The Discovery of Cells: Understanding Cell Structure and Function

Cell Structure & Function Chapter 4 Miss Colabelli

The Discovery of Cells • All living things are made up of one or more cells • A cell is the smallest unit that can carry out life processes

The Discovery of Cells • Robert Hooke • English scientist that studied nature using a light microscope • Looked at thin slices of cork from bark on a cork oak tree • Noted there were empty pores throughout the specimen that resembled cells the monks would live in • Noticed other plant specimen had the same organization of boxes

The Discovery of Cells • Anton van Leeuwenhoek • First person to observe living cells • Made his own light microscope • Observed microorganisms such as algae and protists

The Discovery of Cells • The Cell Theory • A composition of understandings from different scientists that all cells must go by • All living things are composed of one or more cells • Cells are the basicunits of structure and function in an organism • Cells come only from the reproduction of pre-existing cells

Developments in Cell Biology • Timeline history of cells

The Cellular Basis of Life • Microscopes helped biologists clarify the definition of life • All cells carry out the same characteristics that categorize it as being alive • 7 characteristics of life

Cell Diversity • Cell Shape • Reflects the function and location of the cell

Cell Diversity • Cell Size • Cells are limited by the relationship of their outer surfacearea to its volume • As a cell grows, its volume increases much faster than the surface area • Important to know because nutrients and wastes need to move though the cell efficiently • A cell too large would take too long to diffuse these materials and it can harm the cell • Most cells are better off being smaller and keeping their surface area to volume ratio bigger

Plasma Membrane • Cell’s outer boundary • Covers the cell’s surface and acts as a barrier between inside and outside of the cell • Cytoplasm • Area within the cell that contains the fluid, cytoskeleton, and the organelles • Nucleus • Membrane-bound area of the cell that contains genetic information • Controls the function of the cell

Two Basic Types of Cells Eukaryote Contain a membrane-bound nucleus and organelles with membranes Organelles carry out functions for the cell Usually plant and animal cells Prokaryote • Organisms that lack a membrane-bound nucleus and membrane-bound organelles • General area of cell where genetic information is located is called the nucleoid • Usually bacteria and archaea

http://www.wiley.com/legacy/college/boyer/0470003790/animations/cell_structure/cell_structure.htmhttp://www.wiley.com/legacy/college/boyer/0470003790/animations/cell_structure/cell_structure.htm

Plasma Membrane • Membrane Lipids • Made of two layers of phospholipids (phospholipid bilayer) • Membrane Proteins • Specific proteins embedded in the lipid bilayer • These proteins help with transporting molecules across the membrane and act as receptors • Send messages to the rest of the cell

Inner life of the cell http://www.youtube.com/watch?v=B_zD3NxSsD8

Nucleus • Houses and protects the cell’s genetic information • Contains instructions for the structure and function of the organism • Before a cell divides, the DNA condenses to form chromosomes • Nuclear envelope • Double membrane that surrounds the nucleus • Made of two phospholipid bilayers • Contains pores (holes) called nuclear pores for RNA and other materials to enter and leave the nucleus • Nucleolus • Dense area in the nucleus where DNA is concentrated • Where ribosomes are produced

Mitochondria • Organelles that transfer energy from organic matter (foods) to ATP • ATP powers most of the cell’s chemical reactions • Highly active organelles • Two layer of membrane • Outer membrane holds cytosol • Inner membrane has folds called cristae where energy-harvesting chemical reactions take place http://www.youtube.com/watch?v=Ju0HxI5GWTo

Mitochondria • Mitochondrial DNA • Have their own DNA and reproduce on their own • Scientists think mitochondria originated from prokaryotic cells and were incorporated into eukaryotic cells • Called the endosymbiotictheory http://www.sumanasinc.com/webcontent/animations/content/organelles.html

Ribosomes • Small, spherical organelles that are responsible for synthesizing proteins • Do not have a membrane • Made of protein and RNA molecules • Synthesized in the nucleus • Made of two subunits • Some are free in the cytoplasm and some are attached to another organelle called the endoplasmic reticulum

