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Introduction to Biology Chapter 3 Notes_ Cell Structure and Function

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					Introduction to Biology Chapter 3 Notes: Cell Structure and Function

Mr. Grivensky/Mr. Rutkoski

3-1 Early Microscopes

 In the 1600s, a Dutch glassmaker named Anton van Leeuwenhoek discovered that if he placed several magnifying lenses at the proper distances from each other he could greatly magnify small objects.

van Leeuwenhoek is given credit for creating the first microscopes

“Cell Theory Scientists”
 Robert Hooke, an English physicist, at about the same time as Leeuwenhoek, was using a microscope to observe flowers, insects, and slices of cork. In 1665, Hooke published a book of his drawings and named the chambers he observed in plant samples, “cells”. He chose this name because they reminded him of the tiny rooms in a monastery, which are also called cells. Hooke believed that only plants were made up of cells, as did most scientists of his time and nearly 200 years later.  In 1839, a German biologist, Theodor Schwann found that animal tissues also had cell-like structures which lead him to the conclusion that animals were made up of cells also.



..more “Cell Theory Scientists”
 Around the same time as Schwann made his discovery, Robert Brown, a Scottish biologist had found that cells had a structure near the center. We now call this structure the nucleus.  German biologist, Matthias Schleiden, suggested that the nucleus played a role in cell reproduction.  In 1855, German physicist, Rudolf Virchow, studied cell reproduction further and proposed that animal and plant cells were produced by the division of existing cells.

Cell Theory
 The discoveries of these scientists are summarized in the cell theory.  Cell Theory states that:
 A. All living things are composed of cells  B. Cells are the smallest working units of living things  C. All cells come from preexisting cells by cell division

Modern Microscopes
 Compound light microscope  Uses more than one lens to magnify objects  Can magnify an image up to 1000 times  These are what we use at Wyoming Area  Cells and organisms can be studied while they are still alive

Electron Microscopes: TEM
 Use magnets to focus a beam of electrons, much like a television  The beam of electrons can be used to examine a sample  Electron microscopes can magnify 1000x larger than a light microscope (100,000 times) Transmission Electron Microscope (TEM)  Shines a beam of electrons through a sample, and then projects the image onto a fluorescent screen

Electron Microscopes: SEM
Scanning Electron Microscope (SEM)  Uses a beam of electrons to scan the surface of a sample. The SEM collects the electrons that bounce off the sample, and forms an image on a television screen  Both, TEMs and SEMs can only observe nonliving specimens. These specimens must be sliced very thin for use in a TEM, and the SEM only shows the outer surface of the specimen

SEM & TEM Photos

SEM

TEM

Scanning Probe Microscope
 In the early 1980s, the scanning probe microscope was invented  It does not use any lenses, and instead traces the surface of an object with a probe  These microscopes have been used to photograph molecules and atoms.

3-2 Cell Boundaries
 Every cell has a cell membrane along its boundary.  The principal role of the cell membrane is to separate and protect the cell from its surroundings.  The cell membrane is said to be selectively permeable

Selectively Permeable
 Selectively Permeable means that the cell membrane allows some substances through but denies passage to other substances

Lipid Bilayer
The cell membrane is composed of a phospholipid bilayer. A phospholipid has a polar end called the head and a nonpolar end called the tail. The polar heads group together on the outside of the lipid bilayer. The nonpolar heads group together on the inside of the bilayer because they avoid water. The lipid bilayer provides the cell membrane with a tough, flexible barrier that protects the cell from substances.

Cell Membrane

Cell Wall
Found in plants, algae, and bacteria. Located outside the cell membrane. Helps to support and protect the cell. Made up of carbohydrates and protein. The principle carbohydrate is cellulose.  Cellulose provide the cell with rigidity and strength.    

