Previously…

Photosynthesis is…

• The process by which plants use carbon dioxide, water and light trapped by chlorophyll to make food in the form of glucose, with oxygen being given off during the process.

+ +

Photosynthesis

• The process in word equation…

Carbon dioxide Water+

Light

chlorophyll Oxygen

Glucose+

Conditions essential for photosynthesis

Sunlight (light energy)Light energy is converted to chemical energy stored in glucose.

Suitable temperaturePhotosynthesis depends on the reactions of enzymes in the chloroplasts. Enzyme reactions are fastest at a suitable temperature.

ChlorophyllThis green pigment absorbs light energy and changes it into chemical energy needed to manufacture glucose.

Carbon dioxide and waterThese are the raw materials needed to form carbohydrates (glucose).

waterglucose

Importance of photosynthesis

• Why is photosynthesis important?

- Photosynthesis makes chemical energy available to animals

- Photosynthesis removes carbon dioxide and provides oxygen.

Photosynthesis makes chemical energy available to animals

• All living organisms need energy to move, grow, excrete, reproduce and maintain themselves.

Video: energy

Photosynthesis makes chemical energy available to animals

• What is the ultimate source of energy for animals?

Light energy from the Sun.

• During photosynthesis, light energy is absorbed by chlorophyll and transformed into chemical energy.

Light energy

chemical energy

chlorophyll

Cellular Respiration

• Chemical energy is locked up in food molecules such as glucose.

• The chemical energy stored in food molecules is released to living organisms in a process called cellular respiration.

Chemical Energy

(in food)

Energy

(for organisms)

Cellular respiration

Cellular Respiration

• Cellular respiration takes place in all the living cells of organisms

• Since living cells need energy to carry out many vital processes all the time, respiration occurs all the time.

Cellular Respiration

Main Focus

Aerobic Respiration

• Aerobic respiration is the process whereby food substances are broken down in the presence of oxygen with the release of energy in living cells. Carbon dioxide and water are released as waste products.

• Word equation for aerobic respiration:

Glucose Oxygen+ WaterCarbon dioxide

+ Energy+

Video: res in cells

Tissue Respiration

• Tissue respiration is the process by which food substances are broken down in living cells.

• A large amount of energy is released for the cells to perform different activities.

• In tissue respiration, glucose combines with oxygen to release energy, carbon dioxide and water.

Glucose Oxygen+ WaterCarbon dioxide

+ Energy+

External Respiration

• External respirationExternal respiration is the process of is the process of bringing the oxygenbringing the oxygen from the surrounding environment from the surrounding environment to the cells for tissue to the cells for tissue respirationrespiration to take place. to take place.

• External respirationExternal respiration is also responsible for is also responsible for removingremoving from the body the from the body the carbon dioxide and water formedcarbon dioxide and water formed during during tissue respirationtissue respiration. .

• BreathingBreathing is part of external respiration. is part of external respiration.

Importance of Aerobic Respiration

• Most organisms respire aerobically. Energy released is used for:

- Growth (building up of proteins) - Muscle contractions (e.g. heartbeats)- Digestion and absorption of food substances- Cell division

Aerobic Respiration

• Do plants carry out aerobic respiration in the day?

Yes. Plants carry our aerobic respiration all the time.

Aerobic Respiration in Plants

During the day, plants photosynthesise. The oxygen produced is more than what is needed for aerobic respiration. The excess oxygen is released to the surroundings.

At night, photosynthesis stops. Plants take in oxygen from the surroundings for aerobic respiration and give off carbon dioxide to the surroundings.

Video: plant

Aerobic Respiration • Oxygen is taken in from the surrounding air

while carbon dioxide and water are released to the surroundings.

• In plants, these respiratory gases (oxygen, carbon dioxide & water) are exchanged with the surroundings through the stomata.

• In humans, the respiratory gases are exchanged with the surroundings using the respiratory system.

Human Respiratory System

Video: Airway

Human Respiratory System

• Components of the human respiratory system

- nose - nasal cavity - pharynx - trachea - bronchus - bronchioles

- alveoli - diaphragm- lungs

Human Respiratory System

• Components of the human respiratory system

- nose - nasal cavity - pharynx - trachea - bronchus - bronchioles

- alveoli - diaphragm - lungs

In the nose…

• Air enters through two external nostrils. The nostrils lead into two nasal passages which are lined with a moist mucous membrane.

In the nose…Passing the air through the nasal cavity has the following advantages:

1. dust and foreign particles are trapped by the hairs in the nostrils and by the mucus on the mucous membrane.

2. air is moistened and warmed before it enters the lungs.

From the nose to the trachea

The air in your nasal passages enters the pharynx. From the pharynx, air passes into your larynx and then into your trachea.

The trachea and bronchi

The lower end of the trachea divides into two tubes/bronchi. Each bronchus (plural: bronchi) connects to one lung.

