TOPIC 1 - BIOLOGICAL MOLECULES Flashcards
(87 cards)
1
Q
What are examples of monomers?
A
Monosaccharides, amino acids and nucleotides
2
Q
What are examples of polymers?
A
Polysaccharides, polypeptides and polynucleotides
3
Q
What reaction allows two monomers to bond together?
A
A condensation reaction allows two monomers to be joined together by a chemical bond, releasing a water molecule.
4
Q
What reaction breaks the chemical bond between two molecules?
A
A hydrolysis reaction allows the chemical bond to break between two molecules and this happens due to the addition of water.
5
Q
What are carbohydrates?
A
Carbohydrates are molecules which consist only of carbon, hydrogen and oxygen.
6
Q
What is the small unit that makes up a carbohydrate?
A
Monosaccharides
7
Q
What is formed when two monosaccharides go through condensation reaction?
A
A disaccharide is formed
8
Q
What is the special bond that is formed during the condensation reaction between two monosaccharides?
A
A glycosidic bond
9
Q
What is formed when many monosaccharides go through condensation reaction?
A
A polysaccharide is formed
10
Q
What are examples of monosaccharides?
A
- Glucose (α-glucose and β glucose)
- Galactose
- Fructose
11
Q
What is the structure of both α-glucose and β glucose?
A
They both have 6 carbon atoms, α-glucose has its OH group attached at the bottom right and β glucose has its OH group attached at the top right.
12
Q
Which disaccharide is formed when two α-glucose molecules join together?
A
Maltose
13
Q
Which disaccharide is formed when a glucose molecule and fructose join together?
A
Sucrose
14
Q
Which disaccharide is formed when a glucose molecule and galactose join together?
A
Lactose
15
Q
What are the three polysaccharides that are formed from glucose monomers?
A
- Glycogen (formed by the condensation of α-glucose)
- Starch (formed by the condensation of α-glucose)
- Cellulose (formed by the condensation of β glucose)
16
Q
What is starch?
A
Starch is what plants store as excess glucose. When plants require glucose for respiration and energy, starch is broken down into glucose.
17
Q
What mixture does starch consist of?
A
Amylose and amylopectin
18
Q
Describe the structure of starch
A
Amylose is a long, unbranched chain of α-glucose molecules. Due to its specific glycosidic bonding, its shape becomes coiled, which makes it very compact.
Amylopectin is a long, branched chain of α-glucose molecules. It has got many side branches on it.
19
Q
Explain the relationship between the structure and function of starch
A
The coiled and compact shape of amylose allows a lot of energy to be stored, therefore making it good for energy storage.
The side branches on amylopectin allow enzymes to break down the molecule and make it easier to break the glycosidic bond. This means that energy can be released quicker for important functions like respiration.
Starch is also insoluble and therefore do not affect the water potential, so water cannot enter cells by osmosis.
20
Q
Test for starch
A
Add the test sample to iodine solution (potassium iodide solution).
If the solution turns from brown/orange to blue/black, then starch is present.
21
Q
What is glycogen?
A
Glycogen is the main energy storage in animals and it stores excess glucose to be used later on, such as respiration.
22
Q
Describe the structure of glycogen
A
Glycogen has a large number of side branches, similar to amylopectin’s structure
23
Q
Explain the relationship between the structure and function in glycogen.
A
The side branches in glycogen allow it to be broken down much quicker by enzymes, meaning that energy can be released quickly as well.
Also, since it is highly branched, a high amount of energy is released. The energy released can be used for important processes such as respiration.
Glycogen is also insoluble and therefore do not affect the water potential, so water cannot enter cells by osmosis.
24
Q
What is cellulose?
A
Cellulose is the main component found in cell walls to help provide structural support
25
Describe the structure of cellulose
Cellulose is a long, straight, unbranched chains of β glucose molecules. Each chain is linked together by hydrogen bonds to form strong cross links and strong fibres known as microfibrils
26
Explain the relationship between the structure and function of cellulose
The microfibrils help provide structural support for the cell wall, meaning that it can help the cell wall to not burst. when water tries to enter in.
The strength of the cell wall is contributed by the many hydrogen bonds that are between the cellulose chains, making cellulose a strengthening material for plants .
27
Test for reducing sugars
- Add test sample to Benedict's Reagent.
- Heat it gently
- If solution turns brick red, then a reducing sugar is present.
