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Chemistry > Option B: Biochemistry > Flashcards

Option B: Biochemistry Flashcards

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1
Q

Biochemistry

Definition.

A
  • the study of chemical processes in living cells at the molecular level
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2
Q

Metabolism

Definition.

A
  • is all the chemical processes that take place within a living organism to maintain life
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3
Q

Catabolism

Definition.

A
  • is the breakdown of complex moleucules in living organism into simpiler units that is usually accompanied by the release of energy
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4
Q

Anabolism.

Definition.

A
  • is the biosynthesis of complex molecules from simpiler units that usually requires energy
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5
Q

Metabolic Pathway

Definition.

A
  • is a biochemical trasformation of a molecule through a series of intermediates (metabolites) into the final product
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6
Q

Formation of polymers

A
  • functions of biological molecules depend on their  shapes and structures.
  • biopolymers are commonly made of smaller, recurring subunits called monomers
  • form by condensation reactions in which monomers react to form a polymer. This releases water.
  • broken down by hydrolysis reactions in which a polymer breaks up into separate monomers. This requires water.
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7
Q

Photosynthesis

Definition.

A
  • is the biosynthesis of organic molecules from carbon dioxide and water using the energy of light
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8
Q

Photosynthesis

Chemical Formula.

A

6CO2(g) + 6H2O(l) → C6H12O6(aq) + 6O2(g)

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9
Q

Photosynthesis

Explain why photosynthesis is an anabolic process.

A
  • Photosynthesis is an anabolic process as photosynthesis takes CO2 and H2O (somewhat low energy molecules), and then assembles them into glucose, releasing hydrogen.
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10
Q

Respiration

Definition.

A
  • is the metabolic processes that release energy from nutrients consumed by living organisms
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11
Q

Respiration

Explain why respiration is a catabolic process.

A
  • cells generate energy through the breakdown of glucose (smaller molecules)
  • respiration takes place in all living cells all the time.
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12
Q

Respiration

Chemical Formula.

A

C6H12O6(aq) + 6O2(g) → 6CO2(g) + 6H2O(l) + energy

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13
Q

Aerobic Respiration

Definition.

A
  • is the reverse process of photosynthesis, in which carbon dioxide and water are formed from organic molecules and oxygen
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14
Q

Anaerobic Respiration

Definition.

A
  • is the catabolism of organic compounds that does not involve molecular oxygen as an electron acceptor
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15
Q

Anaerobic Respiration

a) In yeast
b) In animals

Chemical Formulas.

A

a) C6H12O6 → 2C2H5OH + 2CO2 (Glucose → Ethanol + CO2)
B) C6H12O6 → 2C3H6O3 (Glucose → Lactic Acid)

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16
Q

Proteins

Definition and Chemical Formula. (5)

A
  • proteins are found in every cell and are fundamental to cell structure and operation
  • are polymers built up from small monomer molecules called amino acids
  • All amino acids have the alpha carbon bonded to a hydrogen atom (H), carboxyl group (COOH), and amino group (NH2)
  • The “R” group varies among amino acids
  • Formula of 2-amino acids: RCH(NH2)COOH
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17
Q

Functions of proteins in the body

Collagen

A
  • provides structural support to the extracellular space of connective tissues
  • found in the skin, bone and tendon
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18
Q

Functions of proteins in the body

Hemoglobin

A
  • found in the blood
  • oxygen transport from lungs to other tissues
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19
Q

Amino Acids Characteristics

Whay are Amino acids amphoteric (so amphiprotic?

A
  • they can act as a Brønsted – Lowery acid or base by donating a proton or accepting a proton
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20
Q

Amino acids Characteristics

Zwitterion

Definition. (2)

A
  • A molecule having separate positively and negatively charged groups
  • zwitterions contains both positive and negative charges so they will cancel each other out and the overall charge will be neutral
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21
Q

Amino acids Characteristics

What is the isoelectronic point of an amino acid?

(1)

A
  • is the pH that the amino acid will exist as a zwitterion
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22
Q

Amino acids Characteristics

What does a low pH for an amino acid mean?