Cell Wall

Passive Transport
 Substances cross the cell membrane without the cell expending energy  Examples1. Diffusion 2. Facilitated Diffusion 3. Osmosis

Diffusion
 Diffusion is the process by which substances spread throughout a liquid or gas.  In diffusion, substances move from regions of high concentration to regions of low concentration

Diffusion

Facilitated Diffusion
 Substances diffuse across the cell membrane through special channels in protein  Example is glucose

Osmosis
 The diffusion of water through a selectively permeable membrane

Hypertonic Solution
 Hypertonic Solution: Solute concentration of solution higher than cell
 More dissolved particles outside of cell than inside of cell  Hyper = more (think hyperactive); Tonic = dissolved particles  Water moves out of cell into solution  Cell shrinks

Hypertonic Solution

Hyoptonic Solution
 Hypotonic Solution: Solute concentration of solution lower than cell
 Less dissolved particles outside of cell than inside of cell  Hypo = less, under (think hypodermic, hypothermia); Tonic = dissolved particles  Water moves into cell from solution  Cell expands (and may burst)

Hypotonic Solution

Isotonic Solution
 Isotonic Solution: Solute concentration of solution equal to that of cell
 No net water movement

Isotonic Solution

Active Transport
 Requires energy  The movement of substances against a concentration gradient  Similar to a pump.  Examples
1. Endocytosis 2. Phagocytosis 3. Exocytosis

3-3 Inside the Cell
 There are two categories of organisms: prokaryotes and eukaryotes  Prokaryotes- organisms that do not contain nuclei and membrane bound organelles (ex.bacteria)  Eukaryotes- organisms that contain a nucleus and organelles

Nucleus
 Control center of the cell  Large and dense  Contains nearly all of the cell’s DNA

DNA
 Contains coded instructions for making proteins  DNA wrapped around special proteins(histones) is known as chromatin  Chromatin condenses to form chromosomes

Chromatin/Chromosomes

Structures in the Nucleus
 Nucleolus- small, dense region found in the nucleus; ribosomes are assembled here  Nuclear envelope- two distinct membranes that contain many holes called nuclear pores

Structures of the Nucleus

Cytoplasm
 Portion of the cell outside of the nucleus  Fluid like material that contains organelles  Organelles-small structure that performs a specialized function within the cell

Organelles
      Ribosomes Rough Endoplasmic Reticulum Smooth Endoplasmic Reticulum Golgi Apparatus Lysosomes Cytoskeleton
1. Microtubules 2. Microfilaments

Organelles- continued
       Cilia Flagella Vacuoles Centrioles Plastids Mitochondria Chloroplast

Ribosomes
 Ribosomes Protein and RNA complex responsible for protein synthesis

Rough Endoplasmic Reticulum
 Rough endoplasmic reticulum (RER) A network of interconnected membranes forming channels within the cell. Covered with ribosomes (causing the "rough" appearance) which are in the process of synthesizing proteins.

Smooth Endoplasmic Reticulum
 Smooth endoplasmic reticulum (SER) A network of interconnected membranes forming channels within the cell. A site for synthesis and metabolism of lipids.

Golgi Apparatus
 Golgi apparatus A series of stacked membranes. Vesicles (small membrane surrounded bags) carry materials from the RER to the Golgi apparatus. Vesicles move between the stacks while the proteins are "processed" to a mature form.

Lysosomes
 Lysosymes A membrane bound organelle that is responsible for degrading proteins and membranes in the cell, and also helps degrade materials ingested by the cell.

Cytoskeleton

 The cytoskeleton extends through out the cytoplasm. Composed of protein fibers called intermediate filaments, microtubules and microfilaments, the cytoskeleton maintains cell shape, allows the cell to move, and moves structures within the cell.

Cilia and Flagella
 Plant cells do not have cilia and flagella. Both are anchored in the cytoplasm by centrioles and extend from the outside surface of the plasma membrane. Flagella are used to propel the cell. Cilia can be used to propel the cell, or move fluids past the cell.

Cilia and Flagella

Vacuole
 Vacuoles Membrane surrounded "bags" that contain water and storage materials in plants.

Centrioles

 A centriole is a short, barrel shaped ring composed of nine microtubules around an empty center. Centrioles are found only in animal cells. They are arranged in pairs that sit perpendicular to one another.

Plastids

 Plastids are a storage organelle unique to plant cells and some photosynthetic protists. They are not found in animal cells. Located in the cytoplasm, the plastids are used to store substances such as pigments and starches.

Mitochrondria
 Mitochondria Surrounded by a double membrane with a series of folds called cristae. Functions in energy production through metabolism. Contains its own DNA.

Chloroplast
 Chloroplasts (plastids) Surrounded by a double membrane, containing stacked thylacoid membranes. Responsible for photosynthesis, the trapping of light energy for the synthesis of sugars.

Animal Cell

Plant Cell


				
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posted:11/9/2009
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