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.
What is a major component of cartilage?
Galactosamine
What is the polymer chitin made from and where is it found?
A derivative of glucosamine
Structural polysaccharide in the skeleton of insects and crustaceans and the cell wall of fungi
What are lipids?
Hydrocarbons that are insoluble in water because of their non-polar covalent bonds
What forces operate between non-polar hydrocarbons?
Van der Waals forces
Why are aggregations of lipids not polymers?
Individual lipid molecules are not covalently bonded, but can be considered polymers of individual lipid subunits
What is the function of fats and oils?
Energy storage
What is the function of phospholipids?
Structural roles in membranes
What is the function of carotenoids?
Help plants capture light energy
What is the function of steroids and modified fatty acids?
Regulatory roles as hormones and vitamins
What is the function of fat in animal bodies?
Thermal insulation
What does a lipid coating around a nerve provide?
Electrical insulation
What is the purpose of oil or wax on the surface of skin, fur of feathers?
Water repelant
What is the difference between oils and fats?
Fats are solid at room temperature /20 degrees Celsius
Oils are liquid at room temperature
What are fats and oils also known as?
Triglycerides
What are the two types of building blocks of triglycerides?
Fatty acids and glycerol
What is glycerol?
A small molecule with three hydroxyl (-OH) groups
This makes it an alcohol
What is a fatty acid made up of?
A long nonpolar hydrocarbon chain and polar carboxyl (-COOH) group
What is the structure of a triglyceride?
Three fatty acid molecules and one molecule of glycerol.
The carboxyl group of a fatty acid bonds with the hydroxyl group of the glycerol to form a covalent bond called an ester linkage.
What are the two types of triglycerides that can form, depending on the hydrocarbons involved?
- Saturated fatty acid
- Unsaturated fatty acid
What is a saturated fatty acid?
A fatty acid where bonds between carbon atoms in the hydrocarbon are single bonds (no double bonds)
All bonds are saturated with hydrogen atoms
What are some characteristics of saturated fatty acids?
Relatively rigid
Pack together tightly
What is an unsaturated fatty acid?
A fatty acid where the hydrocarbon chain contains one or more double bonds
Give an example of a monounsaturated fatty acid.
Oleic acid
What is a polyunsaturated fatty acid?
A fatty acid with more than one double bond.
What do kinks in unsaturated fat molecules do?
Prevent molecules packing together tightly. These determine the melting point of a lipid.
What type of triglycerides do animal fats tend to contain?
Long chain, saturated fatty acids, packed together.
What type of triglycerides do plants tend to have?
Short, unsaturated fatty acids (such as corn oil).
Their kinks mean the fatty acids pack together poorly and have a low melting point.
What biologically important molecules are insoluble in lipids?
Ions, sugars, free amino acids
What is the difference between phospholipids and triglycerides?
Phospholipids have one of several phosphate containing compounds replace on the three fatty acids that are present in triglycerides.
What charge does phosphate groups on phospholipids have? What properties does this feature impart?
Negative electric charge
This feature is hydrophilic- it attracts polar water molecules.
How do phospholipids behave in aqueous environments?
Phospholipids line up in such a way that the non-polar, hydrophobic tails pack tightly together and the phosphate containing heads face outwards to interact with water
This forms a bilayer
What is a bilayer?
A sheet, two molecules thick, with water excluded from the core.
What lipids are not triglycerides?
Carotenoids, steroids, vitamins, waxes.
What are carotenoids?
A family of light absorbing pigments
What does beta-carotene do in plants?
Traps light energy in leaves during photosynthesis
What happens to beta-carotene inside the human body?
It is broken down into two molecules of vitamin A
Vitamin A makes the pigment rhodopsin, required for vision
Where can carotenoids be seen?
The colour of carrots, tomatoes, pumpkins, egg yolks and butter
What are steroids?
A family of organic compounds whose multiple rings share carbons
An important steroid is cholesterol. Where is this synthesized?
In the liver
What are the uses of cholesterol in the human body?
- Important component of membranes
- Starting material for testosterone and other steroid hormones
- Starting material for bile salts used in the break down of dietary fats.
What are vitamins?
Small molecules that are not synthesised by the human body and must therefore be acquired by diet
What does a deficiency of vitamin A cause?
Dry skin, eyes and internal body surfaces
Retarded growth and development
Night blindness
Where is vitamin A acquired?
Green and yellow vegetables in the form Beta-carotene
What vitamins are lipids?
A, D, E, K
What structure do all waxes have?
formed by an ester linkage between a saturated, long chain fatty acid and saturated, long chain alcohol
This is a highly nonpolar structure- accounts for impermeability to water
Why are steroids and some vitamins classed as lipids?
They are made up largely of carbon and hydrogen and are non-polar
What are nucleic acids?
Polymers specialised for the storage, transmission and use of genetic information
What are the two types of nucleic acid?
DNA- deoxyribosenucleic acid
RNA- ribonucleic acid
What is DNA?
A macromolecule that encodes hereditary information and passes it from generation to generation
What are nucleic acids composed of?
Nucleotides
What are nucleotides composed of?
A pentose sugar, a phosphate group and a nitrogen containing base
What are the two forms of bases that a nucleic acid take?
A single ring structure called a pyrimidine
A fused-ring structure called a purine
What is the structure of the backbone of the RNA and DNA macromolecule?
A chain of alternating pentose sugars and phosphate groups joined by a phosphodiester linkage
To which carbons does a phosphate group link?
The 3’ carbon one one pentose sugar to the carbon 5’ in the adjacent sugar
Most RNA is usually single stranded. How is DNA double stranded?
Its two polynucleotide chains are held together by hydrogen bonding between their nitrogenous bases.
The antiparallel orientation of DNA allows the strands to fit together in three-dimensional space. What does antiparallel mean?
The two strands of DNA run in opposite directions
Name the 5 bases and the type of each.
Pyrimidines:
Cytosine
Thymine (DNA only)
Uracil (RNA only)
Purines
Adenine
Guanine
Which bases bond together in complimentary base pairing?
A bonds to T
C bonds to G
In double stranded DNA.
Why is base pairing complimentary?
- The sites of hydrogen bonding on each base
- The geometry of the sugar phosphate back bone (brings opposite bases near each other)
- The molecular size of the paired bases
Why are pyrimidines and purines paired?
Large purines being paired with smaller pyrimidines ensure stability and consistency in the double stranded DNA molecule.
How is the shape of RNA molecules determined?
Complementary hydrogen bonding between ribonucleotides .Hydrogen bonds stabilize it into a three dimensional shape.
What is the central dogma of molecular biology?
DNA codes for the production of RNA and RNA encodes for the production of DNA
What are other roles of nucleotides?
ATP acts as an energy transducer in biochemical reactions
GTP (guanosine triphosphate) serves as an energy source in protein synthesis
cAMP (cyclic adenosine monophosphate) essential in processes such as hormone action and transmission in the nervous system
