ib biology core 3.2: carbohydrates lipids and proteins
DESCRIPTION
A slideshow for students and teachers of IB BiologyTRANSCRIPT
IB Biology3 Chemistry of Life
3.2 Carbohydrates, Lipids and Proteins
Jason de Nys
All syllabus statements ©IBO 2007All images CC or public domain or link to original material.
http://commons.wikimedia.org/wiki/File:Burger_King_Angus_Bacon_%26_Cheese_Steak_Burger.jpg
Carbs
Fats
Proteins & Fats
Rabbit food
3.2.1 Distinguish between organic and inorganic compounds
Organic molecules are based on carbon and are in living things.
Inorganic compounds are everything else plus carbonates (e.g. HCO3⁻ and CaCO3), carbon dioxide (CO2 )and carbon monoxide (CO).
http://commons.wikimedia.org/wiki/File:GraphiteUSGOV.jpg
3.2.2 Identify amino acids, glucose*, ribose* and fatty acids from diagrams showing their structure
ArginineAlanine Leucine
http://commons.wikimedia.org/wiki/File:Alanine.pnghttp://commons.wikimedia.org/wiki/File:Arginine.pnghttp://commons.wikimedia.org/wiki/File:Leucine.png
Here are three of the twenty-one amino acids found in eukaryotes. Identify what parts of their structures are identical.
*glucose and ribose shown in 3.2.3
ArginineAlanine Leucine
Yeah, that bit…
http://commons.wikimedia.org/wiki/File:AminoAcidball.svg
Drawn slightly differently you can see the bit that is always the same and the R Group. The R group is like x in an equation. It is a variable that stands in for a bunch of different side chains
The amine group (NH2)
The acid group (COOH)
A simple H group
Cent
ral (
α) ca
rbon
atom
Look out for this structure
Hmmm… an amine group and an acid group…
What shall we call this classof molecule?
http://commons.wikimedia.org/wiki/File:Filos_tercer_logo.JPG
The amine and acid groups could be at opposite ends, the R could be on top, bottom or side depending on orientation.
Or it could be represented differently:
http://commons.wikimedia.org/wiki/File:Amino_Acids.svg
Don’t freak out, you don’t need to know them all, just the general formula
General structural formula for a fatty* acid
*I prefer “big boned”
Carboxylic group
Chain (or ring) of carbon and hydrogen atoms
H3C (CH2)n C
O
OH
http://www.eufic.org/article/pt/nutricao/gorduras/expid/23/
Glucose has the formula C6H12O6
It forms a hexagonal ring (hexose)
http://commons.wikimedia.org/wiki/File:Glucose_crystal.jpg
5 of the carbons form corners on the ring with the 6th corner
taken by oxygen
3.2.3 List three examples each of monosaccharides, disaccharides and polysaccharides
Glucose is the form of sugar that fuels
respirationGlucose forms the base unit for many
polymers
Monosaccharide #1
Monosaccharide #2
http://commons.wikimedia.org/wiki/File:Galactose-3D-balls.png
Spot the difference
Galactose Glucose
Galactose is also a hexose sugar
It has the same formula C6H12O6
but is less sweet
http://commons.wikimedia.org/wiki/File:Alpha-D-glucose-3D-balls.png
Most commonly found in milk, but also found
in cereals
Monosaccharide #3
Original owner of image unknown
Ribose is a pentose sugar, it has a
pentagonal ring
It forms the backbone of RNA
Deoxyribose differs as shown in the diagram,
and forms the backbone of DNA
Monosaccharide #4You only need 3, this is a bonus!
Fructose is another pentose sugar
It is the sweetest naturally occurring
carbohydrate
http://commons.wikimedia.org/wiki/File:3dfructose.png
Commonly found in fruits and honey
http://commons.wikimedia.org/wiki/File:Red_Apple.jpg
http://www.flickr.com/photos/max_westby/4045923/
Disaccharide #1(Literally “two sugars”)
Lactose (C12H22O11) is most commonly found in milk
http://commons.wikimedia.org/wiki/File:Alpha-lactose-from-xtal-3D-balls.png
The two subunits that make up lactose are
glucose and galactose, our friends from a
couple of slides ago.
http://www.flickr.com/photos/vermininc/2764742483/
Disaccharide #2
The two subunits that make up sucrose are glucose and fructose.
http://commons.wikimedia.org/wiki/File:Sucrose.gif
Sucrose (C12H22O11) is also known as table sugar
http://www.flickr.com/photos/carowallis1/4388310394/
The two monosaccharides that make it up are
glucose and fructose
Disaccharide #3
Gosh! Isn’t it sweet?! The two glucose molecules are holding hands.
Maltose (C12H22O11) is a dimer of glucose
http://commons.wikimedia.org/wiki/File:Maltose_Haworth.svg
http://commons.wikimedia.org/wiki/File:Maltose_syrup.jpg
Polysaccharide #1Glycogen (C6H10O5)n is a
polymer made of repeating glucose subunits
http://en.wikipedia.org/wiki/File:Glycogen_spacefilling_model.jpg
It is not just a simple chain, it branches many times
Polysaccharide #2
http://commons.wikimedia.org/wiki/File:Amylose3.svg
Amylose is a form of starch, and is
made of repeating glucose units
http://www.flickr.com/photos/caroslines/5534432762/
Typically an amylose molecule is made up of 300-3000 glucose units, but it can be many more
Polysaccharide #3
http://en.wikipedia.org/wiki/File:Cellulose_spacefilling_model.jpg
Cellulose (C6H10O5)n is a linear molecule made of repeating glucose
units
http://www.flickr.com/photos/caroslines/5534432762/
Multiple hydrogen bonds form between adjacent strands. Making strong microfibrils.
