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Biology > Chapter 1 - Biological Molecules > Flashcards

Chapter 1 - Biological Molecules Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What are the 4 carbon based compounds?

A
  1. carbohydrates
  2. Lipids
  3. Proteins
  4. Nucleic acids
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2
Q

What is the main function of Nucleic acids?

A

DNA - stores genetic information

RNA - transports genetic information during protein synthesis

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3
Q

KEY property of water 1

Metabolite

A
  • water is a metabolite in many metabolic reactions
  1. Condensation reaction - monomers joined by removal of water
  2. Hydrolysis reaction - monomers are released by addition of a water molecule.
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4
Q

What do the terms metabolite and metabolism mean?

A

Metabolite - a substance formed in or necessary for metabolism

Metabolism - chemical processes that occur within a living organism to maintain life.

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5
Q

KEY property of water 2
Water as a solvent

A

Water is a solvent and dissolves the solute
- it is polar so makes excellent solvent of charged particles

  • molecules need to move around in reactions - lots of KE for colliding
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6
Q

KEY property of water 3
Explain the high heat capacity of water

A

Water has a high heat capacity = lots of energy

  • water molecules stick via hydrogen bonds so lots of energy is needed to get them to move when heating … therefore also needs to lose a lot of energy to cool down
    =BUFFERING CHANGES IN TEMPERATURE
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7
Q

KEY property of water 4
Latent heat of vaporisation

A

Water has a high latent heat of vaporisation due to hydrogen bonds

SWEATING: heat energy transferred to water in body allows us to sweat without too much water loss by evaporation = good for cooling down

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8
Q

KEY property of water 5

What is cohesion and give an example.

A

Cohesion - tendency for molecules to stick together (via hydrogen bonding)
- water has large cohesive forces so can be pulled through a tube e.g. xylem vessels

Adhesion - molecules stick to walls of tubes

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9
Q

KEY property of water 6
What does surface tension refer to?
Explain in terms of water meeting air.

A
  • water molecules are more stable when bonded together
  • Where surface water meets air, they can’t bond with air above so they get really close to each other

… therefore allows small organisms to walk on water (pond skaters)

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10
Q

What are monomers and polymers?
List 3 examples for each

A

Monomers - molecules that can be bonded to other IDENTICAL molecules to form a larger polymer
E.g. monosaccharides, amino acids, nucleotides

Polymers - molecules made from a large number of monomers bonded together
E.g. polysaccharides, protein, nucleic acids

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11
Q

How are monomers joined and broken?

A

Joined: via a condensation reaction
- formation of a chemical bond and involves removal of a water molecule

Broken: via a hydrolysis reaction
- breaks a chemical bonds and involves use of a water molecule

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12
Q

What are carbohydrates made of + what is their chemical formula?

A
  • carbohydrates are made from monosaccharides
    E.g. glucose, galactose and fructose are all monosaccharides
  • ALL have chemical formula of C6H12O6
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13
Q

What is an isomer?

List the two types of glucose isomers.

A
  • molecules that have identical chemical formulae but different structural formulae

E.g. glucose has alpha and beta glucose - both being C6H12O6

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14
Q

DISACCHARIDES
How are they formed and what bond is formed? List an example

A
  • formed by the condensation of 2 monosaccharides which results in a glycosidic bond

MALTOSE is a disaccharide formed by condensation of 2 glucose molecules (broken by hydrolysis)
- chemical formulae of C12H22O11 +H2O (remember condensation = removal of water)

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15
Q

What are sucrose and lactose?

A
  1. SUCROSE is a disaccharide formed by the condensation of a glucose molecule and a fructose molecule
  2. LACTOSE is a disaccharide formed by the condensation of a glucose molecule and a galactose molecule.
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16
Q

How are polysaccharides formed and list the 3 main examples.

A
  • formed by the condensation of MANY glucose units (many monosaccharides)
  1. STARCH + GLYCOGEN are formed by the condensation of alpha glucose
  2. CELLULOSE is formed by the condensation of beta glucose
  • all form glycosidic bonds
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17
Q

List the function of starch

A
  • major glucose (energy) store in plant cells = not found in animals
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18
Q

List the function of glycogen

A
  • major glucose (energy) store in animals = not found in plants
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19
Q

Why are there more branches in glycogen than in starch? Is there a difference in length?

