Introduction to Respiration

IGCSE Biology

What do we need energy for?

You have 2 min as a group to act out different activities your body requires energy for!

How is digested food used by the body?

Glucose, from digested carbohydrates, is an important substance that contains stored chemical energy. This is released when it reacts with oxygen in cells.

The energy is used in many ways, such as for:

The body needs a constant supply of energy which comes from digested food.

enabling muscles to contract Transmitting nerve impulses keeping warm in mammals and birds Cell division building new molecules, cells and tissues – e.g. proteins ACTIVE transport to move substances across cell membranes

What is respiration?Respiration is the process that the body uses to release energy from digested food (glucose).

This type of respiration is called aerobic respiration because energy is released in the presence of oxygen.

How do the glucose and oxygen needed for aerobic respiration get to the all the body’s cells?

oxygencarbondioxideglucose + + water ( energy)+

from the digestive system

from the respiratory

system

waste product (exhaled)

waste product (exhaled)

Equations for aerobic respirationAll of these are fine!....

Equation for Cellular Respiration

6CO2 + 6H20 + e- + 36-38ATP + heat

C6H12O6 + 6O2

YIELDS

There are two kinds of respirationAnaerobic respiration: release of a SMALL amount of energy by the breakdown of food substances in the absence of oxygen IN THE CYTOPLASMAerobic respiration: release of a LARGE amount of energy by the breakdown of food substances in the PRESENCE of oxygen IN THE MITOCHONDRION

Glycolysis: Always the initial stage of respiration

• Location: cytoplasm• Substrate: glucose• Requires input of 2 ATP• Products: pyruvate,

(NADH), 4 ATP Glycolysis is an anaerobic process: no oxygen required

Aerobic respiration

• Takes place in the mitochondria of eukaryotic cells

• Produces LOTS of ATP : 90% of total ATP from respiration

• Also produces carbon dioxide, water and heat

• Oxygen is the final electron acceptor

If no oxygen is available, glycolysis

(anaerobic) is followed by

fermentation (anaerobic)

Fermentation1. Alcoholic fermentation Pyruvate is converted into ethanol plus carbon dioxide and NAD+

2. Lactate fermentation

Pyruvate is converted into lactate and NAD+

Alcoholic fermentation in yeast

‘Alcoholic’ fermentation in yeast

• Pyruvate is produced from glycolysis• 3-carbon pyruvate is converted to 2-carbon ethanol and

carbon dioxide• Generation of carbon dioxide helps bread products to rise• Yeast is used to produce ethanol

Yeast is used for breadmaking AND for wine, beer and spirit production

BREADMAKING• In bread dough, starch in

bread has been broken down by amylase into maltose and glucose

• Yeast respires both aerobically and anaerobically, producing CO2 which makes the bread rise

ALCOHOL PRODUCTION• yeast is dissolved in

warm maltose solution• The yeast respires

anaerobically, making alcohol

• The carbon dioxide makes beer/ wine fizzy

In mammals, anaerobic fermentation produces LACTATE

• Lactate is a 3-carbon molecule

Comparing aerobic and anaerobic respiration

What do you notice about these two equations?

Plants respire too!glucose + oxygen Water + carbon dioxide (+ energy)

Reactants Products

• Aerobic respiration (uses oxygen)• Happens all the time• Overall plants produce more oxygen by photosynthesis than they use by

respiration

YouTube - Plant Physiology: Respiration (Britannica.com)