CE Biology-A Summary

Part 3-Maintenance Of Life 

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Part 1 Food and nutrition

Modes of nutrition

Autotrophic nutrition: the organisms are able to make their own food from simple inorganic substances

Heterotrophic nutrition: the organisms must take in ready make food from other organisms

Saprophytic nutrition- organisms feed on dead organic matter for food

Parasitic nutrition- organisms live on or inside other organisms for food

Holozoic nutrition- organisms feed other organisms for food

Green plants make food by photosynthesis

Mucor/bread mould uses its rhizoid-like hyphae to secrete enzymes to digest the complex organic molecules in bread into simple molecule. Then the digested products are absorbed by the hyphae as nutrient for mucor. (The mycelium consists of a mass of delicate branching hyphae which provide a large surface area to volume ratio for contact with food + thin cell wall)

Tapeworm is a long flat worm, which lives in the small intestine of vertebrates. It absorbs the digested food of the host through its whole body surface. (The long flattened body surface provides a large surface area to volume ratio for the absorption of food + thin body wall)  

Herbivores eat plants only

Carnivores eat animals only

Omnivores eat both plants and animals

Cows

Lions

Human

 

Food required for providing energy, growth and repair.

Food

Structure

Function

Example

Carbohydrates

(Cn (H2O) n)

Monos~Dis/Polys by condensation

Monosaccharides

C6H12O6

To release energy.

As the main transport form of sugar in animals.

Glucose

Fructose

Galactose

 

 

Disaccharides

C12H22O12

As food reserve in some organism.

As the main transport form of sugar in plants

Sucrose

Lactose

Maltose

 

Polysaccharides

(C6H10O5)n

As food reserve in organisms.

As structural material

Starch

Glycogen

Cellulose

Fats (CxHyOz)

Glycerol+ 3 Fatty acid chains

Medium transports and stores fat-soluble vitamins.

As energy source.

As food reserve. (Adipose tissue)

As heat insulator. (Subcutaneous fat)

As waterproof material.

Olive oil

Proteins (H+C+N, sometime S)

Amino acids~polypeptides~proteins by condensation

Long chains of amino acids (a.a)

As structural material.

As metabolic regulators.

As energy source

Keratin

Enzymes

Antibodies

Some hormones

Haemoglobin

Food required for normal health and functioning of the body.

Food

Function

Source

Deficiency disease

Vitamin

- Required in small quantities for health and regulating metabolism

Vitamin A

# Formation of a pigment for night vision

# Protecting the eye surface

# Keeping the lining of gut, the respiratory system and the skin health

Cod-liver oil, carrot, milk

Night-blindness

The cornea becomes dried and thickened

The lining of the respiratory system becomes easily infected

Vitamin C

# Heals wounds quickly

# Keeps germs, teeth and skin health

# Synthesizes and repairs connective tissue

Green vegetables, citrus fruits

Scurvy

Vitamin D

# For strong bone and teeth

# Enhance uptake of calcium and phosphorus

Cod-liver oil, made by skin under sunlight

Rickets

Mineral

- Required in small amount, absorbed in ionic form

Calcium

# Forming bones and teeth

# Involved in blood clotting, muscle contraction

Milk, dairy product, fish

Rickets, haemorrhage

Iron

# Forming haemoglobin

Beer, liver

Anaemia

Water

# Be the major cell component

# Be the metabolite in biochemical reactions

# Acts as a medium of bio reactions

# Acts as a medium of transport

# Acts a coolant when it evaporates

# Acts as a solvent

# To support and keep shape of bodies

Drinking, water contained in food, oxidation of food

 

Dietary fibres/roughage

- Indigestible cellulose fibres

# Give bulk to the diet and stimulate peristalsis

Vegetable

Constipation

 

Food test

Nutrient test for

Procedures

Positive result

Benedict’s test

Reducing sugars

1.      Add 2ml benedict’s solution to about 2ml food solution.

2.      Heat in a water bath for a few minutes

Brick red precipitate

Iodine test

Starch

1.      Add a few drops of iodine solution to the food solution.

Dark blue colour

Spot test

Fats

1.      Put one drop of the food solution on a piece of filter paper

2.      Let dry and observe under a light source

3.      Add some ether on the spot

1.      Permanent translucent spot

2.      The spot disappear if ether added

Emulsion test

Fats

1.      Dissolve the food substance in ethanol in a test tube

2.      Add an equal amount of water

Milky solution

Biuret test

Proteins

1.      Add two drops of sodium hydroxide solution to the food solution

2.      Shake well and then add a drop of copper sulphate solution

Violet colour

DCPIP test

Vitamin C

1.      Add a few drop of the food solution to DCPIP solution in a test tube and shake

DCPIP decolourized

 

A balanced diet contains all food components in correct amount and proportion.

