Unit 1 Organisms and Life Processes
Ch.1: Life Processes
HOW THE CELL GETS ITS ENERGY
Energy Needs of Living Things
• Respiration are the chemical reactions in
cells that break down nutrient molecules
and release energy for metabolism
Glucose+ oxygen = water + carbon dioxide + energy
Respiration releases some
heat energy, but most is
used to make a substance
called ATP (Adenosine
Triphosphate)
Glucose contains stored
chemical energy that can
be converted into other
forms of energy
Burning releases most
of the energy as heat
Use of Energy stored in the ATP molecules
• contraction of muscle cells, producing movement
• active transport of molecules and ions
• building large molecules, such as proteins
• cell division
Cellular Respiration
• Respiration is called an oxidation reaction, because oxygen is used to break down
food molecules
• Carbon dioxide (and water) are released as waste products.
• The energy released as heat is also used to maintain a constant body temperature
in mammals and birds
glucose + oxygen → carbon dioxide + water (+ energy)
C6H12O6 + 6O2 → 6CO2 + 6H2O (+ energy) Small amount
• aerobic respiration-in the cells of humans, animals, plants and many other
organisms-which organelle
• takes place gradually-each step in the process is catalysed by a different
enzyme.
ATP – THE ENERGEY ‘CURRENCY’ OF THE CELL
• A chemical named adenosine triphosphate or ATP
• passing the energy from respiration to the other processes using ATP
• ATP is composed of an organic molecule called adenosine attached to three
phosphate groups
• In a cell, ATP can be broken down losing one phosphate group and forming
adenosine diphosphate or ADP
• ATP transfers energy between the process that releases it (respiration) and the
processes in a cell that use it up- energy currency
ANAEROBIC RESPIRATION
• respire without using oxygen-glucose is not completely broken down, so less
energy is released
• occur in situations where oxygen is in short supply-in yeast cells and muscle cells
• Yeasts are single-celled fungi -used in processes such as making wine and beer and
baking bread
• prevented from getting enough oxygen, they stop respiring aerobically and start to
respire anaerobically instead
• glucose → ethanol + carbon dioxide (+ some energy)
Alcohol formed in wine- Bread dough rise
and beer-making
• Muscle cells can also respire anaerobically when they are short of oxygen.
• If muscles are overworked, the blood cannot reach them fast enough to deliver
enough oxygen for aerobic respiration
Sprint
Lifting a heavy weight
‘Burst’ of activity
glucose → lactate (+ some energy)
Lactic acid
• Anaerobic respiration provides enough energy to keep the overworked muscles going
for a short period.
• During the exercise, the level of lactate rises in the muscle cells and bloodstream.
• After the exercise the lactate is respired aerobically in the mitochondria.
• The volume of oxygen needed to completely oxidise the lactate that builds up in the
body during anaerobic respiration is called the oxygen debt.
