Biological Molecules Flashcards
1
Q
What are carbohydrates primarily composed of?
A
Carbon, hydrogen, and oxygen
Carbohydrates are organic molecules that consist mainly of carbon atoms combined with water.
2
Q
What is the general formula for monosaccharides?
A
(CH₂O)n where n can be 3 to 7
Monosaccharides are simple sugars with a specific range of carbon atoms.
3
Q
What is a monosaccharide?
A
A single sugar molecule
Monosaccharides serve as the basic building blocks of carbohydrates.
4
Q
What is the name for two monosaccharides combined?
A
Disaccharide
5
Q
What are polysaccharides?
A
Long chains of monosaccharides
Polysaccharides are formed by linking many monosaccharides together.
6
Q
Give three examples of monosaccharides.
A
- Glucose
- Galactose
- Fructose
7
Q
What are isomers?
A
Compounds with the same formula but different structures
Glucose has two isomers: α-glucose and β-glucose.
8
Q
What is a reducing sugar?
A
A sugar that can donate electrons to another chemical
All monosaccharides and some disaccharides are classified as reducing sugars.
9
Q
What is the Benedict’s test used for?
A
To test for reducing sugars
10
Q
What happens when a reducing sugar is heated with Benedict’s reagent?
A
It forms an insoluble red precipitate of copper(I) oxide
11
Q
What is the composition of Benedict’s reagent?
A
An alkaline solution of copper(II) sulfate
12
Q
What color indicates the presence of reducing sugars in the Benedict’s test?
A
Orange-brown
13
Q
What does the term ‘semi-quantitative’ mean in relation to the Benedict’s test?
A
It can estimate the approximate amount of reducing sugar present
14
Q
What is the basic monomer unit in carbohydrates?
A
Sugar or saccharide
15
Q
Fill in the blank: A pair of monosaccharides can form a _______.
A
Disaccharide
16
Q
True or False: Only monosaccharides can be reducing sugars.
A
False
Some disaccharides, like maltose, can also be reducing sugars.
17
Q
Describe how to carry out the test for reducing sugars
A
- add 2cm^3 of food sample to be tested to a test tube
- add an equal volume of Benedict’s reagent
- heat the mixture in a gently boiling water bath for 5 minutes
- if the solution turns brick-red from blue then reducing sugars are present
18
Q
What are monosaccharides linked together to form?
A
Disaccharides.
19
Q
What type of bond is formed between monosaccharides during condensation reactions?
A
Glycosidic bond.
20
Q
What is the process called when water is added to a disaccharide to break it down?
A
Hydrolysis.
21
Q
What is the test used to detect reducing sugars?
A
Benedict’s test.
22
Q
Fill in the blank: When monosaccharides combine to form a disaccharide, a molecule of _____ is removed.
A
Water.
23
Q
What must be done to a non-reducing sugar before it can be tested?
A
It must be hydrolysed into its monosaccharide components.
24
Q
True or False: Sucrose is a reducing sugar.
A
False.
25
What is the primary function of polysaccharides?
Storage.
26
How many α-glucose molecules can be joined to form starch?
Between 200 and 100,000.
27
What is the main characteristic of polysaccharides?
They are insoluble.
28
What happens to polysaccharides when they are hydrolysed?
They break down into disaccharides or monosaccharides.
29
What type of reaction involves the giving out of water?
Condensation reaction.
30
What type of reaction involves the taking in of water?
Hydrolysis reaction.
31
Fill in the blank: Polysaccharides are formed by combining many _____ molecules.
Monosaccharide.
32
What are starch grains found in?
Chloroplasts.
33
What must be done to neutralize hydrochloric acid in the test for non-reducing sugars?
Add sodium hydrogencarbonate solution.
34
What color change indicates the presence of a non-reducing sugar after hydrolysis?
Orange-brown.
35
What color does iodine solution turn if starch is present?
Blue-black
## Footnote
This color change indicates the presence of starch in the test solution.
36
What is the procedure to test for starch using iodine solution?
1. Place 1 cm³ of the sample into a test tube or depression.
2. Add two drops of iodine solution and shake or stir.
## Footnote
The presence of starch is indicated by a blue-black coloration.
37
What monomer units make up lactose?
Glucose and galactose
## Footnote
Lactose is a disaccharide composed of these two monosaccharides.
38
What monomer units make up sucrose?
Glucose and fructose
## Footnote
Sucrose is a disaccharide formed from these two monosaccharides.
39
What monomer units make up starch?
Alpha-glucose
## Footnote
Starch is a polysaccharide made of chains of alpha-glucose monosaccharides.
40
What is the chemical formula of sucrose formed from glucose and fructose?
C12H22O11
## Footnote
This formula is derived from the combination of the two monosaccharides.
41
What is one method to hydrolyze a disaccharide?
Boiling with hydrochloric acid
## Footnote
Hydrolysis can also be achieved using enzymes at much lower temperatures.
42
What is starch primarily used for in plants?
Energy storage
## Footnote
Starch serves as a major energy source in most diets.
43
Where is starch predominantly found in plants?
