PBL 2: Biochem

Lipids

defined based on their solubility, they are marginally soluble in water but readily soluble in organic solvents

Function of Lipids

long term energy storage, cell membrane structure and hormone regulation

Fatty Acid Structure

carboxyl group is at the polar end joined to a non polar end hydrocarbon chain

Function of Fatty Acids

long term storage, cell signalling and structure of cell membrane

hydrogenations

the process of adding a hydrogen across a double bond if an unsaturated fatty acid to give it a saturated counterpart when going from oils to fats

Glycerol

a compund made out up of three hydroxyl groups (alcohol groups) and a three-carbon chain

Triglycerol

a compound made up of 3 alcohol groups bound to 3 fatty acids through ester linkages

Functions of Triglycerols

triglycerols accumulate in the adipose tissue and provides a means of storing fatty acids (particularly in animals)

Lipases

An enzyme that catalyses the catabolic reaction of triglycerol, in which the ester linkages are hydrolysed producing glycerol and free fatty acids, which can then be used for energy.

Phosphoacylglycerols

a major type of lipid that form the main structure of all cell membranes

Phosphatidic Acid

Instead of three fatty acids, one of the alcohol groups is estrified to a phosphate group rather than a carboxylic acid

Function of Phosphotidic Acids

Central precursor for lipid biosynthesis and structural component of membranes

Phosphotidyl Ester

A phosphatidyl ester is formed when an alcohol group is esterified to the phosphate group of phosphatidic acid.

Nature of the phosphatidyl ester

depends on the second alcohol group that is estrified to the phosphate group, however a postively charged amino group is contributed

Phosphatidyl Ester Function

Primary structural building blocks of all biological membrane

Sphinogolipids Structure and Function

contain a sphingosine backbone instead of a glycerol backbone

• it is a structural component of cell membranes and active signalling molecule that regulates cell growth, survival and inflammation (particularly abundant in the nervous system)

Sphingosine Structure

has a long hydrocarbon chain, two alcohol groups (–OH), and one amino group (–NH₂). A fatty acid attaches to the amino group through an amide bond, while a polar head group attaches to one of the alcohol groups.

Ceramides

Simplest compound of this class, and has a fatty acid bonded by an amine bond at the amino group of sphingosine

Sphingomyelin

the primary alcohol group of sphingosine is estrified to a phosphate group which is also estrified to another amine alcohol (ethanolamine)

Waxes

complex mixtures of esters of long-chain carboxylic acids and long-chain alcohols

Wax Function

Serve as protective coats for both animals and plants

• animals: skin, fur and feathers

• plants: fruits, leaves and stems

Glycolipids

a carbohydrate (sugar) is bonded to an alcohol group through a glycosidic bond

Function of Glycolipids

markers on cell membrane and play a huge role in organ and tissue specificity

Gangliosides

a complex glycolipid that contains more than three lipids

Steroids

fused ring compounds made up of three six membered rings and one five membered rings

Function of Steroids

Structural Component of cell membranes

Cholesterol

a type of steroid with one hydrophilic group making the molecule highly hydrophobic

Cholesterol Function

in eukaryotes it can be used to increase rigidity of the cell membrane and modify the roles of membrane-bound proteins

also plays a role in developing atherosclerosis and precursor of other steroids and vitamin F3

Cis double bond

functional groups or hydrogen groups sit on the same side causing a kink in the long hydrocarbon chain

Functions of Phosphoglycerides

the primary component of the lipid bilayer and allows small non-polar molecules to flow through the membreane

What is membrane fluidity dependant on

lipid composition, how many saturated vs unsaturated fatty acids are in the inner layer

How does cholesterol increase rigidity

it’s rigid fused-ring stabilises straight saturated fatty acid chains through van der Waals interactions (animals)

Carbohydrates Function

Major energy sources

Oligosaccarides and Polysaccarides Function

Oligosaccharides: cell-to-cell interactions and immune recognition

Polysaccharides: essential structural components of several organisms (cellulose in plants, other polysaccharides in bacterial cell walls) and carbohydrate-storage (starch and glycogen)

Monosaccharide Function

acts as the monomer for more complex carbohydrates and is the primary source of cellular energy

Stereoisomers

molecules that have the same chemical formula and atom connectivity, but differ in how their atoms are arranged in three-dimensional space

Enantiomers

Stereoisomers that are non-superimposable mirror images of each other. Every single chiral center (stereocenter) is inverted

Diastereomers

they are non mirror images of each other as the differ at more than one chiral carbon but not all (must have at least two chiral carbons)

Epimers

A type of diastereomer that differ in their configuration at only one specific chiral center.

Glucose, Ribose and Fructose Function

Glucose: the body's primary source of energy,

Fructose: a fast-acting source of dietary energy and a natural sweetener

Ribose: Structure of nucleic acids

Cyclic Hemiketal and Hemiacetal

occur because of interaction between functional groups C1/C2 carbon with C5 carbon

• anemeric carbon produces two groups: alpha and beta

Anomers

a specific type of stereoisomer of cyclic sugars that differ in configuration only at the hemiacetal or hemiketal carbon, known as the anomeric carbon

Furanose and Pyranose

Furanose: Five membered ring

Pyranose: Six membered ring

Sucrose Structure and Function

• glucose-alpha-1 2-fructose

• Energy needs in the form of table sugar that can be degraded to provide energy

Lactose Structure and Function:

• Galactose-beta-1 4-glucose

• Lactose is a natural sugar in milk that can be hydrolysed to provide energy, help in early development and support mineral absorbtion

Maltose Structure and Function

• glucose-alpha-1 4-glucose

• am intermediate energy source during the breakdown of starch to glucose

Cellulose Structure and Function

• glucose-beta-1 4-glucose, homopolysaccharide

• used as structural material (plant walls) and component of dietary fiber in animals

Starch Structure and Function

• alpha linkages between glucose (amylose and amylopectin)

• Storage molecules that are hydrolysed by enzymes in animals and plants to release glucose when it needs energy

• Amylopectin 1-6 branching (CH2 and and O)

Glycogen Function

• Carbohydrate storage molecule in animal cells and found in the liver and muscle cells

• Also 1-6 branching, average chain length is 13 residues and branch points occur around every 10 residues (12 layers of branching) (qabout 25 in amylopectin)

Glycogenin and Glycogen Phosphorylase

Glycogenin: starts the creation of glycogen in the body

Glycogen Phosphorylase: that breaks down stored glycogen into glucose-1-phosphate

• uses free phosphate instead of water to split the bond, saving cellular energy and then the G1P enters the metabolic pathways for carbohydrate breakdown

alpha and beta amylose

alpha amylose: endoglucosidase: hydrolyse the glycosidic linkage anywhere along to chain to produce maltose and glucose

beta amylose: exoglucosidase: hydrolyse the glycosidic linkage only at the non reducing end producing only maltose