Cell Structure Basics

Cell Structure

Basic Unit of Life: Cells are the fundamental units of structure and function in living organisms.
Types of Cells:
- Prokaryotic Cells:
  - Lack a nucleus and membrane-bound organelles.
  - Examples: Bacteria and Archaea.
- Eukaryotic Cells:
  - Have a nucleus and membrane-bound organelles.
  - Examples: Plant and animal cells.
Main Components:
- Cell Membrane:
  - Semi-permeable barrier that controls the movement of substances.
- Nucleus:
  - Contains genetic material (DNA); controls cellular activities.
- Cytoplasm:
  - Jelly-like substance where organelles are suspended; site of metabolic processes.
- Organelles:
  - Mitochondria: Powerhouse of the cell, producing ATP through cellular respiration.
  - Ribosomes: Sites of protein synthesis.
  - Endoplasmic Reticulum (ER):
    - Rough ER: Studded with ribosomes; synthesizes proteins.
    - Smooth ER: Synthesizes lipids and detoxifies substances.
  - Golgi Apparatus: Modifies and packages proteins and lipids.
  - Lysosomes: Contain digestive enzymes for waste breakdown.
  - Chloroplasts (in plant cells): Site of photosynthesis.

Cell Function

Metabolism:
- All chemical reactions within a cell; includes catabolism (breaking down molecules) and anabolism (building molecules).
Homeostasis:
- Regulation of internal conditions to maintain a stable environment.
Transport Mechanisms:
- Passive Transport: Movement of substances without energy (e.g., diffusion, osmosis).
- Active Transport: Movement of substances against concentration gradient, requiring energy (e.g., sodium-potassium pump).
Cell Communication:
- Mechanisms for cells to communicate with each other (e.g., signaling molecules, receptors).

Cell Division

Purpose:
- Growth, repair, and reproduction of organisms.
Types of Cell Division:
- Mitosis:
  - Process of somatic cell division.
  - Results in two identical daughter cells.
  - Stages: Prophase, Metaphase, Anaphase, Telophase.
- Meiosis:
  - Process of gamete formation (sperm and egg).
  - Reduces chromosome number by half (from diploid to haploid).
  - Involves two rounds of division: Meiosis I and Meiosis II.
Regulation:
- Controlled by a series of checkpoints to ensure proper division and avoid abnormal growth (e.g., cancer).

Cell Structure

The basic unit of life is the cell, functioning as the foundation for structure and activity in all living organisms.
Cells come in two main categories: prokaryotic and eukaryotic.
Prokaryotic cells lack a nucleus and membrane-bound organelles. Examples are bacteria and archaea.
Eukaryotic cells contain a nucleus and membrane-bound organelles. They include plant and animal cells.
The cell membrane acts as a semi-permeable barrier, meticulously controlling the movement of substances into and out of the cell.
The nucleus holds the cell's genetic material (DNA) and serves as the control center for cellular activities.
The cytoplasm, a jelly-like substance, provides a medium to suspend organelles within the cell and acts as the site of metabolic processes.
Organelles are specialized structures within the cell that perform particular functions.
Mitochondria are responsible for generating the cell's energy through cellular respiration, earning them the title of the "powerhouse of the cell."
Ribosomes are essential for protein synthesis, creating the building blocks of life.
The endoplasmic reticulum (ER) plays a critical role in the synthesis of proteins and lipids, with the rough ER being studded with ribosomes for protein synthesis and the smooth ER focusing on lipid synthesis and detoxification.
The Golgi apparatus modifies and packages proteins and lipids, preparing them for transport within the cell or outside.
Lysosomes, filled with digestive enzymes, breakdown waste products within the cell.
Chloroplasts, present in plant cells, are vital for photosynthesis, the process of converting light energy into chemical energy.

Cell Function

Metabolism encompasses all chemical reactions occurring within a cell, divided into catabolism, the breakdown of molecules, and anabolism, the building up of molecules.
Homeostasis refers to the maintenance of a stable internal environment within the cell by regulating internal conditions.
Cell transport mechanisms include passive transport, where substances move across the cell membrane without requiring energy, and active transport, which utilizes energy to move substances against their concentration gradient.
Cell communication is a complex process that allows cells to communicate with one another through signaling molecules and receptors.

Cell Division

Cell division is essential for growth, repair, and reproduction in living organisms.
Mitosis is the process of somatic cell division, resulting in two identical daughter cells. It involves the following stages: prophase, metaphase, anaphase, and telophase.
Meiosis is the process of gamete (sex cell) formation, reducing the chromosome number from diploid to haploid. It consists of two rounds of division: Meiosis I and Meiosis II.
Cell division is tightly controlled by checkpoints, ensuring proper division and preventing abnormal growth, such as cancer.