chapter 2:enzymes
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Higher Human. Unit 1: Cell Function and Inheritance. Chapter 2:Enzymes. Learning Intentions. To revise purpose of enzymes To revise how enzymes work To examine factor affecting rate of enzyme-catalysed reactions. A catalyst is a substance that: - PowerPoint PPT PresentationTRANSCRIPT
Chapter 2:Enzymes
Higher Human
Unit 1: Cell Function and Inheritance
04/20/23 1Mrs Smith
Learning Intentions
• To revise purpose of enzymes• To revise how enzymes work• To examine factor affecting rate of enzyme-
catalysed reactions
04/20/23 2Mrs Smith
• A catalyst is a substance that:– Speeds up the rate of a chemical reaction but remains
unchanged at the end of the reaction.
• Enzymes are biological catalysts (made of protein) that are present in all living cells.
• They speed up the rate of biochemical reactions at relatively low temperatures.
• Without enzymes important biological processes like respiration and photosynthesis would proceed too slowly to maintain life.
04/20/23 3Mrs Smith
Biological Catalyst
Structure
• Globular proteins• One or more polypeptide
chains • Function determined by
structure• Reaction occurs at active
site• Specific for one reaction
due to shape of active site – “lock and key” hypothesis amylase
04/20/23 4Mrs Smith
Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.
Function• Biological catalysts - increase reaction
rates• Approx 40,000 different types in human
cells• Intracellular (inside cell) e.g. catalase• Extra-cellular (outside cell) e.g. pepsin• Needed for respiration, photosynthesis,
digestion, motors, membrane pumps, receptors
04/20/23 5Mrs Smith
Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.
Since we have about 200 trillion cells and each one performs millions of chemical reactions, the total number of chemical reactions in the human body is about 400 billion per second every second of your life.
That's 4 times the amount of stars in our galaxy which is a mere 100 billion
How many chemical reactions happen in our body?
04/20/23 6Mrs Smith
Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.
Reaction Mechanism
04/20/23 7Mrs Smith
Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.
• Enzymes are SPECIFIC = This means that each enzyme can only react with one set of substrate molecules.
• For example amylase cannot act on glucose and potato phosphorylase cannot act on starch.
Specific Enzymes
Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.
04/20/23 8Mrs Smith
• The shape of a molecule of enzyme exactly matches the shape of a molecule of its substrate like a key which fits exactly into a lock. This allows the two molecules to combine briefly at a point called the active site, which brings about the reaction.
• We call this the “LOCK & KEY” theory.
Lock and Key Theory
Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.
04/20/23 9Mrs Smith
Model enzymes
Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.
04/20/23 10Mrs Smith
Model Enzymes – Synthesis reaction.
Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.
04/20/23 11Mrs Smith
Specific Enzymes –Degradation Reaction
Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.
04/20/23 12Mrs Smith
Factors Affecting Enzyme Activity
Enzymes are sensitive to the following:• pH• Temperature• Enzyme concentration• Substrate concentration
04/20/23 13Mrs Smith
Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.
pH
04/20/23 14Mrs Smith
Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.
Optimum pH• Enzymes have an optimum pH at which
they catalyse reactions best.• Most enzymes function at a pH of 5-9 with
an optimum pH of 7 (neutral).• There are exceptions to this rule:
– Pepsin secreted by stomach’s gastric glands optimum pH is 2.5 (very acidic)
– Catalase found in living cells optimum pH is 9 (very alkaline)
Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.
04/20/23 15Mrs Smith
DenaturingEnzymes are denatured (destroyed and
inactive) at extremes of PH:
Too many H+ ions or OH+ ions will alter the shape of the enzymes active site so it can no longer fit with its substrate and catalyse a reaction.
Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.
04/20/23 16Mrs Smith
Optimum pHIn
crea
sin
g r
ate
of
reac
tio
n
pH
Pepsin
1 2 3 4 5 6 7 8 9 10 11 12
Optimum pH
Amylase
Catalase
Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.
04/20/23 17Mrs Smith
Temperature
04/20/23 18Mrs Smith
Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.
Optimum temperature• At low temperatures enzyme activity will be very
slow.• At warmer temperatures the enzyme activity will
increase• The temperature at which the enzyme works
best at is called its “optimum temperature”.• The optimum temperature for most animal
enzymes is 37°C. Some plant enzymes have an optimum temperature around 20°C.
Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.
04/20/23 19Mrs Smith
Denaturing• Enzymes are denatured (destroyed and
inactive) at high temperatures (usually above 420C:
• Increasing the temperature beyond an enzymes optimum will destroy the shape of its active site so it can no longer fit with its substrate and catalyse a reaction.
Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.
04/20/23 20Mrs Smith
Enzyme Concentration
04/20/23 21Mrs Smith
Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.
Enzyme Concentration
04/20/23 22Mrs Smith
• Increasing concentrations increases activity.
• Enzyme activity can be decreased in the presence of INHIBITORS (molecules which will join preferentially to the enzyme).
Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.
Inhibition
• Substrate can’t fit into active site of enzyme
• Reaction rate lowered
• 2 types: – Competitive– Non-competitive
04/20/23 23Mrs Smith
Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.
Competitive Inhibition
04/20/23 24Mrs Smith
• Competitive inhibitors block the active site of the enzyme molecule. This type of inhibition is reversible.
Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.
Non-competitive Inhibition
04/20/23 25Mrs Smith
• Non-competitive inhibitors attach to some other part of the enzyme and in doing so alter the shape of the active site indirectly.
• This is irreversible inhibition.
Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.
Outcome 3
• Assessed practical • “Effect of enzyme concentration on
enzyme action”• Submit write-up by:- Mon 28th June
04/20/23 26Mrs Smith
Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.
Substrate Concentration
04/20/23 27Mrs Smith
Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.
Activation of Enzymes
• Many enzymes require the presence of other substrates to make them work.
• These ACTIVATORS can be mineral ions, vitamins or other enzymes. – Cofactors (coenzymes) required – metal ions – iron (Fe2+), magnesium (Mg2+), copper
(Cu2+)– organic molecules e.g. haem, NAD, coenzyme A
04/20/23 28Mrs Smith
Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.
Inborn errors of metabolism• Metabolism – all the
chemical reactions that occur in an organism
• Error in gene coding for enzyme results in blockage in pathway
• May result in health problems
04/20/23 29Mrs Smith
Aim: To revise the purpose of enzymes, how they work, and examine the factors which affect enzyme catalysed reactions.
Phenylketonuria
• Occurs when enzyme required to breakdown the amino acid phenylalanine present in the diet into tyrosine.
• The excess phenylalanine is broken down into toxic substances which can lead to brain damage and poor mental development in children.
04/20/23 Mrs Smith 30