Ch. 7

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Ch. 7 Cell Structure and Function

• Life is Cellular

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Levels of Organization

• The levels of organization in a multicellular
  organism are individual cells, tissue, organs,
  and organ systems.
• Cells are an organisms basic unit
• Tissues are a group of cells working together.
  Example muscle tissue
• Organs are a group of tissues working together.
  Example the heart.
• Organ systems are a group of organs working
  together. Example the digestive system.

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The Discovery of the Cell

• Discovery of cells was possible with the
  invention of the microscope.
• In 1665 Robert Hooke was the first to use a
  microscope to look at cork cells.
• He called the boxes that he saw cells.

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• At the same time, Anton van Leeuwenhoek was the
  first to look at animals in pond water. He
  called these animals animalcules.

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• Soon, numerous observations made it clear that
  cells were the basic unit of life, and the cell
  theory was developed.
• The cell theory states
• All living things are composed of cells.
• Cells are the basic units of structure and
  function in living things.
• New cells are produced from existing cells.

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Exploring the Cell

• Electron microscopes
• Capable of revealing detail as much as 1000 times
  smaller than those visible with a light
  microscope.
• Two types
• Transmission electron microscopes cells and
  tissues must be sliced thin in order to be
  examined.
• Scanning electron microscopes specimens do not
  have to cut into thin slices.

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• TEM SEM

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• TEM images SEM images

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• Scanning Probe Microscopes
• Power that is so precise, that a single atom can
  be observed.

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Prokaryotes and Eukaryotes

• Prokaryotic cells Do not have a nucleus.
• They are generally smaller than eukaryotes.
• Bacteria are an example of a prokaryote.

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• Eukaryotic cells- contain a nucleus in which
  their genetic material is separated from the rest
  of the cell.
• Some eukaryotes are unicellular like protists.
• Most eukaryotes are multicellular, plants,
  animals, fungi.

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Topic Eukaryotic Cell Structure

• Chapter 7 section 2
• EQ What are the functions of each cell
  organelle?

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Comparing the Cell to a Factory

• In some ways, the eukaryotic cell is like a
  factory, it has many parts and functions.

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Cell Organelles

• Organelle means little organs, these are the
  main structures of the cell.
• Cytoplasm is the portion of the cell that is
  outside the nucleus. It is what other organelles
  float in, and what is used to transport messages
  between other organelles.

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• Nucleus this is the control center of the cell.
• The nucleus contains nearly all of the cells DNA
  and with it the coded instructions for making
  proteins and other important molecules.
• The nucleus is surrounded by a nuclear envelope.
  It is dotted with thousands of pores that allow
  material to move in and out.

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• The granular material in the nucleus is called
  chromatin.
• Chromatin consists of DNA bound to a protein, and
  will condense to form chromosomes.
• The nucleus also contains a nucleolus, which is
  where ribosomes are made.

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• Ribosomes
• Ribosomes make and assemble proteins.
• They get their instructions from the nucleus, and
  are found either free floating in the cytoplasm
  or on top of the endoplasmic reticulum.

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• Endoplasmic reticulum is the site where lipid
  components of the cell membrane are assembled,
  along with proteins and other materials that are
  exported from the cell.
• Endoplasmic reticulum with ribosomes on it is
  called rough ER. If it has no ribosomes it is
  called smooth ER.
• They are also involved in the detoxification of
  drugs in the body.

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• Golgi apparatus or golgi body the function is
  to modify, sort, and package proteins and other
  material from the endoplasmic reticulum for
  storage in the cell or secretion outside the
  cell.
• The golgi apparatus is kind of like the UPS of
  the cell.

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• Lysosomes are small organelles filled with
  enzymes.
• They break down lipids, carbohydrates, and
  proteins that can be used by the cells.
• They also break down dying organelles in the
  cell.

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• Vacuoles store materials like water, salts,
  proteins, and carbohydrates.
• Plants have huge vacuoles to store water.

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• Mitochondria are organelles that convert the
  chemical energy stored in food into compounds
  that are more convenient for the cell to use. In
  other words they make ATP, or energy.
• They have two membranes and their own DNA.

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• Chloroplasts are only found in plants, and
  their job is to convert energy from sunlight into
  food during photosynthesis.
• They contain the pigment chlorophyll which makes
  a plant green.

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• Cytoskeleton A network of protein filaments
  that helps the cell to maintain its shape. The
  cytoskeleton is also involved in movement.
• The cytoskeleton is made up of microfilaments and
  microtubules.

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Cell Boundaries

• Chapter 7, section 3

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Cell Membrane

• The cell membrane regulates what enters and
  leaves the cell and also provides protection and
  support
• The cell membrane is made up of a phospholipid
  bilayer.
• Meaning that the cell membrane has two layers.

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Cell Walls

• Cell walls are present in plants, algae, and
  fungi.
• Cell walls lie outside of the cell membrane.
• The main function of the cell wall is to provide
  support and protection for the cell.
• Cell walls are made up cellulose, which is what
  your paper is made of.

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Diffusion Through Cell Boundaries

• Diffusion when materials pass from an area of
  high concentration to an area of low
  concentration, until the system has reached
  equilibrium.
• Because diffusion depends upon random particle
  movements, substances diffuse across membranes
  with-out requiring the cell to use energy.

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Osmosis

• Osmosis is the diffusion of water through a
  selectively permeable membrane, or semipermeable
  membranes.
• Selective permeability means that some but not
  all substances can pass through the cell
  membrane, some require energy to get through the
  membrane. Osmosis and diffusion do not require
  energy.

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• How osmosis works-
• Some solutions are isotonic meaning that they
  have equal parts.
• Some are hypertonic meaning they have more solute
  than solvent.
• Some are hypotonic meaning they have more solvent
  than solute.
• REMEMBER OSMOSIS IS WATER MOVING FROM AN AREA OF
  HIGH CONCENTRATION TO AN AREA OF LOW
  CONCENTRATION.

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Facilitated Diffusion

• Facilitated diffusion is the movement of
  specific molecules across cell membranes through
  protein channels. Like sugar. Requires no
  energy.

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Active Transport

• Sometimes cells need to move substances from
  areas of low concentration to areas of high
  concentration.
• How cells do this is through active transport.
  This requires energy.
• Sometimes the transport of larger materials
  involves changes in the shape of the cell
  membrane.

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• Types of active transport
• Endocytosis is the process of taking material
  into the cell by means of infoldings, or pockets,
  of the cell membrane. Two types of endocytosis
  are
• Phagocytosis extensions of cytoplasm surround a
  particle and package it within a food vacuole.
  The cell then engulfs it.
• Pinocytosis process by which a cell takes in
  liquid from the surrounding environment.
• Exocytosis the forcing of material out of a
  cell.

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The Diversity of Cellular Life
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Unicellular Organisms

• A single celled organism is also called a
  unicellular organism
• In terms of numbers, Unicellular organisms
  dominate life on earth.
• Example - yeast

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Multicellular Organisms

• Some organisms (like yourself) are made up of
  many cells.
• Cells throughout a multicellular organism can
  develop in different ways to perform different
  tasks. This is called cell specialization.

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• Animal and plant cells are specialized in many
  ways.
• They can transport oxygen, make proteins, store
  food, and digest food.
• They also help organisms to move
• Plant cells help it to make food, and get rid of
  oxygen.