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Biology > 3.1 > Flashcards

3.1 Flashcards

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1
Q

What are monomers and polymers

A

Monomers are small repeating units from which polymers are made up of
Polymers are molecules made up of many monomer units

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2
Q

What happens in condensation and hydrolysis reactions?

A

Condensation- 2 molecules join together forming a chemical bond and releasing water
Hydrolysis- 2 molecules separated breaking a chemical bond and using water

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3
Q

What are monosaccharides?

A

Monomers from which larger carbohydrates are made
● Glucose, fructose, galactose

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4
Q

Describe the difference between the structure of α-glucose and β-glucose

A

Isomers - same molecular formula but differently arranged atoms
● OH group is below carbon 1 in α-glucose but above carbon 1 in β-glucose

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5
Q

What are disaccharides and how are they formed?

A

● Two monosaccharides joined together with a glycosidic bond
● Formed by a condensation reaction, releasing a water molecule

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6
Q

3 monosaccharides and he disaccharide they form

A

glucose+glucose= maltose
glucose+galactose=lactose
glucose+fructose=sucrose

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7
Q

What are polysaccharides and how are they formed?

A

Many monosaccharides joined together with glycosidic bonds
● Formed by many condensation reactions, releasing many water molecules

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8
Q

Basic structure of starch and how it relates to function

A

Energy store in plants
Polysaccharide of alpha glucose
Unbranched amylose bonds 1-4
branched amylopectin bonds 1-4 and 1-6

Compact for storage in cells
Large, insoluble can’t leave cell / cross cell membrane
Insoluble in water → water potential of cell not affected (no osmotic effect)
Branched → compact / fit more molecules in small area
Branched → more ends for faster hydrolysis → release glucose for respiration to
make ATP for energy release

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9
Q

Basic structure of glycogen and how it relates to function

A

Glycogen- energy store in animals
Polysaccharide in alpha glucose
1-4 and 1-6 bonds so much more branched
Branched → compact / fit more molecules in small area
● Branched → more ends for faster hydrolysis → release glucose for respiration to
make ATP for energy release
● Large, insoluble polysaccharide molecule → can’t leave cell / cross cell membrane
● Insoluble in water → water potential of cell not affected (no osmotic effect)

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10
Q

Describe the basic function and structure of cellulose and how it relates to its function

A

Function- Provides strength and support in cell walls
Structure- ● Polysaccharide of β-glucose● 1,4-glycosidic bonds so forms straight, unbranched chains
● Chains linked in parallel by hydrogen bonds, forming microfibrils

Every other β-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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11
Q

Describe the test for reducing sugars

A
  1. Add Benedict’s solution (blue) to sample
  2. Heat in a boiling water bath
  3. Positive result = green / yellow / orange / red precipitate
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12
Q

Describe the test for non-reducing sugars

A
  1. Do Benedict’s test (as above) and stays blue / negative
  2. Heat in a boiling water bath with acid (to hydrolyse into reducing sugars)
  3. Neutralise with alkali (eg. sodium bicarbonate)
  4. Heat in a boiling water bath with Benedict’s solution
  5. Positive result = green / yellow / orange / red precipitate
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13
Q

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

A

● Carry out Benedict’s test as above, then filter and dry precipitate
● Find mass / weight

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14
Q

Suggest another method to measure the quantity of sugar in a solution

A
  1. Make sugar solutions of known concentrations
    (eg. dilution series)
  2. Heat a set volume of each sample with a set
    volume of Benedict’s solution for the same time
  3. Use colorimeter to measure absorbance (of
    light) of each known concentration
  4. Plot calibration curve - concentration on x axis,
    absorbance on y axis and draw line of best fit
  5. Repeat Benedict’s test with unknown sample and
    measure absorbance
  6. Read off calibration curve to find concentration
    associated with unknown sample’s absorbance
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15
Q

Describe the biochemical test for starch

A
  1. Add iodine dissolved in potassium iodide (orange / brown) and shake / stir
  2. Positive result = blue-black
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16
Q

Name two groups of lipid

A

Triglycerides and phospholipids

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17
Q

Describe the structure of a fatty acid (RCOOH)

