This course forms part of many of our more advanced diplomas such as health science advanced diplomas that can be used towards degree programs.
Students enrolled in this course will learn to explain a range of common biochemical processes with an emphasis upon animal and human biochemical processes ranging from gluconeogenesis to nucleotides metabolism and much more. Of course, being part of ACS distance education program, you have the luxury of studying biochemistry at your own pace and in your own home. Take part of this intriguing journey by enrolling now.
- Introduction
- What is metabolism?
- Cell components
- Energy, ATP, oxidation - reduction.
- Glycolysis and Glycogen Metabolism
- What is glycolysis?
- The phases of glycolysis, pyruvate, glycogen and more
- Movement through Membranes
- Transport mechanisms
- Different types of cellular transport.
- Electron Transport and Oxidative Phosphorylation
- Oxidative phosphorylation, citric acid cycle and more.
- Sugar and Polysaccharide Metabolism
- Gluconeogenesis, pentose phosphate pathway and more.
- Lipid Metabolism
- Beta oxidation
- Unsaturated fatty acid oxidation
- Ketone bodies
- Biosynthesis of fatty acids and more.
- Amino Acid Metabolism
- Transamination
- Amino acid catabolic processes
- The urea cycle and biosynthesis.
- Nucleotide Metabolism
- Synthesis and regulation
- Nucleotide degradation
- Purines
- Nucleotide co-enzymes etc.
- Enzyme Activity
- Classification and kinetics, regulation etc.
- Other Processes
- Hormones
- Neurotransmitters and signal cascades and more.
Understanding Metabolism within the Cell
Metabolism within the cell encompasses all those reactions that break up the simpler molecules (monomers) into very small molecular units (intermediates) that are needed to build up cellular components.
The metabolic processes within are cell are closely linked. In many biochemical processes, the by-product of one metabolic process (intermediate) is directed towards another process where it can be re-used. Similarly, converted energy from one process is transferred by cofactors for use in other processes within the cell. Hormones often control these processes.
For this energy to be transferred within the cell, it must be transferred across membranes. This phenomenon is known as electron transport and is carried out by a chain of cofactors.
Catabolic metabolism
Catabolic processes are the breaking down of sugars, proteins and fats (lipids) to form simpler compounds and release energy. For example, during glycolysis glucose is broken down to form two molecules of pyruvate (or pyruvic acid) and exacts a net gain of energy in the form of ATP and NADH. Pyruvate is broken down further by the citric acid cycle, which takes place in the mitochondria. Similar processes occur via several biochemical pathways.
Anabolic metabolism
Anabolic metabolic processes are typically the reverse of catabolic processes, with the difference being the inclusion of a different enzyme or electron transfer system into the process. Anabolic processes build up complex molecules that become part of cells or perform as communication and transport elements in the body. Examples of anabolic pathways include gluconeogenesis, amino acid synthesis and glycogen synthesis.
Energy exchanges
All metabolic processes in living beings occur only when there is an exchange in energy between the reactants. In catabolic processes the energy accumulated in larger molecules in the form of chemical bonds is released when the molecules break down. This energy is then transferred to intermediary molecules which carry it to other metabolic processes, generally building up processes (anabolism).
Thus the energy is not created or destroyed, but only transferred. Energy is then transferred between exergonic processes, that release energy while chemical bonds break down, and endergonic processes, that take up the energy while new bonds are created.
Free energy
All organized living materials – organic matter – possess energy stored within the chemical bonds that keep the matter together.
Free energy (Gibbs energy of G) is the energy released when a high energy reactant A is converted to lower energy reactant B. Free energy exchange is measured by the energy change in the reactants and end products. Free energy is quantified as the difference between the initial energy state and the final energy state. Therefore it is expressed as a differential Δ.
ΔG= Gfinal – Ginitial
Biochemical processes can only proceed when energy is released. Thus they can only happen when the net energy exchange or ΔG is negative: if G final is smaller than G initial, then the above equation would be at the end of the process negative. These are called exergonic processes, as they release energy. They are spontaneous, as they tend to happen naturally.
When a metabolic process has a final G that is bigger than the initial free energy, it cannot proceed naturally. It is called an endergonic process and it will need an external source of energy to happen. Thus cells couple spontaneous processes (exergonic) with non-spontaneous processes (endergonic) in terms for those non-spontaneous processes to have enough energy to proceed.
Another way for these processes to happen is with the help of molecules that lower the energy requirements of the reaction. This role is performed by enzymes, and that is the reason why they are so important.
Enthalpy
The amount of energy that a substance, molecule or whole being, possesses, and the energy that the substance or body can release as energy (as movement, position change, chemical change) is called enthalpy. Enthalpy cannot be measured directly; instead what is measured is a change (increase or decrease) in enthalpy. Enthalpy is thus defined as:
H = E + PV
Where H= Enthalpy, E= Energy, P=Pressure and V=Volume.
In biochemical systems in general pressure and volume are constant, so Enthalpy is equalled to Energy. When a system reacts, lives, moves, enthalpy changes, and that is what we can measure:
ΔH = Hf - Ho
(Enthalpy change equals final Enthalpy minus initial Enthalpy)
Entropy
All living matter is a set of organized molecules that interact constantly with each other. To maintain life, that is, organization at all levels (atomic, molecular, cellular, tissues, organs, whole beings) energy is required. Life is thus an energy-using mechanism. When the sources of energy stop or decrease, living matter tend naturally to disorganization. The state of maximal disorder is called maximal entropy.
Entropy is therefore a measure of the organization of living matter. The more energy an organism has (the more ‘alive’ it is), the less entropy it has.
LEARN ABOUT OXIDATIVE PHOSPHORYLATION
Electron transport and oxidative phosphorylation are, in effect, parts of the same biochemical process. Oxidative phosphorylation is the process where the phosphorylation is actually associated with electron transport. It takes place in the inner membrane of the mitochondria. It involves a series of complexes. ADP joins with inorganic phosphate to give ATP and water. The way the actual reaction occurs is yet to be clearly understood, however, it is known that the proton gradient established as electrons move from NADH to O 2 in the electron transport chain is what results in the phosphorylation of ADP to ATP. This is the Chemiosmotic Hypothesis . The synthesised ATP is then aided out of the mitochondria with the help of an intrinsic membrane protein called the adenine nucleotide translocator; this protein transports ADP to the inside and ATP to the outside.
UNDERSTAND THE PENTOSE PHOSPHATE PATHWAY
In cells the most widely used reducing agent is NADPH which donates electrons in reductive biosynthesis such as fat metabolism. NADPH is produced by the pentose phosphate pathway, which also generates intermediates for incorporation into glycolysis. The pentose phosphate pathway is predominantly active in adipose (fat) cells.
NADPH is produced by the first few reactions of the pentose phosphate pathway, when glucose 6-phosphate is converted to 6-phosphoglucono-d-lactone by the enzyme glucose 6-phosphate dehdrogenase and again by conversion of 6-phosphogluconate to ribulose 5-phosphate by 6-phosphogluconate dehydrogenase. Ribulose 5-phosphate is then converted to ribose 5-phosphate by phosphopentose isomerase.
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