biological molecules A Flashcards
monomer…
small,single molecule,many of which can be joined together to form a polymer
polymer…
large molecule made up of many similar/identical monomers joined together
condensation reaction…
-joins 2 molecules together
-eliminates a water molecule
-forms a chemical bond
hydrolysis reactions…
-separates 2 molecules
-requires addition of a water molecule
-breaks a chemical bond
polymers —> monomers
hydrolysis reaction
monomers—>polymers
condensation reaction
4 examples of monomers…
~ Monosaccharides( Glucose, galactose)
~ Nucleotides
~ amino acid
~ fatty acid or glycerol
what elements do carbohydrates contain?
C,H and O
monosaccharides…
the monomers from which larger carbohydrates are made
disaccharides…
formed by the condensation of 2 monosaccharides
glucose is a ……. sugar
hexose
what are the two types of glucose?
alpha glucose and beta glucose
what type of bond is formed between two monosaccharides as a molecule of water is released ?
glycosidic bond
What is a Sucrose made up of?
Fructose & Glucose
What is Maltose made up of?
Glucose & Glucose
What is Lactose made up of?
Glucose & Galactose
what is the test for reducing sugars?
1.add benedict’s reagent (blue) to sample
2.heat in a boiling water bath
3.positve= green/yellow/orange/red precipitate
what is the test for non reducing sugars?
-heat sample with benedict’s reagent and if it stays blue then there’s no reducing sugar present
-Heat sample in a boiling bath with dilute HCl
-Add sodium hydrogen carbonate
-Heat sample with benedict’s reagent
-Positive result will form a brick red precipitate
which disaccharide is a non-reducing sugar?
-sucrose
which disaccharides are reducing sugars?
-maltose and lactose
are all monosaccharides reducing sugars?
yes
polysaccharides…
When three or more monosaccharides are joined together by a condensation reaction with a glycosidic bond connecting each monosaccharide.
What 2 polysaccharides make up starch?
Amylose and Amylopectin
why is starch a good storage molecule?
-insoluble in water and doesn’t affect water potential
-large molecule so it cannot leave the cell
-helical therefore compact for storage in cell
what happens when a plant needs more glucose for energy?
it breaks down starch to release the glucose
compare amylose and amylopectin
amylose:
-unbranched alpha glucose
-1,4 glycosidic bonds
-helical so compact
amylopectin:
-branched alpha glucose
-1,4 and 1,6 glycosidic bonds
-branched means enzymes can easily access more glycosidic bonds
describe how the structure of glycogen is related to its functions
-branched; can rapidly be hydrolysed to release glucose for respiration to provide energy
-large polysaccharide molecule; cant leave cell
-insoluble in water; water potential of cell not affected
describe the structure of glycogen
-polysaccharide of alpha glucose
-joined by glycosidic bonds
-branched structure
suggest how glycogen acts as a source of energy
-hydrolysed to glucose
-glucose used in respiration
what is the function of cellulose in plants? Explain how its structure accomplishes its function.
-long unbranched chains of beta glucose
-when beta glucose molecules bond they form straight cellulose chains
-cellulose chains are linked by hydrogen bonds to form strong fibres meaning cellulose provides structural support for cells
describe the structure of cellulose and explain how it is adapted for its function in cells
-every other beta glucose molecule is inverted in a long, straight, unbranched chain
-many hydrogen bonds link parallel strands (cross links) to form micro fibrils (strong fibres)
-h bonds are strong in high numbers
-provides strength and structural support to plant cell walls
give similarities between starch and cellulose
-both polysaccharides
-contain glucose
-contain glycosidic bonds
-have 1-4 links
-hydrogen bonding within structure
test for starch
-add iodine dissolved in potassium iodide solution to test sample
-positive result: browny orange to blue black colour
what are lipids made from?
from a variety of different components but they all contain hydrocarbons
why are unsaturated lipids liquid at room temperature?
-presence of the double bond means that the molecule is able to bend
-therefore unsaturated fats cannot pack together tightly, hence its liquid at room temperature
describe how to test for lipids in a sample
1-dissolve solid samples in ethanol
2-add an equal volume of water and shake
3- positive result = milky white emulsion forms
what are micelles?
-tiny droplets consisting of fatty acids and monoglycerides surrounded by bile salts
name the two types of lipids
triglycerides and phospholipids
what are the components of triglycerides?
-glycerol
-three fatty acids which have long tails made of hydrocarbon
why do the hydrocarbon tails make lipids insoluble in water?
they are hydrophobic so they repel water molecules
how are triglycerides formed?
-condensation reaction of glycerol and three molecules of fatty acids
-removal of three molecules of water
-ester bonds formed
name two types of fatty acids
saturated and unsaturated
how can you tell whether the fatty acid is unsaturated or saturated?
unsaturated fatty acids have double bonds between carbon atoms and saturated fatty acids do not
how is an ester bond formed
by a condensation reaction between glycerol and a fatty acid
what are the components of phospholipids?
-phosphate group
-glycerol
-two fatty acids
is the phosphate group hydrophobic or hydrophilic?
hydrophilic as it attracts water
are the fatty tails hydrophobic or hydrophilic?
hydrophobic as they repel water
why are triglycerides used as an energy storage molecule?
-long hydrocarbon tails of fatty acids contain lots of energy and triglycerides have 3 fatty acids so are able to store lots of energy
-insoluble due to hydrophobic tails which means it doesn’t affect water potential
why do the tails face inwards?
to shield themselves from water with their glycerol heads
why do storage molecules have to be insoluble?
otherwise they would dissolve and release whatever they are storing whenever they come into contact with water
what do phospholipids do ?
make up the bilayer of cell membranes which control what enters and leaves the cell
which properties of phospholipids make it suitable to form up the bilayer of cell membranes?
