1.8.1 Cytoplasm

Introduction

The living matter of a cell is called protoplasm. In eukaryotic cells, protoplasm can be divided into two parts: the cytoplasm and the nucleus. The cytoplasm is the region of the cell outside the nucleus but inside the plasma membrane.

Definition

Protoplasm: The living matter of a cell is called protoplasm.

Cytoplasm: Cytoplasm is the region between the nuclear membrane and the plasma membrane.

In simple words: Cytoplasm is the jelly-like substance that fills the cell and surrounds the organelles.

Core Concept

• Cytoplasm
• Nucleus

- Cytoplasm is the region between the nuclear membrane and the plasma membrane.

- Cytoplasm is a common component of both prokaryotic and eukaryotic cells.

- It is about 90% water and forms a solution that contains all the fundamental biochemicals of life.

Detailed Explanation

Composition of Cytoplasm

Cytoplasm is about 90% water. It forms a solution that contains all the fundamental biochemicals of life.

Components of Cytoplasm:

1. Water – About 90% of the cytoplasm.

• Salts
• Sugars
• Amino acids
• Fatty acids
• Nucleotides
• Vitamins
• Dissolved gases

• Proteins
• Lipids
• Carbohydrates
• Nucleic acids

In simple words: Cytoplasm is mostly water, but it also contains many different molecules that are needed for the cell to function.

Cytoplasm in Prokaryotic and Eukaryotic Cells

Note: In prokaryotic cells, the cytoplasm contains the genetic material (DNA) because there is no nucleus. In eukaryotic cells, the DNA is enclosed in the nucleus, and the cytoplasm surrounds the nucleus.

Functions of Cytoplasm

• Many biochemical reactions take place in the cytoplasm.
• Examples: Glycolysis (first step of respiration), protein synthesis (on ribosomes).

• The cytoplasm suspends the organelles.
• It provides a medium for the movement of molecules within the cell.

• Molecules move through the cytoplasm by diffusion and active transport.
• Cytoplasmic streaming helps in the distribution of materials.

• The cytoplasm stores nutrients and other substances.
• Examples: Glycogen granules, lipid droplets.

• The cytoplasm, along with the cytoskeleton, helps maintain cell shape.
• It is involved in cell movement (e.g., amoeboid movement).

Intermediate Level

Cytoplasm vs Protoplasm

Important: In prokaryotic cells, there is no nucleus, so the cytoplasm contains the genetic material. In eukaryotic cells, the cytoplasm is distinct from the nucleus.

What is Dissolved in the Cytoplasm?

The cytoplasm contains:

• Sodium (Na⁺)
• Potassium (K⁺)
• Calcium (Ca²⁺)
• Magnesium (Mg²⁺)
• Chloride (Cl⁻)

• Sugars (e.g., glucose)
• Amino acids
• Fatty acids
• Nucleotides
• Vitamins

• Proteins (enzymes, structural proteins)
• Lipids
• Carbohydrates (e.g., glycogen)
• Nucleic acids (RNA)

• Oxygen (O₂)
• Carbon dioxide (CO₂)

Cytoplasmic Streaming

• Cytoplasm is not static; it moves.
• This movement is called cytoplasmic streaming or cyclosis.
• It helps distribute nutrients, organelles, and other materials throughout the cell.
• It is especially important in large cells where diffusion alone would be too slow.

Cytoplasm and Cell Shape

• The cytoplasm, along with the cytoskeleton, helps maintain the shape of the cell.
• In animal cells, the cytoplasm is more fluid and allows the cell to change shape.
• In plant cells, the large central vacuole pushes the cytoplasm against the cell wall, helping the cell maintain its shape.

