GCSE Biology- Respira3on, Photosynthesis & Plants
RESPIRATION
Respira3on IS NOT the same as breathing!
Breathing: is the physical act of exchanging gases (oxygen and carbon dioxide). Breathing
happens at the lungs.
Respira7on: is a metabolic process that uses oxygen to release energy and produce carbon
dioxide as a waste product. All living things respire. Respira3on happens in ALL cells of the
body.
If a cell cannot respire, they die because they have no energy.
- Respiration is the way we get energy from our food. When we eat carbs, our body
metabolises them i.e. our body sends the carbs down the respiration pathway
- Respiration is the way our body breaks down organic molecules (contain C) to give us energy
- In cells, energy from respiration is stored in a molecule called ATP (adenosine triphosphate)
ATP is the energy currency for the cell
Energy in ATP is
stored in these
phosphate
bonds
ATP is needed:
1. To move things around the cell
2. For active transport: move things in and out of cells against their concentration gradient
3. For muscle contraction = movement of an entire organism
4. Cell division
5. Digestion
6. Growth
7. Protein synthesis (enzymes need energy to make proteins)
8. Generating nerve impulses
9. Maintain a constant body temperature (heat is released when you break the phosphate
bonds in ATP)
Aerobic respiration Anaerobic respiration
Uses oxygen/ happens in presence of oxygen Absence of oxygen
, Reactants: Glucose + oxygen Glucose
Products: CO2 + H2O + energy Products differ depending on the organism that
Makes 38 ATP molecules respires
- Animals: lactic acid + less energy
- Yeast: ethanol + carbon dioxide + less
energy
Makes 2 ATP molecules
Takes place in the cytoplasm and the Takes place in the cytoplasm.
mitochondria of cells. This is why mitochondria
are the energy factory of the cell.
Glucose + O2 à CO2 + H2O + energy Humans:
C6H12O6 + 6O2 à 6CO2 + 6H2O + energy (ATP) Glucose à lactic acid + little energy
Plants & Yeast
Glucose à ethanol + carbon dioxide + less
energy
Aerobic respira,on releases 19 ,mes more energy than anaerobic respira,on from the
same amount of glucose.
PLANTS
• Photosynthesis happens only in plants and in some photosynthetic bacteria
• It is the reverse of aerobic respiration: uses energy to make organic molecules
Respiration Breaks down organic molecules to release energy for cellular processes
Photosynthesis Takes in energy from the sun to make organic molecules
All organisms involved in food chains, feed on those organic molecules
i.e. plants make food for themselves and for the animals that feed on them
• Plants are autotrophs – they make their own food (organic molecules) through photosynthesis
• Energy (from sun) + carbon dioxide + water à glucose + oxygen
The rate of photosynthesis
[CO2] = concentration of carbon dioxide Higher [CO2] = faster rate of photosynthesis, as there
are more carbon dioxide molecules in the same space,
so they are more likely to react
RESPIRATION
Respira3on IS NOT the same as breathing!
Breathing: is the physical act of exchanging gases (oxygen and carbon dioxide). Breathing
happens at the lungs.
Respira7on: is a metabolic process that uses oxygen to release energy and produce carbon
dioxide as a waste product. All living things respire. Respira3on happens in ALL cells of the
body.
If a cell cannot respire, they die because they have no energy.
- Respiration is the way we get energy from our food. When we eat carbs, our body
metabolises them i.e. our body sends the carbs down the respiration pathway
- Respiration is the way our body breaks down organic molecules (contain C) to give us energy
- In cells, energy from respiration is stored in a molecule called ATP (adenosine triphosphate)
ATP is the energy currency for the cell
Energy in ATP is
stored in these
phosphate
bonds
ATP is needed:
1. To move things around the cell
2. For active transport: move things in and out of cells against their concentration gradient
3. For muscle contraction = movement of an entire organism
4. Cell division
5. Digestion
6. Growth
7. Protein synthesis (enzymes need energy to make proteins)
8. Generating nerve impulses
9. Maintain a constant body temperature (heat is released when you break the phosphate
bonds in ATP)
Aerobic respiration Anaerobic respiration
Uses oxygen/ happens in presence of oxygen Absence of oxygen
, Reactants: Glucose + oxygen Glucose
Products: CO2 + H2O + energy Products differ depending on the organism that
Makes 38 ATP molecules respires
- Animals: lactic acid + less energy
- Yeast: ethanol + carbon dioxide + less
energy
Makes 2 ATP molecules
Takes place in the cytoplasm and the Takes place in the cytoplasm.
mitochondria of cells. This is why mitochondria
are the energy factory of the cell.
Glucose + O2 à CO2 + H2O + energy Humans:
C6H12O6 + 6O2 à 6CO2 + 6H2O + energy (ATP) Glucose à lactic acid + little energy
Plants & Yeast
Glucose à ethanol + carbon dioxide + less
energy
Aerobic respira,on releases 19 ,mes more energy than anaerobic respira,on from the
same amount of glucose.
PLANTS
• Photosynthesis happens only in plants and in some photosynthetic bacteria
• It is the reverse of aerobic respiration: uses energy to make organic molecules
Respiration Breaks down organic molecules to release energy for cellular processes
Photosynthesis Takes in energy from the sun to make organic molecules
All organisms involved in food chains, feed on those organic molecules
i.e. plants make food for themselves and for the animals that feed on them
• Plants are autotrophs – they make their own food (organic molecules) through photosynthesis
• Energy (from sun) + carbon dioxide + water à glucose + oxygen
The rate of photosynthesis
[CO2] = concentration of carbon dioxide Higher [CO2] = faster rate of photosynthesis, as there
are more carbon dioxide molecules in the same space,
so they are more likely to react
