Carbohydrates Flashcards
metabolic networks enzymatically coordinate the flow of sugars and fats through synthesis storage and breakdown pathways
ADD IMAGE OF GLYCOLYSIS
Types of pathway :
can be divided into 2 broad classes
those that convert energy from FUELS into biologically useful forms
those that require imput’s of energy to proceed
- catabolic (CATABOLISM): BREAKS THINGS DOWN
the part of metabolism involved in BREAKING DOWN LARGER MOLECULES INTO SMALLER ONES
catabolic pathways are ENERGY YIELDING - generating an energy supply (creates and releases energy) usually in the form of ATP which is available for other cellular processes
condenses all energy into pyruvate at the end of glycolysis
KREBS CYCLE : reduced co-factors - NADH/FADH are electron donors and create electrochemical gradient to produce ATP from oxidative phosphorylation
on balance catabolic reactions are normally ENDOTHERMIC
GLUCOSE : CO2 + H2O+ USEFUL ENERGY
- Anabolic: BUILDS THINGS UP
EG) creates a molecule
Those reactions that require energy (synthesis of glucose, fats or DNA) are called anabolic reactions or anabolism. These are biosynthetic reactions and build things up, e.g.
Acetyl-CoA TO A Fatty Acid (complex molecules)
production of complex molecules within living organisms
- Amphibolic
These do a little of both
catabolic processes :
RELEASE OF ENERGY TO DO WORK
GENERATION OF “REDUCING POWER “
PRODUCTION OF INTERMEDIATED
Release of energy to do work
Glucose has -2880 kJ mol-1 available on oxidation to CO2 and H2O. Some of this can be “harnessed” in the form of ATP to do biological work, e.g. biosynthesis, ion transport, muscle, etc.
In the form of reduced cofactors e.g. NADH + H+. If catabolic pathways are oxidative,(oxidative phosphorylation : ATP is formed as a result of the transfer of electrons from NADH/ FADH2 to O2 by the series of electron carriers) anabolic pathways must be reductive,(gain electrons) and require a source of reducing power. A catabolic pathway provides this.
That may be precursors of other biosynthetic (anabolic) processes.
The catabolism of Glucose
THE BREAKDOWN OF GLUCOSE
Complex carbohydrates are consumed
Starch and glycogen are digested by the pancreatic enzyme ALPHA -amylase.
ALPHA -amylase cleaves ALPHA- 1,4 bonds of starch (creates chains) / glycogen but not the ALPHA -1,6 (creates branches )bonds.
Products are the di/trisaccharides maltose and maltotriose.
Non-digestable material (ALPHA-1,6) is called the limit dextrin.
monosaccharides are produced on the action of maltase (x2 glucose). ALPHA -glucosidase digests maltriose and any other oligosaccharides
The glycosidic link =
bio-uniformity
The GLYCOSIDIC link.
Simple sugars like glucose found throughout nature, linked into polysaccharide macromolecules by the glycosidic link (A chemical bond joining a sugar molecule to another sugar molecule).
Animals, plants, fungi and bacteria all have polysaccharides based on the glycosidic link.
The peptide link =
bio-uniformity
The peptide link.
The peptide link is the fundamental link in the polymerisation of amino acids into proteins.
All forms of life depend upon proteins for a wide variety of structural and functional roles. Moreover, the proteins that do the same “job” in widely different organisms (e.g. the enzyme lactic dehydrogenase) are virtually identical throughout nature
Triglyceride fats =
bio-uniformity
Triglycerides (fats) formed by the esterification of glycerol with the molecules of long chain fatty acids are ubiquitous in nature. ! Glycerol with three fatty acid chains, the combination of the latter determining the name of the triglyceride.
Chiral Carbohydrates, C2-C5
Optical isomerism occurs when there is an asymmetric carbon atom. That is, when a carbon atom has four different groups attached to its four bonds. As is found in the case of triose Glyceraldehyde.
Each asymmetric carbon atom gives rise to two “mirror images”, or enantiomorphs, the images cannot be superimposed.(PLACED OVER EACH OTHER) These are called D or L according to whether the functional group above the “bottom” carbon atom is to the right (Dextro) or to the left (Laevo).
Fischer projections, atoms joined to an asymmetric carbon ( ⏺ ) by horizontal bonds are in front of the plane of the page, vertical bonding is behind the page
A whole series of sugars based upon optical isomers (enantiomorphs) of glucose arise.
Important ones are glucose, mannose, galactose and fructose (which is also a structural isomer, being a ketone, rather than an aldehyde).
Properties of Sugars
It is obvious that to a large extent, the properties of sugars are going to reflect the properties of aldehydes (or ketones in the case of fructose). Therefore monosaccharides are reducing sugars.
A property of an aldehyde is that it can condense with one molecules of alcohol (OH) to form a “hemi-acetal”. Hemi-acetals can take up a second alcohol to form the full acetal
Properties of Sugars: Rings
You will see that the fact of ring closure introduces a new asymmetric carbon atom at C-1. There are therefore two forms of D-glucose, called alpha and beta D-glucose respectively: based upon the position of the OH function at position 1 (α: OH in down position; β the up position). These are both forms of glucose (i.e. they are the same sugar) but the difference is important.
hemi-acetal (yellow border), also the reducing end where polymerisation into chains of polysaccharides occur
Properties of Sugars: Polymerisation
A chain comprising up to eight molecules of a monosaccharide is called an oligosacharide.
A long chain (> 8) macromolecule based upon this structure is amylose, the polysaccharide found in starch. The nutritional store of carbohydrates in plants
the branched polysaccharide energy storage molecule found in animals is known as glycogen, and is stored in the liver.
Bonding makes the molecule easily hydrolysable to release glucose molecules into glycolysis
The catabolism of Glucose is Glycolysis
Virtually ubiquitous in all prokaryotic and eukaryotic cells.
In eukaryotic cells it tales place in the cytoplasm
Glycolysis can be divided into a three stage process.
