Option: B Biochemistry
Title: Lesson 1 B.1 Introduction to Biochemistry
Learning Objectives:
– Understand how the functions of biological molecules depend on their
structures and shapes
– Know what catabolism and anabolism reactions are
Introduction to Biochemistry Video
What is Biochemistry?
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It is the study of chemical processes in living cells at a molecular level
It is generally agreed that life began in an aqueous environment
The key event was the development of a membrane what enclosed and
defined a cell
Within a cell, specific conditions such as temperature, pH, and chemical
concentrations can be generated and controlled
Cells carry out all the life processes
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Metabolism - Exergonic and Endergonic Video
Metabolism
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Metabolism Part 1
Metabolism Part 2
At any one time, thousands of chemical reactions occur
The sum of all these reactions within the organism is the metabolism
Reactions are controlled in sequences and cycles known as metabolic
pathways. The product of each step is the reactant for the next.
Compounds taking part in metabolism are known as metabolites
Each reaction is controlled by a specific catalyst called an enzyme
Reactions can be coupled so that energy from one reaction can drive
another
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Anabolism and Catabolism
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The part of metabolism concerned with building or synthesising is known as anabolism
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Then part of metabolism concerned with breakdown or degradation is known as catabolism
Reactants
The energy from catabolic
reactions is used to drive
anabolic reactions.
Products
Energy rich
Releases
energy
Requires
energy
Products:
Energy poor as there is a release of energy
Reactants
This is known as energy
coupling.
This involves an intermediary
energy carrier called ATP
(adenosine triphosphate)
Anabolic and catabolic processes take place simultaneously, but a separately controlled due to the different
pathways.
Without separate pathways, stable structures would not exist, as they would be broken down as they form. This
would be known as futile cycles.
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Biomolecules are diverse organic molecules (present in
living things)
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Only 27 elements have been found to be essential components of living things
These are found in very small amounts or trace elements
96% by mass of cells is made up of hydrogen, oxygen, carbon, and nitrogen
Sulphur, phosphorous, calcium and iron are also significantly present
Macromolecules have a molecular mass of several thousand
Despite size and complexity, we can describe macromolecules in terms of
small units (linked by covalent bonds)
Most macromolecules are polymers so each unit is a monomer (e.g.
glucose and amino acids)
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Condensation and hydrolysis reactions
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Biopolymers are condensation polymers, because their synthesis involves the loss of
a molecule of water between two monomers
In order to form a polymer, the monomers must have two functional groups or ‘two
active ends’
The loss of a water molecule allows the monomers to ‘link hands’
The reaction is catalyzed by enzymes (known as polymerases)
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The breakdown of these molecules reverses this
reaction – Hydrolysis!
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Breakdown of a polymer into monomers will add a water molecule for each
covalent bond broken
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An example of hydrolysis is chemical digestion
Hydrolysis is also catalyzed by enzymes
Reactions may be favoured by heat, acidic or alkaline conditions
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Other examples of condensation and hydrolysis
reactions
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Synthesis and breakdown of proteins from amino acids
Synthesis and breakdown of polysaccharides from sugars
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The activity of biological molecules is dependent on
their structures and shapes
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There is a relationship between molecular shape and function
E.g. molecules are chosen for their task based on chemical nature and 3D
shape
Examples:
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Collagen and cellulose – tough and soluble
Insulin hormone – interacts specifically with receptor molecules
Enzymes – form a temporary biding to their substrate
Nucleic acids – able to store and transmits genetic information using chemical
sequences
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Living things transform energy
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Living things absorb energy from their environment
Energy is used to synthesise their own complex structures from simple
starting molecules
Energy can also be used for functions such as movement and reproduction
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As energy is used in life processes, most is returned to the environment as
heat
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Examples of living things transforming energy include photosynthesis and
respiration
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Photosynthesis
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Converts light energy into chemical energy
Green plants capture solar energy and use it to synthesise energy
rich biomolecules
No photosynthesis = no life on Earth!
Absorption of light by photosynthetic pigment (e.g. chlorophyll)
Light energy drives a series of redox reactions, where water is
split into hydrogen and oxygen
Oxygen is released as waste, hydrogen ultimately reduces carbon
dioxide to simple sugar molecules.
Photosynthesis transforms energy-poor carbon dioxide into
energy-rich sugar.
Multiple arrows indicate a series of
reactions in between!
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What is respiration?
Respiration is the process by which organisms extract the
energy stored in complex molecules and use it to generate
adenosine triphosphate (ATP).
In this way they obtain energy to fuel their metabolic pathways.
ATP provides the
immediate source of
energy for biological
processes such as active
transport, movement and
metabolism.
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ATP
© Boardworks Ltd 2009
Respiration
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Makes energy available for life processes
Living things obtain energy-rich molecules such as glucose through photosynthesis (plants) or intake of food
(animals and some plants)
Release of energy is controlled inside cells through respiration
Respiration often likened to burning a fuel in oxygen, though is much more complex and
controlled:
Burning/Combustion
Cellular Respiration
Exothermic
Exothermic
Oxidation
Oxidation
Amount of energy released dependent on Amount of energy released dependent on
extent of oxidation
extent of oxidation
Takes place at high temperatures
Takes place in normal temperatures
Chemical process
Biological process
Fast
Slow
Produces H2O and CO2
Produces H2O and CO2
Requires energy-rich molecules
Requires energy-rich molecules
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Types of respiration
During aerobic respiration, a respiratory substrate, e.g.
glucose, is split in the presence of oxygen to release carbon
dioxide and water. A large number of ATP molecules are
produced, releasing the energy from the glucose.
C6H12O6 + 6 O2  6 CO2 + 6 H2O + 36 ATP
In anaerobic respiration, glucose is converted (in the absence
of oxygen) to either lactate or ethanol. The ATP yield is low.
C6H12O6  2 C2H5OH + 2 CO2 + 2 ATP
ethanol
C6H12O6  2 C3H6O3 + 2 ATP
lactate
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© Boardworks Ltd 2009
Stages of respiration
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Up to 50 different chemical reactions (each controlled by
a specific enzyme)
Different metabolites can be used as respiratory
substrates, but usually they are first converted to glucose,
C6H12O6
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1st stage of respiration – glycolysis
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Common to all cells, does not use oxygen (anaerobic conditions)
Only a small amount of energy is released (enough to keep some
cells alive), most is trapped in the products in this stage
Lactate and ethanol are examples of energy-rich products from this
stage
Later stage - In the presence of oxygen (aerobic conditions)
 Oxidation of glucose is complete, much more energy is released
 Carbon dioxide and water are examples of energy-poor products
of this reaction
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• Aerobic respiration involves a series
of coupled redox reactions.
• Reactants known as cytochromes
are successively reduced and reoxidized.
• Oxygen is the terminal electron
acceptor when reduced to water.
An overview of respiration
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© Boardworks Ltd 2009
Summary of photosynthesis and respiration
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Both are metabolic redox processes
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Photosynthesis  anabolic, energy storing process, reduces
carbon dioxide to sugar
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Respiration  catabolic, energy yielding process, oxidises
sugar to carbon dioxide
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Overall they are the reverse of each other, but it does not
involve a reversal of the chemical steps…
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Photosynthesis – carbon sink (removes carbon dioxide
from the atmosphere)
Respiration – carbon source (releases carbon dioxide into
the atmosphere)
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Solutions
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