Transcript Ch3 - Unit3Biology

Chapter 3
Biochemical Processes in cells
Chemical Energy in organic compounds
reading p. 62
“Living organisms require energy in the form of organic compounds to survive”

Heterotrophs (= other feeding)



Rely on an external energy source
Uses organic matter from dead and living organisms or their products to
obtain carbon
Autotrophic organisms (= self feeding)


build organic compounds from simple inorganic compounds such as
carbon dioxide and water.
Use an external source of energy, usually the sun, to build organic
compounds.
Exergonic & Endergonic Reactions
reading p. 62
When organic compounds react to form products with lower energy, such as
inorganic compounds, energy is released (see figure 3.5). Some of this energy
is available as chemical energy and some is released as heat energy. In every
reaction that involves either the transfer or transformation of energy, some
always appears as heat energy.
We (will) consider two types of energy reactions, those releasing energy and those
requiring energy, using the terms exergonic (catabolic) and endergonic
(anabolic) respectively.
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
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Exergonic reaction is oxidation.
Oxidation reactions involve the addition of oxygen to a
substance.
Oxidation reactions are controlled by catalysts or enzymes.
Under control of enzymes, reactions occur at temperatures
and rates that can sustain the living state.
Example: oxidation of glucose through respiration.
Exergonic (Catabolic) Reactions
reading p. 62-64
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
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break down macromolecules into smaller molecules, releasing
energy in the form of ATP (and heat) for use by the organism
occur when large molecules are broken down into smaller ones
rate of reactions controlled by enzymes in living cells
under control of enzymes, reactions occur at temperatures and rates
that can sustain the living state.
Drawing: Figure 3.7

Example: oxidation of glucose in respiration

Oxidation reactions involve the addition of oxygen (or removal of
electrons from) to a substance.
Oxidation reactions are controlled by catalysts or enzymes.

Endergonic (Anabolic) Reactions
reading p. 62-64


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Require energy
endergonic reactions are also known as anabolic reactions.
Occur when a cell makes large molecules from smaller molecules
Examples: DNA synthesis from nucleotides, Photosynthesis.
Reduction reactions are endergonic and involve the removal of
oxygen from organic compounds.
See table 3.1 page 64
Drawing
(a)

•
•
(b)
The change in energy from initial state to final
state is referred to as ΔG.
Exergonic reactions release energy.
Endergonic reactions require the input of
energy.
In Your Books
1.
Use selected examples to explain the difference
between exergonic and endergonic reactions.
Exergonic reactions involve a release of energy.

These occur when the chemical bonds in molecules
are broken.

E.g. Cellular respiration.
Endergonic reactions require an input of energy.

These are reactions in which larger molecules are
constructed from smaller ones, by forming chemical
bonds.

E.g. Photosynthesis.
Energy is required to form bonds.
Atoms or molecules
Energy
8
Energy
+ Energy
Larger molecule
The energy that was used to
form the bonds is now stored in
this molecule.
ATP as the energy currency of cells

Living cells do not have direct access to the energy stored in organic
molecules

Organic molecules must be broken down into smaller molecules to
release their energy

The energy released from such reactions is used to produce ATP
(Adenosine Triphosphate) from ADP (Adenosine diphosphate)

ATP is formed when energy is released during cellular respiration of
glucose.
ATP (Adenosine Triphosphate)
NH2
Base (adenine)
C
N
N
C
CH
HC
OO-
P
O
OO
P
O
P
O
N
N
OO
C
O
CH2
O
C
C
H
H
C
C H
C
OH
OH
3 phosphate groups
Ribose
10
ATP (Simplified Drawing)
3 phosphate groups
A
Sugar (ribose)
11
Base (adenine)
Phosphorylation

12
ATP is synthesized from ADP + Pi. The
process of synthesizing ATP is called
phosphorylation.
ATP as the energy currency of cells
copy
Figure 2
This is the two-dimensional structure of ATP, adenosine triphosphate.
The removal of one phosphate group (green) from ATP requires the
breaking of a bond (blue) and results in a large release of free energy.
Removal of this phosphate group (green) results in ADP, adenosine
diphosphate.
Interesting Fact: In a typical cell, an ATP molecule is used within a minute of its formation.
ATP Stores Energy
Breaking the bond releases
the energy.
This phosphate bond is a
high-energy bond
Energy
A
ATP
14
A
ADP
+ Pi + Energy
ATP is Recycled – copy …

ATP (Adenosine Triphosphate) is an energy-containing molecule used
to supply the cell with energy. The energy used to produce ATP comes
from glucose or other high-energy compounds.

