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Sec 3 Pure Bio > Enzymes > Flashcards

Enzymes Flashcards

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1
Q

Define what a catalyst is

A
  • a substance that alters or speeds up a chemical reaction

- remains chemically unchanged at end of reaction

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2
Q

Define enzymes

A
  • a protein (turn Biuret’s solution from blue to violet during Biuret’s test)
  • functions as a biological catalyst
  • alters or speeds up chemical reactions
  • remains unchanged at the end of reaction
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3
Q

Enzymes lowers activation energy

A

-refers to energy needed to start a chemical reaction

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4
Q

Digestion

A
  • some food molecules are large, insoluble in water
  • these molecules cannot diffuse across the cell membrane
  • have to be converted/digested into smaller, simpler molecules and soluble in water
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5
Q

Examples of digestive enzymes

A
  • Amylase: Digest starch to maltose
  • Maltase: Maltose to glucose
  • Protease: Proteins to amino acids
  • Lipase: digest fats into glycerol and fatty acids
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6
Q

Anabolic reactions

A
  • building up of complex substances

- e.g. building proteins from amino acids, condensation reactions

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7
Q

Catabolic reactions

A
  • break down of complex substances

- e.g. breakdown of glucose during respiration, hydrolysis

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8
Q

Characteristics of enzymes

A
  • speed up chemical reactions
  • required in minute amounts
  • highly specific in action
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9
Q

Speeding up chemical reactions (Characteristic of enzymes)

A

-lowers activation energy needed to start reaction

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10
Q

Enzymes required in minute amounts (Characteristic of enzymes)

A
  • same enzyme molecules can be used over and over again

- can catalyse large no of chemical reactions

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11
Q

Enzymes are highly specific in action (Characteristic of enzymes)

A
  • enzyme specificity: each chemical reaction inside a cell is catalysed only by one unique enzyme
  • e.g. amylase works on starch
  • an enzyme specific due to its 3 dimensional shape
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12
Q

Lock and key hypothesis (Enzyme specificity)

A
  1. enzyme has a specific 3D shape containing an active site, substances that act on is known as substrate
  2. only substrate with 3D shape that is complementary to active site can fit into enzyme to form and enzyme-substrate complex
  3. chemical reaction occurs, substrate converted into products
  4. products detach from active site, enzyme remains unchanged at end of reaction
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13
Q

Define Denaturation

A
  • since specificity of an enzyme due to 3D shape, any factor that causes enzyme to change shape will affect its function
  • change in 3D shape of any enzyme or any protein is known as denaturation
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14
Q

Causes of denaturation

A
  • Heat (extremely high temps)

- Chemicals e.g. acids, alkalis (pH level)

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15
Q

What happens during denaturation?

A
  • loss or change in active site
  • substrate can no longer fit enzyme’s active site (shape of active site no longer complementary to shape of substrate)
  • no reaction take place, no longer act as a catalyst
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16
Q

How temperature affects enzymes (low temp)

A
  • enzymes inactive at low temps
  • kinetic energy low at low temps
  • chances of substrate molecules successfully colliding with enzymes very low
17
Q

How temperature affects enzymes (high temp)

A
  • temp rises, enzyme activity increases
  • increase in kinetic energy
  • increase chances of successful collision between substrate and enzyme
  • increases rate of formation of enzyme-substrate complex
18
Q

How temperature affects enzymes (optimum temp)

A
  • for every 10°c increase in temp, rate of enzyme reaction doubled until opt temp is reached
  • optimum temp is the point when rate of reaction highest, enzyme most active (highest rate of product formation/no .of enzyme-substrate complexes formed)
  • most enzymes opt temp is 40-45
19
Q

How temperature affects enzymes (beyond optimum temp)

A
  • enzyme activity decreases
  • enzymes are proteins, high temp break bonds within the enzyme, changes 3D shape
  • substrate no longer fit into active site
  • enzyme now denatured
20
Q

How pH affects enzymes

A
  • diff enzymes, diff optimum pH values (most active)
  • some work best in slightly acidic/alkaline
  • extreme changes in pH result in denaturation, lose function
21
Q

Examples of optimum pH values

A
  • amylase in saliva: pH 7
  • pepsin in stomach: pH 2
  • trypsin in small intestine: pH 8
22
Q

How enzyme-substrate concentration affects enzymes

A
  • enzyme/substrate concentration is fixed
  • at saturation pt, enzyme/substrate conc is limiting factor
  • all enzymes occupied by a substrate(or the other way round), increasing conc does not affect reaction rate
23
Q

Enzyme catalyse reversible reactions

A
  • some reactions in living cells are reversible
  • can proceed in forward or backward direction
  • e.g. respiration

Sec 3 Pure Bio (16 decks)

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