Endoplasmic Reticulum (ER) • System of membranous tubes • Functions as a highway for molecules to move throughout the cell • Two types of ER • Rough ER • Smooth ER

Rough Endoplasmic Reticulum • System of interconnected tubes covered with ribosomes • Ribosomes make it look “rough” • Area where some proteins are made

Smooth Endoplasmic Reticulum • Lacks ribosomes and looks smooth • Builds lipids like cholesterol and hormones for the body • Helps detoxify drugs and poisons • Liver cells contain a high amount or smooth ER cells • Long-term drug and alcohol users also increase their smooth ER organelles in their cells

Golgi Apparatus • System of flattened sacs • Sacs near the nucleus receive vesicles from the ER that contain newly made proteins and lipids • Vesicles travels through the Golgi • Golgi apparatus “stamps” the vesicles to where they need to travel to in the cell • Like address labels

Vesicles • Small sphere like sacs that are surrounded by a single membrane • Lysosomes • Vesicles that bud from the Golgi and contain enzymes that break down large molecules • Also help break down cells when it is time for the cell to die • Peroxisomes • Similar to lysosomes except contain different enzymes • Neutralize radicals and detoxify alcohol and drugs • Produce hydrogen peroxide as a product in their chemical reactions http://www.stolaf.edu/people/giannini/flashanimat/cellstructures/microtubuletransport.swf

Cytoskeleton • Network of thin tubes and filaments that crisscross the cytosol • Give the cell its shape • Like poles in a tent • Internal tracks where items in the cell move around the cell • Three different types of tubes found in the cytoskeleton • Microtubules • Microfilaments • Intermediate filaments

Microtubules • Hollow tubes made of protein called tubulin • Radiate outward from the center called centrosome near the nucleus • Hold organelles in place • Maintain cell shape • Act as tracks to guide organelles and molecules as they move within the cell

Microfilaments • Smaller than microtubules • Long threads of bead like protein called actin • Contribute to cell movement • Crawling white blood cells • Muscle contraction

Intermediate Filaments • Rods that anchor the nucleus and organelles in place • Maintain internal shape of the nucleus • Make up most of the hair shaft

Cilia and Flagella • Hair like structures that extend from the surface of the cell • Assist in movement • Cilia • Short and present in large numbers • Flagella • Long extensions of the cell, usually one that helps with the cell moving

Centrioles • Two short cylinders of microtubules at right angles to each other • Near the nuclear envelope • Occur only in animal cells • Organize microtubules of cytoskeleton during cell division

Plant Cells • Most of the organelles and parts of the cell are in all eukaryotic cells • Plants have three additional structures • Cell wall • Central vacuole • Plastids

Cell Wall • Rigid layer that lies outside the cell’s plasma membrane • This cell wall is composed of the polysaccharide cellulose • Primary cell wall • On top of the plasma membrane • Can grow in one direction • Secondary cell wall • Between the plasma membrane and the primary cell wall • Does not grow

Central Vacuole • Reservoir that stores large amounts of water, enzymes, wastes, and other materials • Large, fluid filled organelle • May take up 90% of the cell’s volume • When there is a lot of water the vacuole fills up • When there is little water the vacuole deflates

Plastids • Double membrane organelles and contain their own DNA • Chloroplasts • Use light energy and water to make food and oxygen • Used in photosynthesis • Chromoplasts • Contain colorful pigment • May take part in photosynthesis • Give the plant its color

Comparing cells Eukaryote Have a nucleus Membrane-bound organelles Plant and animal cells Prokaryote • Lack a nucleus • No membrane-bound organelles • Region called nucleoid • Bacteria and archaea

Comparing Cells Animal Cell No cell wall No vacuole Contain centrioles Plant cell • Cell wall • Large central vacuole • Contain plastids

The Discovery of Cells: Understanding Cell Structure and Function