- If the solution stays blue, then no reducing sugar is present.
28
Test for non-reducing sugars
After the test for reducing sugars, you should:
- Add dilute hydrochloric acid to the test sample (hydrolyse the polysaccharides/disaccharides into its constituent monosaccharides)
- Then add sodium hydrogencarbonate to neutralise the acid. (Benedict's reagent does not work in acidic conditions)
- Add the sample to Benedict's reagent and then heat the sample.
-If the solution turns brick red then a non-reducing sure is present. If the solution stays blue then there isn't a non-reducing or reducing sugar present.
29
What are lipids?
Lipids are biological molecules that are composed of carbon, hydrogen and oxygen and they are only soluble in organic solvents (such as alcohols) and insoluble in water.
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What are the two types of lipid
Triglycerides and phospholipids
31
How are triglycerides formed?
Triglycerides are formed by the condensation reaction of one glycerol molecule and three fatty acid chains
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What is the bond formed between the glycerol molecule and each fatty acid chain?
Ester bond
33
What is the difference between saturated and unsaturated fatty acid chains?
Saturated fats do not have double bonds between their carbon atoms.
Unsaturated fats do have double bonds between carbon atoms.
34
What does the double bonds cause the fatty acid chain to do?
It causes the fatty acid chain to kink/bend, causing the chain to not be able to pack together tightly and therefore are liquids in room temperature (oils).
35
How does triglyceride's structure relate to their properties?
- Triglycerides have a high ratio of energy storing carbon-hydrogen bonds to carbon atoms and therefore and excellent source of energy.
- Triglycerides has a low mass to energy ratio, meaning that they are a good storage molecules.
- Triglycerides insolubility (due to being large and non-polar) in water means that their storage does not affect the water poteintial of cells
36
How does the structure of a phospholipid molecule look like?
In phospholipids, one of the fatty acid chains is replaced by a phophate group/phosphate head.
37
The phosphate group is _______________ to water and therefore is ______________________.
The phosphate group is attracted to water and therefore is hydrophilic.
38
The fatty acid chains _______________ water and therefore are ________________.
The fatty acid chains repels water and therefore are hydrophobic.
39
How does phosholipid's structure relate to their properties?
- Since phospholipids have a hydrophilic and hydrophobic side, the molecule is polar meaning that when placed in water, they form a bilayer. The hydrophilic head to hold at the surface of the cell membrane.
- This phospholipid bilayer is what forms the cell membranes, which controls what enters and leaves the cell.
- The centre of the bilayer is hydrophobic, meaning water soluble substances cannot enter easily.
40
What is the test for lipids?
The test for lipids is known as the emulsion test.
The steps are:
- Add test sample with ethanol in a test tube.
- Shake it thoroughly
- Pour the solution in water
- If there is a cloudy white/milky colour then this indicates that a lipid is present
41
What are proteins?
Proteins are biological molecules that are composed of carbon, hydrogen, oxygen and nitrogen and they come in all shapes and sizes.
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Monomers of proteins
Amino acids
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What forms when 2 amino acids form
Dipeptide
44
Describe the structure of an amino acid.
- Amine Group (H2N)
- Carboxyl Group (COOH)
- A variable carbon-containing group (R)
- A hydrogen (H)
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How many amino acids can you get?
20
46
What bond is formed during a condensation reaction of amino acids?
A peptide bond is formed between the amino acids.
47
What are the 4 structures that proteins are called and explain them?
They are called:
-Primary structure: The sequence of amino acids that makes up the polypeptides of a protein
-Secondary structure: The way in which the chain of amino acids of the polypeptides of a protein is folded. Hydrogen bonds form between the amino acids, to form 3D shapes like an alpha helix or beta pleated sheet.
-Tertiary structure: the folding of a whole polypeptide chain in a precise way, as determined by the amino acids of which it is composed. Hydrogen bonds, ionic bonds and disulfide bridges are formed.
-Quaternary structure:More than one polypeptide chains linked together and held by bonds.
48
In the tertiary structure, why does the ionic bonds and disulfide bridges from?
Ionic bonds form due the attraction between negative and positive charges on different parts of the molecule. These can easily be broken by pH changes.
Disulfide bridges from when interaction between the amino acid cysteine occur. These are usually strong and not easily broken.
49
What determines the function of a protein?
