Biological Molecules Flashcards
1
Q
What are biological molecules?
A
Biological molecules are molecules that are present in organisms that are essential to biological processes.
2
Q
What are some examples of biological processes?
A
Cell division and development
3
Q
What are the four major classes of biological molecules?
A
Carbohydrates, lipids, proteins and nucleic acids. These molecules may be produced by the organisms or obtained through their nutrition.
4
Q
What are nutrients?
A
Nutrients are chemical substances in food that provide energy and materials needed by the body. Nutrients can grow and repair cells and provide energy.
5
Q
How can nutrients be classified and describe them?
A
Nutrients can be classified into organic (biological molecules derived from living things) or inorganic (not derived from living things e.g. water, mineral salts)
6
Q
What is a carbohydrate?
A
A carbohydrate are organic molecules made up of carbon, hydrogen and oxygen.
7
Q
What are the three functions of carbohydrates?
A
To provide energy for cellular activities 1g carbs release about 17kJ
To form supporting structures (e.g. cell wall) cellulose of plant cell walls
To form nucleic acids (e.g. DNA)
For conversion into other organic compounds as excess sugar can be converted to fat
7
Q
What is the general formula for carbohydrates?
A
CnH2mOm
8
Q
What is the ratio of hydrogen atoms to the oxygen atoms in carbohydrates?
A
2:1
9
Q
What are the three types of carbohydrates?
A
Monosaccharides (Single sugars)
Disaccharides (double sugars)
Polysaccharides (complex sugars)
10
Q
What is the main substrate (ingredient) for ATP generation in cells?
A
Glucose
11
Q
Too much carbohydrate is bad. True of false?
A
True as carbohydrates contain sugar. Generally, anything that is too much in excess is bad.
12
Q
What are some examples of carbohydrates?
A
Rice, bread, noodles, potato, bananas
13
Q
What are some examples of proteins?
A
Generally, meats, nuts and eggs
14
Q
What are some examples of lipids (includes fats, vitamins)?
A
Oil, butter, margarine,
A,B,C,D,E,K vitamin
Fruits, carrot
15
Q
What are some examples of water?
A
Fluids, drinks and water.
16
Q
What is an isomers?
A
Isomers are substances that have the same chemical formula but different structural formula and arrangement of bonding is different.
17
Q
What is an example of an isomer?
A
C4H10 you can try to draw two different structural formula in notability
18
Q
What are the two types of isomers?
A
There is a straight linear molecule and a branch molecule. A straight linear molecule means that the element for e.g. C4 can be connected with just one stroke whereas a branch molecule cannot be connected in one stroke.
19
Q
What are the three simple sugars that you have learnt?
A
Glucose, Fructose and galactose
20
Q
What is the chemical formula of simple sugar?
A
C6H1206
21
Q
What are two facts of simple sugars ?
A
Simple sugars are small molecules which cannot be further digested and can pass through plasma membrane. All simple sugars are reducing sugars.
22
Q
What are the three double sugars?
A
Maltose, sucrose and lactose.
23
Q
What is the chemical formula of double sugars?
A
C12H22011
24
What is the difference between maltose, lactose and sucrose?
Maltose and lactose are reducing sugars while sucrose is a non-reducing sugar.
25
What is a condensation reaction?
A condensation reaction is that double sugars are produced when two simple sugars join.
Two simple substances react and combine together to form a larger molecule and a H2O molecule is lost.
26
What are the three reactions between simple sugars and double sugars? (During condensation)
Glucose + Glucose —> Maltose + Water
Glucose +Fructose—> Sucrose + Water
Glucose + Galactose—> Lactose + Water
Generally:
C6H12O6 + C6H12O6 —>C12H22O11 +H2O
27
What is hydrolysis and the three reactions between double sugar and simple sugar?
A double sugar can be split into two simple sugars.
Maltose + Water—> Glucose +Glucose
Sucrose +Water—> Glucose +Fructose
C12H22O11 +H2O —> C6H12O6 + C6H12O6
28
When you put sucrose (table sugar) into water, would glucose and fructose be produced?
