Chapter 7 Notes
7-1
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The cell theory states that all living things are composed of cells, cells are the basic units of
structure and function in living things, and new cells are produced from existing cells.
Prokaryotic cells have genetic material that is not contained in a nucleus. Eukaryotic cells contain a
nucleus in which their genetic material is separated from the rest of the cell.
1. 1665- Robert Hooke looked at slice of cork, calling the many chambers “cell”.
2. Researchers can use fluorescent labels and light microscopy to follow molecules moving
through cell. Confocal light microscopy makes it possible to build 3-D images of cells.
High-resolution vide tech makes it easy to produce movies of cells.
3. Transmission electron microscopes can explore cell structures and large protein molecules,
but cells and tissues must be cut into ultrathin slices before they can be examined.
4. Scanning electron microscopes produces 3-D images of cells, but samples in both types of
microscopes have to be placed in a vacuum, but SEM’s don’t have to be cut. Electron
microscopy can be used to visualize only nonliving, preserved cells and tissues.
5. Typical cells range from 5-50 micrometers in diameter. All cells have 2 characteristic is
common; they are surrounded by a cell membrane, and they contain DNA. Cells fall into 2
broad categories, depending on whether they can a nucleus: Eukaryotes (contain nucleus)
or Prokaryotes (no nucleus).
6. Prokaryotic cells are smaller and simpler than eukaryotic cells. Some prokaryotes contain
internal membranes. Despite simplicity, prokaryotes carry out every activity associated with
living things: grow, reproduce, respond to environment, some can move. Bacteria is
prokaryote.
7. Eukaryotic cells are larger and more complex than prokaryotic cells. They contain dozens
of structures and internal membranes, and are highly specialized, as well as display great
variety. Some eukaryotes live solitary lives as single-celled organisms, others form large
multicellular organisms. Plants, animals, fungi, protists are eukaryotes.
7-2
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The nucleus contains nearly all the cell’s DNA and the coded instructions for making proteins and
other important molecules.
Proteins are assembled on ribosomes.
One type of endoplasmic reticulum makes membranes and secretory proteins. The other type of
ER makes lipids and helps to detoxify, or remove harmful substances.
The Golgi apparatus modifies sorts, and packages proteins and other materials from the
endoplasmic reticulum for storage or secretion outside the cell.
Mitochondria convert the chemical energy stored in food into compounds that are more convenient
for the cell to use.
Chloroplasts capture the energy from sunlight and convert it into chemical energy.
The cytoskeleton is a network of protein filaments that helps the cell to maintain its shape. The
cytoskeleton is also involved in movement of materials within and outside the cell.
1. Cell biologists divide the eukaryotic cell into 2 major parts: nucleus cytoplasm. Nucleus is
control center of cell; it is surrounded by a nuclear envelope composed of 2 membranes.
Steady stream of proteins, RNA, and other molecules move through the nuclear pores to
and from the rest of cell. Chromatin spread throughout the nucleus, but when cell divides,
chromatin condenses to form chromosomes. Nucleolus is where assembly of ribosomes
begins.
2. Ribosomes produce proteins by following instructions from nucleus. Cells active in protein
synthesis often packed w/ ribosomes.
3. Eukaryotic cells contain internal membrane system called endoplasmic reticulum (ER). Part
of ER involved in synthesis of proteins is rough ER, ribosomes are on surface. Newly made
proteins leave these ribosomes and are inserted into rough ER, where they may be
chemically modified. Proteins that are released from cell are synthesized on rough ER.
Rough ER is abundant in cells that produce large amounts of protein for export.
4. Other portion of ER is smooth ER because ribosomes aren’t found on surface. Smooth ER
contains collections of enzymes that perform specialized tasks, including synthesis of
membrane lipids and detoxification of drugs. Liver cells contain large amounts of S. ER.
5. Golgi apparatus (discovered by Camillo Golgi) appears as stack of closely apposed
membranes. From Golgi appartatus, proteins are then “shipped” throughout the cell or
outside of the cell.
6. One function of lysosomes is the digestion of lipids, carbs, and proteins into small
molecules that can be used by rest of cell. They are also involved in breaking down
organelles that have outlived their usefulness. They remove “junk” that otherwise might
accumulate and clutter up cell.
7. In plant cells, single large central vacuole filled with liquid. Pressure of central vacuole in
these cells makes it possible for plants to support leaves and flowers. Vacuoles found in
some single-celled organisms and in some animals. Contractile vacuole pumps out excess
water. Homeostasis is maintenance of controlled internal environment.
8. All living things require source of energy. Mitochondria are enclosed by 2 membranes. In
humans, all of our mitochondria come from cytoplasm of the ovum, or egg cell.
9. Chloroplasts are biological equivalents of solar power plants. They are surrounded by 2
membranes. Inside the organelle are large stacks of other membranes, which contain green
pigment chlorophyll.
10. Chloroplasts and mitochondria contain their own genetic info in form of DNA molecules.
One group of prokaryotes had ability to use oxygen to generate ATP, evolving into
mitochondria. Other prokaryotes carried out photosynthesis evolved into chloroplasts.
