Cell Theory & Major Cell Types

• Biology is the study of living things.
• Living things must grow and reproduce, respire, produce and excrete waste, require food for energy, respond to the environment, heal and repair themselves, and have a limited lifespan.
• The cell serves as the basic, self-contained unit of living organisms.

Cell Theory

• A few hundred years ago it was believed that living things spontaneously generated from non-living matter.
• All living organisms are composed of cells, which can be unicellular or multicellular.
• The cell is the structural and functional unit of life.
• Cells arise from pre-existing cells.
• Energy flow occurs within cells.
• Hereditary information (DNA) is passed from cell generation to cell generation.
• All cells have the same basic chemical composition.
• Cells come in many sizes, types, lengths, and shapes.
• Cells consist of organelles that work together to form tissues, organs, organ systems, and organisms.

Major Cell Types

• Prokaryotes (Bacteria & Archaea) have ribosomes but lack membrane-bound organelles like a nucleus, evolved earlier, and have simpler cellular machinery.
• Eukaryotes (Animals, Plants, Fungi & Protists) have membrane-bound organelles, evolved later, and feature more complex cellular machinery.
• Humans are eukaryotes; the human body consists of ≈10 trillion body cells with ≈100 trillion prokaryotic cells living on the skin and in the digestive system.
• Cell size is limited to how large cells grow.
• The cell size to volume ratio determines how efficiently materials, nutrients, and waste can travel in and out of a cell to support the function of each organelle.
• The larger the cell, the more volume of organelles must be supported, and the surface area cannot support it.
• Transport of materials like glucose (for energy), amino acids (to build proteins), oxygen, and carbon dioxide across a cellular membrane is a complex process.
• Cells are protein factories and make all living things different; each living thing can make thousands of different proteins.
• Recipes for making proteins are stored in the genes in a cell's nucleus.
• Cells make proteins such as hair, hemoglobin, antibody, melanin, enzyme, and eye color proteins.

Eukaryotic Cell Structure

• Cells have at least one function (job to do) to protect from the external environment (epithelial cells); make chemical substances to digest food (parietal cells that make HCl); carry electrochemical impulses that make muscles contract (neurons).
• The nucleus is the control center of the cell.
• Each somatic human cell nucleus contains 46 chromosomes, which store instructions for the cell's activities.
• For most of the cell cycle, chromosomes look like threads, called chromatin.
• The nucleus directs cellular activity by sending instructions through mRNA to the ribosomes, where proteins are assembled.
• Ribosomes receive instructions from the chromosomes by mRNA.
• A round structure in the nucleus helps the production and storage of RNA called the nucleolus.
• mRNA exits the nucleus through pores and travels to ribosomes in the cytoplasm.
• Proteins are transported through the cells by the endoplasmic reticulum (ER).
• The rough ER walls are studded with ribosomes.
• ER delivers proteins to the Golgi body, which coats proteins with a special molecular layer and allows proteins to leave the cell, transporting through the bloodstream to help the body perform life functions.
• Lysosomes breakdown proteins molecules using enzymes.
• Vacuoles stores incoming nutrients before lysosomes break them down.
• Mitochondria acts like a power house; producing energy in the form the cell can use.
• Plant cells have cell walls that allow plants to have strength and structure and allow certain molecules in and out.
• Chloroplasts are the site of photosynthesis, allowing plants to capture the Sun's energy to create energy-rich molecules and make their own food.

Organelles

• Cell the building block for all living things
• Nucleus controls the cell (directs activities), holds genetic data (DNA), and has a double membrane structure; found in both animal and plants cells
• Nuclear Pores allow molecules to move in/out of the nucleus
• Nucleolus creates ribosomes
• Cell Membrane controls what goes in/out of the cell
• Cell Wall controls the movement of molecules in/out of the cell, provides support.
• Cytoplasm supports organelles
• Mitochondria provides energy for cell process
• Golgi Apparatus, assembles and packages and stores proteins
• Cytoskeleton serves as the "highways' and aids in cell structure
• Endoplasmic Reticulum canals carry molecules through the cell. Rough ER has ribosomes
• Ribosomes produce proteins
• Vesicles transfer and/or store molecule
• Lysosome contains enzymes that break down large molecules and old cell parts
• Chloroplast captures sunlight and creates food for plant cells.
• Vacuole stores container for water, wastes
• Centrioles aids in animal cell reproduction

An overview of cell theory, which states that all living organisms are composed of cells and all cells arise from pre-existing cells. Includes that the cell is the structural and functional unit of life. Also includes brief details on prokaryotes.