-hydrophobic tail and hydrophilic head so they form double bilayer with their heads facing out
-allows them to form a membrane that acts as a barrier to water soluble substances
what test is for lipids?
emulsion test
describe an emulsion test
-shake test substance with ethanol then pour the solution into water
-any lipid will show up as a milky emulsion
- the more lipid there is, the more noticeable the milky colour will be
what are proteins made from?
made up of one or more polypeptides of the monomer amino acid
describe the structure of proteins as enzymes
-spherical shape since the polypeptide chains are tightly folded
-soluble to be used in metabolic processes
-used in digestive enzymes and in biological molecule synthesis
how many amino acids are common in all organisms but differ only in their side group?
20
what bond does the condensation reaction between two amino acid form?
peptide bond
how do dipeptides and poly peptides form?
-condensation reaction forms a peptide bond and eliminates a molecule of water
-dipeptide: 2 amino acids
-polypeptide:3 or more amino acids
how many levels of protein structure are there?
4
define the primary structure of a protein
-sequence of amino acids in the polypeptide chain
-determined by sequence of codons on mRNA
define the secondary structure of a protein
-hydrogen bonds form between the amino acids in the chain
-makes it automatically coil into alpha helix
or
-fold into a beta pleated sheet
define the tertiary structure of a protein and name the bonds present
3D structure formed by further folding of polypeptide
-disulfide bridges
-ionic bonds
-hydrogen bonds
describe each type of bond in the tertiary structure of proteins
-disulfide bridges: strong covalent S-S bonds between molecules of amino acid cysteine
-ionic bonds: relatively strong bonds between charged R groups (pH changes cause these bonds to break)
-hydrogen bonds: numerous and easily broken
define quaternary structure of a protein
-functional proteins may consist of more than one polypeptide
-precise 3D structure held together by the same types of bond as tertiary structure
-may involve addition of prosthetic groups e.g metal ions or phosphate groups
describe the biuret test for protein
-test solution needs to be alkaline, so first you add a few drops of sodium hydroxide solution
-then add some copper(ll) sulfate solution
-if the protein is present, solution turns purple, and if not it stays blue
list 4 types of protein molecules found in organisms
-enzymes
-antibodies
-transport proteins
-structural proteins
what are enzymes?
-biological catalyst for intra and extracellular reactions
-specific tertiary structure determines shape of active site, complementary to a specific substrate
-formation of enzyme-substrate complexes lowers activation energy for metabolic reactions
what does it mean to call enzymes “biological catalysts”?
-they catalyse metabolic reactions at cellular level (respiration) and in the organism as a whole (digestion)
explain why maltase can only catalyse the hydrolysis of maltose?
-active site of enzyme has specific shape
-only maltose can bind
-to form E-S complex
what is activation energy?
the energy required to start a chemical reaction
explain the induced fit model of enzyme action
-shape of active site is not directly complementary to substrate
-conformational change enables ES complexes to form
-this puts strain on substrate bonds, lowering activation energy
explain the lock and key model
-substrate fits into the enzyme like a key fits a lock
-this was before the induced fit model that came based upon new evidence
how do enzymes lower activation energy?
-enzymes attach to substrates and can hold the two substrates close together, reducing repulsion and allowing bonding to occur more easily
-enzymes break up the substrate more easy as it applies strain on the bonds
name 5 factors that affect the rate of enzyme-controlled reactions
-enzyme concentration
-substrate concentration
-concentration of inhibitors
-pH
-temperature
how does temperature affect rate of reaction?
-more heat means more kinetic energy so molecules move faster
-this makes the substrate molecules more likely to collide with the enzymes active sites
-if temperature goes above a certain level, the enzyme vibrates more and this breaks some of the bonds that hold it in shape
-active site changes shape and the substrate can no longer fit
-the enzyme is denatured
what are the 3 aspects to consider when choosing a temperature for an experiment
-sufficient kinetic energy
-does not denature proteins
-optimum
how does pH affect rate of reaction?
-all enzymes have an optimum pH value and most human enzymes work best at pH 7
-above and below the optimum pH, H+ and OH- ions can disrupt the ionic bonds and hydrogen bonds that holds the enzymes tertiary structure in place
-enzyme becomes denatured and active site changes shape
how does substrate concentration affect rate of reaction?
-more substrate molecules means a collision between substrate and enzyme is more likely and so more active sites will be occupied
-then all active sites become full so increase in substrate concentration has no further effect and its beyond saturation
how does enzyme concentration affect rate of reaction?
- more enzyme molecules means more likely a substrate molecule is to collide with one and form a enzyme substrate complex
-if amount of substrate is limited, there’s more than enough enzyme molecules so adding more enzyme has no further effect
How can you measure the rate of an enzyme controlled reaction?
-how fast the product of the reaction appears
-disappearance of the substrate
what do non competitive inhibitors do?
-inhibitor molecule fits onto enzyme away from active site
-inhibitor causes changes that alter active site
-substrate can no longer fit into active site
what do competitive inhibitors do?
-inhibitor fits into active site because it is a similar shape to the substrate molecule
contrast competitive and non-competitive inhibitors
*competitive=
-similar shape to substrate
-do not stop reactions
-increasing substrate concentration decreases their effect
*non-competitive=
- not similar to substrate
-may not stop reaction
-increasing substrate concentration has no impact on their effect