No, this is because chemical reaction needs a certain condition (temp, r.t.p. , etc)
That is why there are enzymes in order to speed up chemical processes
One example of enzymes is sucrase.
29
What are the examples of reducing sugars?
All simple sugars (glucose, fructose and galactose) and double sugars (except sucrose) are reducing sugars.
30
How can the presence of reducing sugars be tested?
The presence of reducing sugars can be tested with Benedict’s test.
31
What are the procedures for the Benedict’s test?
1. If solid, grind the food sample with distilled water using a mortar and pestle before filtering the mixture to obtain the filtrate.
2. In a test tube, add an equal volume of Benedict’s reagent to 2cm cube of the filtrate or liquid food sample
3. Shake the mixture
4. Heat a beaker of water until it boils
5. Leave test tube(s) in boiling water bath for 2 minutes.
32
For Benedict’s test, if you observe that the solution remained blue, what can you conclude?
Reducing sugar is not present
33
What are the two things in a result?
Observation and conclusion
34
For Benedict’s test, if you observe that green precipitate is formed, what can you conclude?
Traces of reducing sugar present
35
For Benedict’s test, if you observe that yellow or orange precipitate formed, what can you conclude?
Moderate amount of reducing sugar present
36
For Benedict’s test, if you observe that brick-red precipitate formed, what can you conclude?
Large amount of reducing sugar present
37
What are complex sugars?
Complex sugars are complex carbohydrates that are made up of many single sugar molecules combined by condensation reactions.
38
What are the three complex carbohydrates/sugars?
Starch, Glycogen, Cellulose
39
How are complex sugars made up of?
Complex sugars are made up of numerous glucose molecules which are linked in different ways. These different structures result in different properties.
40
What are the functions of glycogen?
Storage form of carbohydrates in animals.
Easily digested to glucose to provide energy when needed
41
What are the structure and properties of Glycogen?
Branched macromolecule that is compact (allowing the storage of more glucose monomers per unit volume)
The glucose molecules are arranged in short helical chains with many branches so that they are compact.
42
Where is/are the occurrence of glycogen?
Stored in liver and muscles of animals
43
What is/are the function of starch?
Storage form of carbohydrates in plants
Easily digested to glucose to provide energy when needed
44
What is/are the structure and properties of starch?
Branched macromolecule that is compact (allowing the storage of more glucose monomers per unit volume)
The glucose molecules are joined together in long helical chains with branches, so that they are compact.
45
What is the occurrence of starch?
Found in storage organs of plants e.g. potato tubers
46
What is the function of cellulose?
Structural form of carbohydrates to provide cell walls with mechanical strength and support, to protect plant cells Cannot be digested by humans
47
What is/are the structure and properties of cellulose?
Unbranched macromolecule.
The glucose molecules are arranged in long straight chains, giving them high tensile strength.
48
Where is the occurrence of cellulose?
Present in cell walls of plants
49
What are the differences between glycogen and starch?
1. The glucose molecules are arranged in short helical chains with many branches in Glycogen while the glucose molecules are joined together in long helical chains with branches in starch.
2. The occurrence of glycogen is stored in liver and muscles of animals while the occurrence of starch is found in storage organs of plants e.g. potato tubers.
50
What are the procedures for iodine test for starch?
Add 2-3 drops of iodine solution to food sample
51
Based on the observation that the iodine solution remains orange-brown, what can you conclude?
Starch is not present
52
Based on the observation that the iodine solution turn blue-black, what can you conclude?
Starch is present
53
What is fats?
Fats are a type of lipids ( a class of mostly hydrophobic naturally occurring molecules that includes fats, waxes, steroids, vitamins and phospholipids)
54
What is fats made up of?
Fats are organic molecules made up of carbon, hydrogen and oxygen.
55
What are two things that you need to know about fats?
