Explanation

• Blood is red because of a protein called hemoglobin inside our red blood cells,
• Which contains iron that changes color when it binds to oxygen

Last updated by NS on 5-09-2026

Explanation

• O⁻ (O Negative) is the universal donor blood group.
• It can be transfused to A, B, AB, and O blood groups.
• O⁻ blood lacks A, B, and Rh (D) antigens.

Additional information:

• Universal Recipient: AB⁺ (AB Positive)
• ABO Blood Groups: A, B, AB, O
• Rh Types: Positive (+) and Negative (−)
• Total Common Blood Groups: 8 (A⁺, A⁻, B⁺, B⁻, AB⁺, AB⁻, O⁺, O⁻)

Last verified on 14-07-2026

Explanation

• The ovum (egg cell) is generally considered the largest cell in the human body.
• It is the female reproductive cell and can be seen with the naked eye as a tiny dot.
• The ovum is approximately 0.1 mm (100 micrometers) in diameter.
• In contrast, the sperm cell is one of the smallest human cells.

Last verified on 03-09-2026

Explanation

• Mitochondria are called the powerhouse of the cell.
• Because they produce Adenosine Triphosphate (ATP).
• ATP is the energy currency of the cell.
• ATP provides energy for different cellular activities such as movement, growth, and transport.
• Energy is produced through aerobic cellular respiration using oxygen and الغذائی molecules.
• They are found in the cytoplasm of most eukaryotic cells.
• Richard Altmann first described mitochondria in 1890.

Main Parts of a Cell:

1. Cell membrane → Outer protective layer
2. Nucleus → Controls cell activities
3. Cytoplasm → Jelly-like material between membrane and nucleus

Last verified on 09-05-2026

Explanation

• The nucleus is the control center of the cell.
• It regulates all vital activities like growth, reproduction, and metabolism.
• It contains genetic material (DNA).
• Ribosomes make proteins, and cytoplasm supports cell structure.

Last verified on 04-05-2026

Explanation

• The longest cell in the human body is the nerve cell (neuron).
• Some neurons can extend up to 1 meter in length.
• They transmit impulses throughout the body.

Additional information:

• The smallest cell in the human body is the sperm cell (spermatozoon).
• It is measures approximately 4–5 micrometers (µm) in length.
• It is mainly consisting of a nucleus and a tail.

Last verified on 23-04-2026

Explanation

Chromosomes are made up of:

• Nucleic acid (DNA or RNA)
• Proteins (histones and non-histone proteins)

A chromosome is made up of proteins and DNA organized into genes.

Each cell normally contains 23 pairs of chromosomes.

Explanation

The lifespan of white blood cells ranges from 13 to 20 days, after which time they are destroyed in the lymphatic system.

When immature WBCs are first released from the bone marrow into the peripheral blood, they are called "bands" or "stabs."

Explanation

An atom consists of three subatomic particles:

1. Protons (positively charged)
2. Neutrons (neutral)
3. Electrons (negatively charged)

Additional Information:

A neutral atom has equal protons and electrons; imbalance creates ions.

Discovered by John Dalton in 1808 (Atomic Theory).

Cation = positive ion,
Anion = negative ion,
Isotopes = same element with different neutrons,

Explanation

A vacuole is a sac-like organelle in cells that stores waste materials, water, and nutrients before they are removed or used by the cell.

It plays a key role in maintaining cell homeostasis.