ATP is continuously produced and consumed as illustrated below.
ADP + Pi + Energy  ATP + H2O
(Note: Pi = phosphate group)

ATP
Energy
Energy
(from glucose or
other high-energy
compounds)
15
ADP + Pi
ATP / ADP Cycle
Task
Biozone p.44

The usable energy of ATP is
contained in its three
phosphate bonds. Usually
the energy from only one
bond is released for
biologically useful work. The
resulting ADP (adenosine
diphosphate) is recycled
using energy derived from
the breakdown of glucose.

Formula:
ATP
ADP + Pi (+ 60% as heat)
Energy Supplied
Energy Released
17
Anabolic Reactions
Products
Anabolic reactions
consume energy.
Substrates
(Reactants)
Menu
Energy Supplied
Energy Released
Catabolic Reactions
Substrate
(Reactant)
Catabolic
reactions release
energy.
hen
bonds are broken, energy is released.
18
Menu
ENZYMES
Enzymes
reading page64-67
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
are proteins that act on other molecules
are organic catalysts
are protein molecules that increase the rate of reactions that occur inside
the organism.
are generally intracellular (exception: digestive enzymes)
some require a non-protein cofactor (i.e vitamins, CoQ10) before they can
act
have a region, known as the active site, that alligns with a particular
substrate
the compounds obtained as a result of the enzyme action are called the
products
enzymes are highly specific in their action. Each enzyme acts on a
particular substrate.
Diagram
Substrate
Enzymes
Enzymes are
organic
catalysts.
1
Active Site
Enzyme
Product
Enzyme-Substrate Complex
2
3
Enzyme
Menu
Enzymes
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22
Catalysts are substances that speed up chemical
reactions. Organic catalysts (contain carbon) are called
enzymes.
Enzymes are specific for one particular reaction or group of
related reactions.
Many reactions cannot occur without the correct enzyme
present.
They are often named by adding "ase" to the name of the
substrate. Example: Dehydrogenases are enzymes that remove
hydrogen.
Enzyme Action ‘lock and key’ theory
Reading p65-66

This complementary fitting of shapes is known as the ‘lock
and key’ theory of enzyme action.
See figure 3.10a
Enzyme Action ‘induced fit’ theory
Reading p65-66

in some cases, the shape of the active site varies slightly from
that of the substrate and the two fit only after the substrate
induces a complimentary shape at the active site theory of
enzyme action.

The induced-fit theory assumes that the substrate plays
a role in determining the final shape of the enzyme and
that the enzyme is partially flexible.
Enzyme Action

poisons such as cyanide and arsenic , block the active sites of
enzymes to prevent them from working.


enzymes are typically named for their substrates:
Maltase works on maltose
Lipases works on lipids
Amylase works on amylose
DNA ploymerase
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the ‘ase’ ending tells us that it is an enzyme.
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Task
Biozone p.37-38
Factors Affecting Enzyme Action
reading p.67-68
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each enzyme:
•
has optimal conditions of pH and temperature for its action
•
may be unable to combine with its substrate if pH is not optimal
•
may be denatured if the temperature rises above the optimal

enzymes in human cells work best at pH 7.6 and at 37.4oc

absence of a co-factor may prevent or inhibit enzyme action
rate of reaction will be dependent upon amount of:
•
substrate concentration
•
enzyme concentration
•
cofactors concentration
•
presence of inhibitors such as poisons
Tasks
Quick Check 1-5 p.68
Biozone 39-40
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Factors Affecting Enzyme Action
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Enzyme Concentration
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By increasing the total amount of enzyme present,
the amount of product made by unit-time will
increase.
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Substrate Concentration
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The addition of more substrate increases the
amount of product made, but does not affect the
rate of a reaction.
Factors Affecting Enzyme Action
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Inhibition
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Another substance may compete with the normal
substrate.
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This causes the intruder to block the active site of the
enzyme and not allow the substrate to combine.
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Enzyme inhibition can cause death.
ATP as the energy currency of cells

Living cells do not have direct access to the energy stored in organic
molecules

Organic molecules must be broken down into smaller molecules to
release their energy

The energy released from such reactions is used to produce ATP
(Adenosine Triphosphate) from ADP (Adenosine diphosphate)

