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Biology (Personal) > Biological Molecules > Flashcards

Biological Molecules Flashcards

1
Q

What is a polymer?

A

Molecule made of many monomers

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1
Q

What is a monomer?

A

The small, repeating untis of which polymers are made of

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2
Q

What occurs in condensation reaction?

A
  • 2 Molecules join together
  • Forming a chemical bond
  • Releasing a water molecule
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3
Q

What occurs in a hydrolysis reaction?

A
  • 2 Molecules separated
  • Using a water molecule
  • Breaking a chemical bond
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4
Q

What are monosaccharides?

A

Monomers from which larger carbohydrates are made

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5
Q

Describe the difference between the structure of alpha and beta glucose

A

Alpha Glucose - Hydroxyl group below carbon 1
- Beta glucose, Hydroxyl group above carbon 1

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6
Q

What are disaccharides and how are they formed?

A
  • Two monosaccharides joined together in a glycosidic bond
  • Formed by a condensation reaction, releasing a water molecule
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7
Q

What are polysaccharides and how are they formed?

A
  • Many monosaccharides joined together by glycosidic bonds
  • Formed by many condensation reactions, releasing water molecules
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8
Q

Describe the basic function and structure of Starch

A
  • Energy store in plant cells
  • Polysaccharide of alpha glucose
  • Amylose contains 1-4 glycosidic bonds (unbranched)
  • Amylopectin contains 1-6 glycosidic bonds (branched)
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9
Q

Describe the basic function and structure of glycogen

A
  • Energy store in animal cells
  • Contains 1-4 and 1-6 glycosidic bonds (branched)
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10
Q

Explain how the structure of starch relates to its function

A
  • Starch is helical, compact for storage in cell
  • Large, insoluble polysaccharide molecule, can’t cross cell membrane
  • Insoluble in water, doesn’t affect water potential of cell
  • Amylopectin is branched, more ends for faster hydrolysis - release glucose for respiration to make ATP for energy release
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11
Q

Explain how the structure of glycogen relates to its function

A
  • Branched, so can fit more molecules in a smaller area
  • Branched, more ends for faster hydrolysis, to release glucose for respiration to make ATP for energy release
  • Large, insoluble molecule, can’t leave cell membrane
  • Insoluble in water, doesn’t affect water potential
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12
Q

Describe the basic function and structure of cellulose

A
  • Provide strength / support to plant / algal cell walls
  • Polysaccharide formed of beta glucose subunits
  • 1,4 glycosidic bonds, straight unbranched chains
  • Chains linked in parallel crosslinks by hydrogen bonds forming microfibrils
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13
Q

Explain how the structure of cellulose relates to its function

A
  • Every other beta glucose molecule is inverted in a long, straight, unbranched chain
  • Many hydrogen bonds link parallel strands (crosslinks) to form microfibrils (strong fibres)
  • Hydrogen bonds are strong in high numbers
  • So provides strength to plant cell walls
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14
Q

Describe the test for reducing sugars (e.g, Monosaccharides, Lactose, Maltose)

A
  • Add benedict’s solution (blue) to sample
  • Heat in a boiling water bath
  • Positive result = Green/Yellow/Orange/Red precipitate
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15
Q

Describe the test for non reducing sugars (e.g Sucrose)

A
  • Benedict’s test gives negative result (blue)
  • Heat in a water bath with HCl (to hydrolyse into reducing sugars)
  • Neutralise with an alkali (e.g NaHCO3)
  • Positive: Green/Yellow/Orange/Red precipitate
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16
Q

Suggest a method to find the quantity of sugar in a solution

A
  • Carry out benedicts test, then filter and dry precipitate
  • Find mass
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17
Q

Suggest a method using a calibration curve to find the quantity of sugar in a solution

A
  • Make sugar solutions of known concentrations
  • Heat a set volume of each sample with a set volume of benedict’s solution for same time
  • Use colorimeter to measure absorbance of light of each known concentration
  • Plot a calibration curve - Concentration on X axis, Absorbance of light on Y axis and draw a line of best fit
  • Repeat benedict’s test with unknown sample
  • Read off calibration curve to find concentration associated with sample’s absorbance
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18
Q

