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Haggerston School Biology A-Level

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Presentation on theme: "Haggerston School Biology A-Level"— Presentation transcript:

1 Haggerston School Biology A-Level

2 ‘All truths are easy to understand once they are discovered; the point is to discover them’.
Galileo Galilei

3 Boardworks AS Biology Biological Molecules: Proteins and Lipids
Teacher notes In ‘Slide Show’ mode, click the name of a section to jump straight to that slide.

4 Boardworks AS Biology Biological Molecules: Proteins and Lipids

5 Boardworks AS Biology Biological Molecules: Proteins and Lipids
Introducing proteins Boardworks AS Biology Biological Molecules: Proteins and Lipids 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 Photo credit: Koos Schwaneberg signalling: many hormones and receptors are proteins immunological: all antibodies are proteins.

6 The general structure of amino acids
Boardworks AS Biology Biological Molecules: Proteins and Lipids 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 Teacher notes Students should be made aware that sometimes the R group and H atom from the alpha carbon are sometimes inverted in diagrams (i.e. R at the top and H at the bottom). 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 The 20 naturally-occurring amino acids
Boardworks AS Biology Biological Molecules: Proteins and Lipids

8 Peptide bonds and dipeptides
Boardworks AS Biology Biological Molecules: Proteins and Lipids Teacher notes Condensation reaction and hydrolysis reaction of dipeptides is just the same as for disaccharides, but a peptide bond is formed rather than a glycosidic bond.

9 Boardworks AS Biology Biological Molecules: Proteins and Lipids
Peptides Boardworks AS Biology Biological Molecules: Proteins and Lipids

10 Boardworks AS Biology Biological Molecules: Proteins and Lipids
Polypeptides Boardworks AS Biology Biological Molecules: Proteins and Lipids 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 The structure of proteins
Boardworks AS Biology Biological Molecules: Proteins and Lipids

12 Boardworks AS Biology Biological Molecules: Proteins and Lipids
Protein structure Boardworks AS Biology Biological Molecules: Proteins and Lipids

13 Boardworks AS Biology Biological Molecules: Proteins and Lipids
Bonds in proteins Boardworks AS Biology Biological Molecules: Proteins and Lipids 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 Boardworks AS Biology Biological Molecules: Proteins and Lipids
Fibrous proteins Boardworks AS Biology Biological Molecules: Proteins and Lipids 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. Photo credit: Steve Gschmeissner / Science Photo Library Scanning electron micrograph (SEM) of collagen bundles from the delicate connective tissue endoneurium. Endoneurium wraps around and between individual nerve fibres (axons), providing support and filling space between the nerve fibres. Endoneurium consists of collagen and elastin fibres and is found throughout the peripheral nervous system. Magnification not known. Teacher notes Collagen is the most abundant protein in the body, comprising about 25% of all protein. silk – forms spiders’ webs and silkworms’ cocoons.

15 Boardworks AS Biology Biological Molecules: Proteins and Lipids
Globular proteins Boardworks AS Biology Biological Molecules: Proteins and Lipids 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. transport proteins – such as haemoglobin, myoglobin and those embedded in membranes. Photo credit: National Institutes Of Health / Science Photo Library Molecular graphic of the oxygen-carrying protein myoglobin. Myoglobin consists of a chain of amino acids folded into a globin molecule, which is similar to the four globin subunits in haemoglobin. Coloured spheres here represent atoms in the chain. The dark region in the centre is the haem group, which contains a single iron atom to which a molecule of oxygen can form a temporary bond. Myoglobin is found in muscle tissue, where it stores additional oxygen for use during strenuous exercise. enzymes – such as lipase and DNA polymerase. hormones – such as oestrogen and insulin.

16 Boardworks AS Biology Biological Molecules: Proteins and Lipids
Denaturing proteins Boardworks AS Biology Biological Molecules: Proteins and Lipids If the bonds that maintain a protein’s shape are broken, the protein will stop working properly and is denatured. denaturation: bonds broken Changes in temperature, pH or salt concentration can all denature a protein, although the specific conditions will vary from protein to protein. Teacher notes The black lines in the left-hand illustration represent the various types of bond maintaining the secondary and tertiary structures of the protein. These are absent from the right-hand illustration, indicating that they have been broken during the denaturation process. See the ‘Enzymes’ presentation for more information about denaturing enzymes. Fibrous proteins lose their structural strength when denatured, whereas globular proteins become insoluble and inactive.

17 Biuret test for proteins
Boardworks AS Biology Biological Molecules: Proteins and Lipids

18 Proteins: true or false?
Boardworks AS Biology Biological Molecules: Proteins and Lipids

19 Boardworks AS Biology Biological Molecules: Proteins and Lipids
Teacher notes In ‘Slide Show’ mode, click the name of a section to jump straight to that slide.

20 Introduction to lipids
Boardworks AS Biology Biological Molecules: Proteins and 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. Photo credit: Ramon Gonzalez Like carbohydrates, lipids contain carbon, hydrogen and oxygen, but they have a higher proportion of hydrogen and a lower proportion of oxygen.

21 The structure of triglycerides
Boardworks AS Biology Biological Molecules: Proteins and Lipids

22 Saturated and unsaturated
Boardworks AS Biology Biological Molecules: Proteins and Lipids

23 Boardworks AS Biology Biological Molecules: Proteins and Lipids
Role of lipids Boardworks AS Biology Biological Molecules: Proteins and Lipids 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. Lipids are stored in adipose tissue, which has several important roles, including: heat insulation – in mammals, adipose tissue underneath the skin helps reduce heat loss. Photo credit: David Gregory & Debbie Marshall, Wellcome Images Scanning electron micrograph of adipose tissue, showing lobules rich in adipocytes. Computer-coloured orange. protection – adipose tissue around delicate organs such as the kidneys acts as a cushion against impacts.

24 The structure of phospholipids
Boardworks AS Biology Biological Molecules: Proteins and Lipids Teacher notes See the ‘Cell Membranes’ presentation for more information about the properties and biological roles of phospholipids.

25 Emulsion test for lipids
Boardworks AS Biology Biological Molecules: Proteins and Lipids

26 Boardworks AS Biology Biological Molecules: Proteins and Lipids
Components of lipids Boardworks AS Biology Biological Molecules: Proteins and Lipids

27 Boardworks AS Biology Biological Molecules: Proteins and Lipids
Teacher notes In ‘Slide Show’ mode, click the name of a section to jump straight to that slide.

28 Boardworks AS Biology Biological Molecules: Proteins and Lipids
Glossary Boardworks AS Biology Biological Molecules: Proteins and Lipids

29 Boardworks AS Biology Biological Molecules: Proteins and Lipids
What’s the keyword? Boardworks AS Biology Biological Molecules: Proteins and Lipids

30 Boardworks AS Biology Biological Molecules: Proteins and Lipids
Mystery substance Boardworks AS Biology Biological Molecules: Proteins and Lipids Teacher notes This activity assumes that students are familiar with the biochemical tests for reducing sugars and starch. See the ‘Biological Molecules 1: Water and Carbohydrates’ presentation for more information about these.

31 Boardworks AS Biology Biological Molecules: Proteins and Lipids
Multiple-choice quiz Boardworks AS Biology Biological Molecules: Proteins and Lipids


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