The amount of energy obtained from oxidation of 1g of foodstuff is called its calorific value. (carbohydrate and protein ~17kJg-1, fat ~ 38kJg-1)

The dietary requirement of an individual depends on sex, age, activity and pregnancy.

Nutrition in mammals

Ingestion is the intake of food into body

Structure of a mammalian tooth (molar tooth fixed to jaw bone)

A-    Enamel ~ nor-living hardest part, made of calcium fluoride and calcium phosphate

B-    Dentine ~ living tissue made of calcium salts

C-    Gum

D-    Pulp cavity ~ innermost layer contains living cells, blood vessels (G) and nerves (F)

E-     Cement ~ fix tooth to socket

Types of human teeth

1.      Incisor: sharp and chisel-like, for biting and cutting

2.      Canine: slightly pointed, for tearing

3.      Premolar and molar: with round cusps, for grinding, crushing and chewing

Dentition is the number, kind and arrangement of teeth in mouth of a mammal. (varies according to the animal’s diet)

Human dentition

Milk dentition

Permanent dentition

Dental formula

2 1 2 0

2 1 2 3

2 1 2 0

2 1 2 3

Tooth decay – Bacteria in plague turn sugar and starch dissolved in the plague into organic acid, which can dissolve away enamel of a tooth. When decay reaches the pulp, toothache results and finally the tooth will have to be pulled out.

Care of teeth

1 Good brushing habits

2 Avoiding sugary foods

3 Having a balanced diet

4 Having a regular dental check-ups

Digestion is the breaking down of food into small, soluble and diffusible forms, which can then pass through the selectively permeable wall of the small intestine.

 

When food reaches the basal of the mouth in the form of bolus, it moved down the oesophagus by swallowing. Food then moves along the alimentary canal by peristalsis, which is an alternate contraction and relaxation of the muscle of the alimentary canal wall.

Physical digestion

Food is broken down by physical mean ~ increase the surface of food

Chemical digestion

Food is broken down into simpler molecules by the action of enzymes

 

Part

Secretion

Contents

Mechanical digestion

Chemical digestion

 

Mouth cavity

Salvia – by salivary glands

Amylase, mucus, water (basic)

Food is chewed into small pieces by teeth.

Starch + amylase→maltose

 

Stomach

Gastric juice – by gastric glands

Proteases, hydrochloric acid (acidic)

Food is churned into chyme by contraction of stomach wall.

Protein + protease→peptides

 

Duodenum

Pancreatic juice – by pancreas

Carbohydrases, proteases, lipases

Solid fat is liquefied by body heat.

Emulsifying action of bile salts

Starch + amylase→maltose

Protein + protease→peptides

Fat + lipases→fatty acids + glycerol

Disaccharides + carbohydrases→monosaccharides

Peptides + protease→amino acids

 

Bile – by liver, stored in gall bladder

Bile salts, bile pigments, sodium carbonate (basic)

 

Intestinal juice – by intestinal gland in the wall of duodenum and ileum

Carbohydrases, proteases

Ileum

NIL

 

　

Caecum and Colon

Digestive enzyme – by symbiotic micro-organisms (in herbivore)

Cellulase

NIL

Cellulose + cellulase→βglucose

 

 

 

Secretion of mucus

Mucus is secreted along the alimentary canal to lubricate movement and prevent digestion by its own enzymes

 

Absorption is the uptake of digested food and the water through the walls of gut into the transport system. The small intestine is well adapted for its function of absorption because: 1. It is very long; 2. Its wall has many foldings; 3. It bears a lot of finger-like projections, i.e. villi.

A

Epithelium

B

Blood capillary – glucose, a.a. & water-soluble substances

C

Lacteal – fatty acids & glycerol

D

Blood vessel supplying villus

E

Lymphatic system

Adaptation of villi for absorption

1.      Large surface area for absorption (they bear microvilli on the epithelium).

2.      Thin walled (the epithelium is just one cell thick) to allow easy passage of food.

3.      Richly supplied with blood capillaries and lacteals to transport away absorbed food.

Absorption mainly takes place in ileum where digestion is complete (by diffusion & active transport)

Water is mainly absorbed in colon by osmosis, but most water is absorbed in small intestine.

Assimilation is the process of absorbing and building up products of digestion into new complex substances.