In seeds and storage organs like potato tubers
## Footnote
Starch forms small grains in various parts of a plant.
44
What type of bonds link the monosaccharides in starch?
Glycosidic bonds
## Footnote
These bonds are formed by condensation reactions between alpha-glucose units.
45
How are the chains of starch structured?
They may be branched or unbranched
## Footnote
Unbranched chains are coiled tightly, making starch compact.
46
What is a key feature of starch that aids in its function?
It is insoluble
## Footnote
This property prevents it from affecting water potential in cells.
47
Why is starch not found in animal cells?
Animals use glycogen instead
## Footnote
Glycogen serves a similar role as a storage polysaccharide in animals.
48
What is a structural feature of starch that aids in compact storage?
Helical structure
## Footnote
This arrangement allows for efficient packing of starch molecules.
49
True or False: Starch can diffuse out of cells.
False
## Footnote
Starch is large and insoluble, preventing it from diffusing out.
50
Fill in the blank: The main role of starch is _______.
energy storage
## Footnote
Its structure supports this function effectively.
51
What is the role of branching in starch?
Allows for rapid glucose release
## Footnote
The branched form has multiple ends for simultaneous enzymatic action.
52
What is glycogen and where is it found?
Glycogen is found in animals and bacteria but never in plant cells.
53
How does the structure of glycogen differ from starch?
Glycogen has shorter chains and is more highly branched than starch.
54
Why is glycogen sometimes referred to as 'animal starch'?
It is the major carbohydrate storage product of animals.
55
Where is glycogen primarily stored in animals?
Glycogen is stored as small granules mainly in the muscles and the liver.
56
What are the advantages of glycogen's structure for storage?
* It is insoluble and does not draw water into cells by osmosis
* It does not diffuse out of cells
* It is compact, allowing for storage in a small space
* It is highly branched, enabling rapid breakdown to glucose.
57
What is cellulose made of?
Cellulose is made of monomers of B-glucose.
58
How does the structure of cellulose differ from that of starch?
Cellulose has straight, unbranched chains, while starch forms coiled chains.
59
What contributes to the strength of cellulose?
Hydrogen bonds form cross-linkages between adjacent chains.
60
What is the role of hydrogen bonds in cellulose?
They collectively add strength to the cellulose structure.
61
How are cellulose molecules organized?
Cellulose molecules are grouped to form microfibrils, which are arranged in parallel groups called fibres.
62
What is the function of cellulose in plant cells?
Cellulose provides rigidity to the plant cell and prevents bursting from osmotic pressure.
63
How does cellulose help maintain turgidity in plant cells?
It exerts inward pressure that stops further influx of water.
64
List the structural features of cellulose that contribute to its function.
* Made of B-glucose, forming long straight chains
* Chains run parallel and are cross-linked by hydrogen bonds
* Grouped into microfibrils and fibres for additional strength.
65
True or False: Cellulose molecules are made from a-glucose.
False.
66
Fill in the blank: Glycogen is known as '______' starch.
animal
67
Which carbohydrate stains deep blue with iodine solution?
Starch.
68
Which carbohydrate is known for its structural function?
Cellulose.
69
Identify a monosaccharide found in starch.
a-glucose.
70
Which carbohydrates can be hydrolysed?
Starch and glycogen.
71
Fill in the blank: Cellulose provides ______ to plant cells.
rigidity
72
Give 4 roles of lipids
- source of energy
- waterproofing
- insulation
- protection
73
How are lipids a source of energy?
When oxidised they provide more than twice the energy as the same mass of carbohydrate
74
Why are lipids used for waterproofing?
They are insoluble in water
75
Why are lipids good insulators?
They are slow conductors of heat
76
What are triglycerides made up of?
3 fatty acids and glycerol
77
What bond is formed between each fatty acid and glycerol in a triglyceride?
Ester bond
78
In what reaction are ester bonds formed between each fatty acid and glycerol?
Condensation
79
Why would a fatty acid be described as saturated?
If the hydrocarbon chain attached to it has no carbon-carbon double bonds
80
Why would a fatty acid be described as mono-unsaturated?
If there is a single double bond in the hydrocarbon chain
81
Why would a fatty acid be described as polyunsaturated?
If there is more than one double bond present in the hydrocarbon chain
82
Give two examples of how the structure of triglycerides is related to its properties
- high ratio of carbon-hydrogen bonds to carbon atoms and therefore excellent source of energy
- large, non-polar molecules so insoluble in water meaning their storage does not affect the water potential of cells
83
Which part of a phospholipid is hydrophilic?
The head (phosphate group)
84
Which part of a phospholipid is hydrophobic?
The tail (fatty acid molecules)
85
Give two examples of how the structure of phospholipids are related to their properties
- polar molecules, meaning within aqueous environments they form a bilayer within cell surface membranes, creating a barrier between inside and outside of a cell
- phospholipid structure allow them to form glycolipids by combining with carbohydrates within the membrane, which are important for cell recognition
86
What is the test for lipids known as?
