AS 1.1 Chemical elements and biological compounds Flashcards
1
Q
What is meant by the term inorganic?
A
A molecule or ion that has no more than one carbon
2
Q
What do living organisms need a variety of inorganic ions to survive? Give examples
A
Inorganic ions are important in cellular processes such as muscle contraction, nervous coordination, and maintaining the water potential in cells and blood
3
Q
What are the two groups of inorganic ions?
A
Macronutrients and micronutrients
4
Q
What concentrations of the two types of inorganic ions organisms need?
A
- Macronutrients are needed in small concentrations
- Micronutrients needed in minutes concentrations (zinc and copper)
5
Q
Give examples of micronutrients
A
Zinc and copper
6
Q
Give examples of macronutrients
A
Magnesium, iron, calcium, phosphate
7
Q
Why is magnesium an important inorganic ion? And what happens when there is a lack of magnesium?
A
- Constituent of chlorophyll and needed for photosynthesis
- When lacking in soil, chlorophyll is not made and leaves turn yellow (chlorosis)
- Mammals need magnesium for their bones
8
Q
Why is iron an important inorganic ion and what happens when there is a lack of iron?
A
- Constituent of haemoglobin and important in the transport of oxygen
- Lack of iron from diet leads to anaemia
9
Q
Why is calcium an important inorganic ion?
A
- Structural component of bones and teeth in mammals
- Component of plant cell walls, providing strength
10
Q
Why is phosphate an important inorganic ion?
A
- Needed for making nucleotides including ATP
- Constituent of phospholipids in cell membranes
11
Q
Describe the structure of water
A
- It is dipolar so it has a positively charged end which is the hydrogen and a negatively charged end which is the oxygen, but has no overall charge
12
Q
What does waters structure allow it to do in term of bonding?
A
- Because of its dipolar nature, hydrogen bonds can form between the partially positively charged hydrogen on one molecule and the partially negatively charged oxygen on another
- Hydrogen bonds are weak, but in large numbers it is difficult to separate the molecules
13
Q
What are some of waters properties?
A
- Acts as a solvent
- It is a metabolite
- It has high specific heat capacity
- High latent heat of vaporisation
- Cohesion
- High surface tension
- High density
- Transparent
14
Q
What is water a good solvent?
A
- Because of its dipolar nature, it attracts charged particles and other polar molecules allowing them to dissolve
- Chemical reactions take place in the solution
- Acts as a transport medium
15
Q
Why is water a good solvent and what role does it have in animals and plants?
A
Water acts as a transport medium.
- In animals, plasma transports dissolved substances
- In plants, water transports minerals in the xylem, and amino acids and sucrose in the phloem
16
Q
What is water a metabolite?
A
- Water is involved in many biochemical reactions such as hydrolysis and condensation
- It is a reactant in photosynthesis
17
Q
Why does water have a high specific heat capacity and what does it do?
A
- A large amount of heat energy is needed to raise waters temperature due to the large numbers of hydrogen bonds that need to be broken
- It prevents large fluctuations in water temperature, so it keeps aquatic habitats stable
18
Q
Why does water have a high latent heat of vaporisation and what does it do?
A
- Large amounts of heat energy is needed to vaporise water
- Used as a cooling mechanism such as sweating
19
Q
How does water have cohesion and what does it do?
A
- Water molecules attract each other and form hydrogen bonds between molecules
- Allows water molecules to stick together and columns of water to be drawn up xylem vessels in plants
- Creates surface tension allowing insects to be supported
20
Q
Why does water have high surface tension and what does it do?
A
Cohesion between water molecules at the surface produces surface tension so insects (pond skater) can be supported
21
Q
How does water having a high density support aquatic ecosystems and organisms?
A
- Ice is less dense (hydrogen bonds holding molecules together are further apart) than liquid water so it floats, it acts as an insulator preventing water beneath from freezing, protecting aquatic habitats
- Provides support and buoyancy
22
Q
Why is ice less dense than water?
A
hydrogen bonds holding molecules together are further apart
23
Q
What does water being transparent allow?
