Carbohydrates
Lipids
Proteins
Stephen Taylor
Image: 'Melts In Your Hand' Found on flickrcc.net
http://www.flickr.com/photos/83346641@N00/3661884940
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
3.2.3
List 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
3.2.7
Compare 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
Command terms: http://i-biology.net/ibdpbio/command-terms/
Assessment statements from: Online IB Biology Subject Guide
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.
A generalized amino acid
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.
Amino Group (-NH2)
The amino group is one of the
reasons why nitrogen is an
important element in living things.
Carboxylic Acid Group (-COOH)
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.
Methionine: an amino acid
Methionine 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.
Sulphur forms strong bonds (disulphide bridges)
with other S-containing amino acids.
Although methionine (Met) has quite a large R-group,
we can still identify the amino group and carboxylic
acid group on the amino acid.
The simplest amino acid is glycine,
with H in the R-group position.
http://en.wikipedia.org/wiki/Methionine
Glucose
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.
General formula: C6H12O6
We count the carbons in clockwise
direction, starting with the first carbon
after the oxygen atom in the ring.
Ribose
This is the basic mono-saccharide (single-unit) pentose (5-carbon) sugar
molecule. It is found in RNA and a similar version in DNA.
General formula: C5H10O5
We count the carbons in clockwise
direction, starting with the first carbon
after the oxygen atom in the ring.
Fatty Acids & Glycerol
Fatty 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 Modeling
Which molecule is this? How do you know?
Use the models to make glucose and ribose.
amino acid (glycine)
glucose
glycerol
ribose
this one
(glycine)
Identify these organic molecules.
fatty acid
ribose
glucose
amino acid
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 the
liver to capture blood glucose and
combine molecules of glucose to
make 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 and
then 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
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.
Breastfeeding logo from: http://en.wikipedia.org/wiki/File:Breastfeeding-icon-med.svg
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 Question
Emperor 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?
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