Cell Metabolism + Enzymes (Chapter 3)

Question 1

What are enzymes

Answer 1

Biological catalysts that speed up a reaction but are not consumed in the process. All enzymes are proteins. Enzymes work by lowering the activation energy needed. They provide an alternate pathway

Question 2

Define substrate

Answer 2

the molecule being acted on by an enzyme

Question 3

Induced fit

Answer 3

Same idea but states the active site is not an exact fit, it has wiggle room for the substrate.

Question 4

Define Active site

Answer 4

the location on an enzyme where the substrate fits

Question 5

Why do we need enzymes

Answer 5

Because without them, the chemical reactions in our body wouldnt happen fast enough to sustain us

Question 6

How does temperature affect enzymes

Answer 6

Alll enzymes have a temperature at which they work best at. (known as the optimum temperature) If an enzyme is too cold, it won’t operate until warmed up. However if it is too hot the enzymes become denatured, meaning the chemical structure and so the enzyme is damaged irreversibly.

Question 7

How does pH levels affect enzymes

Answer 7

In the same ways as temperature, however the range is much more narrow.

Question 8

What is substrate concentration

Answer 8

When all enzymes are occupied by substrates and so the extra substrates have no effect.

Question 9

What is enzyme concentration

Answer 9

If we had unlimited enzymes and substrates, then we have an unlimited rate of reaction

Question 10

What are co-factors?

Answer 10

An ion or not protein molecule that catalyses a reaction. It does this by changing the shape of the active site so the substrate fits better. They are inorganic.

Question 11

What are co-enzymes

Answer 11

same as co-factors, but is organic and are needed by different enzymes

Question 12

What is an inhibitor

Answer 12

A substance that slows down or completely stops the enzyme from functioning. Examples are drugs and medicines

Question 13

Metabolism definition + 2 types

Answer 13

• Metabolism is the total of all the chemical reactions that take place in the body.
  Metabolic process can either be regarded as either anabolic or catabolic.
• Anabolic: Small molecules built up into larger ones (requires energy) E.g. protein synthesis
• Catabolic: reactions in which large molecules are broken down to smaller ones (releases energy) E.g. Cellular respiration

Question 14

Organic vs Inorganic nutrients

Answer 14

Organic molecules can include:
-carbohydrates
-proteins (and amino acids)
-lipids
-nucleic acids

Inorganics include:
-water
-vitamins
-minerals
-oxygen
-carbon dioxide

Question 15

Carbohydrates

Answer 15

• Simple Sugars are broken down from complex Carbohydrates in food
• They are the main energy source for cells through the process of cellular respiration
• The ‘building blocks’ of carbohydrates are monosaccharides. They are simplest form of sugar.Eg. Glucose, Fructose

Contain CHO

Question 16

Protein functions

Answer 16

• Make up the structural material of the cell
• Make enzymes that control cellular reactions
• Can be used as an energy source if the supply of carbohydrates or lipids is inadequate.

Question 17

Proteins structure

Answer 17

The building blocks of proteins are amino acids
Amino acids are joined by peptide bonds
A dipeptide is 2 amino acids joined by a peptide bond.
A polypeptide is 10 or more amino acids
Proteins consist of 100 or more amino acids – making them polypeptides.

Always CHON and often S and P

Question 18

Lipid structure and function

Answer 18

Lipids are an important energy source and can be used the same way as carbohydrates.
The glycerol that is broken down can enter the glycolysis pathway to release energy in the same way as glucose.

Each lipid (fat) molecule is made up of one molecule of glycerol and 1-3 molecules of fatty acids

Contain CHO

Question 19

Nucleic acids

Answer 19

They are made up of NUCLEOTIDES, each of which contains a nitrogen base, a sugar and a phosphate.
They provide no energy for the cell, however they are essential in forming DNA and RNA that stores genetic information

Contain CHONP

Question 20

Cell respiration

Answer 20

Cell respiration is the breakdown of carbohydrates and other nutrients (usually glucose) to form CO2 and H2O to release energy for cell activities.
It is expressed in the form of an equation:

C6H12O6 + 6O2 = 6CO2 + 6H2O + ENERGY

Question 21

Anaerobic respiration

Answer 21

-Happens in the cytoplasm
-Glucose broken into two molecules of pyruvate (pyruvic acid) through glycolysis
-Glycolysis produces net two molecules of ATP
-Glycolysis itself does not need oxygen, but if oxygen is available then pyruvate is transported into the mitochondria.

If no oxygen becomes available the pyruvate is converted into lactic acid (less toxic)
-Lactic acid is transported into the liver to eventually combine with oxygen to form glycogen

Question 22

Aerobic respiration

Answer 22

-Happens inside the mitochondria (think: why is mitochondria the powerhouse of the cell?)
-Enzymes needed for these reactions are located on the folded inner membrane surface (think: why is it folded?)
-Two processes; Kreb’s cycle or the citric acid (TCA) cycle followed by electron transport chain (ETC)

Kreb’s cycle:
Happens twice per molecule of glucose or once per molecule of pyruvate
Produces the equivalent of 2 ATP molecules

Electron Transport Chain:
-Generates 34 molecules of ATP by bouncing electrons from enzyme to enzyme
-Creates the water that is expelled later

In total aerobic respiration produces 38 ATP molecules

Question 23

Why is a large amount of fuel needed to make more ATP?

Answer 23

Roughly 60% of energy produced is lost as heat and only 40% is converted into ATP therefore you constantly need fuel to make more ATP