(2)

A
  • A low pH has an acidic environment so there will be many H+ so the NH2 becomes N+H3. It becomes protonated
  • Amino acids at a lower pH than its isoelectric point can be described as a cation
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23
Q

Amino acids Characteristics

What does a high pH for an amino acid mean?

(2)

A
  • A high pH has a basic environment so there will be many OH- so the COOH becomes COO-. It becomes deprotonated
  • Amino acids at a higher pH than its isoelectric point can also be described as an anion
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24
Q

Peptide bonds/Amide Link

How are amino acids linked together in proteins?

A
  • special kind of covalent bond known as a peptide bond or amide link
  • Peptide bonds are formed by condensation reactions. H2O is also released.
  • This bond occurs between a carboxyl group (COOH) on one molecule, and an amino group (NH2) on another molecule
  • Polypeptide chains can be broken down via hydrolysis reactions, which requires water to reverse the process.
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25
Q

Peptides

(7)

A
  • Molecules made from amino acids are called peptides
    • A dipeptide is formed when 2 amino acids join together to form a peptide chain
    • An oligopeptide is formed when 3-10 amino acids join together
    • A polypeptide is formed by many amino acids (>10)
  • Polypeptides built with more than 50 amino acids are called proteins
  • Polypeptides differ from one another by their length, number of amino acids and order of amino acids
  • The amino acid sequence is what gives each polypeptide its unique properties
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26
Q

Protein Structure

How many different levels of protein structure exist?

(4)

A
  • primary structure
  • secondary structure
  • tertiary structure
  • quaternary structure
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27
Q

Protein structure

Primary Structure

(3)

A
  • refers to the sequence of amino acids in the polypeptide chain
  • held together by peptide bonds (amide links)
  • The sequence of a protein is unique to that protein, and defines the structure and function of the protein
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28
Q

Protein Structure

Secondary Structure

A
  • refers to the folding of the polypeptide as a result of hydrogen bonding
  • The folding can be either:
    • α-helix in which the protein twists in a spiraling manner rather like a coiled spring
    • β-pleated to give a sheet-like structure.
  • Hydrogen bonds form between one of the lone oxygen atom and the hydrogen attached to a nitrogen atom (between amine and carboxylic groups)
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29
Q

Protein Structure

Tertiary Structure

A
  • ** refers to the overall twisting and folding of the secondary structure to form a specific 3D shape**
  • is held together by interactions between the side chains (The R groups)
  • These interactions are:
    • Hydrogen bonds
    • Ionic interactions
    • Dispersion forces
    • Disulfide links (sulfur bridges)
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30
Q

Protein Structure

Quaternary Structure

A
  • refers to the interactions between polypeptide chains
  • The bonding is the same as tertiary bonding
  • An example is hemoglobin that has a quaternary structure composed of four polypeptide chains
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31
Q

Fibrous Proteins

Definitions with examples.

A
  • Fibrous proteins are elongated molecules with a well-defined secondary structure
  • Fibrous proteins have cross-linking at intervals to form long fibers or sheets
  • examples
    • α-keratin
    • collagen
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32
Q

Properties of Fibrous Proteins

A
  • long and narrow
  • structural (strength and support)
  • insoluble in water
  • repetitive amino acid sequence
  • less sensitive to changes in heat and pH
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33
Q

Globular Proteins

Definition with examples.

A
  • spherical molecules that have a well-defined tertiary structure
  • usually soluble to some extent in water as the hydrophobic side tends to be in the center
  • examples:
    • hemoglobin
    • insulin
    • catalase
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34
Q

Properties of Globular Proteins

A
  • rounded/spherical
  • functional (catalysts and transport)
  • soluble in water
  • irregular amino acid sequence
  • more sensitie to changes in heat and pH
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35
Q

Gel Electrophoresis

Definition.

A
  • technique used to separate mixtures of DNA, RNA or proteins according to molecular size
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36
Q

How does gel electrophoresis work?

A
  1. A solution of the sample is placed in a well-cut block of special gel
  2. Positive and negative electrodes are connected to opposite ends of the gel, causing the ions in the sample to migrate towards the oppositely charged electrode
  3. When connected to a circuit, the amino acids move according to their electrical charge

gel electrophoresis involves an electrical field. This field is applied such that one end of the gel has a positive charge and the other end has a negative charge. Because DNA and RNA are negatively charged molecules, they will be pulled towards the positively charged end of the gel

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37
Q

Gel Electrophoresis

Since proteins are not negatiely charged, what detergent must they be mixed with?

