1. CARBOHYDRATES, LIPIDS & PROTEINS
Topic 3.2
IB Biology
Miss Werba

2. CARBS, LIPIDS & PROTEINS 3.5 TRANSCRIPTION & TRANSLATION
TOPIC 3 - BIOCHEMISTRY
3.1 ELEMENTS & WATER
3.2
CARBS, LIPIDS & PROTEINS
3.3
DNA STRUCTURE
3.4
DNA REPLICATION
3.5 TRANSCRIPTION & TRANSLATION
3.6 ENZYMES
3.7 CELL RESPIRATION
3.8 PHOTOSYNTHESIS
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3. THINGS TO COVER Organic v Inorganic compounds
Carbohydrates, Lipids & Proteins:
Structure
Types
Examples
Functions
Energy storage
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4. ORGANIC and INORGANIC COMPOUNDS
3.2.1
ORGANIC and INORGANIC COMPOUNDS
Organic compounds:
based on carbon
found in living things
Exceptions: oxides of carbon (eg. CO2, CO)
Anything else is inorganic!
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5. CONDENSATION AND HYDROLYSIS
3.2.5
CONDENSATION AND HYDROLYSIS
Condensation reaction: Removing water from two monomers to form a dimer
Hydrolysis reaction: Adding water can break polymers and dimers back into monomers
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6. CARBOHYDRATES: Examples (Command term = LIST)
3.2.3
CARBOHYDRATES: Examples (Command term = LIST)
Remember: MONO = gives great flavour; DI = largely mid sized, POLY = can get stored
Monosaccharides: Glucose, galactose, fructose
Disaccharides: Lactose, maltose, sucrose
Polysaccharides: Cellulose, glycogen, starch
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7. CARBOHYDRATES: Glucose and ribose
3.2.2
CARBOHYDRATES: Glucose and ribose
Glucose
Ribose
C6H12O6
Formula
C5H10O5
6 carbons
 hexose sugar
Carbons
5 carbons
 pentose sugar
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8. CARBOHYDRATES: Condensation and hydrolysis
3.2.5
CARBOHYDRATES: Condensation and hydrolysis
disaccharide
monosaccharide
maltose + maltose
starch + water
disaccharide
polysaccharide
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9. CARBOHYDRATES: Functions (Command term = STATE)
3.2.4
CARBOHYDRATES: Functions (Command term = STATE)
Animals:
Glucose – energy via cell respiration
Lactose – in milk; energy for infants
Glycogen – short-term energy storage
Chitin – in arthropod exoskeletons
Deoxyribose – in DNA
Plants:
Fructose –in honey; good energy source
Sucrose –used as a transport intermediate
Cellulose –component of plant cell wall
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10. LIPIDS: Fatty acids General Saturated Unsaturated -COOH carboxyl group
3.2.2
LIPIDS: Fatty acids
General
Saturated
Unsaturated
-COOH carboxyl group
-CH3 methyl group
Contains no double bonds
May contain double bonds
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11. LIPIDS: Functions (Command term = STATE)
3.2.6
LIPIDS: Functions (Command term = STATE)
Remember: SHIPS  only need to learn 3
Structure: phospholipids in cell membranes
Hormonal signalling: steroid hormones are lipids (eg. oestrogen, testosterone)
Insulation: fat is an insulator; lipids also insulate neurons
Protection: fats protect internal organs from damage
Storage of energy: fats can be used as a long-term energy storage source
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12. LIPIDS: Condensation and hydrolysis
3.2.5
LIPIDS: Condensation and hydrolysis
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13. ENERGY STORAGE: Carbs vs lipids
3.2.7
ENERGY STORAGE: Carbs vs lipids
Similarities:
Polysaccharides and lipids contain a lot of chemical energy and can be used for energy storage
Polysaccharides and lipids are both insoluble in water - they are not easily transported in the blood
Carbohydrates and lipids both burn cleaner than proteins (they do not yield nitrogenous wastes)
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14. ENERGY STORAGE: Carbs vs lipids
3.2.7
ENERGY STORAGE: Carbs vs lipids
Differences:
Lipids contain more energy per gram than sugars
Lipids are therefore lighter than sugars of equal yield
Carbohydrates more readily digested (short-term)
Lipids less readily digested (long-term storage)
Mono/disaccharides are water soluble; lipids are not
Sugars easier to transport in bloodstream to sites of use
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15. PROTEINS: Amino acids General a central carbon atom 4 side groups:
3.2.2
PROTEINS: Amino acids
General
a central carbon atom
4 side groups:
the amine group (-NH2)
the carboxylic acid group (-COOH)
an H group
the R group – R standing for “the rest” rather than an element
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16. PROTEINS: Condensation and hydrolysis
3.2.5
PROTEINS: Condensation and hydrolysis
peptide bond
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17. Sample questions
Q1. Which type of molecule is shown in the diagram below?
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18. Sample questions
Q2. What is the difference between galactose and lactose?
Lactose is a disaccharide and galactose is a monosaccharide.
Lactose is the product of anaerobic respiration in humans and galactose is the product of anaerobic respiration in yeast.
Lactose is an enzyme and galactose is a hormone.
Galactose is a sugar found in milk but lactose is not found in milk.
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19. Sample questions A1. Peptide / protein
A2. A - Lactose is a disaccharide and galactose is a monosaccharide.
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20. Sample questions
Q3. Compare the use of carbohydrates and lipids in energy storage.
(4 marks)
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21. Sample questions
A3.
both lipids and carbohydrates are primary sources of energy for organisms;
lipids store more energy per unit mass/per gram than carbohydrates / lipids generally provide 2 to 3 times the energy of carbohydrates for a given mass;
lipids provide 38 kJ g–1/ 9 C g–1 whereas carbohydrates have 17 kJ g–1/ 4 C g–1;
carbohydrates are easier to transport (than lipids) making their energy more accessible;
because lipids are insoluble (in water) whereas (small) carbohydrates are soluble (in water);
carbohydrates are more easily taken out of storage making their energy more quickly available;
carbohydrates are short-term storage molecules, whereas lipids provide long- term storage;
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