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Amino Acids and Proteins B.2. there are about 20 amino acids that occur naturally they are the basic “building blocks” of life/proteins.

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Presentation on theme: "Amino Acids and Proteins B.2. there are about 20 amino acids that occur naturally they are the basic “building blocks” of life/proteins."— Presentation transcript:

1 Amino Acids and Proteins B.2

2 there are about 20 amino acids that occur naturally they are the basic “building blocks” of life/proteins


4 Draw the general formula of 2-amino acids (2- because both functional groups are attached to the second carbon) NH 2 CHRCOOH


6 Properties of 2-amino acids (B.2.2) Zwitterion (dipolar) – amino acids contain both acidic and basic groups in the same molecule therefore, are amphoteric (capable of behaving as acids or bases) in nature – amines can accept a proton – carboxylic acids can donate a proton



9 Buffers – buffer solution the pH of the solution is "resistant" to small additions of either a strong acid or strong base used as a means of keeping pH at a nearly constant value – the amphoteric nature of amino acids makes it possible for them to act as buffers in aqueous solutions when in a strong acid, H + is added to an amino acid (the zwitterion accepts the proton) thus minimizing the effect of the acid added if in a strong base, the zwitterion donates H + to neutralize the base (OH - ) to form water

10 Isoelectric point – Kahn academy video (5:25) Kahn academy video (5:25) – the isoelectric point is the pH value at which the negative and positive charges are equal this is unique for each a.a. at a certain pH – used to separate proteins in a process called electrophoresis

11 Condensation Reactions in order to form polypeptides (B.2.3) amino acids will link together to form polypeptides (proteins) enzymes are necessary! the link/bond is between carboxyl group on one a.a. and the amino group on the other water is formed and remaining N and C link together with a peptide bond peptide bonds YouTube (1:14)





16 Primary Structure determined by the number, kind, and order of a.a. in the polypeptide. held together by simple peptide bonds. Proteins have a complex structure which can be explained by defining four levels of structure (B.2.4) What is a protein video 3:38


18 Secondary Structure Two types of spontaneously, regular, repeating structures as the polypeptide is made 1.alpha helix – a coil or zigzag shape that results from the hydrogen bonds along the strand

19 2.beta pleated sheets – back and forth folding of polypeptides because of hydrogen bonds between adjacent polypeptides or in the same strand

20 Tertiary Structure highly specific looping and folding of the polypeptide because of the following interactions between their R-groups: –covalent bonding-- disulfide bridges formed when two cysteine amino acids combine due to sulfur in their R groups –hydrogen bonding-- between polar groups on the side chain –ionic attractions-- formed between polar side groups –van der Waal’s attractions-- between non-polar side groups this tertiary level is the final level of organization for proteins containing only a single polypeptide chain


22 Quaternary Structure linkage of two or more polypeptides to form a single protein in precise ratios and with a precise 3-D configuration. some proteins have a prosthetic group (a non-peptide) – these proteins are called conjugated proteins ex. hemoglobin John Kyrk protein folding Protein folding

23 Quaternary Structure example


25 Analysis of Proteins (B.2.5) there are various analytical techniques that can be used to identify proteins and amino acids main two are: 1.paper chromatography 2.electrophoresis

26 Paper Chromatography break peptide bonds in the protein and obtain constituent a.a. – (use 6 M HCl, 110°C) place sample spot on paper and set paper in solvent amino acids separate based on polarity calculate R f value and compare to amino acids with know values


28 Electrophoresis this technique separates charged molecules based on their ability to migrate when an electric field is applied to the system sample is placed in a gel and electricity applied different a.a. will move at different rates towards a (+) or (-) electrode will stop at different distances – this is its isoelectric point where a particular a.a. will not move as its charges are balanced – distances can then be compared with known values for identification

29 Protein Functions (B.2.6) Structure – fibrous proteins provide structure and strength ( muscle, cartilage, skin, bones, hair) Transport – hemoglobin in the red blood cells is vital in carrying oxygen Hormones – have a regulatory effect on specific cells/organs in the body Immunoproteins – play a key role in the fight against infection (antibodies) Energy Storage – play an important role in the human body as energy storage Enzymes – catalyze biochemical reactions (1000’s) within the body

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