A
Allows light to pass through, allowing aquatic plants to photosynthesise
24
Q
What are carbohydrates?
A
Organic compounds containing carbon, oxygen and hydrogen
25
What are the uses of carbohydrates? Give examples
- Building blocks for more complex molecules (ribose which forms a constituent molecule of RNA)
- Sources of energy (glucose)
- Energy storage in molecules (glycogen and starch)
- Structural support (cellulose and chitin)
26
What are monosaccharides?
Small organic molecules that are the building blocks for larger carbohydrates
27
What is the general formula for monosaccharides?
(CH2O)n
28
What are some properties of monosaccharides?
Sweet tasting and soluble in water
29
Give examples of pentose sugars (monosaccharides) and why are they important?
- Ribose and deoxyribose
| - They are important constituents of RNA and DNA
30
Give 3 examples of a hexose sugars (monosaccharides)
- Glucose
- Galactose
- Fructose
31
Why is glucose an important monosaccharide?
- Starting material for respiration
| - Building blocks of glycogen and other polypeptides
32
What differentiates the two isomers of glucose?
The positioning of the hydroxyl group on the first atom
- Alpha glucose has the hydroxyl group facing down on the first carbon
- Beta glucose has the hydroxyl group facing upwards on the first carbon
33
What are the functions of monosaccharides?
- Source of energy in respiration
- Building blocks for larger molecules
- Intermediates in reactions (triose are intermediates in the reactions of respiration and photosynthesis
- Constituents of nucleotides
34
How are disaccharides formed?
Formed by joining two monosaccharides together in a condensation reactions, losing a water molecule and forming a glycosidic bond
35
How does a disaccharide break down into monosaccharides?
the addition of water which is hydrolysis
36
What are the 3 disaccharides and what monosaccharides are they made of? Give examples of their use
- Maltose is made from 2 glucose monosaccharides and it has a role in germinating seeds
- Sucrose is made from the fructose and glucose monosaccharides and it has a role in the transport in phloem of flowering plants
- Lactose is made from galactose and glucose monosaccharides and it has a role in mammalian milk
37
How do you test for reducing sugars?
- Benedict's test
- Add equal volume of benedict's reagent to the solution and strongly heat
- If a reducing sugar is present, the solution will turn from blue to a brick-red precipitate
38
How does using the benedict's reagent in the test for reducing sugars work?
A reducing sugar donates an electron to reduce blue copper 2+ ions in copper sulphate to red copper 1+ oxide
(blue) Cu2+ + e- → (red) Cu+
39
Is the benedicts test qualitative or quantitative? and why?
This is a qualitative test as you can’t tell the concentration of the reducing sugar
40
What can be used to test for reducing sugars in order to obtain a quantitative result?
by using a biosensor instead as they give concentration values
41
What are the different reducing sugars?
All monosaccharides and maltose and lactose disaccharides
42
How do you test for non-reducing sugars?
1. Heat with HCL, then neutralise by slowly adding alkali until fizzing stops
2. Add benedict's reagent and strongly heat
3. If the solution turns from blue to a brick-red precipitate, then a non-reducing sugar is present
43
Give an example of a non-reducing sugar?
Sucrose
44
Why do non-reducing sugars give a negative result to the reducing sugars test?
they cannot reduce copper 2+ ions in copper sulphate to copper 1+ oxide
45
Why is the test for non-reducing sugars qualitative? And how can a quantitative result be obtained?
- This is a qualitative test as you can’t tell the concentration of the non-reducing sugar
- A quantitative result can be obtained by using a biosensor instead as they give concentration values
46
Why are polysachharides?
A polymer that is formed when when many monosaccharides (monomers) are combined together by glycosidic bonds
47
Why does glucose need to be stored as polysaccharides? And how does it work?
- If glucose isn't stored as a polysaccharide, since it is soluble in water, it would increase the concentration of the cell contents, then water would enter the cell by osmosis
- This is avoided by converting glucose into starch in plant cells and glycogen in animal cells
48
Why are starch and glycogen good energy storage molecules?
