
|
6. Complete the table below:
Structure
|
Functions/Adaptations
for photosynthesis
|
Epidermis
|
Epidermal cells are transparent. This allows light to penetrate the leaf and
reach the light-trapping chloroplasts inside.
|
Xylem
|
Transports water absorbed by the roots to
the leaf.
|
Phloem
|
Transports organic products of
photosynthesis away from the leaf.
|
Guard
cells
|
Regulate the size of the pore.
|
Palisade
mesophyll
|
Packed tightly together in an upright
arrangement near the upper surface of the leaf so they receive maximum amount
of light. These cells have a high
density of chloroplasts.
|
Spongy
mesophyll
|
Cells are loosely arranged and between each
of them are air spaces that connect the mesophyll with the stomata. These large spaces allow easy diffusion of
water and carbon dioxide through the leaf to the palisade cells. The irregular shapes of these cells
increase the internal surface area for the gaseous exchange
|
7. Comparing and contrasting the light reaction and dark reaction.
Light reaction
|
Differences
|
Dark reaction
|
Yes
|
Light energy
required
|
No
|
Grana
|
Site of reaction
|
Stroma
|
Water,
Carbon dioxide, chlorophyll, light energy
|
Substances required
for reaction
|
Hidrogen
atoms
|
Hydrogen
ions, hydroxyl ions.
|
Products of
reaction
|
Glucose,
oxygen
|
8 (a) A balanced diet is the consumption of
foods containing all the seven
classes
of food in appropriate proportion as required by the individual.
(b) (i) Ahmad
: 60% ; Leela : 44.6%
(ii) Ai Mei : 34.3% ; Leela : 30.9%
(iii) Ahmad : 20% ; Ai Mei : 16.3%
© A male teenager
requires more energy (calory) for growth and development of body features
compared to a female teenager.
(d) Leela requires
greater amount of energy compared to Ai Mei for the growth and development of
the foetus in her womb.
(e) The intake of
carbohydrates and proteins by Ahmad and Ai Mei is in appropriate
proportions. On the other hand, Leela
consumes excessive proteins and this may lead to health problems.
9 (a) (i) A (ii) C
(b) Labels : Epithelium, Blood capillary,
lacteal
© (i) Absorption
of digested food
(ii) Long and folded
structure to provide a large surface area of absorption
Villus wall is
semipermeable to allow certain substances to diffuse into the blood capillaries
or the lacteal
Movement of villi
back and forth to make absorption faster
(d) (i) Organ D is a pancreas. It removal causes the enzymes lipase,
amylase and
trypsin to be no longer produced. This
disrupts the digestion of starch, peptones and peptides and also the hydrolysis
of fats.
(ii) Patient has to
reduce the intake of foods containing starch because of the absence of
pancreatic amylase which makes starch cannot be digested in the small
intestine.
(e) Cellulose in the
vegetables cannot be digested in the body, hence, a vegetarian has a large
portion of his food exiting the body as waste instead of being absorbed by the
blood for cell metabolism. The body will
suffer from malnutrition.
10 (a) Photosynthesis is the process of
production of carbohydrates in plants
from
inorganic materials in the presence of light.
(b) To supply or increase the concentration
of carbon dioxide
© Higher intensity of
light increases the rate of photosynthesis because there is more energy for
water photolysis and ATP production.
(d) 1 Concentration
of carbon dioxide and temperature are fixed during
the experiment.
2. Light is brought
closes to the plant.
3. Oxygen bubbles
released is used to measure the rate of photosynthesis
(e)
11 (a) (i) P
: Kwashiorkor
Q
: Obesity
(ii) Deficiency of protein in diet
(b) Children require
more proteins for growth and labours require more carbohyrates to provide
sufficient energy for work.
© (i) Excessive consumption of foods
especially fats and carbohyrates
(ii) The excess food
will be stored in the form of fat (adipose tissue) under the skin and around
the intestine. Over the time, this will
result in obesity.
(d) 1 The problem in individual Q is caused
by the habit of over-eating, whereas anorexia nervosa is rooted to a
psychological problem, that is, the obsession to maintain the body shape
without assuming proper diet.
2 The problem in individual Q brings
about the effect of gaining 20% more weight than the normal weight, whereas
anorexia nervosa results in loss of weight and malnutrition.
12 (a) Human stomach has one compartment, while
the cow’s stomach has 4
compartments.
Cellulose digestion
starts at the cow’s stomach, but for human, it starts in the colon.
(b) i.
Reticulum, rumen omasum,
abomasums
ii The abomasums is the ruminant’s true stomach. In the abomasums, all the processes that take
place in the human stomach take place here.
Here also the gastric juice that contains enzymes which assist in food
digestion.
© In the largest
compartment, the rumen, there are millions of bacteria and protozoans. These microorganisms produce cellulase enzyme
that break down cellulose into starch.
The microbes get food and the cows get the food digested.
(d) The stomach is a
muscular bag whose principal function is acidification for the action of the
pepsin and maceration of the food to the liquid state, and temporary storage
until passes to the intestines. The
stomach is a highly acidic environment, which is necessary for the action of
enzymes. Digestive enzyme such as pepsin
breaks down protein to peptides. Rennin
solidifies milk protein for pepsin to act upon them.
13 (a) Absorb digested food
(b) Lacteal. It absorbs fatty acids and glycerol and joins
the lymphatic system.
© Q/lacteal – consist
of fat droplets, vitamin A, D, E, K
Blood capillaries –
simple sugars, amino acids, minerals, vitamin B and C
(d) The internal surface
of the ileum is covered by finger-like projection called villi, folded into
micro-villi which gives the ileum a far greater internal surface area for food
absorption.
Inside each
villus, there is a dense network of blood capillaries fo food absorption.
Thin wall to
help in food absorption.
14 (a)
(b) Step 1 : Boil the leaf to kill the cells and make its cells more
permeable to
iodine.
Step 2 : Boil the leaf in alcohol to remove the chlorophyll
Step 3 : Dip the leaf into boiling water again to soften the leaf
Step 4 : Spread the
leaf on a white tile and add iodine on it and observe changes.
© i A
blue black colour indicates that starch is present
ii Boil the leaf in
alcohol by using a hot water bath to avoid the risk of fire.
(d) -palisade cells have more chloroplasts
than spongy mesophyll cells
-xylem
vessels are closer to palisade cells than phloem sieve tubes
-the
presence of stomata in the lower rather than upper epidermis
-the
presence of air spaces between the cells of the leaf
(e)
15 (a) (i) chloroplast
(ii)
(b) i. X
: The light reaction in the grana
Y
: The dark reaction in the stroma
ii. Photolysis of
water, where water molecules are split to form oxygen and hydrogen ions
iii. The reduction of
carbon dioxide by the hydrogen ion to form glucose and water
© 24 H2O + 6 CO2 C6H12O6
+ 18H2O +6O2
(d)
The light reaction
|
The dark reaction
|
Occurs in the membrane of grana
|
Occurs in the stroma
|
Temperature sensitive
|
Temperature insensitive
|
Requires light energy
|
Reaction catalysed by an enzyme
|
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