The shape
50
Describe the test for proteins?
The test for proteins is known as the biuret test
The steps are:
- Add the test sample to a test tube.
- Then add sodium hydroxide solution.
- Then add copper(II) sulfate solution.
- If the solution turns from blue to purple, then it indicates that protein is present
51
What is an enzyme?
Enzymes are biological catalysts that increase the rate of reaction by lowering the activation energy of the reaction they catalyse.
52
Which protein structure does enzymes have?
Enzymes have a tertiary structure, which is why enzymes are highly specific.
53
What is the active site on an enzymes?
The active site, which has a specific shape, is the part of an enzymes where the substrate molecules bind to.
54
What is formed when a substrate fits into an enzyme's active site?
An enzyme-substrate complex
55
Explain the induced-fit model.
The induced fit model proposes that when an enzyme and a substrate interacts with each other, a change is induced in the shape of the active site, moulding around the substrate molecule.
The change in shape of the active site puts pressure/strain/stress on certain bonds in the substrate, lowering the activation energy required to break the bond.
56
How are the properties of enzymes relate to their tertiary structure?
Their tertiary structure allows enzymes to be highly specific, meaning that it will usually catalyse one reaction since their active site is complementary to a specific substrate.
Each different enzyme has a different tertiary structure and so a different active site.
57
What are the 6 factors that affect enzyme activity?
- Temperature
- pH
- Enzyme concentration
- Substrate concentration
- Concentration of competitive inhibitors
- Concentration of non-competitive inhibitors
58
How does temperature affect the enzyme activity?
Temperature from start to optimum:
- Increases kinetic energy of molecules
- Molecules move more rapidly
- Increase in chances of successful collisions
- Increases chance of forming enzyme-substrate complex
- increase rate of reaction
Temperature higher than optimum:
- Bonds holding the tertiary structure break
- Active site shape is lost
- Substrate can no longer be complementary
- Enzyme-substrate complex cannot be formed
- Enzyme denatured and rate of reaction decreases
59
How does pH affect the enzyme activity?
- All enzymes have an optimum pH.
- When an enzyme has a pH above or below their optimum temperature, ions found in the acid or alkali cause the bonds that hold the tertiary structure to break.
- Therefore the active site shape is lost and enzyme-substrate complexes can no longer be formed.
- The enzyme is denatured.
60
How does the substrate concentration affect the enzyme activity?
Increasing the substrate concentration means that:
- more chance of successful collisions
- more chance of forming enzyme-substrate complex, therefore increasing rate of reaction
- this continues until the maximum rate of reaction is reached (when all the active sites are full/occupied)
61
How does the enzyme concentration affect the enzyme activity?
Increasing the enzyme concentration means that:
- more chance of successful collisions
- more chance of forming enzyme-substrate complex, therefore increasing rate of reaction
- this continues until the maximum rate of reaction is reached (when all the substrates are used)
62
What is a competitive inhibitor?
A substance with a similar shape to the substrate and a complementary shape to the enzyme's active site.
63
What is a non-competitive inhibitor?
A substance, with a different shape that binds to another site on the enzyme other than the active site.
64
How does the concentration of competitive inhibitors affect the enzyme activity?
A competitive inhibitor binds to the active site, blocking substrates to bind instead, preventing enzyme-substrate complex to form, and rate of reaction increases at a lower rate.
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How does the concentration of non-competitive inhibitors affect the enzyme activity?
A non-competitive inhibitor binds to the another site on the enzyme and this causes the active site's shape to change, meaning that the substrate is not complementary and less enzyme-substrate complexes are formed, meaning that rate of reaction is at a lower rate.
66
Describe the structure of a nucleotide
Made up of a pentose sugar, a nitrogen-containing base and a phosphate group.
67
How is a polynucleotide formed?
A polynucleotide is formed when two nucleotides join together by a condensation reaction between the phosphate group of one nucleotide and the sugar of another.
The chain of phosphates and sugars is known as the sugar-phosphate backbone.
68
What is the bond formed between two nucleotides?
A phosphodiester bond
69
What is DNA?
DNA (Deoxyribonucleic acid) is a molecule found in all organisms. It holds all the genetic information.
70
What is the structure of each DNA nucleotide?
Each DNA nucleotide consists of a deoxyribose sugar, an organic base and a phosphate group.
71
How does the structure of the DNA lead to their properties?
