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Summary Grade 11 Life Science Cellular Respiration Notes
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Notes on Cellular Respiration
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Cellular RespirationWhere does energy come from
Light energy is trapped by chlorophyll molecules during photosynthesis & used to create energy-rich bonds in organic compounds
that are formed
- Living organisms obtain food by breaking these bonds during CR & releasing stored chemical potential energy which is
stored in ATP until needed.
- 40% of chemical energy in glucose is stored in ATP molecules the other 60% is lost as heat
HOw energy is used in living cells
All organisms:
- Growth
- Cell division (for new cells and wounds)
- Active transport of molecules and ions across membranes
- Anabolic reactions (synthesis of proteins, nucleic acids, glycogen and fats etc)
Animals:
- Muscular contraction for movement
- Conduction of nerve impulses
- Keeping warm
- Think & other mental activities
Plants:
- Taking up minerals from soil
- Transporting food substances
, Cellular Respiration
Release of energy from fuel molecules (glucose) in all living cells
- Stored in ATP (cellular energy carrier)
- Different organic compounds can be used as fuel (fats and amino acids) but mostly glucose
- Photosynthesis traps energy and forms chemical energy whilst CR releases energy to perform work
- Fuel molecule is broken down in a series of steps each catalysed by an enzyme so energy is released bit by bit
❏Aerobic respiration
- Most efficient form of CR
- Oxygen is needed
- C6H12O6 + O2 ---> CO2 + H2O + ATP (energy)
- Glucose + Oxygen ---> carbon dioxide + water + ATP
Takes place in the mitochondria and cytoplasm of living cells
- Mitochondria: cells power producers
- Through CR they cause release of chemical energy from fuel molecules which is stored in ATP
- ATP is used by cell for its activities
Three Stages:
a. Glycolysis
Takes place in cytoplasm around mitochondria
- Anaerobic
- Phosphorylation occurs: A molecule of glucose is activated by combining with a high-energy phosphate group
from ATP
- The high energy glucose molecule is broken down into 2 molecules of pyruvic acid (3 carbon compound)
- During these reactions energy is released which together with the PO4 group and ADP forms 2 ATP molecules
What happens next
- The pyruvic acid loses a molecule of CO2 forming pyruvate (a 2 carbon compound) that enters the
mitochondrion
- O2 is necessary for the next 2 stages therefore they are aerobic and happen in the mitochondria
- The more active a cell, the more mitochondria
b. Krebs’ Cycle
The pyruvate is broken down releasing
- High energy hydrogen atoms: a process catalysed by dehydrogenase enzymes. The hydrogen atoms pass into the
next stage
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