The trachea and bronchi

• Each bronchus divides continually and ends in bronchioles. Each bronchiole ends in a cluster of air sacs or alveoli (singular: alveolus).

bronchioles

alveoli

The trachea and bronchi

• Thousands of alveoli are found in lungs, and these alveoli provide a very large surface area for gaseous exchange.

• Gaseous exchange is possible because alveoli are well-supplied with blood capillaries.

bronchioles

alveoli

Video: Gas exchange between the lungs and blood

The trachea and bronchi

• Wall of alveolus is one cell thick → faster rate of diffusion of gases through it

• Thin film of moisture covers surface of alveolus → allows oxygen to dissolve in it

bronchioles

alveoli

Breathing

• The physical process by which respiratory gases are exchanged with the surroundings.

• It is also the movement that brings air into and out of the body.

Breathing

• Inhalation / Inspiration - taking in of air from the surroundings

Breathing

• Exhalation / Expiration - giving out of air to the surroundings

Breathing

Air that we breathe inAir that we breathe in

Inhaled airInhaled air

Air that we breathe outAir that we breathe out

Exhaled airExhaled air

Mechanism of breathing (Enrichment)

• Case 1:Case 1:

When these rib muscles contract, When these rib muscles contract, the rib cage expands. The the rib cage expands. The contraction of ribs and diaphragm contraction of ribs and diaphragm increases the volume of the chest increases the volume of the chest cavity. The space surrounding the cavity. The space surrounding the lungs increases so the lungs lungs increases so the lungs expand. The pressure of the air of expand. The pressure of the air of the lungs falls and the air is drawn the lungs falls and the air is drawn into the lungs.into the lungs.

Mechanism of breathing (Enrichment)

• Case 2:Case 2:

When the diaphragm muscles When the diaphragm muscles and the rib muscles relax, the and the rib muscles relax, the chest cavity becomes smaller chest cavity becomes smaller and the lungs compress. The and the lungs compress. The pressure of the air in the lungs pressure of the air in the lungs increases, hence forcing air out increases, hence forcing air out again.again.

Inhaled Air & Exhaled Airwater vapour

(variable) nitrogen (78%)carbon

dioxide (app. 0.03%)

noble gases (app. 1%)

oxygen (21%)

nitrogen (78%)

water vapour (variable)

carbon dioxide

(4%)

noble gases (app. 1%)

oxygen (16%)

Composition of inhaled air

composition of exhaled air

Inhaled Air & Exhaled AirInhaled air Exhaled air

Oxygen Contains 21% oxygen Contain 16% oxygen

Carbon Dioxide Contain 0.03% carbon dioxide

Contains about 4% carbon dioxide

Water vapour Contain less water vapour than exhaled air

Contain more water vapour than inhaled air.

Question

• Is there more oxygen in inhaled air or exhaled air? Why?

• Is there more carbon dioxide in inhaled air or exhaled air? Why?

• Is there more water vapour in inhaled air or exhaled air? Why?

Video: Composition of air

Respiration & Photosynthesis

Both photosynthesis and aerobic Both photosynthesis and aerobic respiration are complex processes that are respiration are complex processes that are

alike in several ways. alike in several ways.

But in many ways, But in many ways, they are also different.they are also different.

Respiration & PhotosynthesisRespiration Photosynthesis

Uses oxygen Produces oxygen

Does not need chlorophyll Needs chlorophyll

Uses food Produces food

Produce carbon dioxide Uses carbon dioxide

Takes place all the time Requires sunlight

Takes place in all living thing Takes place in green plants

Takes place in all living cells Take place in cells containing chlorophyll

Video: respiration

Respiration & PhotosynthesisRespiration Photosynthesis

Energy is liberated Energy is stored in carbohydrate molecules

Oxygen is used and carbon dioxide and water are given off

Carbon dioxide and water are used and oxygen is given off

A destructive process, resulting in the breakdown of carbohydrate molecules.

A constructive process, resulting in the building up of carbohydrate molecules.

Occurs at all times in all cells, independent of chlorophyll and sunlight

Occurs only in cells containing chlorophyll and in the presence of

sunlight

-Both involve energy.-Both involve enzymes.

Anaerobic Respiration

• Anaerobic respiration is the breakdown of food substances in the absence of oxygen. Anaerobic respiration releases less energy than aerobic respiration.

• Word equation for anaerobic respiration in humans:

• Word equation for anaerobic respiration in yeast:

Glucose EthanolCarbon dioxide

+ Energy+

Glucose Lactic Acid Energy+

Anaerobic Respiration

• Some bacteria are anaerobic.

• Anaerobic respiration in yeast is known as alcoholic fermentation

- yeast respires anaerobically to convert sugar to alcohol in the fermentation process.