The emulsion test
87
Describe how to carry out the test for lipids
- add 2cm cubed of the sample being tested and add 5cm cubed of ethanol
- shake the tube thoroughly
- add 5cm cubed of water and shake gently
- milky-white emulsion indicates the presence of a lipid
88
Every amino acid has a central ______ atom to which are attached to _____ different chemical groups
- carbon
- four
89
What 4 chemical groups are attached to a central carbon atom making up an amino acid?
- amino group (NH2)
- carboxyl group (COOH)
- hydrogen atom
- R group (variable)
90
Which type of bond is formed between two amino acids?
Peptide bond
91
What type of reaction forms a peptide bond between two amino acids?
Condensation reaction
92
Describe how a peptide bond is formed between two amino acids
Combine an -OH from the carboxyl group of one amino acid with an -H from the amino group of another amino acid via a condensation reaction
93
What is polymerisation?
The process by which many amino acid monomers are joined together through a series of condensation reactions
94
What is a polypeptide?
A chain of many amino acids
95
What is the primary structure of a protein?
The sequence of amino acids joined together by peptide bonds to form a polypeptide chain
96
What is the secondary structure of a protein?
The shape which the polypeptide chain forms via folding as a result of hydrogen bonding
- either an a-helix or B-pleated sheet
97
What is the tertiary structure of a protein?
The further twisting and folding of the polypeptide chain to give the complex and 3-D structure
- joined by disulfide bridges, ionic bonds and hydrogen bonds
98
What is the quaternary structure of a protein?
The combination of a number of different polypeptide chains forming a complex molecule
99
Describe how to carry out the test for proteins
- place a sample of the solution to be tested in a test tube and add a few drops of Biuret solution
- mix gently
- if the colour of the solution turns purple from blue then proteins are present
100
How do enzymes speed up reactions?
They provide an alternative pathway which has a lower activation energy
101
What complex is formed when a substrate fits into the active site
Enzyme-substrate complex
102
What are intracellular enzymes?
Enzymes that act within the cells that produce them
103
What are extracellular enzymes?
Enzymes that act outside the cells that produce them, and are secreted
104
What is the first stage of how enzymes bind with substrates?
- enzymes have unique tertiary structures which determine the shape of their active site
- this shape is complementary to the substrate
105
What is the second stage of how enzymes bind with substrates?
The substrate binds to the active site to form an enzyme-substrate complex
106
What is the third stage of how enzymes bind with substrates?
- temporary bonds form between the R groups within the active site and the substrate
- these bonds lower the activation energy to help break down the substrate into products
107
What is the fourth stage of how enzymes bind with substrates?
The products are released from the active site, leaving the enzyme free to be used again
108
Describe the lock and key model of enzyme action
The substrate fits perfectly into the enzyme’s active site
109
Describe the induced fit model of enzyme action
- the substrate does not fit perfectly into the enzyme’s active site
- the active site changes shape and moulds around the substrate as it enters the enzyme
- this puts strain on the bonds which lowers the activation energy
110
What are four factors that affect the rate of enzyme-controlled reactions?
- temperature
- pH
- substrate concentration
- enzyme concentration
111
Describe how an increase in temperature will affect the rate of an enzyme-controlled reaction
- the molecules have more kinetic energy, causing more collisions and enzyme-substrate complexes
- rate of reaction increases until the optimum temperature
- too much kinetic energy causes the active site to change shape and so the enzyme denatures
112
Describe how pH will affect the rate of an enzyme-controlled reaction
- in too acidic conditions, H+ ions break ionic/hydrogen bonds and denature enzymes
- in too alkaline conditions, OH- ions break ionic/hydrogen bonds and denature enzymes
- in between there is the optimum pH where the enzyme works fastest at
113
Describe how substrate concentration will affect the rate of enzyme-controlled reactions
- an increase in substrate concentration means there are more substrate molecules to form more enzyme-substrate complexes
- as it increases further it reaches the saturation point where all active sites are occupied by a substrate and so enzyme concentration becomes the limiting factor
114
Describe how enzyme concentration will affect the rate of enzyme-controlled reactions
- as the enzyme concentration increases there are more enzyme molecules to form more enzyme-substrate complexes
- as it increases further all substrate molecules available are acted upon and so substrate concentration becomes the limiting factor
115
What are the two types of enzyme inhibitors?
- competitive inhibitors
- non-competitive inhibitors
116
What is a competitive inhibitor?
Binds to the active site of an enzyme to prevent enzyme-substrate complexes
117
How can competitive inhibitors bind to the active site of an enzyme?
They have a similar shape to the substrate
118
Competitive inhibitors ___________ the rate of reaction
Decreases
119
How can competitive inhibitors be overcome?
By increasing the substrate concentration
- more likely that substrates bind to active sites rather than inhibitors
120
What is a non-competitive inhibitor?
Binds to enzymes away from the active site (allosteric site) to prevent enzyme-substrate complexes
121
How does a non-competitive inhibitor work?
- binds to an enzyme away from the active site
- this changes the tertiary structure of the enzyme
- this causes the active site to change shape, meaning the active site is no longer complementary to the substrate
