Cell wall, plasma membrane, nucleus, chloroplasts, vacuoles

1. Introduction

1. A cell is the fundamental unit of life.
2. The study of cells is called Cell Biology.
3. Cells contain various organelles that perform specific functions.
4. Key structures in plant and some bacterial cells include the Cell Wall, Plasma Membrane, Nucleus, Chloroplasts, and Vacuoles.

2. Cell Wall

1. The cell wall is a rigid outer layer present in plant cells, fungi, bacteria, and some protists.
2. It provides structural support and protection.
3. In plants, it is primarily made of cellulose.
4. In fungi, it is made of chitin, and in bacteria, it consists of peptidoglycan.
5. It helps prevent cell bursting due to osmotic pressure.
6. The middle lamella, composed of pectin, helps in cell adhesion.

3. Plasma Membrane

1. The plasma membrane, also called the cell membrane, is a semi-permeable structure.
2. It is composed of a phospholipid bilayer with embedded proteins.
3. It regulates the entry and exit of substances.
4. It contains transport proteins that assist in active and passive transport.
5. Functions include communication, transport, and structural integrity.

4. Nucleus

1. The nucleus is the control center of the cell, containing DNA.
2. It is surrounded by a double-layered nuclear membrane with pores for transport.
3. Inside, it contains chromatin (DNA + proteins) and a dense structure called the nucleolus.
4. The nucleolus is responsible for producing ribosomes.
5. The nucleus regulates gene expression and cell division through mitosis and meiosis.

5. Chloroplasts

1. Chloroplasts are the site of photosynthesis in plant cells.
2. They contain the pigment chlorophyll, which absorbs sunlight.
3. They have a double membrane and internal structures called thylakoids.
4. Stacks of thylakoids form grana, where light reactions occur.
5. The fluid inside, called stroma, contains enzymes for the Calvin cycle.
6. Endosymbiotic theory suggests chloroplasts evolved from ancient bacteria.

6. Vacuoles

1. Vacuoles are membrane-bound organelles for storage of water, nutrients, and waste.
2. In plant cells, the central vacuole helps maintain turgor pressure.
3. They are surrounded by a membrane called the tonoplast.
4. In animal cells, vacuoles are smaller and assist in digestion and waste removal.
5. Contractile vacuoles in unicellular organisms help in osmoregulation.

7. Summary

1. Cell Wall provides structural support and protection.
2. Plasma Membrane controls substance movement.
3. Nucleus contains genetic material and regulates cell activities.
4. Chloroplasts perform photosynthesis and generate energy.
5. Vacuoles store materials and maintain pressure in cells.