Biochemical Processes In Cells

Question 1

Why is oxygen considered to be a waste product during photosynthesis?

Answer 1

Oxygen is termed as a waste product because during the first stage chlorophyll splits water molecules to form high-energy electrons (e-) and protons (H+), with oxygen remaining left over therefore being a waste product.

Question 2

Sugars are formed simply by joining molecules of carbon dioxide together in plants. True or false? Explain your answer.

Answer 2

False, sugar formation involves a cyclic set of reactions in which intermediate substances are formed.

Question 3

In which stage of photosynthesis is oxygen formed?

Answer 3

The first stage, the light dependent stage.

Question 4

How many stages of photosynthesis are there? And what are they known as?

Answer 4

There are two stages, first is the light dependent stage and the second stage is the light independent stage.

Question 5

What are producers?

Answer 5

Producers are organisms with the ability to use energy of sunlight to create organic molecules such as sugars from photosynthesis.

Question 6

What are consumers?

Answer 6

Consumers are organisms that depend directly, or indirectly on the organic compounds produced by producers.

Question 7

What is photosynthesis?

Answer 7

Photosynthesis is the process in which light energy is transformed into chemical energy.

Question 8

How can a higher substrate concentration effect enzyme activity?

Answer 8

The addition of more substrate to an enzyme solution initially increases the rate of the reaction if not all active sites of the enzyme present are occupied. However, the enzyme solution contains a set amount of enzyme, and if no more is added the rate of the reaction tapers off as all the active sites of the enzyme molecules become occupied.

Question 9

How does enzyme concentration affect an enzymes activity?

Answer 9

Only a very small amount of enzyme molecules is usually in a reaction and these produce a given amount of product per unit time. If the amount is decreased the enzyme is increased, the amount of product made per unit time increases also.

Question 10

How does temperature affect enzyme activity?

Answer 10

At high temperatures, enzymes become permanently denatured, their structure changes and they remain inactive even when the temperature returns to its optimal temperature. Although ones at low temperatures become active again once put back to normal temperatures.

Question 11

How does pH affect enzyme activity?

Answer 11

Each enzyme acts best at a particular pH, which is known as optimal pH. E.g. Pepsin (is secreted in the human stomach) has an optimal pH of 2. A change in pH from the optimum can change the shape of the enzyme and affect its ability to combine with its substrate.

Question 12

What factors affect enzyme activity?

Answer 12

pH, temperature, enzyme concentration and substrate concentration.

Question 13

The chemical energy in glucose is transferred with 100% efficiency to ATP, true or false?

Answer 13

False, some of the chemical energy is converted to and “lost” as heat energy.

Question 14

What is cellular respiration?

Answer 14

Cellular respiration is the series of energy releasing reactions that break down the organic compounds in food, releasing chemical energy and transferring it to ATP.

Question 15

What are the two types of cellular respiration?

Answer 15

Aerobic respiration and anaerobic respiration

Question 16

What is aerobic respiration?

Answer 16

Aerobic respiration is respiration involving oxidation reactions of glucose.

Question 17

What is anaerobic respiration?

Answer 17

Anaerobic respiration is respiration that occurs in the absence of oxygen.

Question 18

How many stages of cellular respiration are there? And what are they?

Answer 18

There is three stages.

Glycolysis, Krebs cycle and electron transport stage.

Question 19

What happens in the first stage of cellular respiration: glycolysis?

Answer 19

During glycolysis, one molecule of glycose is broken down into two molecules of a 3-C compound known as pyruvate. A net release of energy occurs and some of this energy is used directly to produce two molecules of ATP. During glycolysis, hydrogen atoms are also removed from glucose. These hydrogen atoms, and their electrons are collected by acceptor molecules being NAD. When acceptor molecules are carrying hydrogens, they are termed “loaded” acceptors, such as NADH. Certain reactions involving loaded acceptor molecules release energy that can be coupled to the production of ATP.

Question 20

Where does the first stage of cellular respiration: glycolysis occur?

Answer 20

Glycolysis occurs in the cytosol of cells.

Question 21

Where does the second stage of cellular respiration: Krebs cycle occur?

Answer 21

The reactions of the Krebs cycle occur in cells organelles, known as mitochondria.

Question 22

What happens in the second stage of cellular respiration: Krebs cycle?

Answer 22

Pyruvate molecules leave the cytosol and enter the mitochondria. For each molecule of pyruvate that passes through the Krebs cycle, three molecules of carbon dioxide are formed. One of the intermediate products formed is known as acetyl coenzyme A. As the cycle proceeds, hydrogen atoms are gathered by acceptor molecules, with a total of five “loaded” acceptor molecules being formed (four NADH and one FADH2) for each pyruvate molecule.

Question 23

Where does the final stage of cellular respiration electron transport take place?

Answer 23

Electron transport takes place on the inner membranes of mitochondria. Compounds known as cytochromes, are involved in the process.

Question 24

What happens in the final stage of cellular respiration electron transport?

Answer 24

During electron transport, electrons from “loaded” acceptors (NADH and FADH2) are brought to inner membranes of the mitochondria. The electrons are successfully transferred from one cytochrome to another and are finally accepted by oxygen. When oxygen combines with a pair of electrons, it becomes negatively charged (O2-) and then reacts with hydrogen ions (H+) to form water.
Electron transport releases energy. In general, for each pair of electrons transferred down the electron transport chain, enough energy is released to drive the production of two or three molecules of ATP

Question 25

What is the outcome of the three stages of cellular respiration?

Answer 25

The aerobic respiration of one molecule of glucose to carbon dioxide releases energy that is coupled to the production of 36 molecules of ATP. In cells of your heart, liver and kidneys, two additional molecules of ATP are generated to give you a total of 38 ATP.
This is because the NADH produced during glycolysis in those living cells enters the respiratory chain earlier than NADH produced other kinds of cell.