Chapter 7: Cell Structure and Function

2 The Discovery of Cells Early 1600s Robert Hooke uses an early compound microscope to look at cork. Anton van Leeuwenhoek uses a single lens microscope to look at microorganisms.

3 Cell Theory Schleiden and Schwann concluded that all plants and animals were made up completely of cells. The Cell Theory states that: All organisms are composed of one or more cells. The cell is the basic unit of organization and structure in all organisms. All cells come from pre-existing cells

Exploring the Cell New technology makes exploring cells in more detail possible We can now study the movement and structure in great detail Electron microscope can magnify cells even more visible light microscopes by using waves or beams of electrons 500,000X stronger! 4

5 Two Cell Types There are two basic cell types that you need to be aware of 1. Prokaryotes: Cells that lack internal membrane-bound structures. Genetic material that is NOT contained in a nucleus Single celled = Bacteria

6 2. Eukaryotes: Contain membrane- bound structures. Contain a NUCLEUS, in which their genetic material is placed Single and Multicellular organsims

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8 Eukaryotic Cell Structure Examples are plant and animal cells Structures inside cells act as specialized organs called Organelles

9 Eukaryotic Cell Structure Cytoplasm = portion of the cell outside the nucleus

10 Nucleus The nucleus contains almost all the cell’s DNA Nucleus is surrounded by a nuclear envelope

11 Nucleus Nuclear envelope composed of 2 membranes. Allows things to move in & out of the cell Contains Chromatin- uncoiled DNA Chromosomes contain genetic information that is passed from one generation of cells to the next Also contains the nucleolus- small dense region where ribosome assembly begins

12 Ribosomes Produce proteins Found in the cytoplasm Like a small machine in a factory

13 Endoplasmic Reticulum Lipid components of the cell membrane are assembled, along with protein and other materials that are needed from the cell

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15 2 types of E.R 1. Smooth ER: lacks ribosomes; produces lipids 2. Rough ER: contains ribosomes; helps with protein production

16 Golgi Apparatus Organelle that modifies, sorts and packages proteins from ER for use in the cell or secretion out of the cell Does this so they can be stored or shipped out of the cell

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18 Lysosomes Small organelles filled with enzymes Custodians of the cell Break down lipids, carbohydrates, proteins and small molecules Remove “junk” from cell

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20 Vacuoles Found in plants and some animals Store things (like water, salts, proteins, carbs) Single, large water vacuole in plants

21 Mitochondria Convert chemical energy into compounds for cell use “POWERHOUSE” Organelles in which food molecules are broken down (glucose) to produce energy. Shaped like tiny sausages. Inner membrane forms long, narrow folds called cristae.

22 Cytoskeleton: A network of thin, fibrous elements that provide support for organelles and helps the cell maintain its shape. Microfilaments: Thin, solid protein fibers. Microtubules: Thin, hollow cylinders of protein. Both work together to provide support.

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24 Cilia: Short, numerous, hair-like projections from the plasma membrane of the cell. Often beat synchronously(at the same time) to produce motion. Flagella: Long projections that move in a whip-like motion to produce movement. - Used by unicellular organisms Structures for Locomotion

25 Structures for Locomotion

26 Structures for Locomotion

27 Structures for Locomotion

28 Chloroplasts: Transform light energy into chemicals that can be used to produce food molecules. Mitochondria then change food molecules into energy. Chloroplasts are located in the cells of plants and some green one-celled organisms.

Cell Boundaries Cell membrane regulates what enters and leaves a cell. Phospholipid Bilayer: double layered sheet of 2 lipids thin flexible barrier Lets things in & out of the cell to promote homeostasis (called selective permeability)

30 Cell Membrane Structure form the main structure of the plasma membrane. Proteins are also embedded in this layer Stick out – Markers In PM – Gate way

31 Cell Membrane Structure

32 Fluid mosaic model : theory that the plasma membrane acts more like a liquid rather than a solid, made of many parts. because the lipid layers and proteins can move like fluid and yet still create an barrier against the outside environment.

33 Cell Wall cell wall Plant, fungi, most bacteria, and other cells have a Provides support and protection Cellulose

34 Diffusion Concentration = mass of solute per volume solvent -Universal solvent: _________ Diffusion = particles move from an area of high concentration to an area of low concentration

35 Diffusion Equilibrium: when the concentration of the solute is the same all over Substances diffuse across membrane without using energy! Passive Transport

36 Osmosis Diffusion of water through a selectively permeable membrane

37 How osmosis works….. Water wants to balance things out… Hypotonic (hippo)= more inside than outside Hypertonic = more out than in Isotonic = same strength

38 Osmotic Pressure AKA:Turgor Pressure Pressure exerted on cell walls by Vacuole

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40 Facilitated Diffusion When protein channels in the membrane “help” molecules pass through No energy needed! “helper proteins”

41 Active Transport Uses energy to move molecules from low to high concentration. Proteins act as pumps to move molecules

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43 Types of Active Transport Endocytosis: process of taking material into the cell through pockets in the membrane; pinched off from plasma membrane Exocytosis: when large amount of material are release from the cell

44 Types of Endocytosis 1. Phagocytosis: cell eating, cell engulfs material 2. Pinocytosis: cell drinking, using water to transport material

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46 Cellular Diversity Unicellular Organisms: single celled organism Examples: yeast, algae, bacteria Unicelluar organisms Dominate life on Earth

47 Multicellular Organisms Organisms made up of many cells Can develop in many different ways and perform different functions Cell must communicate and cooperate

48 Multicellular organisms Cell specialization: cell develop in a multicellular organism in different ways to perform different tasks Ex. Red blood cells, pancreatic cells

49 Levels of Organization Cells – Tissues --Organs ---Organ System