A

● Variable R-group - hydrocarbon chain (this may be saturated or unsaturated)
● -COOH = carboxyl group

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18
Q

Describe the difference between saturated and unsaturated fatty acids

A

● Saturated - no C=C double bonds in hydrocarbon chain → all carbons fully saturated with hydrogen
● Unsaturated - one or more C=C double bond in hydrocarbon chain (creating a bend / kink)

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19
Q

Describe how triglycerides form

A

● 1 glycerol molecule and 3 fatty acids
● 3 condensation reactions
● Removing 3 water molecules
● Forming 3 ester bonds

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20
Q

Explain how the properties of triglycerides are related to their structure

A

● High ratio of C-H bonds to carbon atoms in hydrocarbon chain
○ So used in respiration to release more energy than the same mass of carbohydrates
● Hydrophobic / non-polar fatty acids so insoluble in water (clump together as droplets, tails inwards)
○ So no effect on water potential of cell (or can be used for waterproofing)

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21
Q

Describe the difference between the structure
of triglycerides and phospholipids

A

One of the fatty acids of a triglyceride is
substituted by a phosphate-containing group

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22
Q

Describe how the properties of
phospholipids relate to their structure

A

Function: form a bilayer in cell membrane, allowing diffusion of lipid-soluble (non-polar) or very small
substances and restricting movement of water-soluble (polar) or larger substances
● Phosphate heads are hydrophilic
○ Attracted to water so point to water (aqueous environment) either side of membrane
● Fatty acid tails are hydrophobic
○ Repelled by water so point away from water / to interior of membrane

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23
Q

Describe the test for lipids

A
  1. Add ethanol, shake (to dissolve lipids), then add water
  2. Positive result = milky white emulsion
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24
Q