ATP is formed when energy is released during cellular respiration of
glucose.
Task
Biozone p.44
Ecosystem Trophic Levels
Plants provide the world’s organisms with food
Photosynthesis
Photosynthesis


is the process by which plants produce their own food
takes place in chloroplast
6CO2 + 6 H2O + light
C6H12O6 + 6O2
Chloroplast

Organelle where photosynthesis takes place.
Stroma
Outer Membrane
Inner Membrane
Thylakoid
Granum
Thylakoid
Thylakoid Membrane
Granum
Thylakoid Space
Site of Photosynthesis

takes place in chloroplast
Chloroplasts
reading pages 69-71

are (double) membrane-bound organelles found in the cytosol of
(some) plant and algal cells
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are the site of photosynthesis
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internal membranes (thylakoid membrane) forms disks called grana

stack of grana membranes are called granum

the fluid surrounding the thylakoid membrane inside the chloroplasts
is called the stroma and contains enzymes

are not found in every plant cell!
Copy figure 3.16©
Task
Quick check 6-8p.71
Chlorophyll (& Carotenoids)
 is a photon trapping pigment trapping red and blue-violet light
 comes in two kinds (chlorophyll a & b)
 reflect green light
 (carotenoids absorb blue-violet light and appear orange yellow or red)
Chlorophyll Molecules

Located in the thylakoid membranes.

Chlorophyll have Mg+ in the center.

Chlorophyll pigments harvest energy (photons)
by absorbing certain wavelengths (blue-420
nm and red-660 nm are most important).

Plants are green because the green
wavelength is reflected, not absorbed.
Describing Photosynthesis in brief
reading pages 69-71

is light dependent and involves the trapping of sunlight (radiant energy) by
pigments such as chlorophyll by producer organisms
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is the process of converting the energy of sunlight to chemical energy
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the raw materials are carbon dioxide and water, and the products are
carbohydrate and oxygen.
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In plants and algae, photosynthesis occurs in the organelle –chloroplasts
light (photons)
6CO2 + 12H20
C6H12O6 + 6O2 + 6H2O
chlorophyll
Examine diagram page 69
Task
Biozone page 45, 49
*new water!
Photosynthesis Overview
A bit simplified and we will slightly change this
equation momentarily!
More detail is required, but first.
Question:

Why are plants green?
Why Plants are Green?
Why Plants are Green?
Absorption of Chlorophyll
Absorption
violet
blue
green
yellow
wavelength
orange
red
Two Stages in Photosynthesis
reading pages 72
The word ‘photosynthesis’ is made up of two parts: ‘photo’ = light and
‘synthesis’ = put together. The name reflects the two-stage nature of the process.
Stage One:
a light dependent stage involving trapping energy of light (in grana)
Stage Two:
a light independent stage, known as carbon reduction (in stroma)
Light vs. Dark Reactions
Energy &
Reducing Power
Electron Carriers
Electron carriers function in photosynthesis and cellular
respiration. Three major electron carriers are listed below. You
do not need to memorize these, but may come across them in
your reading.
50
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Photosynthesis
 NADP+

Respiration
 NAD+
 FAD

These carriers work to form “electron transfer chains” in many
biochemical pathways.
Stage 1: Light Dependent Stage
reading pages 72
Where:
 occurs within the grana of chloroplasts (particularly the grana
membrane) and the stroma of the discs
Key Materials in this Stage:
Photosystems II
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Photon Energy
Thylakoid Disc/ Chlorophyll
Excited chlorophyll electrons
Electron Carrier Proteins
Stroma
Water releasing H+ ions
Enzyme ATP Synthase
Energy Carrier ADP + Pi
Key Outcomes



ATP
H+ ions
Oxygen
Photosystems I
• boost of Photon energy
• excited H+ electron
• energy carrier NADP
Key Outcomes
• NADPH+
Light to Dark Reaction
Photosynthesis…
Diagram of Light Dependent Stage
Stage 2 Light Independent (Dark) Stage
reading pages 72
Where:
 occurs within the stroma of the chloroplasts
Key Materials in this Stage:

ATP
NADPH+
CO2
PGA
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Enzyme –
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rubisco
Produces
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PGAL (Glycerheldihyde phostphate) universal building block of carbohydrates
Then …
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PGAL can easily be converted into 6 carbon glucose molecule C6H12O6
Stage 2: Light Independent Stage
Sometimes referred as ‘Dark Reactions’ but doesn’t ohave to occur in dark
reading pages 72
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occurs in the stroma of chloroplasts

this stage does not require light but It does not have to take place in the
dark!
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it involves the reduction of carbon dioxide using NADPH and ATP from the
light-dependent reaction.

