Lecture 1 and 2- macromolecules Flashcards
What are carbohydrates?
Molecules containing carbon atoms flanked by hydrogen atoms and hydroxyl groups (H-C-OH)
What are the two main biochemical roles of carbohydrates?
- Energy source: energy can be released in a usable form
- Carbon skeletons: rearranged to form new molecules for new structures and functions
What are the 4 categories of biochemically important carbohydrates?
- Monosaccharides
- Disaccharides
- Oligosaccharides
- Polysaccharides
What is the general formula of a carbohydrate?
CH2O in the proportion 1:2:1, but this differs in di,oligo and polysaccharides because of the loss of two hydrogens and an oxygen during condensation reactions.
Give an example of some monosaccharides.
Glucose, ribose, fructose (simple sugars)
Give an example of some polysaccharides.
Starch, glycogen, cellulose
What are oligosaccharides?
Carbohydrates made up of several (3-20) monosaccharides.
How are monosaccharides produced?
Green plants produce monosaccharides through photosynthesis
What sugar is in every living cell?
Glucose
What are the two forms of glucose?
Straight chained and ring form
Ring form predominates 99% of the time because it is more stable
What are the two versions of the ring form of glucose?
Alpha and beta- differing by the orientation of the H and OH groups on carbon 1.
These interconvert in equilibrium when dissolved in water
What series of optical isomers do most monosaccharides belong to?
D series (as opposed to the L-series that occur predominantly in amino acids)
Some monosaccharides are structural isomers. What does this mean?
They have the same kinds and numbers of atoms but are in different arrangements.
Give an example of structural isomerism in carbohydrates.
Hexoses- formula C6H12O6
Glucose, fructose, mannose, galactose etc.
Which two pentoses are of particular biological importance?
Ribose, deoxyribose- form part of the backbone of RNA and DNA
What is the difference between ribose and deoxyribose?
NOT isomers
One oxygen atom is missing from the carbon 2 atom of deoxyribose
What is the name of the bonds between monosaccharides?
Glycosidic linkages
What are glycosidic linkages?
Covalent bonds that form between monosaccharides during condensation reactions
Sucrose is a disaccharide formed by the glycosidic linkage of which monosaccharides?
glucose and fructose
Lactose contains which two monomers?
glucose and galactose
What determines the type pf glycosidic linkage between monomers?
alpha linkages form between alpha-D-glucose
beta linkages form between beta-D-glucose
What are the similarities and differences between cellubiose and maltose?
Maltose is produced by alpha linkages between two glucose molecules
Cellubiose is produce by beta linkages
Both are structural isomers
They have different properties
Maltose can be hydrolysed in the human body, cellubiose cannot
Certain microorganisms can break down cellubiose
What are some features of oligosaccharides?
- Some have additional functional groups - special properties
- Often covalently bonded to proteins and lipids on the outer cell surface- recognition signals
Such as human blood types, ABO
What are the functions of polysaccharides?
Energy storage
Structural materials
What is starch?
Polysaccharide of glucose with alpha-glycosidic linkages
What is glycogen?
A highly branched polymer of glucose
What is cellulose?
A polysaccharide of glucose with beta-glycosidic linkages
How are different structures of starch distinguished?
The degree of branching that occurs at carbon 1 and 6
Name an unbranched starch.
Plant amylose
Name a moderately branched starch
Plant amylopectin
Starch readily binds to water, what happens when that water is removed?
Unbranched starch forms hydrogen bonds between polysaccharide chains which then aggregate
What is the function of glycogen and starch?
Energy storage compounds in animals and plants, respectively.
Glycogen stores glucose in animal livers and muscles
Why is glucose stored as a polysaccharide?
Reduces osmotic effects on the cell
Where is cellulose found?
Plant cell walls- most abundant organic compound on Earth
Why is cellulose not easily degraded by chemicals or enzymes?
It is more chemically stable because of its beta-glycosidic linkages
This makes it a good structural material to withstand harsh environmental conditions
What do additional functional groups do to carbohydrates?
Change their properties
Why are sugar phosphates important?
They are intermediates in cellular energy reactions
What is fructose 1,6 bisphosphate involved in?
Reactions that liberate energy from glucose
How are sugar phosphates made?
A phosphate group is added to one or more of the -OH sites
How are amino sugars made?
An amino group is substituted for an -OH group
Give examples of amino sugars.
Glucosamine, galactosamine
Where are amino sugars used?
Extracellular matrix- they form glycoproteins to keep tissues together.