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Biology AS > Biological Molecules > Flashcards

Biological Molecules Flashcards

1
Q

Polymers

A
  • Large complex molecules made up of many monomers (small basic molecular units) joined together
  • E.g. Carbohydrates are made from monomers called monosaccharides (glucose, fructose and galactose)
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2
Q

Glucose

A
  • A hexose sugar (6 carbon atoms)
  • Has two isomers (molecules with the same molecular formula but with atoms arranged in a different way)
  • These being alpha-glucose and beta-glucose
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3
Q

Condensation Reaction

A
  • Reactions between monosaccharides

- Form disaccharides with a glycosidic bond and a water molecule is released

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4
Q

Hydrolysis Reaction

A
  • Reactions in carbohydrates break them down to their constituent monosaccharides using a water molecule between the bond
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5
Q

Benedict’s Test

A
  • Monosaccharides are reducing sugars and when heated with Benedict’s reagent they form a coloured precipitate
  • Changing it from blue to either green, yellow, orange or red dependent on the sugar concentration
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6
Q

Non-Reducing Sugars Test

A
  • First broken down into monosaccharides
  • By heating with dilute hydrochloric acid and neutralising with sodium hydrogen carbonate
  • Then carrying out Benedict’s Test for reducing sugars
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7
Q

Disaccharide Examples

A
  • glucose + glucose = maltose
  • glucose + fructose = sucrose
  • glucose + galactose = lactose
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8
Q

Polysaccharides

A
  • Form by the condensation of many monosaccharides

- This makes them large and therefore insoluble and suitable for storage

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9
Q

Starch

A
  • Main energy storage material in plants for excess glucose
  • Formed by the condensation of alpha-glucose
  • Insoluble in water so doesn’t affect water potential
  • Unbranched chain is compact so more can be stored in a small place and branched chain has side branches for enzymes to easily break down and release glucose quickly
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10
Q

Iodine Test

A
  • Add iodine dissolved in potassium iodide solution to sample
  • If starch is present the browny-orange colour turns blue-black
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11
Q

Glycogen

A
  • Stores excess glucose as glycogen in animals in the liver
  • Formed by condensation of alpha-glucose
  • Branched with many side branches which enzymes act on easily to form glucose needed in respiration
  • Compact to store a lot in a small space and insoluble so does not affect water potential
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12
Q

Cellulose

A
  • Found in plants and made of long unbranched chains of beta-glucose
  • Chains run parallel to each other with hydrogen bonds forming cross linkages between adjacent chains
  • Many hydrogen form strong fibres called micro fibrils helping cellulose provide structural support in cell walls
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13
Q

Proteins

A
  • Basic monomers called amino acids combine to form polypeptide chains and these then form proteins
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14
Q

Amino Acid Structure

A
  • Have an amine group (NH2)
  • Carboxyl group (COOH)
  • Hydrogen (H) atom
  • Variable side group (R) attached to the center carbon
  • There are 20 possible amino acids and they differ in their R side groups
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15
Q

Condensation [proteins]

A
  • Amino acids form a peptide bond between amine (NH2) and carboxyl (COOH) of differing amino acids
  • A molecule of water is released
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16
Q

Hydrolysis [proteins]

A
  • A molecule of water is added to a dipeptide of a polypeptide (between the amine and carboxyl joining amino acids)
  • This breaks them down into amino acids
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17
Q

Primary Protein

A
  • Sequence of amino acids in a polypeptide chain

- This determines the 3D shape and any changes in amino acids will alter the shape and function

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18
Q

Secondary Protein

A
  • Hydrogen bonds form between amino acids

- Causing the chain to fold into a 3D shape either by coiling into an alpha-helix or a beta-pleated sheet

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19
Q

Tertiary Protein

A
  • Further folding occurs and three bonds are present
  • Disulfide bonds which need sulfur to be strong
  • Hydrogen bonds which are weak but many
  • Ionic bonds between carboxyl and amine groups that aren’t involved in the peptide bonds
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20
Q

Quaternary Protein

A
  • Several polypeptide chains held together by bonds and may have non-protein (prosthetic) groups in the molecule
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21
Q

Protein/Biuret Test

A
  • Test solution needs to be alkaline so sodium hydroxide is added then copper (II) sulfate solution is added and if a protein is present solution turns purple
  • If there is no protein present the solution remains blue
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22
Q

Lipids

A
  • Lipids are composed of Carbon, Hydrogen, Oxygen and at times Phosphorus
  • They are insoluble in water but soluble in organic (carbon containing) solvents e.g. ethanol
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23
Q