Describe / draw the general
structure of an amino acid

A

● COOH = carboxyl group
● R = variable side chain / group
● H2N = amine group

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25
How many amino acids are common in all organisms? How do they vary?
The 20 amino acids that are common in all organisms differ only in their side group (R)
26
Describe how amino acids join together
● Condensation reaction ● Removing a water molecule ● Between carboxyl / COOH group of one and amine / NH2 group of another ● Forming a peptide bond
27
What are dipeptides and polypeptides?
● Dipeptide - 2 amino acids joined together ● Polypeptide - many amino acids joined together
28
Describe the primary structure of a protein
Sequence of amino acids in a polypeptide chain, joined by peptide bonds
29
Describe the secondary structure of a protein
● Folding (repeating patterns) of polypeptide chain eg. alpha helix / beta pleated sheets ● Due to hydrogen bonding between amino acids ● Between NH (group of one amino acid) and C=O (group)
30
Describe the tertiary structure of a protein
● 3D folding of polypeptide chain ● Due to interactions between amino acid R groups (dependent on sequence of amino acids) ● Forming hydrogen bonds, ionic bonds and disulfide bridges
31
Describe the quaternary structure of a protein
● More than one polypeptide chain ● Formed by interactions between polypeptides (hydrogen bonds, ionic bonds, disulfide bridges)
32
Describe the test for proteins
1. Add biuret reagent (sodium hydroxide + copper (II) sulphate) 2. Positive result = purple / lilac colour (indicating presence of peptide bonds)
33
How do enzymes act as biological catalysts?
● Each enzyme lowers activation energy of reaction it catalyses ● To speed up rate of reaction
34
Describe the induced-fit model of enzyme action
1. Substrate binds to (not completely complementary) active site of enzyme 2. Causing active site to change shape (slightly) so it is complementary to its substrate 3. So enzyme-substrate complex forms 4. Causing bonds in substrate to bend / distort, lowering activation energy
35
Describe how models of enzyme action have changed over time
● Initially lock and key model (now outdated) ○ Active site a fixed shape, complementary to one substrate ● Now induced-fit model
36
Explain the specificity of enzymes
● Specific tertiary structure determines shape of active site ○ Dependent on sequence of amino acids (primary structure) ● Active site is complementary to a specific substrate ● Only this substrate can bind to active site, inducing fit and forming an enzyme-substrate complex
37
Describe and explain the effect of enzyme concentration on the rate of enzyme-controlled reactions
● As enzyme concentration increases, rate of reaction increases ○ Enzyme concentration = limiting factor (excess substrate) ○ More enzymes so more available active sites ○ So more enzyme-substrate complexes form ● At a certain point, rate of reaction stops increasing / levels off ○ Substrate concentration = limiting factor (all substrates in use)
38
Describe and explain the effect of substrate concentration on the rate of enzyme-controlled reactions
● As substrate concentration increases, rate of reaction increases ○ Substrate concentration = limiting factor (too few substrate molecules to occupy all active sites) ○ More enzyme-substrate complexes form ● At a certain point, rate of reaction stops increasing / levels off ○ Enzyme concentration = limiting factor ○ As all active sites saturated / occupied (at a given time)
39
Describe and explain the effect of temperature on the rate of enzyme-controlled reactions
● As temperature increases to optimum, rate of reaction increases ○ More kinetic energy ○ So more enzyme-substrate complexes form ● As temperature exceeds optimum, rate of reaction decreases ○ Enzymes denature - tertiary structure and active site change shape ○ As hydrogen / ionic bonds break ○ So active site no longer complementary ○ So fewer enzyme-substrate complexes form
40
Describe and explain the effect of pH on the rate of enzyme-controlled reactions
● As pH increases / decreases above / below an optimum, rate of reaction decreases ○ Enzymes denature - tertiary structure and active site change shape ○ As hydrogen / ionic bonds break ○ So active site no longer complementary ○ So fewer enzyme-substrate complexes form
41
Describe and explain the effect of concentration of competitive inhibitors on the rate of enzyme-controlled reactions
● As concentration of competitive inhibitor increases, rate of reaction decreases ○ Similar shape to substrate ○ Competes for / binds to / blocks active site ○ So substrates can’t bind ○ So fewer enzyme-substrate complexes form ● Increasing substrate concentration reduces effect of inhibitors (dependent on relative concentrations of substrate and inhibitor)
42
Describe and explain the effect of concentration of non-competitive inhibitors on the rate of enzyme-controlled reactions
● As concentration of non-competitive inhibitor increases, rate of reaction decreases ○ Binds to site other than the active site (allosteric site) ○ Changes enzyme tertiary structure / active site shape ○ So active site no longer complementary to substrate ○ So substrates can’t bind ○ So fewer enzyme-substrate complexes form ● Increasing substrate concentration has no effect on rate of reaction as change to active site is permanent
43
Describe the basic functions of DNA and RNA in all living cells
DNA Holds genetic information which codes for polypeptides (proteins) RNA Transfers genetic information from DNA to ribosomes
44
Name the two types of molecule from which a ribosome is made
RNA and proteins
45
Describe the differences between a DNA nucleotide and an RNA nucleotide
DNA nucleotide Pentose sugar is deoxyribose Base can be thymine RNA nucleotide Pentose sugar is ribose Base can be uracil
46
Describe how nucleotides join together to form polynucleotides