1. The proportions of the elements in fats are not fixed but they contain less oxygen in proportion to hydrogen when compared to carbohydrates.
2. A fat molecule is made up of one glycerol molecule and three fatty acid molecules that is combined through a condensation reaction.
56
What are the three functions of fats?
A source and store of energy
Insulating layer below skin.
Thermal insulation below skin, prevents heat loss
Mechanical protection-Cushions and protects vital organs.
57
What is the test name for fats?
Ethanol Emulsion test
58
What are the procedures for liquid samples to test for fats?
1. Add 2cm cube of ethanol to food sample in a test tube and shake throughly
2. Add 2 cm cube of distilled water and shake
59
What are the procedures for solid sample to test for fats?
1. Cut and grind the food sample into small pieces and place them in a test tube
2. Add 2 cm cube of ethanol and shake throughly
3. Allow a few minutes for solid particles to settle
4. Decant the ethanol (pour off only the top layer of ethanol) into another test tube containing 2 cm cube of distilled water
60
For Ethanol Emulsion test, if you observe that the solution remained clear and colourless, what can you conclude?
Fat is not present
61
For Ethanol Emulsion test, if you observe that a cloudy white emulsion is formed, what can you conclude?
Fat is present
62
What is another way to call fiber?
Cellulose
63
Link structure with _____. Give two examples.
Link structure with function
For e.g. Microvilli
Finger-like protrusions— increased surface area to volume ratio and therefore increasing the rate of absorption.
64
In cow’s stomach, cellulose would be broken down by bacteria to form ________. What is this also known as?
…. To form glucose.
This is also known as mutualism.
65
Carbohydrates are more mass-efficient stores of energy than fats.
True or false?
False, fats are more mass efficient than carbohydrates, that is why excess carbohydrates is converted into fats and allow easier movement. But since plants do not need to move, they store it as starch.
66
Adding water to a grain of sucrose at r.t.p will hydrolysis all the sucrose molecules into glucose+ fructose. True or false?
False. The grain of sucrose would only dissolve. It isn’t so easy for hydrolysis to occur, that’s the purpose of the digestive system in the human body.
67
What are proteins?
Proteins are organic molecules made up of carbon, hydrogen, oxygen and NITROGEN. (sometimes also SULFUR, if the amino acid *cysteine or *methionine is present)
68
What are proteins made of?
1. Proteins are made up of carbon, hydrogen, oxygen and nitrogen. (sometimes also sulfur)
2. Each protein molecules is made up of smaller basic units called amino acids.
69
What are amino acids made up of?
An amino group are made up of
1. an amino group (NH2)
2. An acid group (COOH)
3. A side chain (R)
picture of these in your mind:
C in the centre
H below
H2N at the left of C
R on top of C
COOH to the right of c
Take note when you are needed to draw the full structural formula of amino acids, you ned to show the bonds of NH2, COOH too
70
How are amino acids combined and broken down?
Two amino acid molecules are combined (by condensation reaction) to form a dipeptide
A dipeptide is broken down (by hydrolysis) into its constituent amino acids.
71
Peptide bonds like up many amino acids to form a ______
polypeptide (via *condensation)
72
One or more ______ chains fold to form a 3-D molecule, called ______.
One or more polypeptide chains fold to form a 3-D molecules, called protein.
72
What are the four types of levels of organisation of protein.
Primary level, Secondary level, Tertiary Level and Quaternary level.
73
State primary structure, secondary structure, tertiary structure and quaternary structure of proteins.
Primary level: the sequence of amino acids in the polypeptide chain.
Secondary level: local folding of polypeptide chain causes formation of helices and sheets.
Tertiary level: Further folding of entire polypeptide chain to form 3D shape.
Quaternary level: Association of more than one polypeptide to form final functional protein
74
What are the functions of protein?