Triglycerides

A
  • Glycerol backbone with three fatty acid chains bonded on, where each fatty acid forms an ester bond (covalent) with glycerol in a condensation reaction
  • This is between a hydroxyl (–OH) group on the glycerol and a carboxyl (–COOH) group on the fatty acid and 3 water molecules are released
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24
Q

Saturated Fatty Acids

A
  • Only have single bonds between the carbon atoms

- Long straight chains which are more packed and denser e.g. wax or butter

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25
Q

Unsaturated Fatty Acids

A
  • At least one double bond between carbon atoms

- Bent chain which is less compact and less dense e.g. vegetable oil

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26
Q

Phospholipids

A
  • Structure has two fatty acids attached to a phosphate group and a glycerol
  • Amphipathic due to having a hydrophilic phosphorus head which attracts water and hydrophobic fatty acid tails which repel water
  • Found in cell membranes as they form phospholipid bilayers; hydrophilic heads face out towards the water either side while hydrophobic tails face inwards,
  • Water-soluble substances do not easily pass through the membrane into the center like lipid-soluble ones
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27
Q

Lipid/Emulsion Test

A
  • Helps to identify fat/lipids by shaking test substance with ethanol so it dissolves
  • Pouring solution into water and then any lipid shows up as a milky suspended emulsion
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28
Q

Enzymes

A
  • Globular proteins which makes them insoluble
  • They alter rate of metabolic reactions and are described as biological catalysts (speed up rates of reaction by lowering the activation energy)
  • For them to work they must come into physical contact with a substrate and this must be complementary and fit with their active site
29
Q

Extracellular Enzymes

A
  • Secreted from the cell they are made in but move outside the cell to do their job
  • E.g. lipase is made in the pancreas but moves into the smaller intestine
30
Q

Intracellular Enzymes

A
  • Enzymes are secreted from a cell and used within that cell
31
Q

Anabolic Pathways

A
  • Use energy to synthesise large molecules from smaller ones
32
Q

Catabolic Pathways

A
  • Break down large molecules into smaller molecules and release energy
33
Q

Lock & Key Mechanism

A
  • Enzymes are specific; substrate and active site shapes must be complementary and fit together perfectly to form an enzyme-substrate complex
  • Once they chemically react the substrate either breaks down or joins to a new molecule leaving the enzyme and new products
34
Q

Induced Fit Model

A
  • Substrate and active site are slightly complementary;
  • Active site alters slightly for the enzyme-substrate complex to form
  • Substrate breaks down or joins a new molecule but while still binding to the active site an enzyme-product complex occurs before the bond is broken leaving the enzyme and products separate
35
Q

Temperature [enzyme activity]

A
  • Increase in temperature increases kinetic energy
  • So more collisions occur forming more enzyme-substrate complexes
  • Past the optimum temperature hydrogen bonds break
  • Active site changes so enzyme and substrate no longer fit and the enzyme denatures
36
Q

pH [enzyme activity]

A
  • All enzymes have an optimum pH value where it works fastest
  • Above and below this affects the ionic and hydrogen bonds which affects the tertiary structure
  • Changing active site shape and denaturing the enzyme
37
Q

Enzyme Concentration [enzyme activity]

A
  • The more enzymes present in the solution the more collisions and enzyme-substrates are formed
  • If substrate amount is limited this reaches a maximum where there are no more substrates and the substrate becomes the limiting factor
38
Q

Substrate Concentration [enzyme activity]

A
  • The higher the substrate concentration the more collisions there’ll be so more enzyme-substrate complexes form
  • At a maximum there is a saturation point where all the active sites are full so adding more substrate makes no difference so the enzymes become the limiting factor
39
Q

Competitive Inhibitors

A
  • Have similar shape to the substrate so they compete with the substrate for a position on the active site of the enzyme
  • Inhibitor prevents the substrate from binding to the enzyme
  • Slowed by an increase in substrate concentration
40
Q

Non-competitive Inhibitors

A
  • Don’t compete with substrate for active site; bind to an allosteric site changing the shape of the enzyme and active site
41
Q

DNA

A
  • Deoxyribonucleic acid (DNA)
  • Stores genetic information, passes information from cell to cell and is involved in DNA replication and protein synthesis
42
Q

RNA

A
  • Ribonucleic acid (RNA)
  • Transfers genetic information from DNA to the ribosomes and ribosomes read the mRNA to make polypeptides which form proteins
43
Q

