Topic 1-Biological Molecules Flashcards
1
Q
How are most biological polymers formed from their monomers
A
By condensation reactions
2
Q
What reaction can be used to break down biological polymers?
A
Hydrolysis reaction
3
Q
How does a hydrolysis reaction work?
A
Breaks down the chemical bond between monomers using a water molecule.
4
Q
What are polymers?
A
Large, complex molecules composed of long chains of monomers joined together.
5
Q
What are monomers?
A
Small, basic molecular units that can form a polymer.
6
Q
Give 3 examples of monomer
A
Monosaccharides
Amino Acids
Nucleotides
7
Q
Explain what happens in a condensation reaction between two monomers
A
A chemical reaction is formed between molecules releasing a molecule of water.
8
Q
What is the theory of evolution?
A
The theory that all organisms on Earth are descended from one or few common ancestors and that they have changed and diversified over time.
9
Q
What is the name of the monomers carbohydrates are made from?
A
Monosaccharides
10
Q
Give 3 examples of monosaccharides
A
Glucose
Fructose
Galactose
11
Q
What is a hextose sugar?
A
A monosaccharide with six carbon atoms in each molecule
12
Q
What type of sugar is Glucose?
A
a hextose sugar
13
Q
State the two types of glucose
A
alpha (α)
beta (β)
14
Q
What is an isomer?
A
Molecules with the same molecular formula as eachother, but with the atoms connected in a different way
15
Q
How are alpha and beta glucose isomers?
A
They have same molecular formula as eachother but their H and OH groups are reversed.
16
Q
How is a disaccharide formed?
A
When two monosaccharides are joined together by condensation reaction.
17
Q
What type of bond is formed as two monosaccharides as a molecule of water is released?
A
Glycosidic Bond
18
Q
What do two alpha glucose molecules joined together by a glycosidic bond form?
A
Maltose
19
Q
What type of sugar is sucrose and from which two monomers is it formed?
A
Sucrose is a disaccharide formed from a condensation reaction between a glucose moleule and fructose molecule.
20
Q
What type of sugar is Lactose and from which two monomers is it formed?
A
Disaccharide formed from a glucose molecule and a galactose molecule.
21
Q
What are the two classifications of sugars?
A
Reducing sugars
Non- reducing sugars
22
Q
How do you carry out test for reducing sugars? (3)
A
Add benedicts reagent which is blue to a smaple and heat it in a water bath brought to a boil.
If the test is positive it will form a coloured precipitate
Green-Yellow-Orange-brick red
23
Q
Why may you need to add an excess of benedicts solution when testing for Sugars?
A
To make sure that all the sugar reacts
24
Q
How is a polysaccharide formed?
A
When more than two monosaccharides are joined together with glycosidic bonds by condensation reactions that release a water molecule
25
What polysaccharides of alpha-glucose are starch made off?
Amylose and Amylopectin
26
Describe the structure of amylose and explain how its an advantage
-Long, unbranched chain of α-glucose
1,4 glycosdic bonds
-The angles of glycosidic bonds give it a coilded cylinder like structure
-Making it compact and good for storage as you can fit more into a small space
27
Describe the strucucture of Amylopectin and how this is an advantage (3)
-Long branched chain of α-glucose
-1,4 and 1,6 glycosidic bonds
-Its side branches allow enzymes that break down the molecule to get at the glycosidic bonds easily
-This means glucose can be released quickly
28
How does the stucture of starch relate to its function
It is Helical-compact for storage in cells
Large and insoluble polysaccharide molecule- Cannot leave cell or cross cell membrane
Insoluble in water- Water potential of cell does not affect it
29
What is the function of glycogen
Energy store / Reserve
30
Give two ways the structure of glycogen is an advantage in animals?
-Loads of branches means that stored glucose can be released quickly
-It is a compact molecule so its good for storage
31
Describe the structure of cellulose and what it is made off?
Made of long unbranched chains of beta glucose
Has 1,4 glycosidc bonds
Straight cellulose chains which are linked together in parralel by hydrogen bonds form stong fibres called microfibrils.
32
What makes cellulose good for providing stuctural support?
Its strong fibres (microfibrils)
33
Describe the test for starch
Add iodine dissolved in potassium iodide solution to the test sample
If starch is present sample changes from browny/orange to a dark bluey black colour
34
What two types of lipids do we need to know about?
