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CarbohydratesLipidsProteins

Stephen Taylor

Assessment Statements Obj.3.2.1 Distinguish between organic and inorganic compounds. 2

3.2.2 Identify amino acids, glucose, ribose and fatty acids from diagrams showing their structure. 2

3.2.3List three examples each of monosaccharides (glucose, galactose, fructose), disaccharides (maltose, lactose, sucrose), and polysaccharides (glycogen, cellulose, starch).

1

3.2.4 State one function of glucose, lactose and glycogen in animals and of fructose, sucrose and cellulose in plants. 1

3.2.5

Outline the role of condensation and hydrolysis in the relationships between:• monosaccharides, disaccharides and polysaccharides• fatty acids, glycerol and triglycerides• amino acids and polypeptides

2

3.2.6 State three functions of lipids, including energy storage and thermal insulation (also: protection, membranes, buoyancy, neuron insulation). 1

3.2.7Compare the use of carbohydrates and lipids in energy storage• energy storage per gram (kJ/g)• fast/slow release of energy• demand for oxygen & ease of release of energy

3

Assessment statements from: Online IB Biology Subject GuideCommand terms: http://i-biology.net/ibdpbio/command-terms/

Organic compounds contain carbon and are found in living things.

They usually contain C-H or C-C bonds. The organic compounds we study can be used in metabolic reactions.

Some inorganic compounds also contain carbon.

Amino Group (-NH2) Carboxylic Acid Group (-COOH)

A generalized amino acid

The amino group is one of the reasons why nitrogen is an

important element in living things.

The carboxylic acid group contains an oxygen double-bonded to the carbon and a hydroxyl group (-OH) that can be lost to form new bonds.

The basic structure of the amino acids is common. There are 22 different protein-making amino acids, though only 20 are coded for in genetic code. Each has its own unique R-group. Some are polar, others non-polar and their different properties determine their interactions and the shape of the final protein.

Methionine: an amino acidMethionine is an important amino acid as it is coded by the START codon in mRNA (AUG). This means that is is the first amino acid in all polypeptide chains as it is the first produced in transcription in the ribosomes.

Although methionine (Met) has quite a large R-group, we can still identify the amino group and carboxylic acid group on the amino acid.

Sulphur forms strong bonds (disulphide bridges) with other S-containing amino acids.

http://en.wikipedia.org/wiki/Methionine

The simplest amino acid is glycine, with H in the R-group position.

Glucose

General formula: C6H12O6

We count the carbons in clockwise direction, starting with the first carbon after the oxygen atom in the ring.

This is the basic mono-saccharide (single-unit) hexose (6-carbon) sugar molecule that is used in respiration. It is a chemical store of energy.

Ribose

General formula: C5H10O5

We count the carbons in clockwise direction, starting with the first carbon after the oxygen atom in the ring.

This is the basic mono-saccharide (single-unit) pentose (5-carbon) sugar molecule. It is found in RNA and a similar version in DNA.

Fatty Acids & GlycerolFatty acid chains can be of many lengths, extended by adding CH2 units. They are an efficient store of energy and bond with glycerol (a simple sugar alcohol) to make triglycerides – lipids.

http://avogadro.openmolecules.net/wiki/Main_Page

Physical ModelingWhich molecule is this? How do you know?

Use the models to make glucose and ribose.

ribose

glucose

amino acid (glycine)

glycerol

this one(glycine)

Identify these organic molecules.

fatty acid

amino acid

ribose

glucose

State one function of glucose, lactose and glycogen in animals, and of fructose, sucrose and cellulose in plants.

Glucose is used in cell respiration to produce ATP for use in energy processed in cells.

Glucose + Oxygen Carbon dioxide + water

Glycogen is an insoluble storage molecule in the liver. When blood glucose is high, the pancreas releases insulin, telling theliver to capture blood glucose and combine molecules of glucose tomake the polysaccharide glycogen, through condensation reactions.

This stores energy for later.

When blood glucose drops, the hormone glucagon causes the glycogen to be broken down (hydrolysis reactions) to glucose andthen released back into the blood.

Liver from: http://en.wikipedia.org/wiki/File:Leber_Schaf.jpg

blood glucose too high

blood glucose too low

Lactose

Breastfeeding logo from: http://en.wikipedia.org/wiki/File:Breastfeeding-icon-med.svg

Lactose is a disaccharide produced in mammal mothers.It consists of glucose and galactose and is easily digested by the lactase enzyme in the young animal’s digestive system.

By producing a small disaccharide that can be broken down by lactase, the mother can provide her young with a source of energy that can be quickly digested after feeding and then readily used in respiration.

Condensation reactions make bonds.Hydrolysis bonds break these bonds.

Watch these three animations and make a generalisation about the processes:- function, roles of enzymes, roles of water

http://is.gd/PeptideBond http://is.gd/MaltoseGIF http://is.gd/TriglycerideGIF

Animation: http://is.gd/PeptideBond

Animation: http://is.gd/PeptideBond

http://www.biotopics.co.uk/as/aminocon.html

Carbohydrates vs Lipids for energy storage

Data-based QuestionEmperor Penguin Masses

Page 50 in the Course Companion

Image source: http://www.arkive.org/emperor-penguin/aptenodytes-forsteri/image-G57959.html

What are some uses of lipids in living things?

For more resources.

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