Used in the synthesis of new protoplasm for growth & repair of worn-out cells
May function as:
--Enzymes (biological catalysts)
--Hormones (chemical messengers in the blood) e.g. Adrenaline
--Transport proteins e.g. Haemoglobin
--Structural proteins e.g. collagen (in bones, skin, tendons) keratin (in hair, nails)
--Antibodies (specialised proteins that fight bacteria and viruses)
75
What is the Biuret test for and it tests the presence of _____?
Biuret test for proteins
Tests for the presence of peptide bonds (so it can't test for amino acids!)
76
What are the procedures for Biuret test?
1. add 2cm cube of sodium hydroxide solution (NaOH) to food sample and shake the mixture thoroughly.
2. Add 1% copper (II) sulfate solution (CuSO4) drop by drop, shaking after every drop. (usually just add 2-3 drops)
77
if you observe, based on the result that the solution remains blue, what can you conclude?
Proteins are not present
78
If you observe, based on the result that the solution turns violet what can you conclude?
Proteins are present.
79
What is metabolism?
Metabolism is the sum of all the chemical reactions taking place within a living organism.
80
What is metabolism made up of?
Anabolic reactions and Catabolic reactions
81
What is anabolic reactions?
--Building up of complex substances from simpler substances with absorption of energy (e.g. building proteins from amino acids and photosynthesis since light energy is absorbed by the chlorophyll)
82
What is catabolic reactions?
--Breaking down of complex substances into simpler substances with release of energy (e.g. breakdown of glucose during cellular respiration)
83
For anabolic reactions, what are the reactants/substrates and the products?
Reactants/substrates:
energy + smaller molecules
and then enzymes are also involve in the chemical reaction as it speeds it up
Products: Larger molecule
84
For catabolic reactions, what are the reactants/substrates and the products?
Reactants/substrates: larger molecule
and then enzymes are also involve in the chemical reaction as it speeds it up
Products: energy+ smaller molecules
85
Random collisions means that there is a chemical reaction. True or false? Why or why not?
Random collisions does not necessarily mean a chemical reaction.
Two conditions are needed for successful chemical reaction.
1. Correct orientation
2. Reactants must have enough activation energy. (If there is not enough energy, then it will separate again
86
What is the term that we used to say that
Collisions that lead to a chemical reaction= _______
Effective collisions
87
What is an activation energy?
Activation energy is the minimum amount of energy required for a chemical reaction to occur.
88
What is the relationship between reactions rate and activation energy?
Slower reactions tend to have higher activation energies and faster reactions tend to have lower activation energies.
89
What is a catalyst?
A catalyst is a substance that speeds up a chemical reaction by providing an alternative reaction pathway of lower activation energy. It remains chemically unchanged at the end of the reaction, so they can be reused thus only required in small amounts.
90
Catalyst lower the activation energy of the reaction. True or false? Why or why not?
False. A catalyst speeds up a chemical reaction, it does not lower the activation energy.
91
What are enzymes?
Are biological catalysts
They are proteins, organic(or *RNA) that speed up chemical reactions, while remaining chemically unchanged at the end of the reaction.
92
What will happen if there is an absence of enzymes? Do give an example.
Without enzymes, metabolic processes will not proceed at a rate fast enough to sustain life.
e.g. digestion ( it would both slow down the rate of digestion and result in food not being properly digested.)
93
To obtain nutrients, food molecules which are ___and ____ in _____ have to be digested with the help of ____ into ___, ___ molecules in order to pass through the _______ for assimilation.
To obtain nutrients, food molecules which are large and insoluble in water have to be digested with the help of enzymes into smaller, simpler molecules in order to pass through the plasma membrane for assimilation.
(Just in case you are wondering what assimilation means: the absorption and digestion of food or nutrients by the body or any biological system.) definition from google
94
What are the four types of digestive enzymes?
Amylase, Maltase, Protease and Lipase
95
Catalyst do not ____ reactions to occur, they _____ reactions.
Catalysts do not cause reactions to occur, they catalyse reactions.
Be careful how you write your answer
Always remember to add in the word catalyses/speeds up for catalysts
96
How do enzymes speed up chemical reactions?
