A Level Biology - Energy for Biological Processes

A Level Biology
MAKING SENSE OF
Icons CC – The Pink Group
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Copyright © 2016 Henry Exham
• This topic covers two major biochemical
processes: respiration and photosynthesis.
• In photosynthesis, plants produce their own food
source using the energy from the sun.
• In respiration the energy in food is transferred to
a molecule called ATP which can be used by living
cells to carry out the millions of metabolic
processes they need to do in order to function
normally.
2
Energy for Biological Processes
Introduction

A Level Biology
MAKING SENSE OF
5.1 Aerobic Respiration
5.2 Glycolysis
5.3 Link Reaction and Krebs Cycle
5.4 Oxidative Phosphorylation
5.5 Anaerobic Respiration
5.6 Photosynthetic Pigments
5.7 Photosynthesis
3

• Can you explain that cellular respiration yields
ATP which is used as a source of energy for
metabolic reactions, and the process also
generates heat?
• Are you able to outline the different stages in
aerobic respiration, including:
– glycolysis in the cytoplasm
– link reaction
– Krebs cycle
– oxidative phosphorylation in mitochondria.
4
Objective Questions

• The basic unit of life is a cell.
• In order for a cell to carry out the many metabolic
processes it does it needs energy.
• This energy comes from the chemical bonds in
food molecules.
• This energy is transferred to a molecule called
ATP (adenosine triphosphate) which is then used
for all the cell’s processes.
• Cellular respiration is the process which takes the
energy from food and turns it into ATP.
5
Introduction

• What you should know already is that there
are two types of cellular respiration:
6
Revision

• You should already know the basic summary
equation for aerobic respiration:
7
Revision

• You should also keep in mind the following
basic points:
– This reaction is exothermic (gives out heat)
– The food substance that is broken down is known
as the respiratory substrate. It is most often
glucose but can be other molecules.
8
Basics

• Here is a molecule of ATP.
• There is energy stored in the bonds.
• If you break the covalent bond between the last
two phosphates it releases some energy that the
cell can use.
• This is catalysed by the enzyme ATPase.
9
ATP
Adenine
Ribose
P P P

• However, this reaction is reversible and you can
use the energy from food to ‘recharge’ the ATP
just like a recharging battery. 10
ATP
Adenine
Ribose
P P P
Adenine
Ribose
P P Pi
ATPase
Energy
ATP
ADP

11
ATP
Adenine
Ribose
P P P
Adenine
Ribose
P P P
ATPase
ATPase
ATP
ADP

12
ATP
Try this link to see
more about ATP

• In reality aerobic respiration is a series of reactions.
• Most of which occur in the mitochondria.
13
Aerobic Respiration Summary
Glycolysis Link Reaction
Electron
Transport Chain
Krebs Cycle

• Most of the ATP is made through a series of oxidation
and reduction reactions that occur in the final stage of
the process at the electron transport chain.
14
Oxidation and Reduction
Lose electrons
(Remove hydrogen
or add oxygen )
Gain electrons
(Add hydrogen or
remove oxygen)

• You can remember this easily by
thinking OIL RIG (Oxidation is loss,
reduction is gain).
15
OIL RIG
Lose electrons
(Remove hydrogen
or add oxygen )
Gain electrons
(Add hydrogen or
remove oxygen)

A Level Biology
MAKING SENSE OF
5.2 Glycolysis
5.3 Link Reaction and Krebs Cycle
5.4 Oxidative Phosphorylation
5.5 Anaerobic Respiration
5.6 Photosynthetic Pigments
5.7 Photosynthesis
16

• Do you understand the conversion of
monosaccharides to pyruvate during glycolysis
in the cytoplasm, including:
– The phosphorylation of hexose molecules by ATP
– breakdown to glycerate 3-phosphate (GP)
– production of reduced coenzyme (NADH) and ATP
(details of intermediate compounds and other
reactions are not required).
17
5.2 Glycolysis
Objective Questions

18
5.2 Glycolysis
Aerobic Respiration Summary
Glycolysis Link Reaction
Electron
Transport Chain
Krebs Cycle
This splits the respiratory substrate
(glucose).
This happens in the cytoplasm of a cell and
doesn’t require any oxygen

19
5.2 Glycolysis
Glycolysis
6C Sugar
P
P
This means phosphates are added
2 x ATP
2 x ADP + Pi
glycerate 3-phosphate (GP)
This means splitting
P
P
2 x 3C Sugar
2 x Pyruvate
4 x ATP
4 x ADP + Pi
2 x NAD+ (coenzyme)
2 x NADH
The NADH will go to the
electron transport chain
which is explained later
Two ATPs are actually used
in phosphorylation
The phosphates are added
to the glucose
Then the 6C molecule is
split into two 3C molecules
These are then converted
to pyruvate
Two ATPs are made from
each 3C sugar so four are
made overall at this stage.
NAD+ also known as
coenzyme is reduced to make
NADH which means that it
gains 2 electrons and 2
hydrogens. This will be
explained in more detail later.
So overall 2ATPs and
2NADH are made in
Glycolysis
The pyruvate will now go
into the link reaction

20
End of Sample
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A Level Biology - Energy for Biological Processes

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A Level Biology - Energy for Biological Processes