2A2 Reactions in Living Organisms

Question 1

Define:

concentration gradient

Answer 1

A difference in the concentration of solute across a membrane.

Question 2

What are the three types of transport?

Answer 2

• Passive diffusion
• Facilitated diffusion
• Active transport

Passive diffusion: down the concentration gradient

Facilitated diffusion: down the concentration gradient

Active transport: against the concentration gradient

Question 3

What are the two types of diffusion?

Answer 3

• Passive diffusion
• Facilitated diffusion

Question 4

Define:

diffusion

Answer 4

The process of molecules moving from a higher concentration to a lower concentration.

Question 5

Define:

passive diffusion

Answer 5

Also known as simple diffusion, it occurs when molecules move directly across the membrane.

Does not require energy.

Question 6

Define:

facilitated diffusion

Answer 6

The movement of larger molecules, including charged and polar solutes, through a carrier protein in the cell membrane.

Question 7

What is the role of the carrier protein in facilitated diffusion?

Answer 7

It assists in transporting small particles or ions across the cell membrane through a specific channel.

Question 8

Compare passive diffusion and facilitated diffusion.

Answer 8

• Passive diffusion: occurs by random motion.
• Facilitated diffusion: requires carrier proteins that help transport molecules through membrane channels.

Question 9

Define:

osmosis

Answer 9

The movement of water from where there is a lower concentration of solute to an area with a higher solute concentration.

It controls the balance of water, salt, and volume inside the cell.

Question 10

Define:

active transport

Answer 10

Moving solutes against their concentration gradient, requiring cellular energy or ATP.

Question 11

Define:

thermodynamics

Answer 11

A scientific discipline that studies the relationship of heat, work, and temperature and examines how these variables are related to other parameters like entropy, properties of matter, energy, and radiation.

Question 12

What is the first law of thermodynamics also known as?

Answer 12

The ‘Law of Conservation of Energy’

It states that energy cannot be created or destroyed, only transferred.

An example is when the chlorophyll absorbs light and transforms it into chemical energy.

Question 13

What is the second law of thermodynamics?

Answer 13

It states that the entropy in a system increases with time.

As time goes on entropy- the disorder of energy- increases so there is less energy available to perform useful work

Question 14

Explain the concept of entropy.

Answer 14

It is the measure of energy unavailable for performing useful work.

Question 15

What is the third law of thermodynamics?

Answer 15

It states that the degree of randomness, entropy, tends to a minimum value as the temperature approaches absolute zero.

As the temperature decreases, the entropy (or disorder) of the system also decreases.

Question 16

What is the absolute zero temperature in Kelvin?

Answer 16

0 Kelvin (K)

This is the theoretical temperature at which all molecular motion stops.

Question 17

What is the relationship between kinetic energy and thermal energy?

Answer 17

• The higher the kinetic energy, the higher the thermal energy.
• The lower the kinetic energy, the lower the thermal energy.

Question 18

Define:

anabolism

Answer 18

Takes simpler molecules and builds them into more complex ones, generally using ATP in the process.

Energy is absorbed in anabolic reactions.

Examples:

• Building proteins for growth and muscle development.
• Synthesizing glucose for later use as energy.

Question 19

Define:

catabolism

Answer 19

Breaks down complex molecules into simpler ones, producing ATP in the process.

Energy is released in catabolic reactions.

Examples:

• Breaking down complex molecules for energy production.
• Replenishing the cell’s energy by generating ATP.
• Glycolysis.

Question 20

What is the difference between anabolic and catabolic pathways?

Answer 20

• Anabolic pathways join simple molecules to form complex ones, consuming energy.
• Catabolic pathways break down complex molecules into simpler ones, releasing energy.

Question 21

What are amphibolic pathways?

Answer 21

Pathways that can be both anabolic or catabolic depending on the energy state of the body.

Example: The citric acid (TCA) cycle, which plays a dual role depending on cellular needs.

Question 22

What is the role of ATP in metabolism?

Answer 22

Provides energy for cellular processes.

Question 23

Define:

metabolism

Answer 23

The collection of all the chemical processes that occur within the body, encompassing both energy-producing and energy-consuming reactions.

Question 24

What is cellular respiration?

Answer 24

A group of cellular reactions that harvest energy from nutrients to produce ATP.

Question 25

What are the **steps** of cellular respiration?

Answer 25

* Glycolysis * Pyruvate decarboxylation (link reaction) * Citric Acid Cycle (Krebs Cycle) * Electron Transport Chain (ETC) * Oxidative Phosphorylation

Question 26

What is a **redox reaction**?

Answer 26

An oxidation-reduction (redox) reaction involves the transfer of electrons between two reactants. ## Footnote In this reaction, oxidation is the loss of electrons, and reduction is the gain of electrons.

Question 27

What are some common types of redox reactions?

Answer 27

* Combination * Decomposition * Displacement * Combustion

Question 28

What is the **first step** in balancing redox reactions?

Answer 28

Separating the equation into two half reactions.

Question 29

What is a **half reaction**?

Answer 29

Shows either reduction OR oxidation, but not both. ## Footnote Reduction potential can be used to predict the tendency of a chemical species to acquire electrons.

Question 30

What should be balanced first in redox reactions, excluding oxygen and hydrogen?

Answer 30

All atoms

Question 31

What are the roles of oxidizing agents and reducing agents in redox reactions?

Answer 31

* **Oxidizing agents** are substances that are reduced in the reaction (gain electrons). * **Reducing agents** lose electrons, donating them to the oxidizing agent. ## Footnote Redox reactions cannot occur without both oxidation and reduction.

Question 32

How can you identify an **oxidizing agent** in a redox reaction?

Answer 32

A substance that accepts electrons during a redox reaction. ## Footnote The most commonly identified oxidizing agent in redox reactions is oxygen.

Question 33

How can you identify a **reducing agent** in a redox reaction?

Answer 33

An element or compound that loses an electron and donates them to another atom or element in a redox reaction. ## Footnote Once the reducing agent has lost its electrons, it is said to have been oxidized.

Question 34

What is the process through which organisms use oxygen to **break down food molecules to extract chemical energy** for cell processes?

Answer 34

Oxidative metabolism | (Cellular respiration)

Question 35

What is the process of **cellular respiration** in redox reactions?

Answer 35

Converts nutrients into ATP through a series of redox reactions, producing energy and releasing waste. ## Footnote 32 ATP molecules are created. ATP is the main energy molecule in the body. The creation of this molecule mostly takes place in the mitochondrial matrix.

Question 36

What is the process of **photosynthesis** in redox reactions?

Answer 36

Carbon dioxide and water combine with energy from sunlight to produce glucose and release oxygen. This process oxidizes water and reduces carbon dioxide.

Question 37

During photosynthesis, what energy source for the plant is produced?

Answer 37

Glucose

Question 38

What is the general form of a **decomposition reaction**?

Answer 38

AB -> A + B

Question 39

What does the mnemonic "LEO the lion says GER" describe in redox reactions?

Answer 39

LEO: Lose electrons -- oxidation GER: Gain electrons -- reduction

Question 40

Why is **oxidative metabolism** important for cellular respiration?

Answer 40

The losing and gaining of electrons produces energy that powers essential cellular processes.