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CHAPTER 9- ENERGY
FLOW
C6 ALL CELLS REQUIRE ENERGY
C6.1 know that all living cells use energy for
movement, synthesis and maintenance of a stable
intracellular environment
• Continual transfer of info occurs in cells from
one type to another
• Energy is not created or destroyed-just
changed-law of conservation of energy
• Energy-light, heat, chemical and kinetic
• Generally living cells convert chemical
energy to other forms more useful for the
cell.
MOVEMENT
• Cells move/change shape-sperm can swim
for several days
• Contraction of muscles in larger organisms
• Movement of chromosomes during mitosis
• Packaging of substances by the cell and
movement of them in endo- cytosis and
exocytosis
• Whole cells can change shape because of
contraction of the cytoskeleton
SYNTHESIS
Some cells manufacture or synthesise
various chemicals- this is conversion of
energy
e.g. endocrine cells producing
hormones and when cells undergo DNA
replication and protein synthesis
Cells require energy to break down and
build up molecules
STABLE ENVIRONMENT
• Cells must maintain a stable environment as
stated in last chapter
• So actively regulating the cell
contents/concentrations requires energy
• TEMP regulation needs heat-generated by
the kidney and liver
• Energy for active transport
• Energy changes in the cell are represented
by arrows and the energy chain
• -could be straight but often branched
• ( draw diagram pg 78)
C7. Energy is obtained in physical or chemical form from
the cell’s environment, and energy transformations occur
within the cell
• C7.1 Know that the sun is the main source of energy for life
• Suns energy comes from the reactions of the
hydrogen and helium atoms that it consists of.
• This radiates towards earth from space-solar
energy
• It is about 0 to 40 degrees Celsius-perfect for
living things
• Variations caused by- winds, changes in weather.
• ** remember enzymes work best at the temp of 37-40
• Light falls on leaves –photosynthesis
• Some bacteria are chemoautotrophs-derive energy form
inorganic substances-100 degrees Celsius- thermophiles
• Climatic conditions greatly affected living organisms- no
sun no life.
C7.2 understand that light energy can be used by
some cells in photosynthesis
• All plants have at least some cells that can
absorb light energy-green and called
mesophyll cells
• Contain chlorophyll contained in the
chloroplasts.
• Usually found in the leaves where light is
easily absorbed
• Carbon dioxide is used with the light energy
to synthesise carbohydrates
• = photosynthesis
• Pg 8o draw- or closely observe
THE LEAF….
• Upper edge cuticle
• Made by the cells of the epidermis-contains waxy
materials-protects the leaf from abrasion, water loss
and predators
• Beneath the cuticle- layer of tight packed cells-also
provide protection-no chlorophyll- but thick
protective cell walls
• Beneath the epidermis 1-2 layers of cells – the
palisade mesophyll-full of chloroplasts-chlorophyllphotosynthesis
• When seen under light microscope- one can see
the cytoplasm streaming-this movement is thought
to enable photosynthesis to proceed more
efficiently-like a conveyor belt.
CYTOPLASMIC STREAMING
• http://www.dnatube.com/video/361/Cyclosis-inPlant-cells
• Beneath the palisade-spongy mesophyll-more
regular shape- more air spaces –contains some
vascular tissue- to carry both water from the roots to
the leaves and sap which contains the sugars from
the leaves to other parts of the plants
• Lower surface of the leaf-epidermis-contains the
stomates – which have guard cells/enclosing a tiny
pore
• Water moves into guard cells-swell and open the
pore-TURGID
• Water moves out-cells flaccid and collapses pore
closes
STOMATES
Stomata regulate
water loss
Allow gases to pass
through also
KNOW THE
PHOTOSYNTHESIS
EQUATION!
