PSY4130 Chapter Notes - Chapter 8: Diphtheria Toxin, Lipid Bilayer, Egg White
18 Jun 2018
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Molecular Composition of the Cell
The major atomic constituents that make up all biological macromolecules are carbon, hydrogen, oxygen and
hydrogen. The major constituent of every cell is water, which takes up around 70% of the cell’s volume.
Apart from that, there are:
Carbohydrates:
These are used to provide:
• Energy
• Structure: For example, cellulose, which is a polymer of glucose units and provides strength and rigidity in
cell walls. Also, bacterial cell walls are made of modified sugars.
• Cell recognition: Sugars are found on the surface of many cells which allow the cell to be recognised.
There are various types of carbohydrates:
• Monosaccharides: eg. glucose
• Disaccharides: these are basically two monosaccharides bonded together, eg. sucrose, lactose
• Polysacchariddes: these are used to store energy, eg. starch or glycogen which is stored in our liver and
muscles
Lipids:
Lipids are heterogeneous (have various structures). The classification, then, is based on the physiochemical
property of all being hydrophobic, rather than on their structure. They provide:
• Structure: eg. cell membrane (phospholipid bilayer)
• Energy: lipids can be oxidised to produce energy
• Regulatory molecules: such as hormones, which regulate a variety of functions in the cell, especially in
gene control, eg. oestrogen, testosterone
There are many types of lipids, such as fatty acids, triacylglycerol, and cholesterol-based lipids.
Proteins:
These are the most abundant macromolecules in the cell, and they are the molecules by which cells perform
their functions in the whole organism. Although a full set of DNA is present in every cell of the body, only
certain proteins are produced in certain cells depending on what function the cell will carry out. There are a
huge number of different proteins (there are probably over 100,000 unique proteins in the human body), and
this is mainly because proteins are just polymers, made of many units of amino acids. There are 20 different
amino acids, which can combine in any combination to form a protein, and this leads to a large capacity for
diversity in proteins. The order of amino acids determines the shape of the protein, which determines its
function. Proteins perform a variety of biological functions:
• Structural: eg collagen, a protein which provides strength in skin and bones
• Regulatory: eg insulin, a peptide hormone
• Contractile: eg actin and myosin, muscle proteins
• Transport: eg haemoglobin, which carries oxygen around the body
• Storage: eg egg white (albumin)
• Protective: eg antibodies
• Catalytic: eg amylase, an enzyme
• Toxic: eg diphtheria toxin
Nucleic acids:
Nucleic acids are molecules which store and transmit hereditary information (DNA and RNA). They are
polymers of nucleotides (i.e. they are polynucleotides). Each nucleotide is composed of one phosphate
group, one sugar and one nitrogenous base. In RNA, the sugar is a ribose sugar and the bases are C, G, A
and U, while in DNA the sugar is deoxyribose and the bases are C, G, A and T. Nucleotides are bonded
together through a peptide bond, which bonds the phosphate and sugar.
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Document Summary
The major atomic constituents that make up all biological macromolecules are carbon, hydrogen, oxygen and hydrogen. The major constituent of every cell is water, which takes up around 70% of the cell"s volume. Also, bacterial cell walls are made of modified sugars. muscles. The classification, then, is based on the physiochemical property of all being hydrophobic, rather than on their structure. They provide: structure: eg. cell membrane (phospholipid bilayer, energy: lipids can be oxidised to produce energy, regulatory molecules: such as hormones, which regulate a variety of functions in the cell, especially in gene control, eg. oestrogen, testosterone. There are many types of lipids, such as fatty acids, triacylglycerol, and cholesterol-based lipids. These are the most abundant macromolecules in the cell, and they are the molecules by which cells perform their functions in the whole organism.