- Unable to diffuse out of the cell
- Compact in shape so a lot of glucose can be stored in a cell
- Insoluble in water, so they don't change the water potential, therefore they have no osmotic effect
- Easily hydrolysed into their constituent monosaccharides which can be used in respiration
- They carry a lot of energy in their C-H and C-C bonds
49
What is starch used for and where can it be found?
Main store of glucose in plants, found in starch grains which are found in chloroplasts and seeds
50
What happen to the sugars that are main in photosynthesis?
Sugars made in photosynthesis are stored as starch unless they are required immediately for respiration
51
What is starch made of?
Starch is made of alpha glucose molecules bonded together, forming 2 polymers, amylose and amylopectin
52
What is the structure of amylose?
Amylose is a linear, unbranched molecule with alpha-1-4-glycosidic bonds forming between the first carbon atom onn one glucose monomer and the fourth carbon atom on the adjacent one. This is repeated forming a straight chain, which then coils into a helix
53
What is the structure of amylopectin?
Amylopectin is a branched molecule, it fits inside amylose. It has 1,4-glycosidic bonds and 1,6-glycosidic bonds, When a glycosidic bond forms between the first carbon atom of one glucose and the sith carbon atom of another, it creates a side branch. 1,4-glycosidic bonds then continue on from the start of the branch
54
Which polymer of starch releases more glucose and why?
Amylopectin because of its branched structure, there are more exposed ends that can be hydrolysed, which results in a more rapid release of glucose
55
How do you test for starch? what is the name of the test? How does the test work?
- Iodine-potassium iodide test
- Add iodine solution in sample
- Iodine solution (iodine dissolved in an aqueous solution of potassium iodide) reacts with any starch present resulting in a colour change from orange-brown to blue-black
56
What type of test is the iodine-potassium iodide test?
Qualitative test
57
What is glycogen and what structure does it have?
- Main storage product in animals
- Similar structure to amylopectin as it has alpha-1,4-glycosidic bonds and 1,6-glycosidic bonds
- Glycogen is more branched
58
What is cellulose and where can it be found?
- Structural polysaccharide
| - In plant cell walls
59
What is the structure of cellulose?
- Consists of many beta glucose molecules bonded together with adjacent glucose molecules rotated by 180° forming long straight parallel chains that are cross-linked to each other by hydrogen bonds
- They become tightly cross-linked to form bundles called microfibrils, which are arranged into bundles called fibres
60
Why is cellulose freely permeable even though it is strong?
Despite its strength, the gaps between cellulose fibres in plant cell walls make them freely permeable, allowing water and solutes to penetrate through to the cell membrane
61
What is chitin and where can it be found?
Structural polysaccharide and found in the exoskeleton of insects and cell walls of fungi
62
What are some physical properties of chitin?
It is strong, light and waterproof
63
What is the structure of chitin?
Similar structure to cellulose with many parallel chains of beta glucose molecules with an added acetylamine group cross-linked to each other by hydrogen bonds forming microfibrils, due to adjacent glucose molecules which are rotated by 180°
64
Why are lipids insoluble in water?
They are non-polar compounds
65
What are lipids soluble in?
Organic solvents such as alcohol
66
What are lipids made of and how are they different from carbohydrates?
Contain carbon hydrogen and oxygen like carbohydrates but they have more hydrogen and less oxygen
67
How are triglycerides formed?
Triglycerides are formed by the combination of one glycerol molecule and three fatty acids via a condensation reaction where 3 water molecules are removed and an ester bond is formed between the glycerol and fatty acid (3 ester bonds)
68
What are some key features of phospholipids?
- Type of lipid
- One end is soluble in water and one is insoluble in water
- One fatty acid tail is replaced by a phosphate group
- Fatty acid part is non-polar and insoluble in water and its hydrophobic
- The glycerol group and the phosphate are polar and dissolve in water, they are hydrophilic
69
What are waxes and what role does it have?
Waxes are lipids that melt at high temperatures, they have a waterproofing role in animals (insects exoskeleton) and plants (leafs cuticle)
70
What differentiates the properties of fats and oils?
