2.3 How does cystic fibrosis affect other body systems?

Question 1

The effect of CF on the digestive system

Answer 1

• Problems with the digestion and absorption of nutrients
• High basal metabolic rates
• require 120%-140% of the recommended daily energy intake
• pancreatic duct blocked by sticky mucus- impairs release of enzymes
• food is not fully digested so not all nutrient absorbed > causes malabsorption syndrome
• when enzymes become trapped they damage the pancreas itself causing cysts to form
• if damage occurs to cells that produce insulin- a form of diabetes is developed

Question 2

Exocrine

Answer 2

A gland that secretes substances into a duct is called an exocrine gland. The salivary glands and the pancreas are examples of exocrine glands.

Question 3

Endocrine

Answer 3

A gland that secretes hormones directly into the blood is called an endocrine gland. Glands are organs which secrete particular substances. The pancreas is an endocrine gland because it secretes the hormone insulin into the blood. It is also an exocrine gland because it secretes digestive enzymes into a duct which takes them into the intestine.

Question 4

Catalyst

Answer 4

A substance that increases the rate of a chemical reaction but remains unchanged at the end of the reaction.

Question 5

Enzyme

Answer 5

Enzymes are proteins that speed up chemical reactions in living organisms. For instance, inside a typical cell many different reactions are taking place. Each of these is catalysed by a specific enzyme. Without these enzymes, the reactions would take place very slowly at the temperatures inside cells.

Question 6

Active site

Answer 6

The part of an enzyme molecule into which a substrate molecule fits during a chemical reaction. It is like a pocket on the surface of the enzyme and it has a specific shape. Only a substrate molecule with the complementary shape will be able to fit into this active site.

Question 7

Substrate

Answer 7

In biochemical reactions, a substrate is the molecule on which an enzyme acts. The substrate of the enzyme amylase, for example, is starch while that of maltase is maltose. Enzymes are very specific in their actions. Only a substrate molecule with a particular shape will fit the active site of a particular enzyme.

Question 8

Enzyme–substrate complex, ES complex

Answer 8

In a chemical reaction controlled by an enzyme, one or more substrate molecules fit into the active site of the enzyme to form an enzyme–substrate complex. The substrate molecules are held in such a way that a reaction takes place. Product molecules are produced and released while the enzyme is unchanged.

Question 9

Induced fit theory

Answer 9

Model to explain the way in which an enzyme enables a substrate to participate in a chemical reaction. When the substrate enters the active site, the enzyme changes shape, fitting more closely around the substrate and speeding up the rate of reaction.

Question 10

Activation energy

Answer 10

Before a chemical reaction can take place, bonds must be broken. This requires energy. This activation energy is normally provided by heating the substances involved in the reaction. Enzymes reduce the amount of activation energy necessary, so reactions in living organisms can take place at relatively low temperatures.

Question 11

Intracellular

Answer 11

’Intra’ means inside, so intracellular is inside cells. Intracellular reactions, for example, occur inside cells.

Question 12

Extracellular

Answer 12

‘Extra’ means outside, so extracellular is outside cells. Extracellular digestion, for example, is digestion that takes place outside cells. Bacteria and other saprobionts secrete enzymes onto the surface of their food and digest it outside their cells.

Question 13

Catabolic

Answer 13

A catabolic reaction is a chemical reaction in which large molecules are broken down to produce smaller ones. Examples of catabolic reactions include many of those involved in respiration and digestion.

Question 14

Anabolic

Answer 14

An anabolic reaction is a chemical reaction in which smaller molecules combine together to produce larger ones. Examples of anabolic reactions include photosynthesis and protein synthesis.

Question 15

enzymes:

Answer 15

• are globular proteins
• have an active site that allows binding with a specific substrate
• catalyse reactions
• reduce activation energy required for a chemical reaction to take place
• do not alter the end-product or nature of a reaction
• do not get used up and remain unchanged at the end of the reaction

Question 16

rate of reaction

Answer 16

measured by determining the quantity of substrate used or the quantity of product formed in a given time.

Question 17

The effect of enzyme concentration on the rate of reaction

Answer 17

initial rate of reaction directly proportional to the enzyme concentration.

more enzyme produces more successful enzyme-substrate collisions so increases the rate (substrate always in excess)

Question 18

The effect of substrate concentration on the rate of reaction

Answer 18

at first substrate limiting- increasing substrate concentration produces more successful enzyme-substrate collisions so the rate increases

after enzymes limiting- all active sites are full; increasing substrate concentration has no effect on rate

Question 19

Effect of CF on the reproductive system

Answer 19

• females have a reduced chance of becoming pregnant - mucus plug develops in the cervix. stops sperm reaching egg
• males lack the sperm duct on both sides- sperm cannot leave the testes. If sperm duct present can be partially blocked by a thick sticky mucus layer

Question 20

The effect of CF on sweat

Answer 20

unusually salty sweat as CFTR and ENAC protein don’t allow reabsorption of sodium chloride from sweat

Question 21

Lock-and-key theory

Answer 21

Model to explain the way
in which an enzyme (the lock) helps a substrate
(the key) to participate in a chemical reaction.

Question 22

Hypotonic

Answer 22

A hypotonic solution is any solution that has a lower osmotic pressure than another solution. In the biological fields, this generally refers to a solution that has less solute and more water than another solution