● Condensation reactions, removing water molecules ● Between phosphate group of one nucleotide and deoxyribose / ribose of another ● Forming phosphodiester bonds
47
Why did many scientists initially doubt that DNA carried the genetic code?
The relative simplicity of DNA - chemically simple molecule with few components
48
Describe the structure of DNA
● Polymer of nucleotides (polynucleotide) ● Each nucleotide formed from deoxyribose, a phosphate group and a nitrogen-containing organic base ● Phosphodiester bonds join adjacent nucleotides ● 2 polynucleotide chains held together by hydrogen bonds ● Between specific complementary base pairs - adenine / thymine and cytosine / guanine ● Double helix
49
Describe the structure of (messenger) RNA
● Polymer of nucleotides (polynucleotide) ● Each nucleotide formed from ribose, a phosphate group and a nitrogen-containing organic base ● Bases - uracil, adenine, cytosine, guanine ● Phosphodiester bonds join adjacent nucleotides ● Single helix
50
Compare and contrast the structure of DNA and (messenger) RNA
DNA Pentose sugar is deoxyribose Has the base thymine Double stranded / double helix Long (many nucleotides) Has hydrogen bonds / base pairing RNA Pentose sugar is ribose Has the base uracil Single stranded / single helix Shorter (fewer nucleotides) Does not
51
Suggest how the structure of DNA relates to its functions
● 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
52
Suggest how you can use incomplete information about the frequency of bases on DNA strands to find the frequency of other bases
1. % of adenine in strand 1 = % of thymine in strand 2 (and vice versa) 2. % of guanine in strand 1 = % of cytosine in strand 2 (and vice versa) Because of specific complementary base pairing between 2 strands
53
Why is semi-conservative replication important?
Ensures genetic continuity between generations of cells
54
Describe the process of semi-conservative DNA replication
1-DNA helicase breaks he hydrogen bonds between the base pairs unwinding the double helix 2-Both strands act as a template 3- Free DNA nucleotides attracted to exposed bases and join by specific complementary base pairing 4- Hydrogen bonds form between adenine and thymine and guanine and cytosine 5- DNA polymerase joins adjacent nucleotides on the new strand by condensation reaction forming phosphodiester bonds
55
Why does DNA polymarse move in opposite directions along the DNA strands
DNA has antiparallel strands so arrangement of nucleotides on two ends are different DNA polymerase is an enzyme with a specific shaped active site so can only bind to the end with the complementary shape so works in the 5prime to 3 prime end
56
Meselsons and Stahls work in validating Watsons and Crick of semi conservative replication
1-Bacteria grown in medium containing heavy nitrogen so nitrogen is incorporated into DNA bases - DNA extracted and centrifuged and settles near bottom as pellet 2-Bacteria transferred to medium containing light nitrogen and allowed to divide once -DNA is extracted and centrifuged- settles in middle as all DNA contains one heavy strand and one light strand 3-Bacteria in light nitrogen and allowed to divide again - DNA is extracted and centrifuged- half settles in the middle as contains one original heavy strand and one light strand half settles at the top as two light strands
57
What is ATP
Adenine triphosphate
58
Describe the structure of ATP
Ribose bound to a molecule of adenine and 3 phosphate groups
58
Describe how ATP is broke down
ATP+ water= ADP + Pi Hydrolysis reaction so uses a water molecule Catalysed by ATP hydrolase
59
Give 2 ways in which the hydrolysis of ATP is used in cells
Coupled to energy requiring reactions within cells like active transport and protein synthesis Inorganic phosphate released can be used to phosphorylate other compounds making them more reactive
60
Describe how ATP is resynthesised in cells
ADP+Pi=ATP+ water Condensation reaction removing a water molecule Catalysed by ATP Synthase During respiration and photosynthesis
61
Suggest how the properties of ATP make it suitable immediate source of energy for cells
Releasing energy in small amounts with little lost as heat Single reaction and only one bond hydrolysed to release energy Cannot pass out of cell
62
Explain how the hydrogen bonds occur between water molecules
Water is polar Slightly negative charged oxygen atoms slightly positive hydrogen atoms of other water molecules
63
5 properties of water
Metabolite- Used in condensation/ hydrolysis/ photosynthesis/ respiration Solvent- Allows metabolic reactions to occur, allows transport of substances High specific heat capacity- Buffers change in temperature so good habitat for aquatic animals since more stable than land and helps organisms maintain a constant internal body temperature Large latent heat of vaporisation- Allows effective cooling via evaporation of a small volume so helps maintain an internal constant body temperature Strong cohesion between water molecules -Supports columns of water in tube like columns and produces surface tensions where water meets air supporting small organisms
64
Where are inorganic ions found in the body
In solution in cytoplasm and body fluid, some in high concentrations and some in very low
65
Role of hydrogen ions
Maintain Ph levels in body Affects enzyme rate of reaction as can cause denaturing
66
Role of iron ions
Component of haem group of haemoglobin Allows oxygen to bind for transport as oxyhaemoglobin
67
Role of sodium ions
Involved in co-transport of glucose into cells Involved in action potentials affects water potential of cells and osmosis
68
Role of phosphate ions
Component of nucleotides allowing phoshodiester bonds to form in DNA and RNA Component of ATP Phosphorylates other compounds making them more reactive Hydrophilic part of phospholipids allowing a bilayer to form

Biology (8 decks)

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