Unit 1: Human Cells - Key Area 6 - Metabolic Pathways Flashcards

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1
Q

What are examples of degradation reactions in the human body?

A

HPCOW: hydrogen peroxide + catalyse = oxygen + water
SAM: starch + amylase = Maltose

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2
Q

What are examples of synthesis reactions in the human body?

A

GPS - glucose + phosphorylase = starch

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3
Q

What is cell metabolism?

A

The collective term for all the biochemical reactions that occur in a living cell.

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4
Q

What are metabolic pathways?

A

Metabolic pathways are integrated and controlled pathways of enzyme-catalysed reactions within a cell. They can have REVERSIBLE steps, IRREVERSIBLE steps and ALTERNATIVE ROUTES.

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5
Q

What do metabolic pathways involve?

A

metabolic pathways involve BIOSYNTHETIC PROCESSES (anabolism) and the break down of molecules (catabolism) to provide energy and building blocks.

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6
Q

What are the two types of metabolic pathways?

A

Anabolic and catabolic.

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7
Q

What do anabolic reactions do?

A

Anabolic reactions BUILD UP molecules from small molecules and REQUIRE ENERGY.

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8
Q

What do catabolic reaction do?

A

Catabolic reactions BREAK DOWN large molecules into smaller molecules and RELEASE ENERGY.

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9
Q

In a metabolic pathway, what controls each step?

A

Enzymes.

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10
Q

What are enzymes?

A

Biological catalysts.

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11
Q

What is a catalyst?

A

A catalyst is a substance that speeds up the rate of a reaction by lowering the energy needed to make the reaction proceed but is not used up in the reaction and can be used again after the reaction.

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12
Q

What do enzymes speed up?

A

Biochemical reactions (chemical reactions inside living things).

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13
Q

What is every biochemical reaction catalysed by?

A

A catalyst.

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14
Q

What are enzymes that work inside the cells?

A

Intracellular enzymes.

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15
Q

What are enzymes that work outside the cell?

A

Extracellular enzymes (pepsin in the stomach).

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16
Q

During a chemical reaction what is energy needed for?

A

Energy is needed to break chemical bonds during a chemical reaction.

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17
Q

What is the energy needed to break the chemical bonds in a chemical reaction called?

A

The activation energy.

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18
Q

What do enzymes do to the activation energy needed for a reaction to proceed?

A

Enzymes lower/decrease the activation energy needed for a reaction to take place.

19
Q

What is induced fit?

A

Induced fit is when the active site can change shape slightly when it comes in contact with a substrate molecule for a better fit.

20
Q

What does affinity mean?

A

An attraction for something.

21
Q

If a substrate has a high affinity for the active site, what does the active site do?

A

The active site works by holding the reactants together together in an induced fit. This acts to weaken the chemical bonds in the reactants. This allows the reaction to take place.

22
Q

Once the reaction has taken place what do the products have and what does this cause to happen?

A

The products have a low affinity for the active site and are therefore released.

23
Q

What can enzyme activity be affected by?

A

Temperature, pH, Substrate concentration, Concentration of product, Inhibitors.

24
Q

As the concentration of a substrate increases, what also increases?

A

The reaction rate.

25
Q

When all of the enzyme’s active sites have become occupied with substrates (as substrate concentration is increased), what is now the limiting factor?

A

Enzyme concentration.

26
Q

When all of the enzymes are occupied by substrates what is this called?

A

The point of saturation.

27
Q

What are most metabolic pathways?

A

Reversible

28
Q

What can an enzyme often catalyse a reaction in?

A

Both a forward and a reverse direction.

29
Q

What does the direction an enzyme catalyses a reaction depend on?

A

The concentration of the reactants and the products.

30
Q

When does E.coli only produce β-glactosidase?

A

When lactose (it’s substrate) is present in the cell.

31
Q

What is enzyme induction?

A

The process by which a gene is switched on only when the enzyme is needed.

32
Q

When the enzyme β-glactosidase is not needed due there being no lactose, what happens to the production of the enzyme?

A

The repressor protein is produced by the regulator gene, which then binds to the operator gene. This then blocks the operator gene from telling the structural gene to produce the β-glactosidase (the structural gene is off) and no β-glactosidase will be produced.

33
Q

When the enzyme β-glactosidase is needed due to lactose being present, what happens to the production of the enzyme?

A

The regulator gene still produces the repressor protein but the lactose binds to the repressor protein, which then prevents the protein from binding to the operator gene. This allows the operator gene to tell the structural gene to produce the enzyme β-glactosidase (the structural gene is on).

34
Q

What is the advantage to the bacterium of this switching mechanism?

A

To prevent enzyme being produced which prevents resources from being wasted.

35
Q

What is an inhibitor?

A

An inhibitor is a substance that decreases the rate of an enzyme-controlled reaction.

36
Q

What are the two types of enzyme inhibitor?

A

Competitive and non-competitive.

37
Q

What does a competitive inhibitor do and what does this cause?

A

Competes with the substrate for the active site. The inhibitor has a similar shape that is similar to the substrate, and so when it binds to the active site of the enzyme it prevents the substrate the substrate from binding lowers the reaction rate.

38
Q

How can competitive inhibition be reversed?

A

By increasing substrate concentration.

39
Q

What does a non-competitive inhibitor do and what does this cause?

A

Non-competitive inhibitors do NOT combine with the active site of the enzyme. Instead they bind to another part of the enzyme (called the allosteric site) and indirectly change the shape of the active site. This means the substrate cannot bind to the active site and the reaction rate decreases.

40
Q

Will increasing substrate concentration have any effect on reaction rate in non-competitive inhibition?

A

No.

41
Q

Will increasing substrate concentration reverse non-competitive inhibition?

A

No.

42
Q

How does feedback inhibition do and how does this work?

A

Feedback inhibition occurs when the end product of a series of reactants binds to to an enzyme that catalyses a reaction early in the pathway, reducing that enzyme’s activity. This slows down the series of reactions, preventing the production of more of the end product until its concentration falls and the inhibition is removed.

43
Q

What property of a competitive inhibitor allows it to compete with the substrate?

A

They have similar shaped substrates which are complementary to the active site, which allows it to bind to the enzymes active sites.