Nucleotides

A
  • Nucleotides are a type of biological molecule made from:
  • Pentose sugar (5 carbon atoms)
  • Nitrogenous base
  • Phosphate group
  • DNA and RNA are nucleotides
44
Q

Polynucleotides

A
  • A polymer of nucleotides formed in a condensation reaction between the phosphate group of one nucleotide and the sugar of another
  • This forms a phosphodiester bond and the chain of sugars and phosphates is known as the sugar-phosphate backbone
45
Q

Pyrimidines

A
  • Have a single ring structure making them smaller (these have a ‘y’ in them)
  • E.g. cytosine and thymine
46
Q

Purines

A
  • Have a double ring structure making them bigger molecules

- E.g. adenine and guanine

47
Q

DNA Nucleotide

A
  • Pentose sugar is called deoxyribose, with a phosphate group attached to it as well as one of the four bases: Adenine, Thymine, Cytosine or Guanine
  • DNA molecule is a double helix with two polynucleotide chains held together by hydrogen bonds between complementary bases
  • Adenine pairs up with thymine and these have two hydrogen bonds in-between
  • Cytosine pairs up with guanine and these have three hydrogen bonds in-between
  • The two polynucleotide strands are antiparallel; they run in opposite directions as one strand goes from a 5-prime end to a 3-prime end while the other runs from a 3-prime end to a 5-prime end
  • A gene is a section of DNA that codes for a specific protein product
48
Q

RNA Nucleotide

A
  • Pentose sugar is called ribose, with a phosphate group and one of the four nitrogen-containing bases: Adenine, Cytosine, Guanine and Uracil (which replaces thymine)
  • RNA is a single polynucleotide chain
  • mRNA (messenger RNA) is a complementary strand of the sensory DNA strand which leaves the nucleus to attach to the ribosome and its series of codons are read and the right amino acids are joined together
  • rRNA (ribosomal RNA) codes to make new ribosomes
  • tRNA (transfer RNA) delivers amino acids to the ribosome
49
Q

Semi-conservative

A
  • Half the strands in each new daughter cell are from the original DNA molecule
  • DNA replication
50
Q

DNA Replication

A
  • The enzyme DNA helicase breaks the hydrogen bonds between bases
  • This makes the helix unwind to form two single strands
  • Each strand has exposed bases and acts as a template for complementary bases to attach onto
  • These complementary bases are apart of the free floating nucleotides
  • DNA polymerase joins the nucleotides together forming phosphodiester bonds between the phosphate backbone and the sugar
  • This results in two new DNA molecules each containing one strand from the original DNA molecule and one new strand
51
Q

DNA Polymerase

A
  • In a DNA helix the strands are antiparallel because they run in opposite ends, one strand runs from 3’ (three prime) to 5’ (five prime) and the other goes in the opposite direction
  • The active site of DNA polymerase is only complementary to the 3’ end
  • Therefore enzymes can only add nucleotides to the strand at the 3’ end meaning that the DNA polymerase moves in opposite ways along the antiparallel strands
52
Q

Semiconservative Evidence

A
  • An experiment by Meselson and Stahl using two isotopes of nitrogen (heavy nitrogen 15N) and (light nitrogen 14N)
  • Sample of bacteria were grown, one in a 15N medium and one in a 14N medium and as the bacteria reproduced the nitrogen gradually became part of the bacteria’s DNA
  • When centrifuged the light 14N DNA settled at the top while the heavy 15N DNA settled at the bottom of the test tube
  • The bacteria from the heavy nitrogen was then added to a broth containing only light nitrogen and they were left to replicate and were then centrifuged
  • If DNA replication were conservative the original heavy DNA would stay intact and settle at the bottom while the light DNA stays intact and settles at the top
  • The experiment showed it was semi-conservative as the new DNA molecule had a mixture of heavy and light DNA with one strand from each and settled at the middle of the test tube
53
Q

ATP

A
  • ATP stands for Adenosine Triphosphate and is a nucleotide formed from a molecule of ribose, a molecule of adenine and three phosphate groups
  • All organisms use energy in the form of ATP as it diffuses to the part of the cell that needs energy
  • Energy released from glucose in respiration is one of the ways of making adenosine triphosphate
54
Q

