2. Biological Molecules Flashcards
Chemical formula of monosaccharides?
(CH2O)n
Characteristics of monosaccharides?
1) small
2) sweet
3) soluble in water
4) crystalline
Alpha glucose
OH below the plane of the molecule
Beta glucose
OH above the plane of the molecule
Characteristics of disaccharides? (2)
1) formed by a condensation reaction (loss of water) between 2 monosaccharides
2) broken down by a hydrolysis reaction (gain of water)
3 types of disaccharides?
1) maltose: alpha glucose + alpha glucose (seeds, fruits)
2) sucrose: alpha glucose + fructose (table sugar)
3) lactose: alpha glucose + galactose (milk sugar)
The bond between 2 monosaccharides forming a disaccharide is?
glycosidic bond
Characteristics of polysaccharides? (4)
1) several thousand monosaccharides long
2) not sweet, insoluble, crystalline
3) storage and structural molecules
4) easily converted to sugars by hydrolysis
Describe amylose and amylopectin
amylose: coiled structure, compact, reactive ends at each end
amylopectin: highly branched structure, reactive ends at the end of each branch
What are reactive ends?
enzymes can only attach at reactive ends
less reactive ends = harder to hydrolyse and break down into glucose
Structure of polysaccharide starch? (3)
– storage molecule
– polymer of alpha glucose
– made up of 20% amylose, 80% amylopectin
Structure of polysaccharide glycogen? (4)
– storage molecule
– NOT amylose and amylopectin
– more highly branched than starch
– 1-4, 1-6 glycosidic bonds
Structure of polysaccharide cellulose? (7)
– structural molecule
– polymer of beta glucose
– alternate molecules are rotated 180
– OH groups form H bonds with neighbouring chains
– 60-70 chains form microfibrils (bundles) which form fibres that run in different directions in the cell wall
– high tensile strength, ductile, stretchable
– fully permeable to water and solutes
What is a dipole?
an unequal distribution of charge, dipole molecules are also polar
What is a hydrogen bond?
a weak bond formed by the attraction between a slightly positive atom and a slightly negative atom
What symbol means ‘slightly’?
delta
Characteristics of triglyceride?
1) contains carbon, hydrogen and oxygen
2) non polar
3) insoluble in water
4) soluble in organic solvents (e.g alcohol)
General formula of fatty acids
CH3(CH2)nCOOH
At room temperature, fats are ___ and oils are ___ because they have the same chemical composition
solids, liquids
Triglycerides are formed of?
3 fatty acids and 1 glycerol
What is the bond between the glycerol and the fatty acids?
ester bond, formed through condensation
What are fatty acid tails?
hydrocarbon chains
4 functions of proteins?
1) enzymes are proteins
2) present in cell surface membranes
3) antibodies are proteins
4) keratin is a protein, present in hair and nails
Draw the chemical structure of a protein
amine group on the left, NH2
carboxylic acid group on the right, COOH
central carbon atom with one H branching off the bottom
R group at the top
What is the most basic R group out of the 20 different types?
glycine (a hydrogen)
R groups can make acids…(3)
1) polar
2) acidic
3) basic
What is a peptide bond joining 2 amino acids?
loss of hydroxyl (OH) from a carboxylic group, loss of hydrogen atom from amino group, forming a water molecule
What is primary structure?
the sequence of amino acids in a polypeptide
What is secondary structure and which 2 structures can they form?
when a polypeptide chain bends back on itself, causing hydrogen bonds to form between hydrogen and oxygen
they form:
1) alpha helix
2) beta pleated sheet
What breaks the hydrogen bonds in the secondary structures? (2)
– high temperatures
– pH changes
What is tertiary structure?
3 dimensional coiling of the chain of amino acids
What are 4 types of bonds?
1) hydrogen bond
– many together can be strong
2) disulfide bond
– strong
3) ionic bond
4) hydrophobic interactions
– stay together because they are repelled by the watery environment around them
What is quaternary structure?
3 dimensional arrangement of two or more polypeptides
OR
of a polypeptide and a non-protein molecule
What is a globular protein and its characteristics (3) ?
when polypeptides are folded into a spherical shape
– often water soluble
– metabolically active (e.g enzymes, insulin)
– physiological roles
What is a fibrous protein and its characteristics (2) ?
forms long strands
– not soluble in water
– structural roles
What type of protein is haemoglobin?
a globular protein
How many polypeptide chains in haemoglobin?
4
Which 2 types of globin are used to make haemoglobin?
alpha globin, makes alpha chains
beta globin, makes beta chains
What is a haem group?
present in each of the 4 polypeptide chains in haemoglobin, each haem group has an iron atom which binds with an oxygen molecule
How is the haem group responsible for the colour of haemoglobin?
if the iron atom is combined with the oxygen molecule:
bright red
if not combined:
dark bluish red
What is sickle cell anaemia?
an inherited genetic disorder, caused by a faulty gene coding in haemoglobin that causes it to respires when oxygen concentrations are low, can affect any of the major organs
What type of protein is collagen?
a fibrous protein
How many polypeptide chains are in collagen, and in what shape?
3, helix shape
Which amino acid is found in collagen molecules?
glycine, found on the insides of the strands; its small size allows the 3 strands to lie close together and form a tight coil
What is the structure of collagen fibres?
Covalent bonds form between the helixes lying next to each other, forming fibrils, which have staggered ends to prevent weak spots. These fibrils form fibres.
What is an advantage of collagen?
it is flexible yet has high tensile strength; can withstand intense pulling forces
What is water?
a universal solvent
What are the characteristics of water?
– forms hydrogen bonds to other water molecules, makes it difficult to separate molecules
– high specific heat capacity, resistant to changes in temperatures
– high latent heat of vaporisation
What are the functions of water?
– is a medium for molecules and ions to mix in
– a transport medium because molecules and ions dissolve in water
– stable habitats for aquatic organisms
– evaporation used as a cooling mechanism