The variation in the fatty acids
71
What does saturated fatty acid mean?
The fatty acid is saturated if the hydrocarbon chain only has single carbon-carbon bonds, so all the carbon atoms are linked to the maximum number with hydrogen atoms
72
What physical state do saturated fatty acids have at body temperature and why?
- Saturated fatty acid chains are a straight zigzag, the molecules align readily, so the fats are solid
- Saturated fatty acids remain semi-solid at body temperature
73
What are saturated fatty acids used for and where are they most often found?
- Useful for storage in animals
| - Animal lipids are mostly saturated fatty acids
74
What does it mean by an unsaturated fatty acid?
The fatty acid is unsaturated if the hydrocarbon chain has a carbon-carbon double bond, the chain gets a kink
75
What is the physical state of unsaturated fats at room temperature and why?
Unsaturated fatty acids can’t align uniformly so the lipid doesn’t solidify readily. Unsaturated lipids are oils which remain liquid at room temperature
Plant lipids are usually unsaturated and occur as oils
76
What are lipids called when there is one carbon-carbon double bond present?
mono-unsaturated lipid
77
What are lipids called when there are many carbon-carbon double bond present?
poly-unsaturated lipid
78
What are the roles of lipids?
- Energy reserves
- Thermal insulation
- Protection
- Producing metabolic water
- Structural
- Electrical insulation
- Waterproofing
79
What are the roles of triglycerides and how do the roles work?
- Energy reserves: in both plants and animals because lipids contain more C-H bonds than in carbohydrates so they can release more energy when broken down
- Thermal insulation: When stored under the skin, it acts as an insulator against heat lost in the cold, or heat gain when it is hot
- Protection: fat is stored around delicate internal organs such as kidneys, protecting against physical damage
- Producing metabolic water: triglycerides produce a lot of metabolic water when oxidised. This is important for desert animals as they survive on metabolic water from the respiration of its fat intake
80
How do triglycerides work in thermal insulation?
When stored under the skin, it acts as an insulator against heat lost in the cold, or heat gain when it is hot
81
How do triglycerides provide protection?
fat is stored around delicate internal organs such as kidneys, protecting against physical damage
82
Why are triglycerides better energy reserves in both plants and animals than carbohydrates?
because lipids contain more C-H bonds than in carbohydrates so they can release more energy when broken down
83
Why is it important for desert animals to have fat in their diet?
- Triglycerides in the fat produces a lot of metabolic water when it is oxidised
- This is important for desert animals as they survive on metabolic water from the respiration of its fat intake
84
What are the roles of phospholipids?
- Used for structure in the plasma membranes
- Electrical insulation as phospholipids are a large component of myelin sheath that surrounds neurons which increases the speed at which nerve impulses propagate along the neuron
85
What is the role of wax? And how does it work? Why is it important?
- Waterproofing
- Fats are insoluble in water and are important in land organisms such as insects where the waxy cuticle reduces water loss. Also important in plants as it reduces water loss via the stomata by transpiration
86
What is the test for fats and oils?
- Lipid emulsion test
1. Sample is mixed with ethanol to dissolve any lipids present (lipids are soluble in organic solvents such as ethanol)
2. Sample is shaken with an equal volume of water
3l This causes the dissolved lipids come out of the solution because they are insoluble in water
4. This gives the sample a cloudy white emulsion appearance
87
What are some of the main causes of heart disease?
Fatty deposits on the inner wall of the coronary arteries and high blood pressure
88
What contributes to the risk of heart disease?
A diet that is high in saturated fats, smoking and lack of exercise
89
What happens to lipids and proteins have they are digested?
When food is absorbed at the small intestine, lipids and proteins combine to make lipoproteins which travel around the body in the bloodstream
90
What happens when a diet is high in saturated fats?
If a diet is high in saturated fats, low-density lipoprotein (LDL) builds up and fatty material called atheroma gets deposited in the coronary arteries. As the arteries narrow they lose their elasticity and it restricts blood flow, and therefore, oxygen delivery to the heart. If the vessel is completely blocked, a heart attack occurs
91
What happens if a diet is high in unsaturated fats?
