Bio 2171 Overview of fuel metabolism and building blocks: 19/2/14 Principle remember – P Outline remember – O Detail remember – D Food Composition - All food we eat contains proteins, carbohydrates and fats in different amounts. E.g. cereals contain more carbohydrates, meat contains more protein. - Also contain small amounts of vitamins and minerals. - The macronutrients (protein, carbohydrates and fat) can all be used as fuels or as building blocks Metabolic strategies (I) - Fuels – macronutrients. - Xenobiotics – toxic things. Cannot avoid eating them as all plants produce toxins to avoid being eaten. E.g. alkaloids – but we can eat domesticated forms of these plants that have less toxins, but they still have some. - First step – digestion and breaking down into monomers, and then transport into the cell o Then they can either be used to make new body components
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Bio 2171 Overview of fuel metabolism and building blocks ... · functional forms e.g. haemoglobin. Building blocks for proteins - All proteins are made from the 20 amino acids. -
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Bio 2171
Overview of fuel metabolism and building blocks: 19/2/14
Principle remember – P
Outline remember – O
Detail remember – D
Food Composition
- All food we eat contains proteins, carbohydrates and fats in different amounts. E.g. cereals
contain more carbohydrates, meat contains more protein.
- Also contain small amounts of vitamins and minerals.
- The macronutrients (protein, carbohydrates and fat) can all be used as fuels or as building
blocks
Metabolic strategies (I)
- Fuels – macronutrients.
- Xenobiotics – toxic things. Cannot avoid eating them as all plants produce toxins to avoid
being eaten. E.g. alkaloids – but we can eat domesticated forms of these plants that have
less toxins, but they still have some.
- First step – digestion and breaking down into monomers, and then transport into the cell
o Then they can either be used to make new body components
o Or break them down and use them as energy. Can also store them as fuels in
between.
- Lastly use oxygen to break these fuels down and generate energy from it. Oxygen is released
in the form of carbon dioxide and water. Allows us to keep going, warm, and is the reason
we breathe.
- Also some fats, carbohydrates and proteins will be used as building blocks in biosynthetic
pathways to make new body components. Some demands to renew organism i.e. skin or to
grow – important for a foetus.
- Whatever is left is released as waste products.
Metabolic strategies (II)
- Organic matter contains a lot of energy – e.g. can burn wood to generate lots of heat.
- However, in organism we do not wish to release all the energy that is generated as heat –
would just burn.
- Metabolism allows us to withdraw energy from organic matter without ‘burning’. The end
point however, is still the same (carbon dioxide and water).
o This is done by taking electrons out of the molecule in small steps (oxidising NAD+ to
NADH) and breaking it down into smaller components – e.g. break down to acetyl
CoA and release carbon dioxide in TCA cycle. Electrons used to generate ATP.
o ATP is energy currency in the body (carbohydrates, lipids and proteins are oxidised
to produce ATP, though a small amount of heat is generated).
o It is used for all the other things that we need to do: active ion transport – important
in the brain (basis of thinking), maintaining body temperature (thermogenesis),
biosynthesis and muscle contraction.
- Energy efficiency is important
- Electrons are stored via oxidising or reducing something – NAD+ is reduced to NADH and is
the electron carrier in the body (stores electrons). ATP is used to store energy.
Metabolic strategies (III)
- Cellular compartmentalisation
o Breakdown occurs in the mitochondria. When oxidising to generate energy, uses
NADH. Largely generates ATP
o Biosytneshsis (lipids, cholesterol, amino acisd and derivates, proteins) occurs in the
cytosol. Synthesis uses NADPH. Largely uses ATP
Overview of metabolism
How to make a cell (building blocks)
- What molecules do we need to make a cell?
- Only need a small handful of ‘building blocks’
- Though need to make a membrane, and membranes around organelles.
- Need to Make DNA, RNA, enzymes and proteins
- Need all these to make a new cell
Membranes
- Made up of phospholipid bilayer.
- Require phospholipids.
- These have polar head group (Ethanolamine, Serine, have phosphate – amino
acid/carbohydrate derivatives) and non-polar fatty acid tails held together by glycerol.
Building blocks for membranes – fatty acids
- Nomenclature – omega three means that there is a double bond three carbons from the end
(not the acid side).
- Not all fatty acids can be synthesised – need to get some of them from nutrition
- More double bonds means lower melting temperature. Steric acid is solid at room
temperature, whereas olive oil is not (has more double bonds).
- Cis fatty acids are found in nature, while trans are not. Trans fatty acids are considered not
very good – associated with diabetes, arterial sclerosis. They are generated during industrial
processing of fats.
Building blocks for membranes – cholesterol
- Cholesterol is an essential component of cell membranes. However high concentrations in
blood are associated with heart disease.
- Derived from fats and lipids
Proteins
- Organisms are mostly proteins – is responsible for giving them shape and form. E.g. hair,
nails.
- Come in different shapes and forms and do lots of different things. Have structural and
functional forms e.g. haemoglobin.
Building blocks for proteins
- All proteins are made from the 20 amino acids.
- Sometimes however these amino acids have to be modified to make the protein
- Grouped into different kinds
o Non polar aliphatic – have sidechains that look like small fatty acids
o Aromatic – have aromatic sidechains
o Polar uncharged – have hydrophilic groups
o Sulphur containing – have sulphur
o Charged amino acids – either have extra positive or negative charge in side chain
- All have same stereochemical configuration (L) and an alpha amino group and alpha carboxyl
group. Some bacteria have other stereochemical configuration.
Titration of amino acids
- At acidic pH, protonate carboxyl group and amino groups (+ve charge).