Describe the biochemical test for starch

A
  • Add iodine dissolved in potassium iodide and shake/stir
  • Positive result = (orange/brown) to blue/black
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19
Q

Describe the structure of a fatty acid (RCOOH)

A
  • Variable R group, hydrocarbon chain
  • Carboxyl group
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20
Q

Describe the difference between saturated and unsaturated hydrocarbons

A
  • Saturated hydrocarbons have no C=C double bond
  • Unsatured hydrocarbons have a C=C double bond, which creates a bend
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21
Q

Describe how triglycerides form

A
  • 1 Glycerol molecule and 3 fatty acids
  • Condensation reaction, forming ester bonds
  • Release of 3 water molecules
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22
Q

Explain how the properties of triglycerides are related to their structure

A
  • High ratio of C-H bonds to Carbon atoms, so used in respiration to release more energy than same mass of carbohydrates
  • Hydrophobic/ non-polar fatty acids insoluble in water (clump together as droplets)
  • So no affect on water potential of cell
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23
Q

Describe the difference between the structure of triglycerides and phospholipids

A
  • Phospholipid’s only have 2 fatty acid chains
  • Phospholipids contain a phosphate group
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24
Q

Describe the test for lipids

A
  • Add ethanol, shake (to dissolve lipids) then add water
  • Milky white emulsion = Positive result
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25
Q

Describe the general structure of an amino acid

A
  • Amine Group (NH2)
  • Carboxyl Group (COOH)
  • R Group
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26
Q

How many amino acids are common in all organisms and what do they vary by?

A
  • 20
  • Vary by R group
27
Q

Describe how amino acids join together?

A
  • Condensation reaction, forming a peptide bond
  • Between the Carboxyl group of one and the Amine group of another
  • Releasing a water molecule
28
Q

Describe the primary structure of a protein

A

The sequence of amino acids in the polypeptide chain, joined by peptide bonds

29
Q

Describe the secondary structure of a protein

A
  • Folding of the polypeptide chain into e.g alpha helixes or beta sheets
  • Due to hydrogen bonding between amino acids
  • Between NH of amino acid and C=O (Group) of another
30
Q

Describe the tertiary structure of a protein

A
  • 3D Folding of Polypeptide chain
  • Due to interactions between amino acid R groups
  • Forming Hydrogen/Ionic/Disulphide bonds
31
Q

Describe the quaternary structure of a protein

A
  • More than one polypeptide chain
  • Formed by interactions between polypeptides
32
Q

Describe the test for proteins

A
  • Add biuret’s reagent
  • Positive result = Blue to purple/lilac colour
33
Q

How do enzymes act as biological catalysts?

A
  • Lowers activation energy of reaction it catalyses, speeding up rate of reaction
34
Q

Describe the induced-fit model of enzyme action

A
  • Substrate binds (to not completely complimentary site) active site of enzyme
  • Causes active site to change shape slightly so its complimentary to substrate
  • So enzyme-substrate complex forms
  • Causes bonds in substrate to bend/distort, lowering activation energy
35
Q

Explain the specificity of enzymes

A
  • Specific tertiary structure determines the active site
  • Dependent on primary structure (sequence of amino acids)
  • Active site is complimentary to specific substrate
  • Only this substrate can bind to the active site, inducing fit and forming an enzyme-substrate complex
36
Q

Describe and explain the effect of temperature on enzyme-controlled reactions

A
  • As temperature increases to optimum, rate of reaction increases
  • More KE, so more E-S complexes form
  • As temperature increases above optimum, rate of reaction decreases
  • Enzymes denature, tertiary structure changes and active site changes shape
  • As hydrogen/ionic bonds break
  • Active site no longer complimentary
  • Fewer E-S complexes form
37
Q

Explain the effect of PH on the rate of enzyme controlled reactions

A
  • As PH increases/decreases above optimum PH, rate of reaction decreases
  • Enzymes denature, tertiary structure changes and active site changes shape
  • As hydrogen/ionic bonds break
  • Active site no longer complimentary
  • Fewer E-S complexes form
38
Q