Important Points

• 1. Protoplasm is the living matter of a cell.
• 2. In eukaryotic cells, protoplasm can be divided into:
• - Cytoplasm
• - Nucleus
• 3. Cytoplasm is the region between the nuclear membrane and the plasma membrane.
• 4. Cytoplasm is a common component of both prokaryotic and eukaryotic cells.
• 5. Cytoplasm is about 90% water.
• 6. It forms a solution that contains all the fundamental biochemicals of life.
• 7. Essential ions and small molecules in true solution include:
• - Salts
• - Sugars
• - Amino acids
• - Fatty acids
• - Nucleotides
• - Vitamins
• - Dissolved gases
• 8. Large molecules in the cytoplasm include:
• - Proteins
• - Lipids
• - Carbohydrates
• - Nucleic acids
• 9. In prokaryotic cells, the cytoplasm contains the genetic material (DNA) because there is no nucleus.
• 10. In eukaryotic cells, the DNA is enclosed in the nucleus, and the cytoplasm surrounds the nucleus.
• 11. Functions of cytoplasm:
• - Site of metabolic reactions
• - Support and suspension of organelles
• - Transport of materials
• - Storage of nutrients
• - Cell shape and movement

Remember

• - Protoplasm = living matter of the cell
• - Protoplasm = Cytoplasm + Nucleus (in eukaryotes)
• - Cytoplasm = region between nuclear membrane and plasma membrane
• - Cytoplasm is about 90% water
• - Cytoplasm contains:
• - Ions and small molecules (salts, sugars, amino acids, fatty acids, nucleotides, vitamins, dissolved gases)
• - Large molecules (proteins, lipids, carbohydrates, nucleic acids)
• - Cytoplasm is present in both prokaryotic and eukaryotic cells
• - Functions: metabolic reactions, support, transport, storage, cell shape

Common Mistakes

• 1. Confusing cytoplasm with protoplasm – Protoplasm = cytoplasm + nucleus. Cytoplasm = region outside the nucleus.
• 2. Thinking cytoplasm is only water – Cytoplasm is about 90% water, but it also contains many ions, small molecules, and large molecules.
• 3. Thinking cytoplasm is only in eukaryotic cells – Cytoplasm is present in both prokaryotic and eukaryotic cells.
• 4. Forgetting that prokaryotes have cytoplasm – Prokaryotes have cytoplasm, but they lack a nucleus. Their DNA is in the cytoplasm.
• 5. Thinking cytoplasm is static – Cytoplasm is dynamic; it moves (cytoplasmic streaming).
• 6. Forgetting the functions of cytoplasm – It is the site of metabolic reactions, supports organelles, transports materials, stores nutrients, and helps maintain cell shape.
• 7. Confusing the composition of cytoplasm with the composition of the cell – The cytoplasm is just one part of the cell; it does not include the nucleus or the organelles.
• 8. Thinking all cells have the same amount of cytoplasm – The amount of cytoplasm varies depending on the cell type and function.

Quick Revision

• Protoplasm is the living matter of a cell.
• In eukaryotic cells, protoplasm can be divided into two parts: cytoplasm and nucleus.
• Cytoplasm is the region between the nuclear membrane and the plasma membrane.
• Cytoplasm is a common component of both prokaryotic and eukaryotic cells.
• It is about 90% water and forms a solution that contains all the fundamental biochemicals of life.
• Essential ions and small molecules in true solution include:
• Salts
• Sugars
• Amino acids
• Fatty acids
• Nucleotides
• Vitamins
• Dissolved gases
• Large molecules include:
• Proteins
• Lipids
• Carbohydrates
• Nucleic acids
• In prokaryotic cells, the cytoplasm contains the genetic material (DNA).
• In eukaryotic cells, the DNA is enclosed in the nucleus, and the cytoplasm surrounds the nucleus.
• Functions of cytoplasm:
• Site of metabolic reactions
• Support and suspension of organelles
• Transport of materials
• Storage of nutrients
• Cell shape and movement

60-Second Revision

• Protoplasm = living matter
• Protoplasm = Cytoplasm + Nucleus (eukaryotes)
• Cytoplasm = between nuclear membrane and plasma membrane
• 90% water
• Contains: ions, small molecules, large molecules
• Present in: prokaryotes and eukaryotes
• Functions: metabolic reactions, support, transport, storage, cell shape
• Cytoplasmic streaming = movement of cytoplasm
• Warning: Cytoplasm is not the same as protoplasm. Prokaryotes have cytoplasm but no nucleus. Cytoplasm is not just water; it contains many molecules.