Routes of absorbed nutrients

1 Water-soluble substances

villi→blood capillaries→hepatic portal vein→liver→hepatic vein→vena cava→heart→body tissues

2 Fat-soluble substances

villi→lacteals→lymphatic vessels→vena cava→heart→body tissues

Fate of absorbed nutrients

Glucose

To release energy

Excess glucose is converted into glycogen and stored in liver and muscles

Excess glucose is converted into fat for storage

Fats

As energy reserve

Stored beneath skin and around internal organs

Amino acids

Build up body tissues

Replace worn out tissues

Excess amino acids are deaminated in the liver to form urea

 

Function of liver

1.      Regulate blood glucose level

2.      Store glycogen

3.      Store vitamins and iron

4.      Detoxification

5.      Deamination of excess amino acids into urea

6.      Break down old blood cell and form bile pigments

7.      Produce bile

8.      Store blood

 

Egestion is the removal of indigestible and unabsorbed material from the alimentary canal. Faeces are stored temporarily in the rectum and removal at interval.

Nutrition in plants

Photosynthesis is a process, which converts solar energy into chemical energy in carbohydrates.

Overall reaction:

1.      Light energy absorbed by chlorophyll is used to split water molecules into hydrogen and oxygen;

2.      Oxygen is released as a by-product;

3.      Hydrogen combines with carbon dioxide to form carbohydrates

The fate of carbohydrate products in plants

1.      For energy release in respiration

2.      For storage

3.      For conversion into other products for growth

 

Detection of photosynthesis in plants

1.      Presence of starch (in most plants)

2.      Release of oxygen (in aquatic plants)

 

Test for starch in green leaves

Plants have to be destarched (put into darkness for 24 hours) first so that any starch detected later in the experiment must be formed in the course of investigation.

1.      Kill the leaf in boiling water to stop all biochemical reaction.

2.      Boil the leaf in alcohol to remove chlorophyll.

3.      Soften the decolourized leaf in warm water and remove excess alcohol.

4.      Add iodine solution to leaf. Region with starch will turn dark blue. Region without starch will turn brown.

A

Cuticle

Prevent water loss, protecting the leaf

B

Upper epidermis

Protect inner tissues

C

Palisade mesophyll

Absorb maximum sunlight for photosynthesis

D

Xylem

Transport water, support the leaf

E

Phloem

Transport food

F

Spongy mesophyll

Carry out photosynthesis, for gaseous exchange

G

Lower epidermis

 

H

Guard cell

Control opening of stoma

I

stoma

As passage of gases

Carbohydrates formed in photosynthesis provide the carbon skeleton for synthesis of plant material. However other elements have to be absorbed from soil.

Mineral

Function

Deficiency symptom

Nitrogen

Forming proteins & chlorophyll

Stunted growth, strong chlorosis

Phosphorus

Forming nucleic acids & ATP

Stunted growth

Magnesium

Forming chlorophyll

Chlorosis (pale yellow leaves)

Calcium

Forming middle lamella between cell walls

Strunted growth, flaccidity

In agriculture, chemical fertilizers are used as addition sources of minerals to replenish the fertility of the soil for crop production.

Part 2 Respiration and gaseous exchange

Respiration is a series of biochemical reactions, which break down food (mainly glucose) through oxidation to release energy in a controlled and gradual manner in living cell.

Some of the energy released is used in organism for

1.      Synthesis of various material;

2.      Doing work, e.g. nervous transmission;

3.      Movement;

while the remaining is lost as heat.

 

Overall reaction:

 

Food + oxygen  enzymes   carbon dioxide + water +energy

 

In the absence of oxygen, some organisms (anaerobes) can carry out anaerobic respiration. Anaerobic respiration enables the organisms/ tissues to survive for a certain period of time in condition of low oxygen supply.

 

Plant tissue (e.g. yeast)   enzymes    ethanol + carbon dioxide +energy

 

Animal tissue (e.g. muscle cells during vigorous exercise)  enzymes  lactic acid + energy

 

Anaerobic respiration of muscle will cause dull pain in muscle/ muscle fatigue.

Extra oxygen is needed to remove lactic acid formed. The amount of extra oxygen needed is called oxygen debt.

(In liver, lactic acid is oxidized to glucose or glycogen)

 

Comparison between aerobic and anaerobic respiration

 

Aerobic respiration

Anaerobic respiration

Oxygen

Required

Not required

Glucose

Completely broken down

Partially broken down

End products

Low energy compounds

(carbon dioxide, water)

High energy compounds

(ethanol, lactic acids)

Energy released

Large amount (38 ATP)

Small amount (2 ATP)

Gaseous exchange is the process by which organisms exchange gases with their environment. It is necessary organisms to obtain gases for their respiration and photosynthesis and for organism to remove unwanted gases form the body.

