Problem 9 - Biology of Humans: Concepts, Applications, and Issues

Question

Mitochondria a. process energy for cells. b. lack ribosomes and DNA. c. are bounded by a single membrane. d. function in cell digestion.

Step-by-Step Solution

Answer

a. process energy for cells.

Step 1: Identify the organelle

Understand that the question is about mitochondria and their functions and characteristics.

Step 2: Analyze each option

Review each of the given options to determine if they correctly describe mitochondria.

Step 3: Evaluate Option (a)

Mitochondria are known as the powerhouse of the cell, meaning they process energy for cells. This is correct.

Step 4: Evaluate Option (b)

Mitochondria possess their own ribosomes and DNA, making this statement incorrect.

Step 5: Evaluate Option (c)

Mitochondria are actually bounded by a double membrane, so this option is incorrect.

Step 6: Evaluate Option (d)

Mitochondria are not involved in cell digestion; this is the role of lysosomes. Therefore, this statement is incorrect.

Key Concepts

cellular energy

Mitochondria are often referred to as the 'powerhouses' of the cell. This is because they generate most of the cell's supply of adenosine triphosphate (ATP), which cells use as a source of chemical energy.
ATP is produced through a process known as cellular respiration. During cellular respiration, mitochondria convert oxygen and nutrients from food into energy. The stages include glycolysis, the Krebs cycle, and the electron transport chain.

• Glycolysis: This occurs in the cytoplasm and breaks down glucose into pyruvate, producing a small amount of ATP.
• Krebs Cycle: Also known as the citric acid cycle, this takes place in the mitochondrial matrix and processes pyruvate to produce high-energy molecules like NADH.
• Electron Transport Chain: This occurs in the inner mitochondrial membrane and uses the high-energy molecules from the Krebs cycle to produce a large amount of ATP.

The energy produced by mitochondria is essential for many cell functions, from movement to growth and repair.

organelle function

Mitochondria serve several essential functions beyond energy production. They play a role in:

• Metabolizing Fatty Acids and Amino Acids: Mitochondria help break down fatty acids and amino acids to provide energy and building blocks for the cell.
• Calcium Storage: They store calcium ions, which are crucial for processes like muscle contraction and cell signaling.
• Apoptosis: Mitochondria are involved in programmed cell death, which helps control cell growth and development.
• Heat Production: In brown fat cells, mitochondria generate heat to maintain body temperature.

All these functions make mitochondria a multifaceted organelle essential for maintaining cellular and physiological balance.

mitochondrial DNA

Unlike other organelles, mitochondria have their own DNA (mtDNA) and ribosomes. This is believed to be due to their evolutionary origin from ancient prokaryotic cells that entered into a symbiotic relationship with early eukaryotic cells.
Mitochondrial DNA is circular and contains genes crucial for mitochondrial function, such as those coding for proteins involved in the electron transport chain.
Because mitochondria have their own DNA, they can produce some of their own proteins. However, they still rely on the cell's nuclear DNA for most of their protein needs.
Mitochondrial DNA is inherited maternally, which means it is passed down from the mother only. This unique inheritance pattern is useful in studies of genetic diseases and ancestry.

double membrane

Mitochondria are enveloped by a double membrane, which is key to their function.

• Outer Membrane: This membrane is smooth and contains proteins called porins that allow the passage of ions and small molecules.
• Inner Membrane: This membrane is highly folded into structures known as cristae, which increase the surface area for chemical reactions.

The compartmentalization created by the double membrane allows for efficient separation of different metabolic pathways. The intermembrane space (the area between the two membranes) and the mitochondrial matrix (inside the inner membrane) each have distinct roles in cellular respiration and energy production.
This architectural design maximizes the mitochondria's ability to produce energy and maintain cellular health.