Why Study Cell Biology? The key to every biological problem must finally be sought in the cell, for every living organism is, or at some time has been, a cell. E.B. Wilson, 1925 Cells are Us Cells are Us Cilia on a protozoan Sperm meets egg Cells are Us A person contains about 100 trillion cells. That’s 100,000,000,000,000 or 1 x 1014 cells. There are about 200 different cell types in mammals (one of us). Red and white blood cells above vesselforming cells. nerve cell CELL SIZE • Smallest cell in the human body is the sperm cell • Largest cell in the human body is the egg cell Most cells are small 1. Surface to volume ratio: cell has to be small enough to get – Waste out – Nutrients in 2. The nucleus can only control a certain size cell Robert Hooke • Used a microscope to look at small object and coined the term “cells” • They looked like little boxes that monks lived in called “cells” Anton von Leewenhoek • FIRST person to OBSERVE and DESCRIBE MICROSCOPIC ORGANISMS and LIVING CELLS. • Matthias Schleiden : “plants are made of cells” Schleiden • Theodor Schwann : “Animals are made of cells” Schwann The Cell Theory The cell theory (proposed independently in 1838 and 1839) is a cornerstone of biology. Proposed by Rudolph Virchow 1. All living things are made of cells. 2. Cells are the basic unit of structure and function 3. New cells come from preexisting cells. *cells are different shapes and sizes based on their function A Sense of Scale and Abundance – Bacteria on the Head of a Pin Two Fundamentally Different Types of Cells Us vs. Them Eukaryotes and Prokaryotes • Organisms whose cell contain a nucleus and other membrane bound organelles are called EUKARYOTES • Organisms whose cells never contain (or lack) a nucleus and other membrane bound organelles are called PROKARYOTES Major Divisions of the Eukaryotic Cell 1. NUCLEUS 2. CYTOPLASM 3. CELL MEMBRANE A rat liver cell (with color enhancement to show organelles) It’s Crowded In There An artist’s conception of the cytoplasm - the region of a cell that’s not in the nucleus or within an organelle. It’s Crowded In There A micrograph showing cytoskeleton (red), ribosomes (green), and membrane (blue) Animal and Plant Cells Have More Similarities Than Differences Cellular Anatomy We’ll start by seeing what role these parts play in making and moving proteins. The Nucleus •Control center of the cell •Surrounded by a nuclear envelope with pores •DNA is in the form of chromatin which condenses down into chromosomes Ribosomes and the Endoplasmic Reticulum Ribosome • Ribosomes Are Not Surrounded by a membrane. They are the site of PROTEIN SYNTHESIS (Production or Construction) in a cell. The Rough Endoplasmic Reticulum Studded with ribosomes Protein synthesis (about half the cell’s proteins are made here). Protein movement (transport) Smooth ER • SMOOTH ER IS NOT Covered with RIBOSOMES and processes LIPIDS and CARBOHYDRATES. The Smooth ER is involved in the synthesis of steroids in gland cells, the regulation of calcium levels in muscle cells, and the breakdown of toxic substances by liver cells. Cystic Fibrosis Click here to see the article. Golgi Apparatus • Processing, Packaging and Secreting Organelle of the Cell that is made of flattened SAC The Lysosome Functions: Digesting food or cellular invaders Recycling cellular components The Lysosome This bacterium about to be eaten by an immune system cell will spend the last minutes of its existence within a lysosome. Many Diseases are Caused by Lysosome Malfunction Cellular Anatomy The Mitochondrion Think of the mitochondrion as the powerhouse of the cell. Both plant and animal cells contain many mitochondria. Mitochondrial Diseases Mitochondria and Health Animal vs. Plant Cells – Chloroplasts Are a Big Part of the Difference Cells In a Leaf The Chloroplast Think of the chloroplast as the solar panel of the plant cell. Only plants have chloroplasts; they perform photosynthesis Two Other Unique Features of Plant Cells The central vacuole may occupy 90% of a plant cell. A Consequence of Cell Walls – the Great Strength of Woody Plants The Central Vacuole Controls Turgor Pressure Flaccid – no water Turgid – full of water Cellular Anatomy The Cytoskeleton The name is misleading. The cytoskeleton is the skeleton of the cell, but it’s also like the muscular system, able to change the shape of cells in a flash. Maintains the shape of the cell Aids in movement An animal cell cytoskeleton A Cytoskeleton Gallery The Cytoskeleton in Action A white blood cell using the cytoskeleton to “reach out” for a hapless bacterium. The Cytoskeleton in Action Cilia on a protozoan Beating sperm tail at fertilization Smoker’s cough is due to destruction of cilia linking the airways. Cell membrane • The Cell Membrane is a complex barrier separating the cell from it's external environment. The "Selectively Permeable" Membrane regulates what passes into and out of the cell. Cell Wall • Plant cells have a cell wall. A Cell Wall DOES NOT REPLACE the Cell Membrane; Cells with WALLS also have a CELL MEMBRANE. Plant Cells are covered by a Rigid Cell Wall that lies Outside the Cell Membrane.