In human

Structure

Function

Nostril

Hairs to remove dust

Nasal cavity

With blood capillaries to warm incoming air, with mucus to moisten incoming air and trap dust

Soft palate

Close the nasal cavity when swallowing

Pharynx

Passage for air and food

Epiglottis

Cover trachea during swallowing

Vocal cord

Can vibrate and produce sound

Larynx

Passage for air

Trachea

Passage for air, cover with ciliated epithelial cell and mucus-secreting cell –dust and bacteria are trapped in mucus and carried upward by the waving movement of the cilia, away from the lung

C-shaped cartilages

Support trachea

Bronchus (right)

Passage for air to right lung

Circular rings of cartilage

Support bronchi

Bronchiole

Passage for air

Alveolus

For gaseous exchange

Pleural membranes

Form pleural cavity, carry pleural fluid

Ribs

Protect the lungs and help in breathing

Intercostal muscles

Move the ribs

Diaphragm

Help in breathing

Thorax

Sternum + Ribs + Intercostal muscles + Vertebral column

Breathing is the process of drawing air in and out of the lung repeatedly.

 

Inhaled air (atmospheric air)

Exhaled air (breathed air)

Oxygen

21%

16%

Carbon dioxide

0.03%

4%

Moisture

Varies

Saturated

Temperature

Varies

About 37oC

 

The movement of ribs and diaphragm brings about breathing.

Mechanism of breathing

Inspiration

Expiration

External intercostal muscles contract, the ribs and sternum move upwards and outwards.

Capacity of thorax is increased

 

External intercostal muscles release, the ribs and sternum move downwards and inwards.

Capacity of thorax is decreased

Diaphragm muscles contract, diaphragm descends/ flattens

Diaphragm muscles release, diaphragm ascends/ returns to dome shape

Pressure inside thorax decreases

Pressure inside thorax increases

Lungs expand to fill thoracic cavity

Lungs return to normal volume

Air pressure in lungs is now less than atmospheric pressure

Air pressure in lungs is now higher than atmospheric pressure

Air is sucked into the lungs

Air is forced out of the lungs

Ventilation is the moment of air to and from the respiratory surface. It is brought about by breathing in human.

Ventilation and continuous flowing of blood maintain the concentration gradient of oxygen and carbon dioxide between the blood and alveoli so that diffusion of blood can take place.

 

 

 

Vital capacity

Maximum volume of air which can be exchanged from full inspiration to full expiration

Residual volume

The volume of air which cannot be expelled even during forced expiration

Tidal volume

Volume of air exchanged during normal quiet breathing

Gaseous exchange in air sacs

Oxygen dissolves in the moisture film and diffuses across the epithelium into the blood capillary. Then it combines with the haemoglobin in red blood cells, which go to other parts of the body

Carbon dioxide travels in an opposite direction and it is carried by plasma and red blood cells.

Adaptive features of air sacs for gaseous exchange

Thin-walled

To allow rapid movement of gases across the surface

Richly supplied with blood vessels

To allow efficient transport of gases

Large surface area

To allow rapid exchange of gases

Moist

To allow diffusion of gases in solution form

 

Control of breathing

The respiratory centre in the medulla of the brain controls breathing rate. The centre is sensitive to the concentration of carbon dioxide in blood.

When carbon dioxide concentration increases, the rate and depth of breathing will increase. Thus more oxygen is supplied for the rapidly respirating tissue to release more energy and carbon dioxide is removed in a higher rate.

When carbon dioxide concentration decreases, the rate and depth of breathing will decrease.

(Only diaphragm will move when you breathe at rest)

 

Smoking and health

Cigarette smoke contains harmful ingredients such as tar, nicotine and etc. These substances stimulate mucus secretion, stop movement of cilia and cause narrowing of bronchi.

Diseases: lung cancer, chronic bronchitis, emphysema and coronary heart diseases

Passive smoking also leads to smoking-related diseases.

In plant

Gaseous exchange mainly takes place through the stomata on leaves and lenticels on stems by diffusion.

Stomata open in daytime or when light is sufficient. They become smaller or closed at night or in darkness.

As light intensity increases, the rate of photosynthesis increases.

In region A, as light intensity is low, the photosynthetic rate is lower than respiratory rate.

