CHAPTER 6
Metabolism
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Cells differ in shapes and sizes
They carry out chemical processes that keep the organism alive.
All the chemical processes or reactions occurring in a living organism is made up of 2
different chemical reactions.
o Catabolism-> breaks down molecules
o Anabolism-> building up molecules
Organic compounds
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Substances in metabolism are organic
Organic compounds always contain:
o Carbohydrates
o Amino acids
o Proteins
o Lipids
o Nucleic acid
Inorganic compounds do not contain carbon and if they do they have VERY small molecules
of carbon dioxide.
o Water
o Oxygen
o Carbon dioxide
o Minerals
Carbohydrates
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Are sugars
Always contain carbon, hydrogen and oxygen
Always x2 as many hydrogen atoms as oxygen atoms
Provide energy for body cells
Monosaccharides
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Simple sugars or single-unit sugars; e.g. glucose, fructose and galactose.
Disaccharides
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Two simple sugars joined together; e.g. sucrose, maltose and lactose
Polysaccharides
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Large number of simple sugars joined together; e.g. glycogen, cellulose and starch.
Protein
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Always contain carbon, hydrogen, oxygen and nitrogen, often sulphur and phosphorus.
Made of large number of smaller molecules, amino acids.
About 20 amino acids e.g. glycine, alanine, valine and glutamic acid.
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Bond between amino acids is called a peptide bond.
Two amino acids joined by a peptide bond is a dipeptide
Ten or more amino acids joined is a polypeptide.
Proteins consist of 100 or more amino acids.
Each protein chain of amino acids is folded in a unique way.
Proteins are important structural materials in body.
Enzymes= proteins .˙. proteins are involved in all the chemical reactions of the body.
Nucleic acids
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Large molecules
Made of carbon, hydrogen, nitrogen and phosphorus
Made up of nucleotides
o Nitrogen base
o Sugar
o Phosphate
Main types of nucleotides
o Ribonucleic acid (RNA)
o Deoxyribonucleic acid (DNA)
RNA carries information from the DNA in the nucleus to parts of the cell where proteins are
made.
Lipids
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Contain carbon, hydrogen and oxygen, much less oxygen than the amount of oxygen in
carbohydrates.
Example of lipids
o Fats; stored in the body as energy reserves
o Phospholipids; important in cell membranes
o Steroids; cholesterol and in sex hormones
Each fat molecule is made of 1glycerol molecule and 1, 2 or 3 fatty acid molecules.
Type of fat stored in the body (98% of fat in foods) is triglyceride – glycerol + 3 fatty acids.
DNA
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Consists of 2 chains of nucleotides that contain the sugar deoxyribose.
DNA is the genetic material in the nucleus that stores inherited information.
o AT-CG-TA-GC
RNA
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Consists of a single chain of nucleotides that contain the sugar ribose.
RNA carries information from the DNA in the nucleus to parts of the cell where proteins are
made.
Enzymes
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Proteins used by cells to lower activation energy of a reaction.
o Active site – site on enzyme surface where reactant fits
o Binding site – site on reactant that binds to enzyme
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Enzyme only speeds up its reaction.
Enzyme + substrate -> enzyme – substrate complex -> enzyme + products
Reactant and products
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Exergonic – products contain less energy than reactants.
Endergonic – products contain more energy than reactants.
Activation energy – extra energy required to destabilise chemical bonds and initiate a
chemical reaction.
Factors affecting enzyme activity
It may alter the enzymes 3-dimensional shape.
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Concentration of enzyme
Substrate concentration
Removal of product
Temperature
PH
CO. factors
Concentration of enzyme and substrate
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Higher the concentration of the enzyme, the faster the rate of chemical reaction.
Increasing substrate concentration also increases the rate of the reaction.
Enzyme and temperature
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Temperature rise = enzymes work faster
Heat destroys the special shape of the protein chain and the substrate doesn’t fit.
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Work best at certain PH
Optimum at 7 (neutral) some prefer acid (low PH), some prefer alkaline (high PH).
PH
CO. factors
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Ions or non-protein molecules which help to catalyse a reaction.
CO enzyme – non-protein organic molecule acting as a CO. factor. E.g. Vitamins
Enzyme inhibitors
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Slow or stop enzyme activity
Can control reactions
Many drugs are inhibitors
o Penicillin inhibits enzyme in bacteria that is involved in construction of the cell wall.
Cellular respiration
Glucose + Oxygen -> Carbon dioxide + water + energy
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Simplified takes place>20 separate reactions
Intermediate compounds formed, catalysed by different enzymes. Controlled release of
energy.
o Glycolysis (lysis means breakdown)
-> anaerobic
o Krebs cycle
->aerobic
o Electron transport system
->aerobic
Energy
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Glucose breakdown results in 60% heat (maintains constant body temp).
Remaining energy is used to form ATP.
ATP is formed when an inorganic phosphate group is joined to molecule of ADP.
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ADP is reused.
ATP is a way of transforming energy to cell processes.
ATP CYCLE
Anaerobic Respiration
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Glycolysis – occurs in the cytosol (anaerobic respiration enzymes located there)
Glucose -10 steps-> 2 pyruvic acids + 2 ATP
-no O2 available-> lactic acids -> travels to liver + O2 (produces glucose and
glycogen)
Aerobic respiration
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Occurs in the mitochondria (where the folded inner membrane has a higher surface area –
contains enzymes needed for aerobic respiration).
Aerobic respiration creates 6CO2, 6H2O and heat as products.
Pyruvic acid -enters mitochondria
 Krebs cycle ->2 ATP
 Electron transport system ->34 ATP
Energy use by the cell
Cells need energy that is temporarily stored in ATP molecule.
Synthesis
Process of combining of small molecules to make larger molecules <- same as anabolism.
Cells at work
Water- Most valuable item
Vitamins- compounds that com in either fat soluble or water-soluble form
-Vitamin C-> improves iron absorption
-Vitamin K-> crucial to blood clotting
-Vitamin B-> important in the production of ATP from glucose
Minerals- Calcium. Magnesium and Phosphorus –> harden bone
-iron-> crucial part of haemoglobin
-potassium, sodium and chlorine -> maintain your body’s PH balance
Carbohydrates- monosaccharides -> simple sugars
-disaccharides -> big lots of simple sugars
-polysaccharides -> starches from vegies or grains
-glucose -> (monosaccharide) essential in ATP production
-Catabolize -> turning ATP to glucose
Lipids- stored in the adipose, used for the phospholipids, myelin…
Proteins- Muscles, connective tissue and ion channels. MAKE ENZYMES!