for C3 plants (and photosynthetic bacteria), the carbon reductions begin
with the Calvin cycle,

the carbon dioxide is fixed by combining it with a 5-carbon compound –
ribulose biphospate (RuBP) This forms an unstable 6-carbon compound
Continued …
Light Independent stage – C3 plants

The 6-carbon compound breaks down into two molecules of the 3-carbon glycerate 3phosphate (Phosphoglycerate - PGA). Carbon-Dioxide Fixation

ATP and NADPH (from the light-dependent reaction) are used to convert PGA into
glyceraldehyde 3-phosphate (PGAL).
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PGAL can be converted into glucose. Some of it is used to regenerate RuBP
.
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ADP and NADP return to the light-dependent stage
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Each time the cycle precedes, one CO2 molecule is fixed and reduced. To produce a
6 carbon glucose molecule, 6 turns of the cycle must take place
Task
See figure 3.22 & Complete Biozone 47/ 47
Summary of photosynthesis
reading pages 75-77

one important product formed in the calvin cycle is PGAL
(phosphoglceraldehyde), a compound that contains 3C atoms.

PGAL can react to form various sugars, including glucose, fructose,
sucrose.

sucrose is the form in which carbohydrates are transported through
the phloem.

Starch (a polysaccharide) is the storage carbohydrate in plant cells.
Tasks
Quick Check 9 - 11
Calvin Cycle

Carbon Fixation (light independent rxn).

C3 plants (80% of plants on earth).

Occurs in the stroma.

Uses ATP and NADPH from light rxn.

Uses CO2.

To produce glucose: it takes 6 turns and
uses 18 ATP and 12 NADPH.
Light Independent Stage
Photosynthesis Overview
Light Independent stage – C4 plants

in a small number of plants, a series of reactions preceeds (goes before) the Calvin
cycle
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these plants are known as C4 plants

the first step in C4 plants, one 3c compound is fixed to form a C4 compound Occurs
in mesophyll cells
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the C4 compound undergoes further reactions and is transported to cells surrounding
the vascular bundles

Here the C4 plant releases a molecule of CO2 which enters the Calvin cycle
Task
Biozone page 47-48
C4 Plants
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Hot, moist environments.
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15% of plants (grasses, corn, sugarcane).
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Divides photosynthesis spatially.
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Light rxn - mesophyll cells.
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Calvin cycle - bundle sheath cells.
C3 and C4 plants
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Differ in leaf anatomy
C4 plants have a ring of photosynthetic cells known as bundle
sheath cells around vascular bundles as well as mesophyll cells.
C3 plants have only the mesophyll cells that are photosynthetic.
The first step of carbon fixation occurs more rapidly in C4 plants.
The first step in C3 plants occurs in the mesophyll cells. These
are close to stomata and air spaces.
C4 plants are able to use CO2 more efficiently and carry out
photosynthesis are a higher rate.
C4 plants occur in the hot dry deserts where the stomata are
often closed during the day.
C3 plants are high producers in the forests and ecosystems in
temperate regions.
Redox Reaction

The transfer of one or more electrons from
one reactant to another.

Two types:
1. Oxidation
2. Reduction
Oxidation Reaction


The loss of electrons from a substance.
Or the gain of oxygen.
Oxidation
6CO2 + 6H2O 
C6H12O6 + 6O2
glucose
Reduction and Oxidation
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When a molecule gains a hydrogen atom or
electron during a reaction it is said to have been
reduced.
When it loses a hydrogen atom or electron, or gains
an oxygen atom, it is said to have been oxidised.
So a reduction and oxidation reaction occur
together.
If one substance is oxidised the other is reduced.
When a substance goes from being reduced to
oxidised, energy is released. Eg. Fuels burning in
the air.
Reminder:
Photosynthesis - Overview
+ Energy
Cellular Respiration
reading pages78-79
Respiration - Overview
Cellular Respiration
reading pages78-79
The chemical energy in glucose and other organic compounds is not
directly used by cells. This energy is transferred to other compounds, typically ATP, before it
can be used by cells. Cells carry out a series of reactions that release chemical energy
and transfer it to ATP (then immediately available to the cell)… The series of energy
releasing reactions that break organic compounds of foods (lipids, proteins &
carbohydrates), releasing chemical energy that is trapped in the form of ATP is
known as Cellular Respiration
Cellular Respiration:

The series of energy releasing reactions that break organic compounds of foods
(lipids, proteins & carbohydrates), converting this to the usable form, ATP

Glucose (C6H12O6) is an energy rich m’cule and can be used as an energy source.

