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A Level Biology Y1 > Biological Molecules > Flashcards

Biological Molecules Flashcards

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1
Q

What is a condensation reaction?

A

Joins two or more molecules together with the formation of a chemical bond and involves the elimination of a molecule of water.

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2
Q

what is a Hydrolysis Reaction

A

A chemical reaction that breaks apart a larger molecule with the use of a molecule of water

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3
Q

What is glucose?

A

A monomer of carbohydrate, simple sugar.
Has two isomers: Alpha and Beta Glucose

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4
Q

Disaccharide Reactions (3)

A

Glucose + Glucose = Maltose + Water
Glucose + Fructose = Sucrose + Water
Glucose + Galactose = Lactose + Water

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5
Q

What is Starch

A

Storage carbohydrate in plants
Long branched chains of α-glucose held together by glycosidic bonds

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6
Q

Properties of Starch (3)

A
  • large insoluble molecule (osmotically inactive)
  • Helical shape- More compact
  • Branched - Glucose easily released for respiration
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7
Q

Properties of Glycogen (2)

A

It is insoluble = osmotically inactive
Heavily branched = hydrolysed more rapidly to release glucose quicker

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7
Q

What is glycogen?

A

Storage carbohydrate in animals formed by condensation of α-glucose
Stored heavily in liver and muscle tissues

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8
Q

What is cellulose?

A

Polysaccharide that reinforces plant-cell wall and is a polymer of β-glucose

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8
Q

Benedict’s Test (Reducing Sugars)

A
  • Small amount of sample put in a test tube with same volume of Benedict’s
  • Heat solution in a 95C water bath
    -Blue= Negative, Brick red = Positive
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9
Q

Properties of Cellulose (3)

A

-Insoluble = osmotically inactive
-Long straight chain
-Hydrogen bonds between adjacent chains (large number of H-bonds are strong)

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10
Q

Test for Non-reducing sugars

A
  • Heat with Benedict’s and confirm negative result
  • Hydrolyse substance with a dilute acid and neutralise with an alkali.
  • Heat with Benedict’s Brick red precipitate indicates non- reducing sugar was originally present
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10
Q

how to make the Benedict’s test quantitative

A
  • Perform the Benedict’s Test with known sugar concentrations
  • Use colorimeter to measure the absorbance value of each known concentration
  • Plot graph of known concentrations against absorbance value and draw a line of best fit

-Repeat test with unknowns and use absorbance value to extrapolate the concentration.

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10
Q

how are lipids hydrolysed

A

They are hydrolysed by heating with an acid/alkali or using lipase and optimum temp. + pH

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11
Q

Lipids Test

A
  • Add small amount of sample to Ethanol
  • Shake the mixture so the fat dissolves
  • Add the mixture to water and mix
  • Positive = Cloudy white emulsion
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11
Q

What do lipids contain?

A

Contain carbon, hydrogen, and oxygen and are insoluble in water

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11
Q

how to make the Benedict’s Test Semi-quantitative

A

Determine how much sugar depending on their colour

Green—>Red = Least—>Most Sugar

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11
Q

what do amino acids consist of and how do they bind

A
  • all have an amine (-HNH-) and carboxylic acid (-COOH-) group but have different R groups

-Joined by peptide bonds (-CONH-) to create a polypeptide

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12
Q

what do phospholipids consist of and what bonds do they form?

A
  • 2 fatty acids and a phosphate group are attached to glycerol
  • Forms ester bonds

-Hydrophobic tails , Hydrophilic head

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12
Q

what do phospholipids form in water

A

Bi-layers or micelles

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12
Q

what do triglycerides consist of and what bonds do they form?

A
  • 3 fatty acids attached to glycerol
  • Forms ester bonds
12
Q

Triglyceride Properties (3)

A
  • Osmotically inactive
  • High proportion of carbon-hydrogen bonds = release 2x energy than carbohydrates in respiration
  • High ratio of Hydrogen to Oxygen so it releases water when respired
12
Q

what are the monomers of proteins

A

-amino acids

12
Q

Secondary Structure of protein

A

Chain folds due to hydrogen bonds between amino acids into structures like α-helix and β-pleated sheet

12
Q

Primary Structure of protein

A

Sequence of amino acids in a polypeptide chain which determines the shape of the protein

13
Q

Tertiary Structure of protein

A

-Further folding due to Hydrogen, Ionic and Disulphide bonds between R groups

  • Tertiary Structures determines the shape of the active site and its function
14
Q

Quaternary Structure of protein

A

> 1 polypeptide chain

-Multiple chains held together by Hydrogen Ionic and Disulphide bonds

15
Q

How are proteins hydrolysed

A

Proteins can hydrolysed either by heating with acid or by using enzymes ( proteases)

16
Q

How are proteins denatured and what bonds are broken by what?

A
  • Caused by Hydrogen (Heat) and Ionic (pH) bonds breaking

-Disulphide bonds are stronger than both Ionic and Hydrogen bonds

17
Q

Protein Test

A
  • Add Biuret Reagent
  • Positive = Purple/Lilac
  • Negative = Blue
18
Q

bonding in water?

