Transcript File - Hope Christian College Parent and Student Portal

Energy – Cells need energy to do
work and to catalyse reactions
•Energy is also needed for growth, cell division,
movement and to get rid of waste products.
•Energy comes in different forms but cells use chemical
energy.
•Chemical energy is stored in bonds or the connections
that join the atoms to molecules.
•Once a bond is broken energy is released.
•Things like sugars, fats and proteins which you will
remember are all made of chains of smaller molecules
contains lots of bonds and energy.
ATP…….
• Usable energy for cells.
• The molecule contains a bond which when broken
releases lots of energy to be used by the cell.
• Once released, the energy is called adenosine diphosphate (two)
• ADP can be recharged again and recycled.
• As always this
conversion of energy
means some is lost
as heat
Where does ATP come from?
•
•
Food is broken down by the digestive system into smaller molecules such as
glucose.
Tho body then breaks the glucose down further in the cells by a series of
steps, controlled by enzymes to release ATP.
This process occurs in the mitochondria and uses the oxygen we breathe in
and is called AEROBIC RESPIRATION
This allows energy to be used for movement contraction of muscles, nerve
transmission of messages, transport, warmth, growth, cell division and
moving molecules against the concentration gradient.
Complete aerobic breakdown of glucose:
•
Glucose + oxygen
•
MUST MEMORISE ABOVE FORMULA!
•
•
•
carbon dioxide + water + energy
Aerobic respiration
• Means there is always a complete breakdown of the glucose
molecule.
• Occurs in 3 steps: Glycolysis, Krebs cycle, Electron Transport
Chain
• The 36-38 units of ATP are produced from one molecule of
glucose and six oxygen molecules.
• If there is no oxygen present then anaerobic respiration occurs –
this happens in the cytoplasm not mitochondria and only
produces about 2 molecules of ATP
• What happens:
~ glucose diffuses into the cytoplasm
~ about 7 different enzymes breakdown the glucose in small steps
and produce a substance called pyruvic acid (if this doesn’t
proceed to the mitochondria with oxygen then lactic acid is
produced)
Aerobic respiration
Comparison
Aerobic
Anaerobic
Occurs in the
mitochondria
Requires oxygen
Occurs in the cytoplasm
Complete breakdown of
glucose molecules
Incomplete breakdown of
original glucose
molecules
Minimal amount of
energy produced (2 ATP)
Large amount of energy
produced (36 ATP)
No oxygen required
Anaerobic respiration- fermentation
in animals
• When no oxygen is present.
• If this happens in the muscles (think of a marathon
runner who after some time was running out of fuelhadn’t eaten so had no more glucose…was tired and
finding it difficult to get enough oxygen….)
• The marathon runners muscle cells would start burning
stored fuel and only undergo the process of glycolysis.
• This produces lactic acid (the thing that gives you
cramp..)
• Therefore, the pyruvate produced in glycolysis
undergoes fermentation into lactic acid in most animals
• READ and note Page 42
Anaerobic respiration – fermentation
in plants and microorganisms
• The pyruvate produced in glycolysis undergoes fermentation into
carbon dioxide and alcohol in most plants, and in
microorganisms such as yeast and bacteria.
• Yeast respires by converting the sugar to alcohol and carbon
dioxide and when they have produced a lot the yeast does not
survive.
• Alcohol is made with sugar, yeast and water.
• Need warm conditions for fermentation to occur
• Need to allow carbon dioxide to escape and prevent bacteria
getting in (if bacteria gets in we may end up with vinegar).
• READ and note pg 43-44
• Answer the key questions on pg 44