-Triglycerides
-Phospholipids
35
How are triglycerides formed?
By the condensation of one molecule of glycerol and three molecules of fatty acid
36
What makes lipids insoluble in water?
Fatty acid molecules have long tails made of hydrocarbons which are hydrophobic making lipids insoluble in water.
37
What is the difference between saturated and unsaturated fatty acids?
Saturated dont have any double bonds between their carbon atoms and is 'saturated' hydrogen.
Unsaturated do double bonds between carbon atoms which cause the cahin to kink.
38
Describe what the R group of a fatty acid is...
the hydrocarbon tail which can either be saturated or unsturated
39
What is the structure of phospholipids?
Made of two fatty acids, glycerol and a phosphate group
40
Why do triglycerides bundle together as insolubles droplets in cells
because tails are hydrophobic and its face shift inward, shielding themsleves from the water with their glycerol heads
41
Why are triglycerides good at being energy storage molecules?
Long hydrocarbon tails of the fatty acid contains lots of chemical energy, because of tails lipids contain twice as much energy per gram as carbohydrates.
42
What type of glucose is starch made from?
a glucose polymers
43
What is a chain of amino acids called?
Polypeptide chain
44
Draw the structure of A glucose the structure of maltose
45
Describe the test for reducing sugars
Add bendics solution to sample. This is blue. Heat in boiling water bath. A positive result will show green/yellow/orange/red precipitate
46
Describe the test for non reducing sugars
Do the bendicts test and the solution stays blue. Headt in a boiling water bath with acid to hydrolyse into reducing sugars. Neutralise with an alkali like sodum bicarbonate. Heat in a boiling water bath with bendicts solution. A positive result should hsow gree/yellow/orange/red precipitate
47
Suggest a method you use to measure the quantity of sugar in a solution
Carry out bebdicts solution test. FIlter and dry precipitate and weigh to find mass
48
Suggest another method to measure the unknown quantity of sugar in solution using a calorimeter
Make sugar solutions of known concentrations
(eg. dilution series)
2. Heat a set volume of each sample with a set
volume of Benedict’s solution for same time
3. Use colorimeter to measure absorbance (of
light) of each known concentration
4. Plot calibration curve - concentration on x axis,
absorbance on y axis and draw line of best fit
5. Repeat Benedict’s test with unknown sample and
measure absorbance
6. Read off calibration curve to find concentration
associated with unknown sample’s absorbance
49
Describe the biochemical test for starch
Add iodine dissolved in potassium iodide which is an orangey brown to the sample. The positve result is blue/black
50
Name to two groups of lipids
Triglycerides and phospholipids
51
Describe the stucture of a fatty acid
Variable R group on hydrocarbon chain attached to a -COOH (carboxyl group)
52
How are triglycerides formed?
1 glycerol molecule and 3 fatty acids
condensation reaction
Removes 3 water molecules and forms 3 ester bonds
53
Describe and explain the properties of triglycerides in relation to their structure
High ratio of C-H bonds to carbon atoms in hydrocarbon chain- So used in respiration to release more energy than same mass of carbohydrates
Hydrophobic / non-polar fatty acids so insoluble in water (clump together as droplets) So no effect on water potential of cell (or can be used for waterproofing)
54
Describe the difference between the strucure of triglycerides and phospholipids
One of the fatty acids in a triglyceride is substitued for a phosphate group
55
Describe the test for lipids
Add ethanol and shake to dissolve the lipid then add water. The postive result is a milky white emulsion
56
What bonds do phospholipids contain
ester bonds
57
How many amino acids are common in all organisms and how do they vary?
20 amino acids are common in all organisms and they only differ only in their side group (R)
58
Describe the primary structure of a protein
Sequence of amino acids in a polypeptide chain joined by peptide bonds
59
Describe the secondary structure of a protien
Repeating patterns of polypeptide chains e.g alpha helix and beta pleated sheets. Due to hydrogen bonding between amino acids between NH and C=O groups
60
Describe the tertiary structure of a protein
3D folding of polypeptide chain due to interactions between amino acid R groups. Thsi forms hydrogen bonds, ionic bonds and disulfide bridges
61
Describe the quaternary structure of a protein
More than one polypeptide chain formed by interactions between polypeptides forming Hydrogen and ionic bonds and disulfide bridges
62
Describe the test for proteins
Add biuret reagent (NaOH + Cu2SO4)
Positive result is a purple/lilac colour that indicates the presence of peptide bonds but negative stays blue
63
How do enzymes act as biological catalysts?
