AQA GCSE Biology Year 10: Respiration and Decomposition

Why do materials have to be reused?

All materials in the living world are recycled to provide the building block for future organisms

What does the carbon cycle do?

Returns carbon from organisms to the atmosphere as carbon dioxide to be used by plants in photosynthesis

What does the water cycle do?

. Provides fresh water for plants and animals on land before draining into the seas

. Water is continuously evaporated and precipitated

What elements are living organisms mainly made up of?

. Carbon

. Oxygen

. Hydrogen

. Nitrogen

What are decomposers?

. Group of microorganisms

. Include bacteria and fungi

. Feed on waste droppings and dead organisms

Which organisms often start the process of decay and how?

. Detritus feeders / detritivores

. E.g maggots and some types of worms and beetles

. Eat dead animals and produce waste material

What happens after detritus feeders start the process of decay?

. Decomposers digest everything (dead animals, plants, detritus feeders, and their waste)

. They use some of the nutrients to grow and reproduce

. Release CO2, water, and mineral ions as waste products

. Mineral ions (including nitrates) return to soil for plants to make proteins and other chemicals in their cells

. CO2 can be used by producers in photosynthesis

. Decomposers remove the bodies of all dead organisms - they 'clean up'

What are the main stages of the water cycle?

. Evaporation

. Condensation

. Precipitation

. Respiration

. Transpiration

What is condensation?

. As moist air rises it cools

. Water vapour condenses back into liquid water droplets producing clouds

What is precipitation?

As water droplets in clouds get heavier they fall as rain, snow, or hail

How is respiration involved in the water cycle?

Water passes through the bodies of animals and plants, released during respiration in their lifetime, as well as when organisms decay

How do plants release water into the atmosphere other than in respiration?

Transpiration

What is percolation?

When water trickles through gaps in soils and rocks

How is carbon (dioxide) taken out of the atmosphere?

. Photosynthesis

. Feeding on plants

How is carbon (dioxide) released back into the atmosphere?

. Respiration

. Combustion

What form does carbon generally take in the atmosphere?

. CO2

. In the air

. Also dissolved in water, particularly oceans

What factors can affect the rate of decay of biological material?

. Temperature

. Water availability

. Oxygen availability

How does temperature affect the rate of decay?

. Decay processes require enzymes

. Temp affects enzyme-controlled reactions (see digestion quizlet for how)

How does oxygen availability affect the rate of decay?

. Most decomposers respire aerobically

. Means they need oxygen to break down food and transfer energy, grow, and reproduce

. So decay is more rapid when there's plenty of oxygen available

How does water availability affect the rate of decay?

. Most microorganisms grow faster in moist conditions

. Moisture makes it easier for them to digest food and prevents them drying out

. So decay takes place more rapidly in moist conditions

. Also, chemical reactions of decay need water to take place in

How do gardeners and farmers use decay?

. Try to provide optimum conditions for rapid decay of waste biological material

. Compost produced is used as a natural fertiliser for growing garden plants or crops

How can decay help generate power?

. Anaerobic decay produces methane gas

. Biogas generators can be used to produce methane gas as a fuel

What type of reaction is cellular respiration?

An exothermic reaction which is continuously occurring in living cells

What does the energy cellular respiration releases do?

The energy transferred supplies all the energy needed for living processes

What are the 2 types of respiration in cells?

. Aerobic (using oxygen)

. Anaerobic (without oxygen)

Both of these transfer energy.

What do organisms need energy for?

. The continual enzyme controlled processes of metabolism that synthesis new molecules (Chemical reactions to build larger molecules)

. Movement

. Keeping warm

What is the word equation for aerobic respiration?

glucose + oxygen → carbon dioxide + water

What is the chemical symbol C₆H₁₂O₆ ?

glucose

What is the equation for anaerobic respiration in muscles?

glucose → lactic acid

How does the amount of energy transferred by aerobic and anaerobic respiration compare and why?

. The oxidation of glucose is incomplete in anaerobic respiration

. So much less energy is transferred than in aerobic respiration

What is the word equation for anaerobic respiration in plant and yeast cells?

glucose → ethanol + carbon dioxide

What is anaerobic respiration in yeast cells called and how do humans use it?

. Fermentation

. Has economic importance in the manufacture of bread and alcoholic drinks

What happens to the human body during exercise?

It reacts to increased demand for energy so:

. The heart rate, breathing rate, and breath volume increase to supply the muscles with more oxygenated blood

What happens if insufficient oxygen is supplied to the muscles during exercise?

. Anaerobic respiration takes place in the muscles

. The incomplete oxidation of glucose causes a build up of lactic acid and creates an oxygen debt

. During long periods of vigorous activity muscles become fatigued and stop contracting efficiently

. Blood flowing through the muscles transports the lactic acid to the liver where it is converted back into glucose

What is oxygen debt?

The amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from the cells

What is metabolism?

The sum of all the reactions in a cell or the body

What are some examples of what metabolism includes?

. Conversion of glucose to starch, glycogen, and cellulose

. The formation of lipid molecules from a molecule of glycerol and 3 molecules of fatty acids

. The use of glucose and nitrate ions to form amino acids which in turn are used to synthesise proteins

. Respiration

. Breakdown of excess proteins to form urea for excretion