A
  • sodium dodecyl sulfate
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38
Q

Gel Electrophoresis

What are the different ways bands representing molecule can be detected?

(3)

A
  • Adding a dye that binds to them and fluoresces (glows) in UV light
  • Adding radioactive probes that bind to them; the radiation is then used to expose a photographic plate
  • Shining lasers onto fragments that have a fluorescent dye incorporated into their structure
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39
Q

Paper Electrophoresis

Definition.

A
  • is similar to gel electrophoresis, but instead the mixture is placed on the middle of a paper
40
Q

Paper Electrophoresis

What happens when the amino acid’s pH is equal to their isoelectronic point?

A
  • the amino acids will not move because they carry no net charge
41
Q

Paper Electrophoresis

What happens when the amino acid’s isoelectronic point is below its pH?

(3)

A
  • negatively charged
  • amino acids exist as anions
  • moe to the positie charged size (the anode)
42
Q

Paper Electrophoresis

What happens when the amino acid’s isoelectronic point is above its pH?

A
  • positively charged
  • amino acids exist as cations
  • move to the negative charged size (generally the cathode
43
Q

Paper Chromatography

Definition.

A
  • a technique which is used to separate low-molecular-mass compounds based on their distribution between stationary phase and mobile phase
  • can also be used to separate a mixture of amino acids

he amino acids all differ in their ability to dissolve in the solvent (the mobile phase) and also in their ability to bind to the stationary phase. Therefore, they will move up at different rates and reach different heights. Ninhydrin is often used as locating agent to make the spots visible

44
Q

Paper Chromatography

What values can be compared to identify amino acids?

A
  • the Rf alue
45
Q

Paper Chromatography

State the Rf formula:

A
  • Rf = distance moved from origin by amino acid/ distance moved by solvent from origin
  • Rf is always less than or equal to 1 and has no units
46
Q

Enzymes

Definition.

A
  • are globular proteins that act as biological catalysts, increasing reaction rates of biological processes without being used up in the process
  • control the manufacture of complex substances, such as skin and blood as well as the breaking down of chemicals to provide energy
47
Q

Enzymes

Emzymes (compared to inorganic catalysts)

A
  • complex globular proteins
  • synthesized by living cells
  • usually highly specific in action
  • sensitive to changes in pH and temperature
  • only function in aqueous solution
48
Q

Enzymes

Inorganic Catalyst (compared to enzymes)

A
  • generally are ions or simple molecules
  • not produced by living cells
  • less specific in action
  • less sensitive to changes in pH and temperature
  • some function in aqueous solution
49
Q

Enzymes

Active Site

A
  • the region of the enzyme that binds the substrate
  • usually a flexible hollow or cavity within the molecule
50
Q

Enzymes

Induced-fit model

A
  • a theory that says the active site will change shape to enfold a substrate molecule
51
Q

Enzymes

Key and Lock Model

(outdated)

A
  • The selectivity of enzymes is one of their most important features
  • It happens because the shape and functional groups in the active site of the enzyme allow it to bind only with certain substrates.
52
Q

Enzymes

A reactant molecule, known as the substrate is maneuvered into the site and it is there at the surface of the enzyme that the reaction takes place…..

A
  1. The reactant (substrate) enters the active site
  2. Bonds formed between the enzyme and substrate weaken lowering the reaction’s activation energy
  3. The substrate breaks or rearranges into new products and these products are released
53
Q

Enzymes

What are the 4 types of active site and substrate interactions?