Describe and explain the effect of concentration of competitive inhibitors on
the rate of enzyme-controlled reactions

A
  • As the concentration of competitive inhibitors increases, rate of reaction decreases
  • Similar shape to substrate
  • Competes for active site
  • Substrates can’t bind to active site, so E-S complex can’t form
  • Increasing the concentration of subsrate reduces the effect of competitive inhibitors
39
Q

Describe the effect of concentration of non-competitive inhibitors on the rate of enzyme-controlled reactions

A
  • As concentration of non competitive inhibitors increases, rate of reaction decreases
  • Binds to allosteric site
  • Changes enzyme tertiary structure/active site
  • Active site no longer complimentary to substrate
  • Substrate can’t bind so E-S complex can’t form
  • Increasing substrate concentration has no effect as change to active site is permenant
40
Q

Describe the basic functions of DNA and RNA in all living cells

A

DNA: Holds genetic information which codes for polypeptides
RNA: Transfers genetic information from DNA to Ribosomes

41
Q

Name the 2 types of molecule from which a ribosome is made

A

RNA and Protein

42
Q

What are the differences between a DNA nucleotide and an RNA nucleotide?

A
  • DNA nucleotide pentose sugar is deoxyribose, and it has a thymine base
  • RNA nucleotide pentose sugar is ribose, and it has a uracil base
43
Q

Describe how nucleotides join together to form polynucleotides

A
  • Condensation reaction between the pentose sugar of one nucleotide and the phosphate group of another
  • Releasing water molecules
  • Forming an phosphodiester bond
44
Q

Describe the structure of DNA

A
  • Polymer of nucleotides
  • Each nucleotide formed from deoxyribose, a phosphate group and a nitrogenous base
  • Phosphodiester bonds join adjacent nucleotides
  • 2 Polynucleotide chains held together by hydrogen bonds between bases (A-T, C-G)
  • Double helix shape
45
Q

Describe the structure of mRNA

A
  • Polymer of Nucleotides
  • Each nucleotide made from ribose, a phosphate group and a nitrogenous base
  • Bases: Uracil, Adenine, Cytosine, Guanine
  • Single Helix
  • Phosphodiester bonds join adjacent nucleotides
46
Q

Suggest how the structure of DNA relates to its functions

A

-● Two strands → both can act as templates for semi-conservative replication
● Hydrogen bonds between bases are weak → strands can be separated for replication
● Complementary base pairing → accurate replication
● Many hydrogen bonds between bases → stable / strong molecule
● Double helix with sugar phosphate backbone → protects bases / hydrogen bonds
● Long molecule → store lots of genetic information (that codes for polypeptides)
● Double helix (coiled) → compact

47
Q

Describe the process of semi-conservative DNA replication

A
  1. DNA helicase breaks hydrogen bonds between complementary bases, unwinding the double helix
  2. Both strands act as templates
  3. Free DNA nucleotides attracted to exposed bases and join by specific complementary base pairing (A-T, C-G)
  4. Hydrogen bonds form between adenine-thymine and guanine-cytosine
  5. DNA polymerase joins adjacent nucleotides on new strand by condensation reactions
  6. Forming phosphodiester bonds
48
Q

Use your knowledge of enzyme action to suggest why DNA polymerase
moves in opposite directions along DNA strands

A

● DNA has antiparallel strands
● So shapes / arrangements of nucleotides on two ends are different
● DNA polymerase is an enzyme with a specific shaped active site
● So can only bind to substrate with complementary shape (phosphate end of developing strand)

49
Q

Describe the Nitrogen experiment to support the Semi-Conservative replication theory

A
  1. Bacteria grown in medium containing heavy nitrogen (
    15N) and
    nitrogen is incorporated into DNA bases
    ● DNA extracted & centrifuged → settles near bottom, as all
    DNA molecules contain 2 ‘heavy’ strands
  2. Bacteria transferred to medium containing light nitrogen (
    14N)
    and allowed to divide once
    ● DNA extracted & centrifuged → settles in middle, as all DNA
    molecules contain 1 original ‘heavy’ and 1 new ‘light’ strand
  3. Bacteria in light nitrogen (
    14N) allowed to divide again
    ● DNA extracted & centrifuged → half settles in middle, as
    contains 1 original ‘heavy’ and 1 new ‘light’ strand; half
    settles near top, as contains 2 ‘light’ strands
50
Q

What is ATP?