Enzymes provide an alternative reaction pathway with lower activation energy for the reaction to take place.
97
An enzyme has a complex three dimensional structure.
(i) Name the part of the enzyme’s structure that binds to substrates.
(ii) Describe how the structure in (i) recognises substrate molecules.
The active site in enzymes recognise substrates when the substrate molecules has a complementary shape to that of the active site to fit into the enzyme and form an enzyme-substrate complex. The active site also has a specific 3D shape that is complementary to that of the substrate. (Remember to refer back to the notes).
98
The Benedict’s test is
(A) qualitative test
(B) semi-quantitative test
(1) A
(2) B
(3) All of the above.
(4) None of the options.
Explain.
Ans: 3
The Benedict’s test is not only a qualitative test, but also a semi-quantitative test.
Explain why the Benedict’s test is semi-quantitative test.
Benedict’s test given an approximation of the concentration of reducing sugars in the sample through: colour of precipitate (green, yellow/ orange, brick-red), the rate of colour change/coloured-precipitate formation, mass of precipitate obtained.
99
Suggest why a water bath is used instead of direct heating using a Bunsen flame?
Water bath ensures that a constant, uniform temperature is maintained during heating. Direct heating with a Bunsen flame may cause the hot solution in the test tube to spill out and scald people nearby. Moving the test-tube in and out of the Bunsen flame may be inconvenient and a greater safety risk (increase likelihood of causing harm).
100
Suggest why prolonged boiling of the sample discouraged for the Benedict’s test.
Prolonged boiling may hydrolysis other kinds of carbohydrates (e.g. sucrose) into reducing sugars, giving false positives.
101
Which statement about proteins and lipids is false?
A Both molecules can be found in the cell surface membrane.
B Both molecules are large molecules made of many repeating units.
C Fats is a store and source of energy.
D Hormones can be made of either molecule.
B
B is wrong because fats is not a repeating unit, it is made up of one glycerol and three fatty acids.
C is correct (refer to notes)
D is correct because hormones can be, for example, made of insulin (peptide-> protein) or testosterone—> lipid
102
What is the molecule that gives positive result with Benedict’s test only after hydrolysis?
Sucrose
This is because Sucrose +water—> fructose + glucose
Fructose and glucose give positive result with Benedict’s test as they are reducing sugars.
103
Explain why there is a high percentage of carbohydrate in plant tissues.
Photosynthesis produces glucose and it store excess energy as starch. The main component of plant cell wall is cellulose. Glucose, starch and cellulose are all carbohydrates which is why there is a high percentage of carbohydrate in plant tissues.
104
Protein:
1. Plant tissues (5% of the total mass)
2. Animal tissues (20% of the total mass)
Fats:
1. Plant tissues (1% of the total mass)
2. Animal tissues (15% of the total mass)
Suggest reasons for the differences in the protein and in the fat content of the plant and animal tissues.
Point form:
Excess energy stored as farts in animals
Protein: muscles largely protein
Skin largely protein
Fat:
Muscles contain fat
Animal cells/tissues/skin contains fat
Fat in animals insulates against heat loss
Explain plants:
……. Sorry i need to sleep think of it as plants don;t need to move so excess energy does not need to be converted to fats for easier movement.
105
What are the building blocks of enzymes?
Amino acids.
106
How do enzymes speed up chemical reactions?
Enzymes provide an alternative reaction pathway with lower activation energy for the reaction to take place.
107
Describe how the active site recognises substrate molecules.
The active site has a specific 3D shape that is complementary to that of the substrate.
Characteristic: highly specific in their action (substrate-specific)
108
State the optimum temperature for enzymes to work in the human digestive system.
37.0 degrees celcius
109
Explain, in terms of the “lock-any-key” model, how the enzyme will change when it is denatured, leading to a lack of enzyme activity.