Cellular respiration may occur in the absence of oxygen, this is called anaerobic
respiration

Cellular respiration may occur in the presence of oxygen, this is called aerobic
respiration

Aerobic respiration yields (much) more ATP molecules per unit of organic material
than does anaerobic respiration

Aerobic respiration gives 36 (38 in some cases) m’cules of ATP

Anaerobic produces 2 m’cules of ATP for each molecule of glucose.
EQUATION FOR
RESPIRATION
CARBON
DIOXIDE
GLUCOSE
C6H12O6 + 6O2
OXYGEN
36 – 38 ATP
6CO2 + 6H2O + ENERGY
WATER
Mitochondria: Site Of Respiration In Eukaryotes
Mitochondria
See figure 3.29 page 82

Are membrane bound organelles suspended in the cytosol of
eukaryotic cells

Are the site of some stages of aerobic respiration

(double membrane bound!): Have an outer membrane and a
highly folded inner membrane, called cristae

Fluid inside called matrix

Contain respiration enzymes on the internal membranes

Are the production site of most ATP
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occur in larger numbers in cells with a higher energy requirement
Anaerobic Vs Aerobic
reading page80 (Table 3.2)
Anaerobic
Aerobic
Oxygen not required
Oxygen required
Rapid ATP Production
Slow ATP Production
Mammals sustain over a short
period (60 secs)
Sustain indefinitely
Less efficient energy transfer
More efficient energy transfer
2 mole of ATP produced per 1
mole of glucose used
36 mole of ATP produced per 1
mole of glucose used (some 38)
Various waste products: lactic
acid, water (Humans)
Ethanol, CO2 (Yeasts)
Butyl alcohol (bacteria)
Waste Products:
CO2 and water
Biozone: Page 50
Aerobic Respiration
reading page 81
E
C6H12O6 + 6O2
36-38 ATP
6CO2 + 6H2O
Respiration Summary Reaction
The three "stages" of Respiration
1. Glycolysis - involves the initial oxidation (and partial breakdown) of
Glucose
2. Krebs Cycle - is the further removal of the electrons from the
remnants of Glucose (called Pyruvate).
3. Electron Transport Chain - is where the energy of the electrons from
the above Redox reactions is used to make ATP.
Stage 1: Glycolysis
reading page 82

glycolysis occurs in the cytosol of cells. each step is catalysed by a
specific enzyme.

the aim of glycolysis is to transform 6 carbon glucose molecules into
3 carbon pyruvate molecules. in the process 2 ADP molecules are
charged into ATP (note energy transfer)

Hydrogen atoms are removed from glucose and collected by
acceptor molecules, nicotinamide adenine dinucleotide:
2NAD
2NADH to be used in step 3

the pyruvate molecules move into and are used for the second stage
of respiration – the krebs cycle.
Step 1: Glycolysis

Glycolysis simplified:
6 Carbon Glucose
2 ADP + Pi
2 NAD
2 ATP
2 NADH
2 x 3 Carbon Pyruvate
GLYCOLYSIS
Energy will be released from molecules as the electrons are
removed and Oxygen atoms are added. In Respiration, this occurs
Carbon by Carbon until each of the six Carbons in the Glucose has
been completely oxidized to Carbon Dioxide. The process starts with
Glycolysis, which is the splitting of the the six-carbon sugar Glucose
into 2, 3-Carbon sugars (each is called Glyceraldehyde). After this, the
3-Carbon Glyceraldehyde is oxidized as the electrons are removed. This
eventually provides our cells with Energy in the form of ATP.
The reactions of Glycolysis
The term Glycolysis mean "Sugar-splitting”
Step 2: Krebs Cycle
reading page 82-83
definition: a cyclic series of biochemical
reactions, usually in the mitochondria, that
represents the final common pathway in all
aerobic organisms for the oxidation of amino
acids, fats, and carbohydrates, and that
converts the citric acid, etc. from food into
carbon dioxide and ATP
Step 2: Krebs Cycle
reading page 82-83

occurs on the inner membranes (cristae) of mitochndria

uses the pyruvate from glycolysis.

pyruvate molecules leave the cytosol and enter the mitochondia.

hydrogen atoms are gathered by acceptor molecules, with a total of
4 NADH and one FADH2 for each pyruvate molecule (note 6
Hydrogen in – 6 out!)

another intermediate product formed is Acetyl Coenzyme A.

for each molecule of pyruvate used – 3 carbon dioxide molecules
are formed.

