Explain Cellular
Processes

Understand cell structure and how cells divide through mitosis and meiosis.

GED Science

The Cell Is the Basic Unit of Life

Every living thing is made of cells. A cell is the smallest unit that can carry out all the processes of life: taking in energy, growing, and reproducing.

Key Cell Structures

DNA, Genes & Chromosomes

Inside the nucleus, DNA is the molecule that stores genetic instructions. DNA is organized into structures called chromosomes. Humans have 46 chromosomes (23 pairs) in most body cells.

Why Cells Divide

Growth

An organism grows larger by making more cells, not bigger ones.

Repair

New cells replace damaged or worn-out cells, like healing a cut.

Reproduction

Sex cells are made so a new organism can begin.

Mitosis: One Cell Becomes Two Identical Cells

Meiosis: One Cell Becomes Four Sex Cells

Mitosis vs. Meiosis: The Key Difference

Mitosis

2 identical daughter cells, full chromosome count \( 2n \). Used for growth and repair of body cells.

Meiosis

4 unique sex cells, half the chromosome count \( n \). Used only for reproduction.

How to Identify the Process

1

Count the daughter cells. Two cells means mitosis; four cells means meiosis.

2

Check the chromosome number. Same as parent \( (2n) \) is mitosis; half \( (n) \) is meiosis.

3

Ask the purpose. Growth or repair points to mitosis; making eggs or sperm points to meiosis.

Example 1: Healing a Cut

A person scrapes their knee. New skin cells form to close the wound. Which process makes these new cells?

Example 2: Counting Chromosomes

A human body cell has \( 2n = 46 \) chromosomes. After meiosis, how many chromosomes does each sex cell have?

Example 3: Restoring the Count

During fertilization, a sperm cell joins an egg cell. If each has 23 chromosomes, how many will the new cell have?

Common Mistakes

✕ Mixing up cell counts

Mitosis makes 2 cells; meiosis makes 4. Don't swap these numbers.

✕ Forgetting the halving

Only meiosis halves the chromosome number to \( n \). Mitosis keeps it at \( 2n \).

✕ Wrong cell types

Meiosis happens only in sex cells, not in ordinary body cells.

Summary Comparison

	Mitosis	Meiosis
Daughter cells	2	4
Chromosome count	\( 2n \) (full)	\( n \) (half)
Are cells identical?	Yes	No
Cell type	Body cells	Sex cells
Purpose	Growth, repair	Reproduction

Question 1 of 5

Which cell structure stores the DNA in a cell?

The nucleus holds the DNA. The membrane controls what enters, mitochondria make energy, and lysosomes break down waste.

Question 2 of 5

How many daughter cells does mitosis produce from one parent cell?

Mitosis makes 2 identical daughter cells. Meiosis is the process that makes 4 cells.

Question 3 of 5

A human body cell has \( 2n = 46 \) chromosomes. After meiosis, how many does each sex cell have?

Meiosis halves the number: \( n = \dfrac{46}{2} = 23 \). Each sex cell gets 23 chromosomes.

Question 4 of 5

Which process would a plant use to grow taller by making more body cells?

Growth requires identical body cells with the full chromosome set, so the answer is mitosis. Meiosis is only for sex cells.

Question 5 of 5

A sperm cell with 23 chromosomes joins an egg cell with 23 chromosomes. How many chromosomes does the new cell have?

The two half-sets combine: \( 23 + 23 = 46 = 2n \). Fertilization restores the full chromosome number.

Explain CellularProcesses

The Cell Is the Basic Unit of Life

Key Cell Structures

DNA, Genes & Chromosomes

Why Cells Divide

Mitosis: One Cell Becomes Two Identical Cells

Meiosis: One Cell Becomes Four Sex Cells

Mitosis vs. Meiosis: The Key Difference

How to Identify the Process

Example 1: Healing a Cut

Example 2: Counting Chromosomes

Example 3: Restoring the Count

Common Mistakes

Summary Comparison

Question 1 of 5

Question 2 of 5

Question 3 of 5

Question 4 of 5

Question 5 of 5

You've Got the Big Picture

Explain Cellular
Processes