A
  • starch is found in plants, glycogen in found in animals
  • need to be more branches in glycogen as animals are more active so there are more branches for enzymes to be able to catalyse reactions on
  • glycogen branches are shorter
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20
Q

Shape and structure of glycogen and starch

A
  1. Helical = more compact
  2. Insoluble in water = osmotically inactive
  3. Branched = glucose easily released for respiration
  4. Large molecule = cannot escape from cell across cell surface membrane
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21
Q

Where is cellulose found and what is its function?

A
  • found in cell walls of plants
  • makes cell wall strong and stops cells from bursting due to osmotic pressure (PRESSURE FROM WATER UPTAKE)
22
Q

What is the shape and structure of cellulose like?

A
  1. Straight - beta glucose monomers are used in which beta glucose molecules are alternately flipped over.
  2. Strong - cellulose fibre made of many micro fibrils = rigidity and strength
  3. Side by side - weak hydrogen bonds but strong when together
23
Q

What are the 4 key roles of lipids?

A
  1. Source of energy: when oxidised they provide twice as much energy as carbohydrates do at the same mass. Also release valuable water
  2. Waterproofing: insoluble in water so plants have waxy cuticles to conserve water
  3. Insulation: slows conductors of heat to retain heat
  4. Protection: stored around important organs
24
Q

LIPID 1 - TRIGLYCERIDE

How are they formed? Refer to what bond it forms and the special type of group.

A
  • formed by condensation of 1 molecule of glycerol and 3 molecules of fatty acid which forms an ESTER bond
  • RCOOH group: COOH = carboxyl group/ carboxylic acid
  • R = variable “r” group which can be saturated or unsaturated - hydrocarbon chain
25
Q

LIPID 1 - TRIGLYCERIDE

Describe the different types of “r” groups in terms of saturation.

A
  1. Saturated - no double bonds between carbon atoms
  2. Mono unsaturated - one double bond between carbon atoms
  3. Poly unsaturated - more than 1 double bond between carbon atoms
  • double bonds cause molecule to bend = cannot pack together = liquid at room temperature = oils
26
Q

LIPID 2 - PHOSPHOLIPID

Describe how they are formed and it structure. Refer to its tail and head.

A
  • formed by the condensation of one glycerol, 2 molecules of fatty acid and a phosphate containing group (phosphorus + oxygen)
  1. Hydrophilic head = attracted to water (due to phosphate group)
  2. Hydrophobic tail = repels water (due to fatty acids)

This creates a structure called a phospholipid bilayer = essentially cell membranes

27
Q

What are proteins made of and what is the general structure?

A
  • made by the condensation reaction of monomers called amino acids
          R.   = variable side chain
      | H2N—C—COOH
      |
      H
28
Q

What is a dipeptide? Is it a polymer?

A
  • a condensation reaction between 2 amino acids forms a peptide bond and a dipeptide

= NOT A POLYMER AS NOT MANY REPEATING UNITS

29
Q

What is a polypeptide and how many polypeptides does a functional protein have?
List 2 examples of functional proteins and how many polypeptides they have.

A
  • a polypeptide is a POLYMER formed by condensation of MANY amino acids
  • a functional protein may contain 1 or more polypeptides

AMYLASE - 1 polypeptide chain
HAEMOGLOBIN - 4 polypeptide chains

30
Q

LEVELS OF PROTEIN STRUCTURE 1

Primary structure

A

This is the sequence of amino acids in a polypeptide chain, specific to each polypeptide chain.

31
Q

LEVELS OF PROTEIN STRUCTURE 2

Secondary structure

A

This is where there is folding of a polypeptide chain due to hydrogen bonding between N-H group of one peptide bond and C=O group of another e.g. alpha helix + beta sheets

32
Q

LEVELS OF PROTEIN STRUCTURE 3

Tertiary structure

A

Specific 3D folding of a protein occurs due to bonding between R groups, specifically:

  1. Hydrogen = weakest
  2. Ionic = medium
  3. Covalent = strongest (disulfide bridge)
  • hydrophobic R groups in middle, away from water
33
Q

LEVELS OF PROTEIN STRUCTURE 4

What is the Quaternary structure

A

2 or more polypeptide chains bonded together to make final protein - not all proteins have this

E.g. haemoglobin has 4 chains

34
Q

Describe the test for reducing sugars

A

Benedict’s test

  • heat sample with Benedict’s reagent (blue)
  • positive result: red or orange precipitate forms
35
Q

Describe the test for non reducing sugars

A

Non reducing sugar = disaccharide

  • do Benedict’s test and it should stay blue (negative)
  • with fresh sample, boil with acid then neutralise with alkali
  • heat with Benedict’s reagent again and should from red/orange precipitate
36
Q

