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 In human body some of our cells are called erythrocyte (red blood cells), megakaryocyte (bone marrow cells that produce thrombocytes such as platletes needed for normal blood clotting), monocyte (white blood cells), connective tissue macrophages (cells that go out and eat bacteria ), skin cells known as epidermal Langerhans cells (skin cells), osteocytes (bone cells).

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 Cell theory basically states that all living things have cells.

Microscope Technology Compound Light Microscope Utilizes a series of glass lenses and visible light to produce a magnified image Maximum magnification is around 1000X. Electron Microscope Utilizes magnets to aim a beam of electrons at a cell to produce images Specimens must be nonliving

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 They lack organelles or other internalmembrane-bound structures. Therefore, they do not have a nucleus, but, instead, generally have a singlechromosome: a piece of circular, double-strandedDNA located in an area of the cell called the nucleoid.

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. PC = Ecoli, Streptoccous, Staphloccus EC = Protists, Plants, Animals and fungi

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) Cytoplasm = The jelly-like fluid that fills a cell is called cytoplasm. It is made up of mostly water and salt. The motion transports nutrients, proteins, and organelles within 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). The cytoskeleton has a variety of functions including, giving shape to cells lacking a cell wall, allowing for cell movement, enabling movement of organelles within the cell, endocytosis (A process of cellular ingestion by which the plasma membrane folds inward to bring substances into the cell.), and cell division (the division of a cell into two daughter cells with the same genetic material.). intermediate filaments is to provide mechanical support for the plasma membrane where it comes into contact with other cells or with the extracellular matrix. They also serve a transportation function, as they are the routes upon which organelles move through the cell.  Microfilaments in muscle tissue. They are called myofibrils when you find them in muscles. The two proteins myosin and actin work together to help the muscle cells relax and contract.

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 are the most numerous of the cell’s organelles (Plant & Animal Cells) The ribosome is the site of protein synthesis. (Protein factories)

Ribosomes

Powerhouse of the cell. Ex: Muscles in the heart.

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. Cellulose is an indigestible type of polysaccharide plant fiber.

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)