A
  • Hydrogen bonding
  • Ionic interactions
  • Ion-dipole
  • Dispersion force
54
Q

Enzymes

Characteristics of enzymes:

A
  • biological catalysts
  • made of proteins
  • very specific
  • affected by change in pH and temperature
55
Q

Enzyme

Denaturation

A
  • The catalytic activity of an enzyme depends on its tertiary structure. A slight change in its three-dimensional shape can render an enzyme inoperative as if the structure is disrupted, the substrate can no longer bind to the active site
  • Loss of tertiary structure is known as denaturation (irreversible). It can be caused by: temperature, pH levels, heavy metal ions and concentration
56
Q

Enzymes

Temperature

A
  • Increasing temperature also increases enzyme activity at around double for every 10°C
  • This is because collisions between substrate and active site happen more frequently at higher temperatures due to faster molecular motion
  • However, at high temperature the enzymes will become denatured and stop working. This is because the heat causes vibrations inside the enzymes which break bonds needed to maintain the structure of the enzyme
57
Q

Enzymes

pH levels

A
  • Increasing pH increases enzyme activity to an optimum point. Increasing pH beyond this optimum point will reduce enzyme activity as about a certain pH the alkalinity denatures the enzyme so it can’t catalyze the reaction at all
58
Q

Enzymes

Heavy Metal Ions

A
  • Heavy metals can poison enzymes by reacting with -SH groups replacing the hydrogen atom with a heavy metal atom or ion so that the tertiary structure is altered
59
Q

Enzymes

Concentration

A
  • Increasing substrate concentration increases enzyme activity. This is because random collisions between substrate and active site happens more frequently with higher substrate concentrations
  • However, at high substrate concentrations the active site of the enzyme is saturated therefore raising the substrate concentration has little effect on enzyme activity
60
Q

B.3 Lipids

Fatty Acids

A
  • key components of lipids, in plants, animals and microorganisms
  • consist of a straight chain of an even number of carbon atoms, with hydrogen atoms
  • all have a methyl group (CH3) on one end and a carboxyl group (COOH) at the other end
  • In the middle is a chain of anywhere between 11-23 CH2 groups
  • Fatty acids can be classified as follows: saturated fatty acids and unsaturated fatty acids
61
Q

Saturated Fatty Acids

A
  • Saturated fatty acids only have single bonds between carbon atoms therefore they have a straight structure
  • These fatty acids are saturated because the carbons are carrying as many hydrogen atoms as they can
  • Because there are no bends, saturated fatty acids can pack more tightly together, therefore saturated fatty acids are solid at room temperature
  • General formula: CnH2n+1COOH
62
Q

Unsaturated Fatty Acids

A
  • Monounsaturated fatty acids have one double bond somewhere in the chain therefore they have a bent structure
  • Polyunsaturated fats have at least two double bonds in their chain therefore have many bends/kinks in the chain
  • Because they can’t pack closely together they are liquid at room temperature
  • General formula of monounsaturated fatty acid: CnH2n-1COOH
  • General formula of polyunsaturated fatty acid: CbH2n-3COOH
63
Q

Lipids

A
  • Lipids are a diverse group of hydrophobic compounds that include molecules like fats, oils, phospholipids and steroids
  • Most lipids are hydrocarbons: molecules that include many non-polar carbon-carbon or carbon-hydrogen bonds
  • Lipids are carbon compounds made by living organisms that are mostly or entirely hydrophobic
  • There are three main types of lipids: phospholipids, triglycerides, and steroids.
64
Q

Phospholipids

A
  • **Phospholipids have only two fatty acids condensed onto the glycerol molecule
  • The third –OH position of the glycerol molecule is occupied with a phosphate group**
  • Phospholipids are characterized by having a polar or hydrophilic head and two non-polar hydrophobic tails
  • As a result- phospholipids form a phospholipid bilayer which maximizes the interactions between the non-polar tails and water
  • Phospholipids bilayers provide the basis of membrane structures
65
Q

Triglycerides

A
  • A triglyceride molecule is derived from two types of molecular components:
    • Polar head: This is derived from a single glycerol molecule. Glycerol is composed of three carbons, five hydrogens and three hydroxyl groups
    • Non polar tail: The non polar fatty acid tail group consists of three hydrocarbons (a functional group composed of C-H bonds) and also have a polar carboxyl functional group
  • The number of carbons in the fatty acid may range from 4-36
  • Fats contain saturated fatty acids, whereas oils contain unsaturated fatty acids.
  • **Oils and fats are triglycerides, while other lipids like phospholipids and steroids have different structures
  • Fats and oils are formed by condensation reactions** between a single molecule of glycerol and three molecules of fatty acids
  • Triglycerides are broken down by hydrolysis reactions to produce a single molecule of glycerol and three molecules of fatty acids
  • Triglycerides at standard room temperature:
    • Liquid = Oil
    • Solid = Fats
66
Q

