History of the Cell Theory 1665 Robert Hooke

History of the Cell Theory • 1665, Robert Hooke made a simple microscope • Cell-the basic structural and functional unit of all living organisms • Late 1600’s Anton Van Leeuwenhoek designed his own microscope

The Cell Theory • Fundamental idea of modern biology that includes these three principles: v. All living organisms are composed of one or more cells v. Cells are the basic unit of structure and organization of all living organisms v. Cells arise only from previously existing cells, with cells passing copies of their genetic material on to their daughter cells

Basic Cell Facts • Cells exists in various shapes and sizes • Cells differ based on their function they perform for the organism • All cells have at least one physical trait in common - the plasma membrane

Categories of Cells 1. Prokaryotic Cells – Cells without specialized internal structures – Unicellular – Similar to the first organisms on Earth

2. Eukaryotic Cells v. More complex than prokaryotic cells v. Contain a structure called a nucleus (a distinct central organelle that contains the cell’s genetic material in the form of DNA) and other organelles (specialized structures that carry out specific cell functions) v. Generally one to one hundred times larger than prokaryotic cells

7. 2 The Plasma Membrane • Main idea: The plasma membrane help’s to maintain a cell’s homeostasis • Objectives: – Describe how a cell’s plasma membrane functions (in left column of Cornell notes) – Identify the roles of proteins, carbohydrates, and cholesterol in the plasma membrane (in left column of Cornell notes) • Review Vocabulary – Ion: an atom or group of atoms with a positive or negative electric charge

Plasma Membrane • Found in all cells • Primarily responsible for homeostasis in the cell • A thin, flexible boundary between a cell and its environment that allows nutrients into the cell and allows waste and other products to leave the cell

Selective Permeability • A key property of the plasma membrane which allows some substances to pass through while keeping others out • Controls the substances in and out of the cell

Plasma Membrane Structure • The plasma membrane is composed of the phospholipid bilayer. • Phospholipid is a molecule that has a glycerol backbone, two fatty acid chains, and a phosphate-containing group • Phospholipid bilayer is two layers of phospholipids arranged tail to tail

Plasma Membrane Structure

Plasma Membrane Structure • Phosphate group makes the head polar and are hydrophilic (mix with water) • The two fatty acid tails are non-polar and hydrophobic (repel, not mix with water) • The phospholipids are arranged in such a way that the polar heads can be closest to the water molecules and the non-polar tails can be farthest away from the water molecules

Components of the Plasma Membrane A. Proteins – Transmit signals inside the cells (receptor proteins) – Acts as a support structure to give the cell its shape – Provide pathways for substances to enter and leave the cell (transport proteins)

B. Cholesterol § Prevents fatty acid tails of the phospholipid bilayer from sticking together § Helps maintain cell homeostasis

C. Carbohydrates • Help cells identify chemical signals

Eukaryotic Cell Structures & Organelles • Main idea: Eukaryotic cells contain organelles that allow the specialization and the separation of functions within the cell. • Objectives – Identify the structure and function of the parts of a typical eukaryotic cell (add to left column of Cornell Notes) – Compare and contrast structures of plant and animal cells (add to left column of Cornell Notes) • Review vocabulary – Enzymes: a protein that speeds up the rate of a chemical reaction.

Cytoplasm and Cytoskeleton • Cytoplasm - a semi-fluid material that constitutes the environment inside the plasma membrane (Plant & Animal Cells) • Cytoskeleton - a supporting network of long, thin protein fibers that form a framework for the cell and provide an anchor for the organelles inside the cell (Plant & Animal Cells)

Cytoskeleton • A framework for the cell within the cytoplasm that rapidly assemble and disassemble and slide past one another. This allows cells and organelles to move. – Microtubules-long, hollow protein cylinders that form a rigid skeleton for the cell and assist in moving substances within the cell – Microfilaments-thin protein threads that help give the cell shape and enable the entire cell or parts of the cell to move

Cytoskeleton

Cell Structures • Nucleus - brain of the cell; directs the cell processes (Plant & Animal Cells) – Contains most of the cell’s DNA, which stores information used to make proteins for cell growth, function, and reproduction – Nuclear envelope - double membrane with nuclear pores that surrounds the nucleus – Nuclear pores - allow larger-sized substances to move in and out of the nucleus – Nucleolus – site of ribosome production – Chromatin – the complex DNA attached to protein; spread throughout the nucleus

Nucleus

Ribosomes • Ribosomes - are the most numerous of the cell’s organelles (Plant & Animal Cells) • The ribosome is the site of protein synthesis. (Protein factories) • Composed of RNA & protein • The concentration or distribution of ribosomes in the cells depends on how the proteins they produce will be used. • Proteins used by the cells are made by free floating ribosomes. • Exported proteins are made by ribosomes that are attached to the ER.

Ribosomes

Endoplasmic Reticulum (ER) • The “ER” is a membrane system of folded sacs and tunnels (Plant & Animal Cells) • Rough ER are covered with ribosomes • Smooth ER have little or no ribosomes and function primarily as an intercellular highway, a path which molecules can move from one part of the cell to another – Also the site of carbohydrate and lipid synthesis

ER

Golgi Apparatus • The processing, packaging and secreting organelle of the cell (Plant & Animal Cells) • Notice that the Golgi Apparatus consists of a stack of membranes. • It operates like a production line in a factory, where a product is assembled at one end, then packaged, and finally shipped out. • The protein vesicle is modified as it passes from sac to sac. Finally it is released to be sent out of the cell.

Golgi Apparatus

Vacuole • A membranebound vessicle for the temporary storage of materials • Plant cells-one large; Animal cells-a few small

Lysosomes • organelles that contain powerful digestive enzymes (Animal Cells Only) • They destroy foreign bodies that get into the cell • They also digest food vacuoles to help feed the cell • They destroy the cell when it is too old or damaged. This is why they are sometimes called the “suicide sacs of the cell”

Lysosomes

Centrioles • tiny t-shaped structures in the cell that function in helping the cell when it divides to form two new cells (Animal Cells and most Protists) • Protists – single celled organisms

Mitochondria • They provide energy for the cell. • respiration centers of the cell (Plant and Animal Cells) • They are called the “powerhouse of the cell” • Mitochondria have their own DNA. • The number of mitochondria in a cell depends on the needs of the cell.

Mitochondria

Chloroplasts • organelle responsible for making food (Plants Cells Only) • This process is called photosynthesis. • They use sunlight + Water + Carbon dioxide and make glucose (sugar). • The waste product of this is oxygen and water vapor.

Cell Wall • rigid covering of a plant cell that provides shape and protection (Plant Cell Only) • It is made primarily of cellulose (carbohydrate) • Pores in the cell wall allow ions and molecules to pass to and from the cell membrane.