Using ATP

A
  • ATP stores it’s energy in the high energy bonds between phosphate groups
  • When energy is needed by a cell a water molecule is added which breaks a phosphate bond turning ATP into ADP (Adenosine Diphosphate) as there are now only two phosphates remaining and an inorganic phosphate is also produced
  • This is known as a hydrolysis reaction catalysed by ATP hydrolase
  • ATP + H20 ⇒ ADP + Pi + Energy
  • The reaction that synthesises ATP is a condensation reaction between ADP and Pi and this can happen via respiration or photosynthesis and this is catalysed by ATP synthase
55
Q

Phosphorylation

A
  • This is the synthesis of ATP, - Where energy is used to add phosphates and there are three types
  • Photophosphorylation: In plant cells containing chlorophyll during photosynthesis
  • Oxidative Phosphorylation: In plant and animal cells during respiration
  • Substrate-level Phosphorylation: In plant and animal cells when phosphate groups are transferred from one donor molecule to ADP
56
Q

Advantages Of ATP

A
  • Immediate source of energy: instability of phosphate bonds which have high energy
  • Energy released in smaller quantities: each ATP molecule releases less energy than each glucose molecule so it’s more manageable
  • Mobile & transports chemical energy to where its needed in the cell
  • Universal energy carrier used in: metabolic, movement, active transport, secretion and activation of molecules
57
Q

Water

A
  • Water (H2O) is made up of one atom of oxygen joined to two hydrogen atoms by shared electrons
  • It is a polar molecule so the slightly negatively charged oxygen atoms of one water molecule attract the slightly positively charged hydrogen atoms of another water molecule creating hydrogen bonding
58
Q

Metabolite [water]

A
  • It is involved in metabolic reactions
  • This can be as either a reactant or product e.g. it is a reactant in hydrolysis reactions used to break bonds but is a product released in condensation reactions when new bonds are created
59
Q

High Latent Heat Of Vaporisation [water]

A
  • A lot of energy is needed to break the hydrogen bonds between water molecules
  • This means it has a high latent heat of vaporisation as a lot of energy is used up when water evaporates
  • This is useful for living organisms as it means they can use the water lost through evaporation to cool down without losing too much water
60
Q

High Specific Heat Capacity [water]

A
  • Hydrogen bonds between water molecules can absorb a lot of energy because water has a high specific heat capacity
  • This means that water takes a lot of energy to heat up
  • So large amounts of water can be buffered (won’t experience rapid changes) and this means that underwater habitat temperatures can stay stable and internal body temperatures inside organisms can also stay stable
61
Q

Solvent [water]

A
  • Many substances in metabolic reactions are ionic (they are either positively charged or negatively charged)
  • Water is polar so the positive end of the water molecule will attract to the negative ion while the negative end of the water molecule attracts to the positive ion
  • The ion is then completely surrounded by water molecules and dissolves
62
Q

Cohesion [water]

A
  • Cohesion is the attraction between molecules of the same type, water molecules are very cohesive (stick together) due to being polar
  • Strong cohesion helps water to flow making it great for transporting substances e.g. it flows up the xylem tubes of plants to reach all the areas of the plant
  • Having strong cohesion also means that water has a high surface tension when it comes into contact with air e.g. this is why sweat forms droplets
63
Q

Ions

A
  • An ion is an atom/group of atoms that has an electric charge
  • Positively charged ions are called cations
  • Negatively charged ions are called anions
64
Q

Inorganic Ions

A
  • Have no carbon

- They can be found in solution, in the cytoplasm of cells and in the body fluid of organisms

65
Q

Iron Ions

A
  • Essential in haemoglobin
  • The Fe2+ binds to the oxygen in haemoglobin and temporarily becomes an Fe3+ ion until the oxygen is released
  • Haemoglobin: a large protein that carries oxygen around the body in red blood cells, it has four polypeptide chains each with an Fe2+ iron ion in the center
66
Q

Hydrogen Ions

A
  • pH is calculated based on the concentration of hydrogen ions (H+) in the environment
  • The more H+ present the lower the pH and the more acidic the environment
  • Enzyme-controlled reactions are all affected by pH
67
Q

Sodium Ions

A
  • Help transport glucose and amino acids across membranes
  • A molecule of glucose or an amino acid can be transported into a cell across the cell-surface membrane alongside sodium ions (Na+)
  • This is called co-transport
68
Q

Phosphate Ions

A
  • Essential component as DNA, RNA and ATP all contain phosphate groups
  • When a phosphate ion (PO43-) is attached to another molecule it’s known as a phosphate group
  • The bonds between phosphate groups store energy in ATP
  • The phosphate groups in DNA and RNA allow nucleotides to join up with phosphodiester bonds to form polynucleotides

Biology AS (7 decks)

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