Steroids

A
  • Steroids are a type of lipid
  • The steroid backbone is formed by the four rings of carbon.
  • Although they do not resemble other lipids they are classified as lipids because they are largely composed of carbons and hydrogens
  • Cholesterol is the most common steroid. It is used as a precursor of many biomolecules, including other steroids and the sex hormones
  • Uses of steroids:
    • Used to build up depleted muscle due to lack of activity and to assist in recuperation from an illness
  • Abuses of steroids:
    • Anabolic steroids are sometimes used by athletes to increase muscle and strength for an unfair advantage in sport
  • Effects on males:
    • Infertility, breast development, shrinking of balls, male pattern baldness
  • Effects on females:
    • Decrease in breast size and body fat, deepening of the voice, excessive growth of body hair
67
Q

Functions of Lipids

A
  • Hormones
  • insulation
  • cell membranes
  • energy storage
68
Q

Iodine Number

A
  • The iodine number of a fat or an oil is the mass of iodine that reacts with 100g of the lipids
  • The addition of iodine to unsaturated fats can be used to break the carbon double bonds, since one mole of double bonds reacts with one mole of I2
  • The iodine will bond to the double bonds so the mass of iodine used will depend on the number of double bonds
    • Stearic/Palmitic/Lauric acids: no double bonds
    • Oleic acid: one double bond
    • Linoleic acid: two double bonds
    • Linolenic acid: three double bonds
  • The more unsaturated an oil is, the higher its iodine number will be
69
Q

Rancidity of fats

A
  • When fats used in the food industry are stored for long periods of time, they can undergo chemical change which causes them to become rancid. The result is fats and oils that cause a disagreeable smell, texture or appearance
  • The two main causes of this are hydrolytic and oxidative rancidity
70
Q

Hydrolytic Rancidity

A
  • Hydrolytic rancidity is the hydrolysis of triglycerides to produce glycerol and (smelly) fatty acids
  • Hydrolytic rancidity occurs more quickly in the presence of heat and moisture
  • It is catalyzed by the enzyme lipase
  • The rancid smell is due to the release of fatty acids
  • Hydrolytic rancidity can be reduced by refrigeration
71
Q

Oxidatice Rancidity

A
  • Oxidative rancidity is caused by the oxidation
  • This reaction is catalyzed by light, or enzymes and metal ions
  • It occurs in fats and oils with a high proportion of carbon to carbon double bonds
  • It can be controlled with antioxidants
72
Q

Cholesterol: HDL and LDL

A
  • Cholesterol is transported through the body inside of lipoproteins. Lipoproteins consists of both lipids and proteins
  • There are two types of lipoproteins: high density lipoprotein (HDL) and low-density lipoprotein (LDL)
  • HDL has more protein and less fat, LDL has less protein and more fat
    • **HDL is known as “good cholesterol” as it removes cholesterol from the arteries
    • LDL is called “bad cholesterol” as it deposits cholesterol on the arteries **
  • Too much cholesterol in your arteries may lead to a buildup of plaque known as atherosclerosis
  • A high ratio of LDL to HDL can lead to an increased risk of heart disease, obesity, atherosclerosis and blocked arteries
73
Q

Carbohydrates

A
  • Carbohydrates is another term for a sugar
  • Carbohydrates have several carbon atoms that have a hydrogen and a hydroxyl group
  • All carbohydrates have an aldose or ketose group:
    • Aldose carbohydrates contains one aldehyde group per molecule
    • Ketose carbohydrates contain one ketone group per molecule
  • Carbohydrates can be written as a straight chain structure or Haworth projections
    • Haworth projections represent the 3D (cyclic) structures of monosaccharides
74
Q

Monosaccharides

A
  • The building blocks of carbohydrates are simple sugars called monosaccharides
  • All monosaccharides have the molecular formula C6H12O6 (Empirical formula: CH2O)
    = All monosaccharides contain a carbonyl (C=O) group and have at least two hydroxyl (-OH) groups
  • In solution, isomers of monosaccharides are in equilibrium – two with ring structures and a straight chain molecule
75
Q