Each enzyme lowers activation energy of reaction it catalyses to speed up rate of reaction
64
Describe the induced fit model of enzyme action
The substrate binds to the active site of the enzyme but it is not completely complementary. This causes the active site to change shape slightly so it is complementary to the substrate. This causes enzyme-substate complex to form. This causes bond in substate to distort lowering AE.
65
Describe how models of enzyme action have changed over time
Intitial lock and key model is outdated and the active site was a fixed shape complementary to one substrate, however, the induced fit models show unture
66
Explain the specifity of enzymes
Specific tertairy structure determines the shape of their active site. This is dependent on the sequence of amino acids. Active site is only complementary to a specific substarte. Only this substarte can bind to active site, inducing fit and forming enzyme-substrate complex.
67
Desckieb and explain the effect of enzyme concentration on the rate of enzyme controlled reactions
As encyme conc increases the rate of reaction increases. Enzyme concentration (excess substrate) is the limiting factor, more enzymes are available so there are more active sites . More enzyme substrate complexes form. At a certain point reaction stops increasing as all subsrtate is in use and substrate conc is the limiting factor
68
Descrieb and explain the effect of substrate concentration on the rate of enzyme controlled reactions
As substrate conc increases the rate of reaction increases, Substrate conc is the limiting factor as there are too few wnxyme molecules to occupy all actiuve sites. More enzyme substrate complexes form. At a certain pintthe rate of reaction stops increasing and the enzyme conc is the limiting factor as all the active sites are saturated/occupied
69
Describe and expalin the effect of temperature on the rate of enzyme controlled reactions
As the temperature increases up to optimum, rate of reaction increases as there is more kinetic energy so more enzyme substrate complexes form. As temp increases above optimimum rate, rate of reaction decreases. Enzymes denature so their tertiary structure and active site change shape, Hydroen and ionic bonds break and active site is no longer complementary so fewer enzyme substrate complexes form
70
Descrieb and explain the effect of pH on the rate of enzyme controlled reactions
As the pH increases or decreases at optimum rate, the rate of reaction decreases as enxymes denature, the tertiary structure and active site changes shape. Hydrogen and ionic bonds break. Actibe site is no longer complementary and so fewer Enzyme substrate complexes are formed
71
Describe and explain the effect of concentration of non competitive inhibitors on the rate of enzyme controlled reactions
As conc of non competitive inhibitors increase the rate of reaction decreases. It binds to site other than the active site and changes the enzymes tertiary structure and active site shape. The active site is no longer complementary to the substrate. Substrate cannot bind and so fewer enzyme and complexes form. Increasing substrate cocn has no effect on the rate of reaction as change to active site permanent
72
Give examples of variables that could affect the rate of an enzyme controlled reaction
Enzyme- conc/vol
Substrate- conc/vol
Temperature of solution
pH of solution
Inhibitor conc
73
Describe how the temperature of enzyme controlled reaction can be controlled
Thermostatically controlled water baths
Monitors using a thermometer at regular intervals and add hot/cold water as it temp fluctuates
74
Why were the enzyme and substrate left in the water bath 10min before mixing?
So solutions equilibrate/ reach the temperature of the water bath
75
Describe how pH can be controlled
Using a buffer solution
Monitor using a pH merer at regular intervals
76
Suggest a safety risk when measuring the rate of enzyme controlled reactions
Handling enzymes may cause an allergic reaction and can be avoided by wearoing colves and eye protection
77
Expalin why using a colourimeter to measure colour change is better than comparison to colour standards
Not subjective to eye quality
More accurate
78
Explain a procudere that can be used to stop enzymic reactions where independent variable is: enzyme conc temperature, Conc of inhibitor
1) Boil/ add strong acid or alkali to denatureenzyme
2)Put in ice to lower kinetic energy so no enzyme substrte complexes form
3)Add high conc of inhibitor so no Enzyme substrate complexes form