A

Weak hydrogen bonds form between water molecules due to the slightly positive hydrogen ions and slightly negative oxygen ions

19
Q

Water in Metabolic Reactions

A
  • Required for photosynthesis
  • Metabolic product of respiration which is important for organisms in dry habitats
  • Hydrolysis and Condensation Reactions
20
Q

Water as a solvent

A
  • to transport nutrients e.g blood in glucose, sucrose in phloem
  • to remove excretory products e.g urea in ammonia
  • as a medium in which metabolic reactions occur
21
Q

Water for Temperature Regulation

A
  • High heat capacity = absorbs large amount of heat energy (hydrogen bonds) before changing temperature preventing dangerous fluctuations on temperature in aquatic habitats

-Large latent heat of vaporisation = energy is required to break the hydrogen bonds and so a cooling effect is provided with little loss of water

22
Q

Water for internal support

A
  • Cohesive forces between water molecules support water columns in tube like transport cells (e.g. xylem) which allows transport
  • Water is not easily compressed and therefore provides support in non woody plants via turgor pressure and sometimes in animals ( hydrostatic skeleton in earthworms)
23
Q

Water for external support

A
  • Strong cohesive forces between the water molecules provide surface tension where the water meets the air and allows organisms such as pond skaters and mosquito larvae to be suspended at the surface
  • Provides buoyancy for aquatic creatures (e.g. whales)
24
Q

What are the 4 Inorganic Ions

A

Sodium - Co-transport of glucose and amino acids across cell membranes

Iron - Component of haemoglobin which transports oxygen

Hydrogen - Important in determining pH and thus affecting protein structure and enzyme activity

Phosphate - Important as a structural component of DNA, RNA and ATP

25
Q

What are enzymes

A

Biological catalysts that speed up the rate of reaction without being used up by lowering the activation energy

26
Q

Describe the Induced Fit model

A
  • Substrate enters the active site of the enzyme
  • Active site slightly changes shape to fit the substrate perfectly
  • An enzyme-substrate complex is formed
  • Products leave and active site returns to original shape
27
Q

Describe the Induced Fit model in Hydrolysis Reactions

A
  • Enzyme puts a strain on the substrate molecule
  • Strain distorts the particular bond
  • Lowers the activation energy needed to break the bond
28
Q

Describe the Induced Fit model in Condensation Reactions

A
  • Pulls molecules closer together
  • Makes sure they are the right orientation making them more likely to react
29
Q

Describe the effect of substate concentration

A
  • Rate of reaction initially increases as more particles means more collisions
  • Rate of reaction then levels out as all the enzyme actives sites are saturated (occupied)
  • Enzyme concentration is now the limiting factor
30
Q

Describe the effect of Temperature on enzyme activity

A
  • As temperature increases the rate of reaction also increases due to the molecules moving at a higher speed and therefore more collisions
  • This continues until the optimum temperature where the rate of reaction is at its fastest
  • After the optimum temperature the enzymes start to denature and less enzyme-substrate complexes form decreasing the rate of reaction
31
Q

Describe the effect of enzyme concentration

A

When the concentration of substrate is in excess:

  • More enzyme molecules means there are more active site available
  • Increased number of collisions means more enzyme-substrate complexes formed
32
Q

Describe the effect of pH on enzyme activity

A

All enzymes work best at optimal pH. above and below the optimal pH the rate of reaction decreases. Extreme pH changes can denature the enzyme.

33
Q

What are Enzyme Inhibitors

A

A number of chemicals can act as enzyme inhibitors, slowing down the rate of enzyme catalysed reactions

34
Q

Describe how Competitive Inhibition works

A
  • the inhibitor has a similar structure to the normal substrate molecule and competes with it for attachment to the active site
  • the rate of reaction is reduced as substrate cannot bind to active site when inhibitor molecule is occupying it
  • competitive inhibition can be reduced by increasing the concentration of the substrate
35
Q

Describe the Hydrolysis of ATP

A
  • the hydrolysis of ATP is catalysed by ATP Hydrolase and produces ADP and an Inorganic Phosphate
  • Also releases energy which is used for things like protein-synthesis, active transport, cell division etc.
36
Q

What is ATP and what is it made of

A
  • the immediate energy source for biological processes used by cells
  • made from a molecule of ribose, a molecule of adenine and three phosphate groups
36
Q

Describe how Non competitive inhibition works

A
  • non competitive inhibitor is not similar in structure to substrate
  • it combines away from the active site to form an enzyme-inhibitor complex altering the tertiary structure and shape of the active site of an enzyme
  • substrate cannot attach as it is no longer complimentary to active site
  • a high concentration of substrate will not reduce non-competitive inhibition
37
Q

What can the Inorganic Phosphate formed from the hydrolysis of ATP be used for?

A
  • Pi can be used to phosphorylate other compounds making them more reactive
38
Q

Describe the Condensation of ATP

A
  • the condensation of ADP and Pi is catalysed by the enzyme ATP Synthase and produces ATP which requires energy from respiration/photosynthesis
  • ATP is continuously recycled into ADP and Pi and vice-versa

A Level Biology Y1 (8 decks)

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