C7.3 know that some molecules contain energy
that can be released when chemical bonds are
broken and new bonds are formed
• Particle theory of matter- all matter made of atomsconstantly moving-made of smaller particlesprotons/neutrons/electrons
• Usually atoms are joined with others-molecules
• Represented by symbols- i.e. O oxygen- combined
with other atoms as in H2O –atoms joined by
chemical bonds-SHARED ELECTRONS
• Big molecules-more bonds-more stored energy
• Plants store energy in the macromolecule –starch
• Animals – glycogen
ENERGY RELEASE:
• Organisms obtain energy as bonds are broken-the
breakdown of organic molecules during cellular
respiration
• Energy must first be digested in soluble forms-then
absorbed into the blood stream
• The bonds in glucose are broken and new
chemicals made like carbon dioxide-less energy in
the bonds-only 40% of the energy in glucose is
transferred to ATP
• THE REST IS LOST AS FREE ENERGY OR HEAT
C7.4 Explain how the ATP/ADP conversion
provides energy for use in cells
• As large molecules are broken down- stored
energy in bonds is converted to ATP…..most is
released as heat.
• ATP- adenosine Tri-Phosphate- IMMEDIATE source of
energy for the cell
• Made up of three parts
• An adenine base
• A 5 carbon (pentose) sugar
• Three phosphate groups linked
Note: bond between the last phosphate is weak bond and
easily broken-to release free energy- this converts ATP to ADP
ATP/ADP CYCLE
• http://www.youtube.com/watch?v=Lx9GklK0xQg
• http://www.youtube.com/watch?v=rrFi7GWt_GY&f
eature=related
• USE 2ND LINK AS LECTURE
ATP/ADP
• Should have notes from the U tube video
• Ensure you understand
• ATP/ADP is a continuous cycle
• Involves synthesis and breakdown of
molecules
• Anabolism and catabolism
• ATP is made in the mitochondria- through
the process of cellular respiration
C7.5 explain why energy pathways involve
many small regulated steps
• In any chemical reaction- toast burning in the
toaster- etc. heat energy is released
• Molecules are generally broken down from large to
small
• If you ate the piece of bread a chemical reaction
occurs again- but this occurs more slowly and the
energy needs to be released in a way that is useful
to your body
• If energy release was not managed carefully in
living things there would be SPONTANEOUS
COMBUSTION, due to such vast amounts of heat
being released at once.
C7.5 CONTINUED
• Your body generally releases the energy in
about 30 small steps/reactions to ensure that
energy can be utilised in small amounts for
each smaller reaction or step in the processthis may involve: removing atoms from large
molecules, transporting electrons across a
membrane, - pumping of hydrogen ions
• This is oxidative phosphorylation
SEE PAGE 85 TEXT
•Lipids , Proteins, and
carbohydrates can all
be interconverted and
yield energy-as the
usable form of ATP.
C7.6 Describe how the metabolic pathway is
controlled by a specific enzyme at each step
• Metabolism- all the chemical reactions that are
going on in the body- includes catabolism and
anabolism already discussed
• Remember- breaking molecules releases energy
• Enzymes- specific for their substrate (remember)
which means that each step in the pathway has a
different enzyme that controls it- the product of one
enzyme reaction is the substrate for the next and so
on
THIS MEANS LITTLE BITS OF ENERGY RELEASED IN EACH
STEP TO BE USED TO HELP THE NEXT ALONG AND SO
ON…….
C7.6 CONT:
• If there is an issue with an enzyme…i.e it has
an enzyme inhibitor in its pathway or
conditions like pH are not right the reaction
will not continue.
• Aerobic respiration uses 50 enzymes or so,
each fixed to a part of the mitochondria's
inner membrane the cristae to ensure the
procedure occurs in the correct step order.
• In photosynthesis they are attached to the
membrane of the chloroplasts
AND THERE’S MORE ! C7.6
• If there is a defective gene then what
happens……?
• This changes the protein code in the m RNA
and the enzyme produced is
incorrect…..can affect a particular enzyme
controlled pathway and result in some issues
i.e. Haemophilia etc. pg. 87
C7.7 Understand that each step produces
intermediate compounds an loses some
energy as heat
• WE HAVE ELUDED TO THE FACT THAT SMALL
PACKETS OF ENERGY ARE RELEASED AT EACH
STEP………
• If some is lost as heat what does this mean?
• This heat is useful in warm blooded animals
(you!) to provide a constant body temperature
and in those that are more exothermic it can
help warm them up enough to enable them to
be active and eat etc.
• Generally we use about 40% of the energy in
food we take in- quite efficient compared to
cars- 20%