1 ATP also produced for each pyruvate
Pyruvate (3 carbon molecule is converted to
a 2 carbon molecule, Acetyle coenzyme A
prior to stage 2 – Krebs Cycle. Carbon
Dioxide is formed from this oxidation reaction.
Step 2: Krebs Cycle
Cytosol
Pyruvate
Mitochondria
NAD
CO2
NADH
Coenzyme A
3NADH
3NAD
Acetyl Coenzyme A
FADH2
CO2
Krebs Cycle
FAD
CO2
ATP
ADP + P
Step 3: Electron Transport
reading page 83

takes place on compounds within the inner membrane of the mitochondria (cristae)

compounds called cytochromes

Requires oxygen as an input (substrate)

involves reactions of loaded ‘acceptor’ molecules such as NADH and FADH2 from
the previous two stages.

during ET electrons from loaded acceptors (NADH & FADH2) are successively
transferred from one cytochrome to another until the hydrogen are finally accepted by
an oxygen.

when oxygen combines with this loose hydrogen – 6 water molecules are produced.

In total 32 ATP produced
Step 3: Electron Transport
NADH
NAD
ADP + P
ATP
ADP + P
ATP
ADP + P
FAD
ATP
FADH2
Oxygen
Water (H2O)
CYTOPLASM
RESPIRATION
PROTEINS
GLYCOLOSIS
HAPPENS HERE!
CARBS
(SUGARS)
FATS
(LIPIDS)
AMINO
ACIDS
GLUCOSE
C6H12O6
GLYCOLOSIS
IN CYTOPLASM
NO OXYGEN!
MAKES
2 ATPS
ATP TOTALS
GLYCOLOSIS=2
PYRUVIC
ACID
Krebs + ETC =36
minus 2
Overall =36!
ACETYL-CoA
CO2 IS
RELEASED
O2 ENTERS
HERE
MITOCHONDRIA
RESPIRATION HAPPENS IN
THIS ORGANELLE!
KREBS CYCLE
AND
ELECTRON
TANSPORT
MAKES
36 ATPS
Outcome Of The Three Stages
reading pages 83-84
Tasks
Examine Table 3.3 & 3.32 & 3.4
Quick Check 14 & 15
Biozone pages: 51-52
Anaerobic Respiration
in Some Human Tissue
reading page 89-92
Glucose + 2 ADP + 2Pi









2 ATP + lactic acid
when the body undertakes strenuous short term exercise, in some
tissues (ie muscle) a process called anaerobic glycolysis occurs
does not require oxygen
is a series of reactions in the cytosol
transfers some of the chemical energy in glucose to chemical energy
in ATP
glucose is converted to Pyruvate which in turn is converted into
Lactate
acceptor molecule (NAD) used in process of converting pyruvate
produces a net gain of two ATP molecules for each glucose molecule
produces waste called lactate
Lactate is toxic and in excess causes pain and fatigue in the tissue.
Anaerobic Respiration
To Produce Bread and Beer

anaerobic Respiration in yeasts is called Fermentation.

during fermentation, pyruvate is broken down to carbon dioxide and ethanol
(alcohol).

beer is made by fermenting barley grains.
spirits are made by fermenting:




Vodka – Potatoes
Fruit Juice – Brandy
Molasses – Rum
Glucose + 2 ADP + 2Pi
Tasks
Quick Check 16-18
Biozone 53
2 ATP + ethanol + CO2
What Happens During Starvation?
Reading page 93

animals require a continuous supply of energy and matter for survival

when an animal is starved it uses energy from body tissue.

after glucose is used up, fats and then proteins are used.

during starvation people use up to 97% of fat tissue, 31% of skeletal muscle
and 27% of blood.

when an animal reaches this stage, it is called autophagia (feeding off self).

see fig 3.42 page 93
Tasks
Quick Check 19-20

Students to complete Biochallenge page 96

Students to complete Chapter review
Pg 97 – 99