3.2.4 State one function of glucose, lactose and glycogen in animals, and of fructose, sucrose and cellulose in plants
After expending 10 slides on a “List” question, let’s answer this one in a table!
Carb. Molecule FunctionGlucose Monosaccharide Used in respiration to
produce ATP
Lactose Disaccharide Energy source in milk
Glycogen Polysaccharide Short term energy storage in liver and muscles
Fructose Monosaccharide Energy source in fruits and honey
Sucrose Disaccharide Convenient form for transferring energy around plants
Cellulose Polysaccharide Structural component of the cell wall
http://www.flickr.com/photos/93387088@N04/8527309132/
http://www.flickr.com/photos/pasma/575078217/
3.2.5 Outline the role of condensation and hydrolysis in the relationships between monosaccharides, disaccharides and polysaccharides; between fatty acids and triglycerides; and between amino acids and polypeptides.
Two ways to help you remember what happens in condensation:• Water (H20) is formed, like condensation on a glass• The former separate molecules have “squished up“
together and are “condensed”http://www.flickr.com/photos/good_day/315807334/
Hydrolysis(water- splitting)
H2O is split in the process of breaking apart a polymer, typically one H will bind to one of the resultant molecules and OH will bind to the other.
Original source of glucose maltose image unknown
Condensation reactions joining two glucose molecules to
make maltose + water
The bond between saccharide units is called a glycosidic bond
You might see the term “dehydration reaction” mentioned interchangeably with condensation reaction.
Technically a dehydration reaction is when the water molecule has come from one of the reactants.
Whereas for a condensation reaction, part of each water molecule has come from each reactant.
In the case of the previous slide, OH from one glucose and H from the other.
http://www.flickr.com/photos/zachd1_618/5738829330/
http://commons.wikimedia.org/wiki/File:Amylase_reaction.png
http://commons.wikimedia.org/wiki/File:Lactose_hydrolysis.svg
Hydrolysis reactions break starch down into maltose
molecules.
Amylase in saliva at work
See 6.1
Hydrolysis of lactose into galactose and
glucose
Lactase at workSee 3.6.5
http://commons.wikimedia.org/wiki/File:Peptidformationball.svg
Condensation reactions between amino acids lead to dipeptide molecules
Keep adding amino acids and you end up with a polypeptide.
These reactions are catalysed by ribosomes in cellsSee 3.5 and HL 7.4
http://commons.wikimedia.org/wiki/File:Amino_acid4.png
Hydrolysis reactions break peptides down into their constituent
amino acids. The body can then use
those amino acids to make new
peptides/proteins.
Pepsin is an enzyme in the stomach that hydrolyses proteins
See 6.1
Glycerol Three Fatty Acids
3H2O
Triglyceride
Condensation reaction between glycerol and fatty acids
Lipids are glycerol combined with 1, 2 or 3 fatty acids, therefore triglycerides are lipids
Hydrolysis is the reverse of this process, catalysed by lipase
3.2.6 State 3 functions of lipids
1) Insulation: look how round
this seal is!http://www.flickr.com/photos/ucumari/2585053774/
2) Energy Storage: the fat on this bacon was a piggy’s bank
of energyhttp://www.flickr.com/photos/johnnystiletto/5411371373/
3) Cell membranes: look all those lovely phospholipids!
Take a moment to review 2.4 cell membranes and name all of the bits in this diagram
http://commons.wikimedia.org/wiki/File:Cell_membrane_detailed_diagram_blank.svg
3.2.7 Compare the use of carbohydrates and lipids in energy storage
http://www.flickr.com/photos/markscott/162791929/
Energy Ratio by mass Fat : Carbs : Protein
2 : 1 : 1So it makes the most sense for
animals to store long term energy reserves as fat. The same amount of energy stored as carbohydrates
would mass twice as much.The energy stored in lipids is primarily in the fatty acid side
chains, so triglycerides are used for energy storage rather than diglycerides or monoglycerides
Glycogen is the medium-term energy storage molecule in animals. It is stored in the liver and muscles. The energy stored in glycogen is
more readily available than the energy stored in fat.
Glucose in the bloodstream is for immediate use and will either be used in respiration to yield ATP or converted to glycogen or fat
An analogy:
You arepaid in cash
Wallet
Bank
Spend it!
Deposit in the
Put it in your
(Glycogen)
(Fat)
(Glucose)
(Respiration)
easy to get to, would be too big if you put
in all your money
Can put lots of money here, more of a hassle to get it back out
Unlike most animals, most plants do not
need to move, so they store their energy as
carbohydrates.
http://www.flickr.com/photos/87106931@N00/8359169832/
Especially plants with storage roots, shoots or tubers
Seeds are the exception, they need to disperse to spread the species. So
they use lipids for energy storage.
Thus sunflower oil, canola oil etc
Further information:
Three of the best sites for IB-specific Biology information. The top link takes you to the PPT by Stephen Taylor