Enzyme is the lock and substrate is the key. (Secure this first mark)
It will cause the enzyme to be denatured, causing a loss/change in 3D change of enzyme and its active site, hence active site no longer complementary/ cannot bind to substrate, and there is no formation of enzyme-substrate complex.
110
When carrying out the Benedict’s and Biuret tests, what is the purpose of crushing with a small amount of water?
The purpose of crushing is to increase the surface area to volume ratio that the food is expose to water and a small amount of water is used to make it more concentrated for extraction for testing.
111
What is the difference between starch and glycogen vs cellulose?
Starch and glycogen are both storage form of carbohydrates while cellulose is the structural form of carbohydrates.
112
These complex sugars are made up purely of the single sugar ________.
Fill in the blank.
Glucose
113
What are some advantages of fats as sources and stores of energy compared to carbohydrates?
Fats release around 39kJ per gram while carbohydrates release around 17kJ per gram when oxidised, thus fats is a more efficient storage of energy per unit mass; more energy can be carried and stored per unit mass.
114
Describe the effects of temperature on enzyme activity.
Increasing temperature below optimum temperature
-Increase temperature—> Increase kinetic energy (of enzymes and substrates)
-More substrate particles have kinetic energy greater than activation energy
-Higher frequency of collisions between enzymes and substrates.
Increase frequency of effective collisions
Increase frequency of enzyme-substrate complex formation
Increase rate of enzyme activity
At optimum temperature
Highest frequency of effective collisions
Highest frequency of enzyme-substrate complex formation
Highest rate of enzyme activity
Increasing temperature above optimum temperature, denaturation is irreversible
Thermal agitation/high temperature disrupts/breaks the bonds that holds enzyme and its active site in specific 3D shape.
Enzyme denature
Shape of active site no longer complementary to substrate
No enzyme activity
115
2cm cube of sucrose and 2cm cube of sucrose are mixed together in a test tube at optimum pH and temperature. The mixture is tested with Benedict’s reagent and biuret’s reagent separately.
A Benedict’s test (blue solution) Biuret test (blue solution)
B Benedict’s test (blue solution) Biuret test (violet solution)
C Benedict’s test (orange precipitate) Biuret test (blue solution)
D Benedict’s solution (orange precipitate) Biuret test (violet solution)
D
Water + Sucrose—(Sucrase)—> Glucose +Fructose
Glucose and fructose are both reducing sugars and hence the results of the Benedict’s test would be positive, in this case orange precipitate.
Sucrase is an enzyme and enzymes are protein, thus for the Biuret test, it will be a positive test which is the violet solution.
116
Suggest what enzyme this detergent contains that allow it to work effectively against grease stains.
Lipase.
Grease is like oil.
117
Which of the following activities or properties reveals the protein nature of enzymes?
A Enzymes are inactivated at low temperature.
B Enzymes catalyse chemical reactions.
C Enzymes reactions decrease rapidly above 50 degrees celcius
D Enzymes remain unchanged during a chemical reaction.
C
A is wrong because this option doesn’t specifically relate to enzymes being proteins. Many substances, not just proteins, show reduced activity at lower temperatures.
B is wrong because Chemical catalysts (e.g., platinum, iron) also catalyze reactions without being proteins. So, while this statement is accurate about enzymes' function, it doesn't directly point to their protein structure.
D is wrong because chemical catalysts also remain unchanged during a chemical reaction
118
In what condition of temperature, will an enzyme denature?
The change in the three dimensional shape of an enzyme’s active site is due to exposure to high temperature and is known as desaturation (thus it is not because of low temperatures)
119
Will an enzyme be affected by differences in water potential of the surroundings? Explain.
An enzyme is not a cell or organelle bound by a partially permeable membrane, thus will not be affected by differences in water potential of the surroundings.
120
When temperature increases, what will the graph of the amounts of substrates look like?
121
When temperatures increases, what will the graph of the enzyme activity look like?
Increase and then decrease
122
The rate of reaction usually ____ for every 10 degrees celcius of increase.
The rate of reaction usually doubles