At point C, the compensation point, respiratory rate = photosynthetic rate. There is no net gaseous exchange with the atmosphere outside the plant.

In region B, as light intensity is high, the photosynthetic rate is higher than respiratory rate.

After point D, the rate of photosynthesis reaches a maximum and stays unchanged despite of further increases in light intensity, as light is no longer the limiting factor. Other factors are limiting, e.g. temperature, CO2 concentration.

Part 3:Water and organism

Water is important to life:  (similar to that of 3.1, for reference)

1.      It is a universal solvent serves as transport medium and medium for chemical reactions to take place.

2.      It is a metabolite in reactions, e.g. photosynthesis, hydrolysis.

3.      It is the major cell component.

4.      It is adhesive and has a high surface tension and, allowing formation of a continuous water column in plants for water transport.

5.      It has a high specific heat capacity, helping keep temperature constant, which is essential for a stable environment for aquatic life.

6.      It has a high latent heat of vapouration, thus is a good evaporative coolant.

7.      It has a high latent heat of fusion, so aquatic environment and cell contents are slow to freeze in cold environment.

8.      It has a high transparency, allowing light penetration for photosynthesis of submerged plants.

9.      Water is incompressible, providing turgidity for plants and support for animals with hydro-skeleton.

10.  It is the medium for gametes/ sperms to swim, allowing fertilization.

Plants and animals lose water continuously. To ensure that there is enough water in their body to keep them working properly, the water loss must be replaced to keep the level constant.

In animals, in order to have a stable internal environment, they have to control the concentration of body fluid of their bodies, i.e. osmoregulation.

Red blood cell in saline

A

In hypotonic solution

Haemolysis – swells and bursts to release the haemoglobin

B

In isotonic solution

Remain unchanged as a biconcave disc

C

In hypertonic solution

Crenation – shrinks and wrinkles

In plant

A

In hypotonic solution

Water enters by osmosis.

Cell wall prevents cell from bursting.

The cell becomes fully turgid.

B

In isotonic solution

No net water movement.

The cell dose not change

C

In hypertonic solution

Water leaves by osmosis.

Vacuole shrinks.

Finally cytoplasm tears away from cell wall.

The cell becomes plasmolysed and flaccid.

# Plasmolysis can be reversed by placing the plasmolysed cell into a hypotonic solution.

Transpiration is the loss of water by evaporation from the aerial part of a plant.

1

Water diffuses out through stoma.

2

Water evaporates into the sub-stomatal air space.

3

Water is lost from the cell surface, this is replaced by water in the cell. Each cell then pulls water from its neighboring cell.

4

Eventually, water is pulled from the xylem.

5

Water moves into the xylem of leaf.

6

Water moves upward through the xylem vessel of the stem.

7

Water moves along cell wall and from cell to cell through the root until it reaches the xylem vessel.

8

The root hairs take water from soil

Distribution of stomata in leaves

Land plants

More stomata on their lower surface to reduce water loss

Aquatic plants

Very few or no stomata are found as there is no danger of evaporation

The forces which pull water up the xylem and which cause transpiration are called the transpiration pull.

Factors affecting transpiration

Transpiration is faster when

1.      Temperature increase

2.      Light intensity increase

3.      Relate humidity decrease

4.      Air movement increase

Transpiration rate can be measured by a potometer (e.g. a bubble potometer). But a simple potometer has its limitations:

1.      It only measure water absorption rate.

2.      It can only use a small plant or a leaf shoot.

3.      Movement of bubble is affected by friction.

A

Root hair zone

B

Elongation zone

C

Vascular tissue

D

Root hair – absorb water and minerals from soil
E

Growing point (meristemic zone) – forming new cells

F

Root cap – protect the inner meristem

G

Epidermis

H

Xylem – transport water and minerals

I

Phloem – transport food

J

Cambium – forming new xylem and phloem

K

Endodermis

L

Cortex

Water absorption by roots

Plants absorb water in soil by the root system. Water is absorbed by osmosis mainly through the root hair region and is transported across the root along the water potential gradient. The water is set up and maintained, as water is continuously lost from the leaves by transpiration so that water has to be moved from the root upwards.

Adaptive features of roots in relation to water absorption

1.      Roots are long and much branched to increase the surface area.

2.      Small root hairs for penetrating soil particles to absorbing water.

3.      No cuticle.

4.      Roots are positively geotropic and hydrotropic.

5.      Xylem vessels help to transport water away from the root.

　

Cont' in Bio Section 3.4 & Afterwards...