Explanation for non reducing sugars test

A

Step 1: proves sample is not a reducing sugar
Step 2: uses acid to HYDROLYSE disaccharide into its reducing monosaccharides ; acid then neutralised since Benedict’s test needs alkali conditions
Step 3: test for presence of these monosaccharides

37
Q

Describe the test for starch

A
  • ADD iodine in potassium iodide solution (yellow)
  • Positive result should show solution turn blue/ black
38
Q

Describe the test for lipids

A

Emulsion test

  • add ethanol then add water and shake
  • positive result: white milky emulsion

An emulsion is tiny insoluble droplets of one liquid forming in another

39
Q

Describe the test for proteins

A
  • add biuret reagent (blue) and it should become PURPLE/ LILAC if protein is present
40
Q

What are enzymes and what sort of reactions do they catalyse?

A

Enzymes are biological catalysts that speed up chemical reactions in an organism.

  • they catalyse a wide range of intracellular (inside cell) and extra cellular (outside cell) reactions
41
Q

Can an enzyme be reused?

A

YES
It starts and ends in the same state so can be reused.

42
Q

What determines the shape of the active site?

A
  • enzymes are proteins
    Therefore the TERTIARY structure determines shape of active site + its ability to bind to complementary substrates.
43
Q

What is the activation energy and describe how enzymes change this?

A
  • it is the energy needed to start a reaction.

Enzymes LOWER the activation energy of the reaction that it’s catalyses from around 800c to 37c for reactions to occur in the body!

44
Q

Describe the induced fit model of enzyme action. [4]

A
  1. Before the reaction, the active site is not fully complementary to the substrate;
  2. Induced fit causes the shape of the active site to change as the substrate binds so that an enzyme-substrate complex forms;
  3. In turn this bends bonds in the substrate, allowing the reaction to occur with a lower activation energy;
  4. Bonds in the substrate are then broken so that new bonds can form;
45
Q

Factors affecting enzyme activity 1

ENZYME CONCENTRATION

A
  • increased enzyme concentration increased the rate of reaction
  • This is because:
    1. More active sites available, increasing the chance that substrate molecules collide with and enter active sites
    2. More enzyme - substrate complexes therefore form
  • rate of reaction increases until SUBSTRATE CONCENTRATION becomes limiting factor, at which point the graph plateaus.
46
Q

Factors affecting enzyme activity 2

SUBSTRATE CONCENTRATION

A
  • increased substrate concentration increases the rates of reaction

This is because:
1. It increases the chance that substrate molecules collide with and enter active sites
2. More enzyme-substrate complexes form

  • rate of reaction increases until ENZYME CONCENTRATION becomes limiting factor, at which point the graph levels off as all active sites are SATURATED.
47
Q

Factors affecting enzyme activity 3

PH

A
  • Low PH = increase in the concentration of H+ which attach to amino acids (R groups) of the enzyme
  • This disrupts hydrogen and ionic bonds in protein= changed tertiary structure + active site shape
  • enzyme becomes DENATURED so no E-S complexes can form
  • Therefore rate of reaction decreases
48
Q

Factors affecting enzyme activity 4

TEMPERATURE

A
  • At higher temperature = increased KE of both enzyme and substrate
  • this increases chance of collisions between enzyme and substrate = more E-S complexes = increases rate of reaction

Beyond optimal temp:
1. Polypeptide chain undergoes major vibrations which break hydrogen and ionic bonds = tertiary structure unfolds
2. Active site changes shape = denatured enzyme
3. So no more E-S complexes can form and rate of reaction decreases

49
Q

What is enzyme inhibition?

A

Enzyme action stopped/slowed down by another substance

50
Q

What are competitive inhibitors?
What do they do and are they substrates?

A
  • competitive is where the inhibitor has a similar shape to the substrate therefore…
    1. It fits in the active site of the enzyme and prevents formation of E-S complexes
    2. Instead Enzyme-inhibitor complexes form
  • they ARE NOT SUBSTRATES - not involved in reaction, just prevent it.
51
Q

What is meant by competitive inhibitors being reversible?

A

The inhibitors rapidly dissociates from active site then attempts to rebind

52
Q

What is a non competitive inhibitor?
Where do they bind?

A

Has a different shape to substrate

  • instead binds to the ALLOSTERIC SITE which is away from the active site
  • causes tertiary structure of enzyme to change so the active site changes shape and substrates can no longer bind.

-also reversible and due to being non competitive substrate cannot out-compete inhibitor

Biology (22 decks)

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