T3 Flashcards

1
Q

Catalyst

A

A substance which increases the rate of a chemical reaction without itself being changed at the end of the reaction

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2
Q

Enzymes

A

Organic (biological) catalysts which are used to catalyse a vast number of chemical reactions within
living organisms at relatively low temperatures that is between 5 and 40°C

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3
Q

Structure of enzyme molecule

A
  1. Enzymes are globular protein
  2. Soluble
  3. Large molecules (usually much larger than the substrates they act on)
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4
Q

Site of enzymes in cells

A
  1. Intracellular

2. Extracellular

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5
Q

Intracellular enzymes

A

Enzymes which are formed and retained in the cell

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6
Q

Extracellular enzymes

A

Enzymes which are produced in the cell and packaged to be secreted from the cell and work externally

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7
Q

Mechanism of enzyme action

A
  1. Lock and key hypothesis

2. Induced fit hypothesis

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8
Q

Lock and key hypothesis

A
  1. The active site of an enzyme has a specific shape into which the substrate fit exactly
  2. Only the substrate molecule whose shape is complementary to the shape of the active site of an enzyme molecule will fit into the active site to form a temporary structure called the enzyme-substrate complex
  3. The substrate is analogous to the ‘key’ that fits exactly into the enzyme ‘lock’.
  4. Once the product are formed, they no longer fit into the active site & escape into the surrounding medium, leaving the enzyme molecule unchanged and the active site free to bind with further substraet molecules
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9
Q

Induced fit hypothesis

A
  1. The active site have more flexible structures
  2. The binding of substrate to the active site induces a conformational change in the shape of the active site, which allows the active site to mould itself into a precise shape around the substrate
  3. This suggest that the active site of an enzyme has a shape complementary to that of the substrate only after the substrate is bound
  4. A suitable analogy would be that of a hand changing the shape of the globe as the glove is put on
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10
Q

Properties of enzymes

A
  1. Most enzymes are globular protein
  2. They are biological catalyst
  3. They are highly specific
  4. They are efficient
  5. Enzymes lower the activation energy of the reaction they catalyse
  6. Rate of enzyme-catalysed reaction is affected by changes in temperature, pH, substrate concentration and enzyme concentration
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11
Q

Factors affecting the rate of enzyme-catalysed reaction

A
  1. Effects of varying temperature
  2. Effects of varying pH
  3. Effects of varying enzyme concentration
  4. Effects of varying substrate concentration
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12
Q

How enzymes break down substrates

A
  1. Enzymes have active sites (tertiary structure), complementary to substrate
  2. Random movement of enzyme and substrate brings them together, binds by active site
  3. Enzyme-substrate complex forms temporarily
  4. R groups of amino acids in active site interacts with substrate and break it apart
  5. Enzyme-product complex forms temporarily
  6. Product molecules leave active site, enzyme remains unchanged
  7. Enzyme ready to bind with other substrate
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13
Q

Enzyme inhibitor

A

A molecule which prevents an enzyme from catalysing its own reaction. It does so by combining with they enzyme to form an enzyme-inhibitor complex, which thus prevents substrates from entering the enzyme’s active site. The overall effect is to reduce the rate of an enzyme-catalysed reaction.

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14
Q

Inhibitors can be divided into two which is

A
  1. Competitive inhibitor

2. Non-competitive inhibitor

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15
Q

Shape of competitive inhibitor

A

Shape that is sufficiently similar to that of the normal substrate.

or

Has a shape that is complementary to that of the active site of an enzyme molecule and thus is able to fit into the active site

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16
Q

Characteristic features of a competitive inhibition

A
  1. Inhibition is always reversible

2. At higher substrate concentration, the rate of reaction increases

17
Q

Shape of non-competitive inhibitor

A

Has a shape that is different to that of the normal substrate

18
Q

Characteristic features of non-competitive inhibition

A
  1. Inhibition is irreversible
  2. An increase in substrate concentration does not affect the rate of reaction. The rate of reaction will never attain its Vmax
19
Q

Enzyme cofactors

A

Cause the enzyme to function more efficiently

20
Q

Cofactors

A

Enzymes that requires non-protein molecules

21
Q

Three types of cofactors

A
  1. Activators
  2. Prosthetic groups
  3. Coenzymes