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1 of 29© Boardworks Ltd 2008 Haggerston School Biology A-Level
2 of 29© Boardworks Ltd 2008 All truths are easy to understand once they are discovered; the point is to discover them. Galileo Galilei
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5 of 29© Boardworks Ltd 2008 Introducing proteins Proteins are a diverse group of large and complex polymer molecules, made up of long chains of amino acids. They have a wide range of biological roles, including: structural: proteins are the main component of body tissues, such as muscle, skin, ligaments and hair catalytic: all enzymes are proteins, catalyzing many biochemical reactions signalling: many hormones and receptors are proteins immunological: all antibodies are proteins.
6 of 29© Boardworks Ltd 2008 The general structure of amino acids All amino acids have the same general structure: the only difference between each one is the nature of the R group. The R group therefore defines an amino acid. amino group carboxylic acid group R group The R group represents a side chain from the central alpha carbon atom, and can be anything from a simple hydrogen atom to a more complex ring structure.
7 of 29© Boardworks Ltd 2008 The 20 naturally-occurring amino acids
8 of 29© Boardworks Ltd 2008 Peptide bonds and dipeptides
9 of 29© Boardworks Ltd 2008 Peptides
10 of 29© Boardworks Ltd 2008 Polypeptides When more amino acids are added to a dipeptide, a polypeptide chain is formed. A protein consists of one or more polypeptide chains folded into a highly specific 3D shape. There are up to four levels of structure in a protein: primary, secondary, tertiary and quaternary. Each of these play an important role in the overall structure and function of the protein.
11 of 29© Boardworks Ltd 2008 The structure of proteins
12 of 29© Boardworks Ltd 2008 Protein structure
13 of 29© Boardworks Ltd 2008 Bonds in proteins The 3D shape of a protein is maintained by several types of bond, including: hydrogen bonds: involved in all levels of structure. hydrophobic interactions: between non-polar sections of the protein. disulfide bonds: one of the strongest and most important type of bond in proteins. Occur between two cysteine amino acids.
14 of 29© Boardworks Ltd 2008 Fibrous proteins Fibrous proteins are formed from parallel polypeptide chains held together by cross-links. These form long, rope-like fibres, with high tensile strength and are generally insoluble in water. collagen – the main component of connective tissue such as ligaments, tendons, cartilage. keratin – the main component of hard structures such as hair, nails, claws and hooves. silk – forms spiders webs and silkworms cocoons.
15 of 29© Boardworks Ltd 2008 Globular proteins Globular proteins usually have a spherical shape caused by tightly folded polypeptide chains. The chains are usually folded so that hydrophobic groups are on the inside, while the hydrophilic groups are on the outside. This makes many globular proteins soluble in water. enzymes – such as lipase and DNA polymerase. hormones – such as oestrogen and insulin. transport proteins – such as haemoglobin, myoglobin and those embedded in membranes.
16 of 29© Boardworks Ltd 2008 Denaturing proteins If the bonds that maintain a proteins shape are broken, the protein will stop working properly and is denatured. Changes in temperature, pH or salt concentration can all denature a protein, although the specific conditions will vary from protein to protein. Fibrous proteins lose their structural strength when denatured, whereas globular proteins become insoluble and inactive. denaturation: bonds broken
17 of 29© Boardworks Ltd 2008 Biuret test for proteins
18 of 29© Boardworks Ltd 2008 Proteins: true or false?
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20 of 29© Boardworks Ltd 2008 Introduction to lipids Lipids are a diverse group of compounds that are insoluble in water but soluble in organic solvents such as ethanol. The most common types of lipid are triglycerides (sometimes known as true fats or neutral fats), but other important lipids include waxes, steroids and cholesterol. Like carbohydrates, lipids contain carbon, hydrogen and oxygen, but they have a higher proportion of hydrogen and a lower proportion of oxygen.
21 of 29© Boardworks Ltd 2008 The structure of triglycerides
22 of 29© Boardworks Ltd 2008 Saturated and unsaturated
23 of 29© Boardworks Ltd 2008 Role of lipids Lipids are stored in adipose tissue, which has several important roles, including: The major biological role of lipids is as an energy source. Lipids provide more than twice the amount of energy as carbohydrates – about 38 kJ/g. heat insulation – in mammals, adipose tissue underneath the skin helps reduce heat loss. protection – adipose tissue around delicate organs such as the kidneys acts as a cushion against impacts.
24 of 29© Boardworks Ltd 2008 The structure of phospholipids
25 of 29© Boardworks Ltd 2008 Emulsion test for lipids
26 of 29© Boardworks Ltd 2008 Components of lipids
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28 of 29© Boardworks Ltd 2008 Glossary
29 of 29© Boardworks Ltd 2008 Whats the keyword?
30 of 29© Boardworks Ltd 2008 Mystery substance
31 of 29© Boardworks Ltd 2008 Multiple-choice quiz
Proteins Carbohydrates Lipids Water Edited by Janet A Renshaw School of Biological Sciences.
1 of 30© Boardworks Ltd 2008 Haggerston School Biology A-Level.
1 Biochemistry of Cells Copyright Cmassengale. 2 Uses of Organic Molecules Americans consume an average of 140 pounds of sugar per person per year Cellulose,
Unit 1 Cell and Molecular Biology Section 4 Molecules.
AS Biology Biological molecules. OBJECTIVES All should : be able to describe the structure of a water molecule,the H bonds that hold them together & and.
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Copyright © 2009 Pearson Education, Inc. PowerPoint Lectures for Biology: Concepts & Connections, Sixth Edition Campbell, Reece, Taylor, Simon, and Dickey.
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Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings CHEMISTRY PART 2.
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Copyright 2009, John Wiley & Sons, Inc. Unit 2: Biochemistry and Cells Review.
Organic Compounds (carbon-based compounds). Functional Groups the unique properties of organic compounds are due to their size, shape, & functional groups:
Anatomy and Physiology Chapter #2. Molecules and Compounds A molecule is formed when two or more atoms combine. If atoms of different elements combine,
CHEMICAL BASIS OF LIFE AT THE CELLULAR LEVEL: CHEMISTRY BECOMES BIOLOGY -body functions depend on cellular functions -cellular functions result from chemical.
Structure and Function of Macromolecules. What is a Macromolecule? Organic molecules that weigh more than 100,000 daltons are referred to as macromolecules.
Organic Chemistry Chapter 03. Organic Chemistry 2Outline Organic vs Inorganic Functional Groups and Isomers Macromolecules Carbohydrates Carbohydrates.
C 24:The chemistry of life Biomolecules. Primary Organic Compounds 1. Carbohydrates 2. Lipids 3. Proteins 4. Nucleic Acids You are expected to learn the.
Ch. 5 The Molecules of Life. 5.1 Carbon is the main ingredient of organic molecules.
Biochemistry of Cells 1. Carbon-based Molecules Although a cell is mostly water, the rest of the cell consists mostly of carbon-based molecules 2 Organic.
Chapter 5: Biological Molecules Carbon based compound Consist of C, H, O atoms Sometimes P, N, S atoms Properties depends on : Arrangement of carbon.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece.
SC.912.L.18.1 Describe the basic molecular structure and primary function of the four macromolecules Carbohydrates Proteins Lipids Nucleic acids.
The Chemicals of Living Cells ©The Wellcome Trust.
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