Disaccharide

A
  • Disaccharides: A molecule formed by condensation reactions between two monosaccharides
  • As a result, a glyosidic bond is formed
  • Like monosaccharides, disaccharides dissolve in water, taste sweet and are also called sugars
76
Q

Polysaccharide

A
  • Polysaccharides are polymers of carbohydrates made by linking monosaccharides into a chain
  • Polysaccharides are polymers of glucose molecules linked together in different ways by condensation reactions
  • Digestion of polysaccharides involves the hydrolysis (adding water) of the bonds between the monosaccharide residues
  • Enzymes catalyze these reactions in the digestive tract of animals, including humans
  • Polysaccharides are insoluble in water as they are much larger molecules compared to monosaccharides/disaccharides
  • Most plants use starch as a store of carbohydrates and thus energy
  • Cellulose is a polymer of D-Glucose contains 1,4 linkages
  • Cellulose, together with lignin, provides the structure to the cell walls of green plants
  • Most animals, including all mammals do not have the enzyme cellulase so are unable to digest cellulose or other dietary fiber polysaccharides
  • One of the most important polysaccharides is starch. Starch exists in two forms: amylose and amylopectin
77
Q

Amylose

A
  • Amylose is a straight chain polymer of D-glucose units with 1,4 glycosidic bonds
  • soluble in water
78
Q

Amylopectin

A
  • Amylopectin consists of D-glucose units with both 1,4 and 1,6 glycosidic bonds
  • insoluble in water
79
Q

Function of Carbohydrates

A
  • To provide energy: Foods such as bread, biscuits, cakes, potatoes and cereals are all high in carbohydrates
  • To store energy: Starch is stored in the liver of animals in the form of glycogen. Glycogen has almost the same chemical structure as amylopectin
  • As precursors for other important biological molecules
80
Q

Vitamins

A
  • Vitamins are organic micronutrients which cannot be synthesized by the body and must be obtained from suitable food sources (except vitamin D)
  • The ability of vitamins to be transported and stored in the essentially aqueous environment of the body is important, so vitamins are classified as either fat-soluble or water-soluble
  • **Water solubility of any organic molecule depends on forming many hydrogen bonds (many –OH groups)
  • Vitamins that consist almost entirely of carbon and hydrogen are fat-soluble**
  • All vitamins have two common functional groups: carbon-carbon double bone and hydroxyl group
81
Q

Vitamin A (Retinol)

A
  • Fat soluble as there are non-polar hydrocarbon chain and ring
  • Vitamin A is important for low-light vision
  • A lack of vitamin A causes night blindness
82
Q

Vitamin C (Ascorbic Acid)

A
  • Water soluble as there is a large number of polar OH groups which are able to form hydrogen bonds with water molecules
  • Due to its solubility in water, it is not retained by the body for long periods
  • Water soluble vitamins such as vitamin C are sensitive to heat and are destroyed by cooking
  • Keeping food containing vitamin C in the refrigerator slows down this process
  • A lack of vitamin C causes scurvy
83
Q

Vitamin D (Calciferol)

A
  • Fat soluble: non-polar hydrocarbon chain and ring
  • Vitamin D stimulates the uptake of calcium ions, important for healthy bones and teeth
  • Vitamin D is made in the body by the action of sunlight on the skin
  • A lack of vitamin D can cause rickets
84
Q

Vitamin Deficiencies

A
  • The absence of a regular, balanced supply of the diverse nutrients needed in the diet is known as malnutrition
  • Malnutrition occurs when either too much food is consumed, which leads to obesity, or the diet is lacking in one or more essential nutrients
85
Q

Causes of vitamin deficiencies:

A
  • Lack of distribution of global resources
  • Depletion of nutrients in the soil
  • Lack of education about balanced diets
86
Q

Solutions to vitamin deficiencies:

A
  • Taking nutritional supplements
  • Genetically modifying foods to increase vitamin content
  • Educating people about balanced diets
87
Q

Biodegradability

A
  • Biodegradable plastics and compostable plastics can be broken down or consumed by bacteria or other living organisms through natural processes.
  • Specific enzymes have been developed to help in the dispersal and breakdown of oil spills and other industrial wastes
  • Bioplastics can be broken down in hydrolysis reactions due to the presence of ester linkages or glyosidic links (requires heat and moisture)/ When some biodegradable plastics decomposed in landfills, they produce methane gas which is a very powerful greenhouse gas (anaerobic conditions)
88
Q

However, although some plastics are organic in origin they are petroleum based so cannot easily be broken down by natural organisms and cause big pollution problems….