A

Adenosine Triphosphate

51
Q

Describe the structure of ATP

A

Ribose bound to a molecule of adenine (base) and 3 phosphate groups
- It’s a nucleotide derivative

52
Q

Describe how ATP is broken down

A

● ATP (+ water) → ADP (adenosine diphosphate) + Pi (inorganic phosphate)
● Hydrolysis reaction, using a water molecule
● Catalysed by ATP hydrolase (enzyme)

53
Q

Give 2 ways in which the hydrolysis of ATP is used in cells

A

● Coupled to energy requiring reactions within cells (releases / provides energy)
○ Eg. active transport, protein synthesis
● Inorganic phosphate released can be used to phosphorylate (add phosphate
to) other compounds, making them more reactive

54
Q

Describe how ATP is resynthesised in cells

A

Describe how ATP is resynthesised in cells
● ADP + Pi → ATP (+ water)
● Condensation reaction, removing a water molecule
● Catalysed by ATP synthase (enzyme)
● During respiration and photosynthesis

55
Q

Suggest how the properties of ATP make it a suitable immediate source of
energy for cells

A

● Releases energy in (relatively) small amounts / little energy lost as heat
● Single reaction / one bond hydrolysed to release energy (so immediate release)
● Cannot pass out of cell

56
Q

Explain how hydrogen bonds occur between water molecules

A

● Water is polar molecule
● Slightly negatively charged oxygen atoms attract slightly positively
charged hydrogen atoms of other water molecules

57
Q

Explain how water being a metabolite is important in biology

A

Used in condensation / hydrolysis / photosynthesis / respiration

58
Q

Explain how water being a universal solvent is useful in biology

A
  1. Allows metabolic reactions to occur (faster in solution)
  2. Allows transport of substances eg. nitrates in xylem, urea in blood
59
Q

Explain how water having a high specific heat capacity is useful in biology

A

● Buffers changes in temperature
● As can gain / lose a lot of heat / energy without changing temperature
1. Good habitat for aquatic organisms as temperature more stable than land
2. Helps organisms maintain a constant internal body temperature

60
Q

Explain how water having a high latent heat of vaporisation is important in biology

A

● Allows effective cooling via evaporation of a small volume (eg. sweat)
● So helps organisms maintain a constant internal body temperature

61
Q

Explain how water being cohesive is important in biology

A
  1. Supports columns of water eg. transpiration stream through xylem in plants
  2. Produces surface tension, supporting small organisms (to walk on water)
62
Q

Where are inorganic ions found in the body?

A

In solution in cytoplasm and body fluid, some in high concentrations and others in very low concentrations.

63
Q

What are the roles of H+ ions in the body?

A

● Maintain pH levels in the body → high conc. = acidic / low pH
● Affects enzyme rate of reaction as can cause enzymes to denature

64
Q

What are the roles of iron ions in the body?

A

● Component of haem group of haemoglobin
● Allowing oxygen to bind / associate for transport as oxyhaemoglobin

65
Q

What are the roles of Sodium ions in the body?

A
  1. Involved in co-transport of glucose / amino acids into cells
  2. Involved in action potentials in neurons
  3. Affects water potential of cells / osmosis
66
Q

Explain the role of Phosphate ions in the body

A

. Component of nucleotides, allowing phosphodiester bonds to form in DNA / RNA
2. Component of ATP, allowing energy release
3. Phosphorylates other compounds making them more reactive
4. Hydrophilic part of phospholipids, allowing a bilayer to form

Biology (Personal) (15 decks)

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