Chapter 7 Cellular Structure Function 7 1 Cell

Chapter 7 Cellular Structure & Function • • 7. 1 Cell Discovery & Theory 7. 2 Plasma Membrane 7. 4 Cellular Transport 7. 3 Structures & Organelles

7. 1 Cellular Discovery & Theory. History of the Cell Theory: • 1665, Robert Hooke made a simple microscope • What is a cell? - A cell is the basic structural and functional unit of all living organisms

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

Microscope Technology • Compound Light Microscope • Utilizes a series of glass lenses and visible light to produce a magnified image • Maximum magnification is around 1000 X.

Electron Microscope • Transmission Electron Microscope = Form images using electrons that are transmitted through a specimen. • Scanning Electron Microscope= utilize electrons that have bounced off the surface of the specimen.

Basic Cell Types • 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

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

Differences between Eukaryotic and Prokaryotic Cell • Prokaryotic Cell -No Nucleus. - No membrane covered organelle. - Circular DNA in a circle. - Found in bacteria. • Eukaryotic Cell -Nucleus -Membrane bound organelle. -Linear DNA in a line. -All other cells.

Plasma Membrane • 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

Other Components of the Plasma Membrane • 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)

Proteins

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

Carbohydrates • Help cells identify chemical signals

Fluid Mosaic Model • The components of the plasma membrane are in constant motion (fluid) • The different substances in the plasma membrane creates a pattern (mosaic) on the surface

7. 4 Cellular Transport Ms. Idris

Passive Transport • Movement of particles across the cell membrane without using energy is passive transport.

Diffusion • Movement of particles from an area of high concentration to an area of lower concentration • Diffusion Rate Factors – Concentration – Temperature – Pressure

Dynamic equilibrium • Reached when diffusion of material into the cell equals diffusion of material out of the cell • Molecules continue to move, but the overall concentration remains the same.

Diffusion in a cell

Facilitated Diffusion • Movement of materials across the plasma membrane using transport proteins – Channel proteins-water filled transport protein that opens and closes to allow the substance to diffuse through the plasma membrane – Carrier proteins – change shape to move particles through the membrane

Channel Proteins

Carrier Proteins

Osmosis • Diffusion of water across a selectively permeable membrane • Three types of solutions – Isotonic – the cell is at equilibrium – Hypotonic – lower concentration of solute – Hypertonic – higher concentration of solute

Isotonic Solution • Water and dissolved substances diffuse into and out of the cell at the same rate.

Hypotonic Solution • Solute concentration is higher inside the cell • Water diffuses into the cell • Cell swells and may burst

Hypertonic Solution • Solute concentration is higher outside the cell • Water diffuses out of the cell • Cell wilts or shrinks

Active Transport • Requires energy to move substances against a concentration gradient or from low to high concentration • Active transport using carrier proteins or pumps to maintain cell homeostasis. Ex. Na+/K+ ATPase Pumps – moving 3 Na+ ions out of the cell and 2 K+ ions into the cell

Transport of Large Substances • Endocytosis - Process by which the cell surrounds and takes particles into the cell • Exocytosis - Secretion of material out of the plasma membrane

7. 3 “Structures and Organelles” Ms. Idris

Cytoplasm • Cytoplasm - a semi-fluid material that constitutes the environment inside the plasma membrane (Plant & Animal Cells)

Cytoskeleton • 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).

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 – Regulates movement of molecules in and out of the nucleus. – Nuclear pores – Transports ribosomal proteins from the nucleus to the cytoplasm. – Nucleolus – site of ribosome production – Chromatin – Material in the cell that contains DNA and carries genetic information to the cell.

Ribosomes

Cell Wall • A Cell Wall is the 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.

Cellular Projections • The Cilia is a hair-like cellular projection that functions in movement both of an organisms and of moving particles. (Some Animal Cells). • The Flagella is a whip-like tail cellular projection that is long and help movement in unicellular organisms and some individual cells such as the sperm on the right. (Some Animal Cells)