A
  • PLA (polylactide) is a biodegradable plastic derived from renewable resources such as corn starch
  • The breakdown of starch based plastics (bioplastics) produces carbon dioxide and water
  • Starch based polymers constitute over 50% of the biodegradable plastics as it is easily broken down by microorganisms and being renewable it is good alternative to fossil fuel based plastics
  • Starch grains in the plastic will swell when they come in contact with water (e.g. in a landfill). This breaks the plastic up into many much smaller pieces, which increases the overall surface area and consequently the rate of the breakdown reactions
89
Q

Advantages of Biodegradability

A
  • Renewable resource
  • Broken down by bacteria or other organism
  • Reduces plastic waste
  • Reduce use of petrochemicals
90
Q

Disadantages of Biodegradability

A
  • Require use of land
  • Increases use of fertilizes and pesticides
  • Might breakdown before end of use
  • Release of methane/greenhouse gas during degradation
91
Q

Host-Guest chemistry

A
  • Host-guest complexes are composed of two or more molecules or ions that are held together through non-covalent bonding
  • Host–guest chemistry is very similar to enzymes as it uses host molecules (like enzymes) that bond with specific guest molecules (like substrates) to form host-guest complexes (like enzyme-substrate complexes)
  • The difference between host-guest complexes and enzyme-substrate complexes is that in host-guest chemistry the host is a synthetic molecule specially developed to bond to a specific ‘target’ molecule (guest)
  • as in enzyme-substrate complexes – the bonds that hold the host-guest complex together are all non-covalent attractions, e.g. hydrogen bonds and dipole-dipole, ionic and hydrophobic attractions
  • Host-guest chemistry can be applied to the removal of xenobiotics in the environment
  • The binding between a xenobiotic and a host produces a supramolecul
92
Q

Biomagnification and Bioaccumulation

A
  • Biomagnification: A process that leads to increasing concentrations of (unwanted) substances in animals as you go higher up the food chain
  • Bioaccumulation: The accumulation (build up) of a substance within an organism over time
  • An example includes DDT:
  • DDT is an insecticide that was used to control mosquito populations that spread diseases such as malaria and typhus
  • DDT is readily soluble in fat and does not break down therefore it accumulates in fatty tissue
  • In the 1960s bird of prey such as ospreys suffered a decline in numbers which was due to the toxic effect of DDT
  • The use of DDT as an insecticide was banned in many countries in the 1970s
93
Q

Xenobiotics

A
  • Xenobiotics are chemical substances found within an organism that are not naturally produced by or expected to be present within an organism
  • Antibiotics are xenobiotics in animals as they are not produced by animals, nor are they part of a normal diet
94
Q

Dioxins and PCBs

A
  • **Dioxins and polychlorinated biphenyls (PCBs) are toxic chemicals that persist in the environment
  • Once dioxins enter the body, they accumulate due to their chemical stability and can be absorbed by fatty tissue**
  • Long term exposure to these substances causes a range of adverse effects on the nervous, immune, and endocrine systems
  • They may also be carcinogenic (cancer causing)
95
Q

Green Chemistry

Definition.

A
  • is an approach to chemical research and engineering that seeks to minimize the production and release to the environment of hazardous substances.
96
Q

What are the 5 principles that aim to acheive green chemistry?

A
  1. Developing water based processes and products instead of solvent-based processes and products
  2. Efficient use of energy in processes such as developing new catalysts for lower production temperatures
  3. Efficient use of reactants in processes. i.e. developing a reaction with high atom economy
  4. Developing processes that can use renewable reactants
  5. Developing waste-free products

Chemistry (12 decks)

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