What are the four different types of carbohydrates and how are they classed ?
Monosaccharides - single sugar unit
Oligosaccharides - short chain of 2-20 monosaccharides
Polysaccharides - Long chain of >20 monosaccharides
Glycoconjugates - carbohydrates linked to proteins or lipids
what are the two types of monosaccharides ?
Aldoses (contain an aldehyde) and ketoses (contains a ketone)
What are the smallest monosaccharides ?
Trioses (3C sugars)
What determines the D or L configuration of a molecule ?
Based on the chiral carbon further away from the aldehyde/ketone
Which isomer classification of monosaccharides are most common in nature ?
D - isomers, L - isomers are less common but do exist in some biological systems
What is the classification of monosaccharide isomers based on and what does it mean ?
Fischer projection of glyceraldehyde
D - form has hydroxyl group on the right
L - form has hydroxyl group on the left
Why do hexoses and pentoses form cyclic rings ?
Intermolecular relation of the carbonyl with a hydroxyl group. They form Hemiacetals (from aldoses) or Hemiketals (from ketoses).Two possible anomers are alpha(OH below the ring) and beta (OH above the ring)
What bond links together monosaccharides ?
Glycosidic bonds
How does a glycosidic bond form ?
The anomeric carbon reacts with an -OH group of another sugar
What is the source of starch and what is it a mixture of ?
Plants
Mixture of amylose(a1–> 4) and amylopectin (a1–>4,a1–>6) branches every 24-30residues
What is the source of glycogen and what is its structure ?
Animals
Similar to amylopectin but more branched (a1-->6 every 8-12 residues). Highly compact and rapidly metabolised.
What is the function of cellulose and what is its structure ?
Plant cell walls
B1-4 linkages, linear unbraced chain's
hydrogen bonds between chains, microfibrils
What is the function of chitin and what is its structure ?
Exoskeleton of insects, fungi walls
similar to cellulose but has N-acteylcglucosamine residues instead of glucose
What are glycoproteins ?
proteins with attached carbohydrates
What are the main amino acids involved in glycosylation ?
Serine and threonine - O linked glycosylation
Asparagine - N linked glycosylation
What are the two types of glycosylation ?
N linked - Sugar molecules attached to the amino group of asparagine
O linked - Sugar molecules attached to the hydroxyl group of either serine or threonine
Whta is an example of a glycoprotein and its function and type of glycosylation ?
O linked glycosylation attached to either serine or threonine
Glycoprotein with carbohydrates stabilising it in blood
Breaks down elastin, protein found In connective tissue
What is the composition of a nucleotide ?
5 carbon sugar (ribose/deoxyribose)
Nitrogenous base : Purine (A&G) Pyrimidines (C,T&U)
Phosphate group
What is the 4 function of lipids ?
Structural components of membranes
Energy storage
Hormones and vitamins
Bile acids
What are the 4 major lipid families and what are their key features ?
Triacylglycerols- glycerol backbone
Glycerolphospholipids- glycerol backbone, phosphate moietites, can include glycol-conjugates
Sphingolipids- Built on sphingosine backbone unit, often Glycoconjugates
Isoprenoids - steroids, lipid vitamins and hormone
What are fatty acids ?
Long hydrocarbon chains
What are 3 reasons as to why fatty acid chains vary ?
Chain length - typically between 12-20 carbon atoms in their hydrocarbon tail
Degree of unsaturation - cis fatty acids have double bonds therefore lower boiling point and trans are vice versa
Position of double bonds
What are triacylglycerols, their function and structure ?
-Major form of fat storage
-3 fatty acids esterified to a glycerol molecule
-hydrophobic, stored in cells as fat droplets
-efficient for long term storage, as they pack tightly
What are Glycerophospholipids, their function, structure and features ?
-glycerol backbone,two fatty acids esterified to it, third carbon of the glycerol is linked to a phosphate group
-Most abundant lipid, make duo cell membrane
-amphipathic, allows it to form bilayers
What is a sphingolipids, their structure function and features ?
-large family of lipids, import component of biological membranes (plasma membrane )
-do not have a glycerol backbone, have a sphingosine backbone (3 carbon molecule)
-amphipathic, hydrophobic tail and hydrophilic head
-various groups attached to their pilar heads : ceramide, sphingomyelin, Glycosphingolipids
What are the various heads that can be attached to the polar head of Sphingolipids and their structure ?
Ceramide - head group is just a hydrogen
Sphingomyelin - head group is phosphocholine (a choline group linked to phosphate)
Glycosphingolipids - where the head group contains sugars or oligosaccharides.
Where are sphingolipids abundant in and what is their function ?
membranes of eukaryotic cells
Involved in : cellular processes, cell signalling, recognition and communication
What are steroids and what are they classed as ?
-lipids classified as isoprenoids (Derived from 5 carbon unit isoprene)
–four rings structure distinct from other lipid classes
What is the structure of a lipid ?
-fused ring system - four fused carbon rings ( 3 6-membered rings, one 5 membered ring,D)
-rigid structure, less flexible compared to fatty acid chain
What are 3 examples of steroids and their function ?
Cholesterol - structural components of cell membranes, modulates membrane fluidity by inserting itself between phospholipid molecules, makes membrane more stable and less permeable
Steroid hormone - estrogen,testosterone,cortisol and other hormones are steroids derived from cholesterol, import for regulation of various physiological processes
Bile acids - derived from cholesterol, essential for digestion and adoption of dietary fats, emulsify fats in the digestive tract