Chapter 3 - Biological Molecules Flashcards
what is a polymer
long chain molecules made up by the linking of multiple monomers in a repeating pattern
what is a condensation reaction
a reaction which joins monomers by chemical bonds and it involves the elimination of a water molecule
what is hydrolysis
when water is added to break a chemical bond between two molecules
what chemical elements make up carbohydrates
carbon, hydrogen and oxygen
general formula: Cx(H2O)x
what chemical elements make up lipids
carbon, hydrogen and oxygen
what chemical elements make up proteins
carbon, hydrogen, oxygen, nitrogen and sulfur
what chemical elements make up nucleic acids
carbon, hydrogen, oxygen, nitrogen and phosphorous
structure of water (polar)
- each hydrogen shares a pair of e- with oxygen
- e- closer to oxygen as it has a greater affinity for them
- oxygen δ- and hydrogen δ+
- molecule is polar as it has two charged regions
how do hydrogen bonds occur between water molecules
the δ- charge on the oxygen attracts the δ+ hydrogen on another water molecule
high boiling point of water
- has a high specific heat capacity due to many stable hydrogen bonds between molecules
- large amount of energy required to break the bonds
why is ice less dense than water
below 4oC hydrogen bonds fix the positions of H2O molecules further apart than in liquid state
cohesion of water molecules
give eg
water molecules attract each other and move as one mass
eg. plants draw water up from roots/ surface tension
adhesion of water
water molecules are attracted to other surfaces
water as a coolant
high specific heat capacity buffers temperature changes on chemical reactions eg. for enzymes that may denature
other uses of water
habitat
what is a hexose monosaccharide,
has 6 carbons
types of glucose
alpha and beta
alpha glucose
OH on carbons 1 and 4 on same plane
down on carbon1
beta glucose
OH on carbons 1 and 4 on opposite planes
up on carbon1
solubility of glucose
polar due to OH groups so hydrogen bonds can form with water
dissolved in cytosol of cell
type of bond between monosaccharides
glycosidic
general condensation reaction of sugars
monosaccharides —> disaccharide + h2o
which carbons does a glycosidic bond form between usually
1 and 4
glucose + glucose
maltose
glucose + fructose
sucrose
glucose + galactose
lactose
examples of hexose monosaccharides
glucose, fructose and galactose
what is a pentose monosaccharide
sugars that contain 5 carbons
examples of pentose sugar + explain
ribose: sugar present in RNA nucleotides
deoxyribose: sugar present in DNA nucleotides
how do polysaccharides break down into simpler sugars
hydrolysis reactions
what 2 polysaccharides make up starch
amylose and amylopectin
what is starch
chemical energy store of glucose made in photosynthesis for plants
structure of amylose
alpha glucose joined by 1,4-glycosidic bonds
coiled chain in helix stabilised by hydrogen bonding
helix shape = compact and less soluble than glucose
structure of amylopectin
alpha glucose joined by 1,4-glycosidic bonds and some 1,6-glycosidic bonds
branched structure due to 1,6 bonds
structure of glycogen
alpha glucose 1,4 and 1,6-glycosidic bonds
more branching so more compact as animals have higher metabolism
what is the benefit of branched polysaccharide chains
free ends for glucose to break off quicker
structure of cellulose
beta glucose molecules 1,4-glycosideic bonds, alternate molecules rotate 180 degrees due to position of OH groups
straight chain
how do cellulose chains join together
form hydrogen bonds with eachother forming microfibrils that join to make macrofibrils that join to form insoluble fibres in plant cell walls
What are triglycerides made up of
1 glycerol 3 fatty acids
What is the synthesis of triglycerides called, what type of reaction is it
Esterification, condensation
‘Equation’ for esterification
Glycerol + 3fatty acids -—-> triglyceride + 3H2O
Name of bond between fatty acids and glycerol
Ester bond
How much water does the hydrolysis of a triglyceride require
3 molecules
Saturated fat (triglyceride)
No C=C bonds in fatty acids
Saturated fat (triglyceride)
No C=C bonds in fatty acids
Monounsaturated fatty acid
1 C=C bond in fatty acid
Polyunsaturated fat
More than one C=C bond in fatty acid
Structure of phospholipid
- hydrophilic polar phosphate head
- 2 hydrophobic non polar fatty acid tails
Cholesterol function
Stabilise cell membranes and regulate membrane fluidity
Primary structure of protein
The sequence of amino acids in the polypeptide chain
Secondary structure of a protein
The folding of a polypeptide chain into an alpha helix or beta pleated sheet by hydrogen bonding
Tertiary structure of a protein
The 3D folding of a polypeptide chain by interactions between R-groups
Interactions between side groups of tertiary protein structure
Hydrogen bonds
Ionic bonds
Discúlpate bridges
Hydrophobic interactions
Hydrophilic interactions
Quaternary protein structure
2 or more polypeptide chains joined together
Globular protein structure
Globe shaped
Hydrophilic side groups
Water soluble
Types of globular protein
Insulin
Protease
Haemoglobin
Properties of insulin and protease as globular proteins
Can diffuse through cells to bind to specific receptors
What is a conjugated protein
Containing a non-amino acid part in its structure (prosthetic group)
Haemoglobin
Globular, conjugated
4 haem groups (prosthetic) that contain iron
Structure of fibrous proteins
Proteins made up of strands and fibres
Hydrophobic side groups
Insoluble in water
Types of fibrous proteins and their functions
- collagen: strengthens tendon, bones and blood vessel walls
- elastin: increase flexibility in cartilage eg. Alveoli and artery walls
- keratin: strengthens hair, skin and nails
Biuret test
- Biuret (NaOH and CuSO4) added to sample, mixed and left
- if protein present, colour change from blue to purple
Iodine test
- iodine dissolved in potassium iodide
- added and mixed into sample
- if starch present colour change from yellow/ brown to purple/ black
Emulsion test
- mix sample with ethanol then water and shake
- if lipid present a white emulsion will form
Benedict’s test for reducing sugars
- sample in boiling tube
-add equal volume Benedicta solution - heat gently in water bath
- reducing sugar present colour change ( red precipitate)
Example of reducing sugar
Maltose and lactose
What to do if testing a solid sample
Grind up with water
Test for non-reducing sugars
- Benedicts test (negative)
- hydrolyse by boiling with dilute hydrochloride acid
- Benedicta test positive
Example of non reducing sugar
Sucrose