If a diet is high in unsaturated fats, the body makes more high-density lipoprotein (HDL) which carries harmful fats away to the liver for disposal
92
What is important to lower the risk of cardiovascular disease?
To have the ratio of HDL:LDL in the person's blood high
93
How do proteins differ from carbohydrates and lipids?
Proteins differ from carbohydrates and lipids as they always contain nitrogen, some contain sulphur and some contain phosphorus
94
What are proteins and what are they made of?
Proteins are polymers made of monomers called amino acids
95
What is a chain of amino acids calle?
polypeptide
96
What is the proteins shape and function determined by?
The sequence of amino acids in the polypeptide chain
97
What is the structure of an amino acid?
- Amino group at one end
- Carboxyl group at the other end
- A hydrogen atom
- R functional group which is different in each amino acid
98
What happens to amino acids at the pH of 7?
- They form zwitterions
- The amino group is basic, at pH7, the pH of the cell, it gains an H and becomes positively charged
- The carboxyl group is acidic and at pH7 it loses an H, becoming negatively charged
- At pH7, an amino acid has both a positive and negative charge
99
How are peptide bonds form?
A condensation reaction occurs between the amino group of one amino acid and the carboxyl group of another, eliminating water. The bond formed is called a peptide bond and the resulting compound is a dipeptide
100
What is the primary structure?
The sequence of amino acids in a polypeptide chain
101
What is the secondary structure?
The folding of the primary structure into a 3D shape which is held together by hydrogen bonds creating an alpha helix and beta pleated sheet
102
Where do the hydrogen bonds occur in the secondary structure of a protein?
The hydrogen bonds are between the =O in on the -COOH groups and the H on the NH2 groups
103
What is the tertiary structure?
The folding of the alpha helix into a more compact shape, which is maintained by hydrogen bonds, ionic bonds, disulphide bridges, and hydrophobic interactions
104
What is the quaternary structure?
The Combination of two or more polypeptide chains in tertiary form combined. These are often associated with non-protein groups and sometimes form large complex molecules (haemoglobin)
105
What are the two types of proteins?
Globular and fibrous proteins
106
What functions do fibrous proteins have?
Structural functions
107
What is the structure of a fibrous protein?
- Fibrous proteins have long, thin molecules and their shape makes them insoluble in water
- The polypeptides are in parallel chains or sheets, with many cross-linkages forming long fibres (e.g. protein in hair)
- A single fibre consists of three identical polypeptide chains twisted around each other like a rope and the chains are linked by hydrogen bonds, making the molecule very stable
108
What physical properties do fibrous proteins have?
Fibrous proteins are strong and tough (e.g. collagen is a fibrous protein, providing strength and toughness needed in tendons)
109
What is the structure of globular proteins and what is its function?
- Compact and folded into spherical molecules
| - Soluble in water and they have many functions
110
Give examples of globular proteins
- enzymes, antibodies, plasma proteins and hormones
- Haemoglobin, whhich consists of four folded polypeptide chains, at the centre of each have a haem, an iron-containing group
111
How do you test for proteins?
- Biuret test
1. Add a few drops of biuret reagent to your sample
2. If proteins are present, the colour will change from blue to purple
112
What happens to the result of the biuret test at varying concentrations of protein?
- At low protein concentration, colour change is difficult to tell by the eye
- The more concentrated the protein, the darker the purple colour
113
What type of test is the biuret test?
Qualitative test
114
What are the two ways of testing for proteins in order to obtain a semi-quantitative result? Why are both these methods semi-quantitative?
- When doing the biuret test, you could compare the intensity of purple in two identically treated solutions
- You could measure the absorbance of the purple biuret in a colorimeter using a yellow filter to estimate the concentration of proteins.
- This is semi-quantitative as the actual protein concentration is not measured
115
How could you test for proteins and obtain a quantitative result?
Biosensor is needed
