Introduction To Carbohydrates Flashcards
How are carbohydrates produced ?
They are produced by photosynthesis in plants.
32ATP per glucose
What are the different types of carbohydrates ?
Monosaccharides
Disaccharides
Polysaccharides
Monosaccharides
The simplest carbohydrates
Disaccharides
Consists of 2 monosaccharides
Polysaccharides
Consists of many monosaccharides
How do monosaccharides react ?
Hydrolysis
What do monosaccharides consist of ?
3-6 carbon atoms
A carbonyl group
Several Hydroxyl groups
What are 3 functions of carbohydrates ?
Energy storage
Components of complex molecules
Recognition of events in protein folding
Aldose
Monosaccharide with an aldehyde group (C=O at the end of a carbon chain) and many hydroxyl groups (-OH)
Ketose
Monosaccharide with a ketone group (C=O between 2 carbons) and many hydroxyl groups (-OH)
Chiral molecules
Non-superimposable mirror images
A carbon with 4 substituent groups that can be mirrored
Fischer projection
Used to represent carbohydrates
The most oxidised group is at the top
Chiral carbons are represented at intersections between vertical and horizontal lines.
L-form isomer
The -OH group on the chiral carbon FARTHEST from the carbonyl group is on the LHS
D-form isomer
The -OH group on the chiral carbon FARTHEST from the carbonyl group is on the RHS
What are form are naturally occurring amino acids ?
L-form isomers
What are form are naturally occurring carbohydrates ?
D-form isomers
Where is D-glucose found ?
Found in fruits and honey
Blood Sugar
What is the name of a D-glucose ?
Aldohexose
What is the difference between D-glucose and D-galactose ?
The body cannot digest galactose.
It must be converted into glucose first.
-OH group attached to C4 is on different sides
D-glucose RHS
D-galactose LHS
Can the body digest galactose ?
NO ! It must be converted into glucose first.
Galactosemia cause
Lack of enzymes required for galactose metabolism
Effects of galactosemia
Accumulation of galactose intermediates
Toxic effects in liver, brain, kidneys and eyes.
What are cyclic structures ?
More prevalent form of monosaccharides with 5/6 carbon atoms.
When do cyclic structures form ?
When the hydroxyl group on C5 reacts with the aldehyde or ketone group.
3 steps of cyclic structure formation of glucose
- Number the carbon chain
- Turn the chain clockwise to form a
linear open chain - Fold the linear chain into a hexagon
- C5 bonds to C1
- C6 group is placed above the ring
- Add the -OH groups
- C1 receives new -OH
(down = Alpha form) (up=Beta form)
What happens when alpha/beta glucose is placed in solution ?
The cyclic structure opens and closes.
Glucose is converted between alpha and beta forms through a DYNAMIC FLOW.
What is a reducing sugar ?
A sugar that will reduce inorganic ions e.g. Cu++ (Fehling’s reagent)
What are examples of reducing sugars ?
All monosaccharides are reducing sugars.
What is a reducing agent ?
One which donates electrons and gains protons.
Function of Fehling’s reagent
Determines the levels of glucose in the blood
What are the 3 main steps in Fehling’s reaction ?
- Glucose is oxidised
- Copper is reduced
- Colour change occurs in the presence of a reducing sugar.
blue ——> orange
How do you determine the amount of reducing sugar in a persons blood ?
The amount of colour is directly proportional to the concentration.
What is the glucose oxidase test ?
More practical application of glucose level testing.
Used in clinical settings.
Disadvantage of Fehling’s test
It requires boiling, and so isn’t very practical.
It is not specific for glucose.
How does glucose enter red blood cells ?
In a non-insulin dependent manner.
What are the results of uncontrolled hyperglycemia ?
Uncontrolled hyperglycemia results in a covalent linkage between
glucose and the NH2 terminal amino acid of the hemoglobin β chain.
The resulting adduct is designated as HbA1c.
Glycation
Non-enzymatic natural addition of sugar
What is lactose ?
Disaccharide of beta-D-galactose or beta/alpha-D-glucose.
Sucrose
Glucose + fructose
Maltose
Glucose + glucose
Galactose
Glucose + lactose
What causes a lactose intolerance ?
Lack of lactase enzyme in SMALL INTESTINES.
Results of Lactose intolerance
Lack of lactase in small intestine
Lactose passes into colon
Bacteria start to ferment lactose
Stomach cramps, bloating, flatulence
Function of lactase enzyme
Splits lactose into glucose and galactose.
What is the most common polysaccharide in animal cells ?
Glycogen
What is the function of glycogen ?
The storage form of glucose
Where is glycogen found ?
In the liver and muscle
Structure of glycogen
Highly branched polysaccharide made of multiple glucose units linked by alpha-1,4 and alpha-1,6-glycosidic bonds.
What is an advantage of the branched structure in glycogen ?
Lots of ends so can release lots of glucose easily. So, this makes it an efficient store.
What is starch ?
The plant form of carbohydrate ingested by humans.
What are the 2 forms of starch ?
Amylose
Amylopectin
Amylose structure
Unbranched starch comprised of glucose units
Amylopectin structure
Branched form of starch
Which enzyme hydrolyses amylose and amylopectin ?
alpha- amylase secreted by the salivary glands and the pancreas.
Function of cellulose
Storage in plants
What is an important source of diversity ?
Blood groups
Viral protein coats
Is cellulose digestible by humans ?
NO ! Humans don’t have cellulases to recognise the inverted/flipped structure of cellulose.