- As solution becomes more alkaline the carboxyl group is deprotonated as it is quite acidic.
- Eventually, R group may be deprotonated and finally the amino group loses its proton and at
basic Ph, the amino acid has negative charge.
- The alpha amino is always deprotonated about pH 9 (pKa = 9) and the alpha carboxyl group
is usually deprotonated at pH 2 (pKa = 2). However if there are more than one carboxyl
group the pKa will be higher.
- This is very important in enzyme catalysis – charge may or may not be required (as amino
acids vary with pH)
Nucleic Acids
- Whole lot of metabolism behind nucleic acids
- Be aware that they exist – but not dealing with it so much.
Building blocks for nucleotides
- Carbohydrate (ribose), phosphate and the nucleic bases
- Can be synthesised from other materials, but all things we can eat will also contain them.
- Can synthesise with amino acids, carbon dioxide and formic acid.
Carbohydrates as building blocks
- Some lipids contain carbohydrates and nucleotides contain carbohydrates.
- Ribose (carbohydrate) used to build ATP.
- Lactose (disaccharide) required to make breast milk
- Contain lots of hydroxyl groups (where the name carbohydrate comes from)
Carbohydrates are important
- Chondroilin 6-sulfate – found in bone
- Heparin – found in blood
- Hyaluronate – found in cartilage
- Keratan sulphate – found in hair
- Dermatan sulphate – found in skin
o All are polymers of glucose which have been slightly modified (added sulphate) so
that they can bind water and make complex meshes and networks – provide skin
with elasticity.
- Skin is mesh of proteins and carbohydrates that produce structure that binds water, is tear
resistant etc.
Tiny bit of chemistry
Summary
- Food provides the body with energy and building blocks
- Energy is provided by oxidation of nutrient, particularly glucose and fatty acids
- Energy is store as ATP and NADH
- Carbohydrates, fatting acids, AA also form building blocks of all cells.
- The framework of organic chemistry explains the reactivity of biochemical compounds
Carbohydrates and Energy (24/2/14)
Carbohydrates are everywhere – sugars, starch
Carbohydrates in nutrition
- Sucrose – found in fruits. Broken down into sucrose and fructose – sweet
- Lactose – not so sweet, found in milk
- Amylose – contained in starch, subunit. Alpha -1,4 glycosidic bond (O atom points down).
Can digest easily
- Amylopectin – branch in starch. Alpha -1,6- bond. Very frequently used in food industry –
makes food less liquid (solidifies it).
- Cellulose – Beta -1,4- bond (O atom points up). Cannot digest – very small difference in the
conformation of a molecule can change whether it is digestible or not.
Cyclic and linear forms of glucose
- Most glucose present in circular form – < 95%. Other >5% in linear form. Different forms are
in equilibrium.
- In linear form glucose is an aldehyde, which is a reactive molecule due to the partial positive
on the carbon. Means that groups with a free electron pair can add to the aldehyde.
Advanced glyction end products (AGE’s)
- This causes a problem in diabetes, where people have a higher than normal blood glucose
concentration.
- This means that there will be more than normal glucose in the linear chain form – with an
exposed aldehyde group.
- This means there will be more advanced glycation end products (AGE’s) being formed, as the
aldehyde in glucose can react with the amino group in an amino acid (e.g. to an amino acid
in Haemoglobin) to produce a Schiff base which creates a glycated haemoglobin – called an
AGE which can lead to protein cross linking.
- The measure of glycated haemoglobin is an indicator for the severity of diabetes in people,
and they are indicated to cause some of the side affects of diabetes – such as glucose
reacting with blood vessels of cells and cause vascular problems i.e. vascular sclerosis and
other things – cataracts.
- So high blood glucose can cause damage to cells over long periods of times – uncontrolled
levels of glucose in the blood is bad, as it will eventually result in these problems. (glucose is
a reactive molecule and can cause protein modification if the concentration is sufficiently
high).
Overview of energy production from glucose
- Energy is made in biological systems is via glycolysis, the TCA and then the electron transport
chain – energy is made by extracting electrons.
- Overall energy of the reaction of burning glucose can be obtained using a bomb calorimeter
(2800kJ/mol)
- In biological system burning is not useful – want ATP and NADH (takes out electrons) as we
can do work with it.
- Want to get the energy out in bits and pieces (this is what these two molecules do).
Major questions:
What is the role of ATP?
What is the role of NADH?
Tim tams slide?
- Energy required is dependant upon what activity a person is undertaking?
Energy flow in chemical reactions
- If ΔG is negative – will accumulate products – backwards reaction will not be spontaneous. If
ΔG is positive, will accumulate reactants – forward reaction will not be spontaneous.
- If ΔG is zero, reaction will be at equilibrium
- ΔG – any change of free energy
- ΔG0 – change of free energy starting with concentrations of 1M.
- ΔG0’ – change of free energy under biochemical conditions (250C, pH 7.0, water 55.5M).
Free energy and equilibrium (I understand this right?)
- If we have more products than substrate at equilibrium (high equilibrium constant), than will
have greater free energy (maxiumum amount of work that can be obtained from the
reaction).
- Equilibrium is directly correlated to the amount of energy that can be made in a biochemical
system.
Thermodynamics vs. kinetics
- The ΔG represents the amount of energy that can be made from the reaction. It is the net
energy change in the reaction.
- The ΔG does not say anything about the speed of a reaction – the activation energy
determines the speed.
- The activation energy must be overcome for the reaction to proceed
- E.g. Tim tams have lots of energy, but it does not combust spontaneously as its compounds
are quite stable – requires an enzyme to reduce the activation energy to break it down.