The double stranded feature helps DNA to become more stable and act as template in semi-conservative replication.
The coiled feature helps the DNA to be more compact.
The complementary base pairing ensures semi-conservative replication to occur as the hydrogen bonds between the bases are weak and can easily be broken during semi-conservative replication.
71
What is the structure of a DNA molecule
A DNA molecule is twisted into a double helix composed of two separate strands of polynucleotides joined together by a hydrogen bonds between complementary bases
71
What are the 4 possible bases that can be found in a DNA molecule and which bases are complementary to each other.
The possible bases are adenine, guanine, cytosine and thymine.
Adenine pairs with thymine and guanine pairs with cytosine.through complementary base pairing.
72
Describe the process of DNA replication
DNA replication occurs in interphase by semi-conservative replication.
DNA helicase is used separate strands and break the hydrogen bonds between both strands.
Both strands act as template and free complementary nucleotides bind to the exposed bases of the template strands.
Complementary base pairing betwen adenine and thymine and guanine and cytosine.
DNA polymerase joins nucleotides and the hydrogen bonds reform.
Semi-conservative replication is finally done with new DNA molecules containing one old strand (template strand) and one new strand
73
What is the structure of each RNA nucleotide?
Each RNA nucleotide consists of a ribose sugar, an organic base and a phosphate group
73
What is RNA?
RNA (Ribonucleic acid) is a molecule found in all organisms. It transfers genetic information from the DNA to the ribosomes.
There are two types of RNA and they are called mRNA (messenger RNA) and tRNA (transfer RNA).
74
What is the structure of a RNA molecule.
An RNA molecule is relatively short and it is single stranded
75
What is ATP?
ATP (Adenosine triphosphate) is an energy carrier molecule that delivers energy for life processes
76
What is the structure of ATP?
ATP is made from 1 adenine base, 3 phosphates and a ribsose sugar
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How does ATP help release energy?
ATP get broken down into ADP (Adenosine Diphosphate) and Pi (Inorganic phosphate ion) in a hydrolysis reaction using ATP hydrolase, meaning energy is released from the bonds.
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How does ATP reformed?
ATP get reformed when ADP (Adenosine Diphosphate) and Pi (Inorganic phosphate ion) join together during a condensation reaction using ATP synthase, meaning energy is carried and stored in its bonds.
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What makes ATP a good deliverer of energy?
ATP is an immediate source and only need to break one weak bond. It is also a manageable source as it releases samll amount of energy
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What are the different uses of ATP in organisms?
- protein synthesis
- organelle synthesis
- DNA replication
- cell division (mitosis)
- active transport
- metabolic reactions
- movement
- maintaining body temperature
- To add inorganic phosphate to other substances and make them more reactive and change their shape. This is known as phosphorylation.
81
State the properties of water?
- Water is an important metabolite that is used in many important metabolic reactions, including condensation and hydrolysis.
- Water has a high specific heat capacity as water takes a lot of heat energy to heat it up due to the presence of the hydrogen bonds. This allows water to buffer changes in temperature.
- Water has a large latent heat of vaporisation as it takes a lot of energy to break the hydrogen bonds between water molecules, allowing water to evaporate.
- Water has a strong cohesion and high surface tension due to their polarity, which helps water molecules to stick together.
- Water is also a place where solutes can be separated out and dissolved based on their charge. This is due to the polarity of water.
82
What is the importance of water in living organisms?
The high specific heat capacity allows certain habitats to not be affected. For example, when water freezes it becomes ice, which is less dense than liquid, so it floats on the surface insulating the water beneath it, prevent it from freezing and providing a habitat for the organisms
The ability to dissolve solutes is very useful in important processes like diffusion and active transport.
The high latent of heat vaporisation allows organism to cool down and this happens when humans sweat. We cool down when the sweat evaporates.
The high cohesion between water molecules is very useful when water is transported in plants (thorugh the xylem) and transport in other organisms.
83
What are inorganic ions?
Inorganic ions occur in solution in the cytoplasm and body fluids of organisms, some in high concentrations and others in very low concentrations.
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What are the examples of inorganic ions?
- hydrogen ions to determine pH, higher the hydrogen concentration, lower the pH
- iron ions are a component of haemoglobin
- sodium ions are involved co-transport of glucose and amino acids
- phosphate ions are a component of DNA and ATP
