Cell Structure and Function

Cell Structure

• Cells are the basic structural and functional units of all living organisms.
• They are enclosed by a membrane that regulates the passage of materials in and out of the cell.
• Cells contain various organelles that perform specific functions.

Types of Cells

• Prokaryotic cells lack a nucleus and other membrane-bound organelles.
• Eukaryotic cells have a nucleus and other membrane-bound organelles.
• Examples of eukaryotic cells include animal cells and plant cells.

Cell Membrane

• The cell membrane is a phospholipid bilayer that separates the intracellular environment from the extracellular environment.
• It is selectively permeable, controlling the movement of substances into and out of the cell.
• Proteins embedded in the membrane facilitate transport of specific molecules.
• The fluid mosaic model describes the structure of the cell membrane.

Cytoplasm

• The cytoplasm is a jelly-like substance that fills the cell.
• It contains numerous organelles and is the site of many metabolic reactions.
• It provides a medium for chemical reactions to take place.

Nucleus

• The nucleus is the control center of the cell, containing the cell's genetic material (DNA).
• It is enclosed by a double membrane called the nuclear envelope.
• It contains chromosomes, which are structures that hold DNA.
• The nucleolus is a region within the nucleus that produces ribosomes.

Ribosomes

• Ribosomes are the protein synthesis machinery of the cell.
• They can be free-floating in the cytoplasm or attached to the endoplasmic reticulum.
• Ribosomes synthesize proteins using mRNA as a template.

Endoplasmic Reticulum (ER)

• Rough ER has ribosomes attached to its surface and is involved in protein synthesis and modification.
• Smooth ER lacks ribosomes and is involved in lipid synthesis and detoxification.

Golgi Apparatus

• The Golgi apparatus modifies, packages, and sorts proteins and lipids for secretion or transport to other organelles.
• It is a stack of flattened sacs.

Mitochondria

• Mitochondria are the powerhouses of the cell, generating ATP (adenosine triphosphate) through cellular respiration.
• They have a double membrane structure, with an inner membrane that is highly folded.

Lysosomes

• Lysosomes contain digestive enzymes that break down waste materials and cellular debris.
• They are essential for cellular homeostasis and removing harmful substances.

Vacuoles

• Vacuoles are membrane-bound sacs that store water, nutrients, or waste products.
• Plant cells typically have a large central vacuole that maintains turgor pressure.

Cytoskeleton

• The cytoskeleton is a network of protein filaments that provides structural support and facilitates intracellular transport.
• It is composed of microfilaments, intermediate filaments, and microtubules.

Cell Wall

• Plant cells have a rigid cell wall that provides structural support and protection.
• It is primarily composed of cellulose.

Specialized Cell Structures

• Some cells have specialized structures that perform specific functions.
• Examples include cilia for movement and flagella for propulsion.

Cell Division

• Cells reproduce through cell division (e.g., mitosis or meiosis).
• Cell division is essential for growth, repair, and reproduction.
• Mitosis produces two identical daughter cells.
• Meiosis produces four genetically different daughter cells, involved in sexual reproduction.

Cellular Processes

• Cells carry out numerous vital processes, including respiration, photosynthesis, and protein synthesis.
• These processes allow cells to maintain homeostasis and perform their specific functions.

Cell Signaling

• Cells communicate with each other through various signaling mechanisms.
• These mechanisms enable cells to respond to their environment and coordinate activities within a multicellular organism.