Biology Chapter: The Cell and Its Structures

Study Notes

The cell theory states that:
- All living things are made up of cells.
- Cells are the basic unit of structure and function in living things.
- All cells arise from pre-existing cells.

Prokaryotic cells are simple cells that lack a nucleus and other membrane-bound organelles.
Prokaryotes are single-celled organisms, such as bacteria and archaea.

Eukaryotic cells are more complex cells that have a nucleus and other membrane-bound organelles.
Eukaryotes can be single-celled organisms, such as protists, or multicellular organisms, such as plants, animals, and fungi.

Plasma membrane: The outer boundary of the cell, regulating what enters and exits the cell.
Cytoplasm: The gel-like substance within the cell, where many cellular processes take place.
Nucleus: The control center of the cell, containing the genetic material (DNA).
Ribosomes: Sites of protein synthesis.
Endoplasmic reticulum (ER): A network of membranes involved in protein and lipid synthesis and transport.
- Rough ER: studded with ribosomes
- Smooth ER: lacks ribosomes
Golgi apparatus: Processes and packages proteins and lipids for secretion or use within the cell.
Lysosomes: Contain enzymes that break down cellular waste and debris.
Vacuoles: Store water, nutrients, and waste products.
Mitochondria: The "powerhouse" of the cell, responsible for cellular respiration and ATP production.
Chloroplasts (plants only): Sites of photosynthesis, converting light energy into chemical energy.
- Chloroplasts contain chlorophyll, the green pigment that absorbs light energy.

Cellular respiration: The process of breaking down glucose to release energy (ATP). Occurs in the mitochondria.
Photosynthesis: The process of using light energy to convert carbon dioxide and water into glucose and oxygen. Occurs in chloroplasts (plants only).

Mitosis: The process of cell division that produces two identical daughter cells. Used for growth and repair.
Meiosis: The process of cell division that produces four genetically diverse daughter cells. Used for sexual reproduction.

Cells are the basic unit of life and are found in all living organisms.
The cell membrane encloses the cell and controls what enters and exits.
The cytoplasm is the gel-like substance that fills the cell and contains organelles.
The nucleus is the control center of the cell containing the cell's DNA.
The ribosomes are responsible for protein synthesis.
The endoplasmic reticulum (ER) is a network of membranes involved in protein and lipid synthesis.
The Golgi apparatus packages and modifies proteins for secretion.
Mitochondria are the powerhouses of the cell, responsible for cellular respiration.
Lysosomes break down waste materials and cellular debris.

Cells carry out a variety of processes for life, including:
- Respiration: conversion of glucose to energy (ATP).
- Photosynthesis: production of glucose using sunlight, water, and carbon dioxide.
- Protein synthesis: production of proteins from amino acids.
- Cell division: the process by which cells reproduce.

Prokaryotic cells are simple cells lacking a nucleus and membrane-bound organelles.
- Examples: bacteria and archaea
Eukaryotic cells are complex cells with a nucleus and membrane-bound organelles.
- Examples: plants, animals, fungi, and protists.
Both prokaryotic and eukaryotic cells have certain structures in common, including:
- Cell membrane
- Cytoplasm
- Ribosomes
- DNA

Cells can specialize to perform specific functions in organisms.
This specialization is achieved through gene expression.
Some examples of specialized cells:
- Nerve cells: transmit electrical signals.
- Muscle cells: contract and relax.
- Blood cells: transport oxygen and fight infection.

Cells communicate with each other through various mechanisms:
- Chemical signals: hormones and neurotransmitters.
- Physical contact: gap junctions and plasmodesmata.
Cell communication is essential for:
- Coordination of cellular activities.
- Maintaining homeostasis.
- Responding to environmental changes.