This idea is called endosymbiotic theory.
11. Cytoskeleton helps support the cell. Microfilaments and microtubules are 2 principal
protein filaments that make up cytoskeleton. Microfilaments are structures made up of
actin. They form extensive networks in cells and produce a tough, flexible network that
support cell. Microfilaments help cell move.
12. Microtubules are hollow structures made of tubulin, maintaining cell shape. They also
important in cell division, forming the mitotic spindle, which helps separate chromosomes.
In animal cells, tubulin used to form centrioles (not found in plant cells).
13. Microtubules help build projections called cilia and flagella that enable cells to swim
through liquids; Cilia and flagella produce considerable force.
7-3
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All cells have a cell membrane. The cell membrane regulates what enters and leaves the cell and
also provides protection and support. Some cells also have cell walls. Cell walls provide additional
support and protection.
Diffusion causes many substances to move across a cell membrane but does not require the cell to
use energy.
Osmosis is the diffusion of water through a selectively permeable membrane.
1. There are 2 layers of lipids in a cell membrane (lipid bilayer) which gives cell membranes a
flexible structure that forms a barrier between cell and its surrounding. Cell membranes
contain protein molecules embedded in lipid bilayer. Carb molecules attached to proteins.
Proteins form channels/pumps that help move material across cell membrane. Carbs allow
individual cells to identify one another.
2. Cell walls are porous enough to allow water, oxygen, carbon dioxide to pass through easily;
cell walls made from fibers of carbs and protein which are produced within cell and
released at surface of cell membrane. Plant cell walls composed mostly of cellulose.
3. One of most important functions of cell membrane is to regulate movement of dissolved
molecules from liquid on one side of membrane to liquid on other side.
4. Cytoplasm of cell contains solution of different substances in water. Concentration is mass
of solute in given volume of solution (mass/volume)
5. When concentration of solute same throughout a system, system reached equilibrium. If
substance can cross cell membrane, its particles will tend to move toward area where its
less concentrated until equilibrium is reached. Even when equilibrium is reached, particles
of solution will continue to move across membrane in both directions.
6. If substance is able to diffuse across membrane, it is said to be permeable to it. A
membrane is impermeable to substances that can’t pass across it. Water passes easily
across most membranes though many solute molecules can’t, Osmosis. Water will tend to
move across membrane until equilibrium is reached, so concentrations of water and sugar
will be same on both sides, which is isotonic.
7. Osmosis exerts pressure known as osmotic pressure on hypertonic side of a permeable
membrane. Osmotic pressure can cause problem for cell b/c cell is filled with salts, sugars,
proteins, it will always be hypertonic to fresh water, causing volume of cell to increase,
causing cell to burst.
8. Cell membranes have protein channels that make it easy for certain molecules to cross
membrane, which is called facilitated diffusion, which is fast and specific. A net movement
of molecules across cell membrane occurs only if there is higher concentration of molecules
on one side than on the other side.
9. Active transport requires energy; in small molecules/ions, it is carried out by transport
proteins found in the membrane. Larger molecules and clumps can be actively transported
across cell membrane by endocytosis and exocytosis.
10. Many cells use proteins to move calcium, potassium, sodium ions across cell membranes.
Changes in protein shape play important role in pumping process. Lots of energy used by
cells in daily activities devoted to providing energy to keep active transport working.
11. Larger molecules and solid clumps of material may be transported by endocytosis. The
resulting pocket breaks loose from cell membrane and forms vacuole within cytoplasm. 2
examples of endocytosis: phagocytosis and pinocytosis.
12. Phagosystosis- extensions of cytoplasm surround particle and package it within food
vacuole, cell then engulfs it. Pinocytosis- cells take up liquid from surrounding
environment, forming pickets along the cell membrane
13. Exocytosis- membrane of vacuole surrounding material fuses with cell membrane, forcing
contents out of cell. This removing of water is example of active transport.
7-4
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Cells in multicellular organisms develop in different ways to perform particular functions within the
organism.
The levels of organization in a multicellular organism are individual cells, tissues, organs, and organ
systems.
1. Cells are basic living units of all organisms, but a single-celled organisms is called a
unicellular organism. These organisms row, respond to environment, transform energy,
reproduce. Unicellular organisms dominate life on Earth (example, yeast)
2. Organisms that made up of many cells called multicellular. All multicellular organisms
depend on communication and cooperation among specialized cells. Red blood cells
specialized to transport oxygen and contain protein that binds O in lungs and transports O
throughout body.
3. Human ability to move result of specialized structures of muscle cells which generate force
by using overdeveloped cytoskeleton. Skeletal muscle cells packed with actin microfilaments
and myosin. When they contract, muscle cells use chemical energy to pull these fibers past
each other, generating force.
4. Plant rapidly exchanges carbon dioxide, oxygen, water vapor, through stomata. Guard cells
monitor plant’s internal conditions, changing their shape according to those conditions.
5. In multicellular organisms, cells are 1st level of organization. Similar cells grouped into
tissues. Most animals have 4 main types of tissue; muscle, epithelial, nervous, connective
tissue.
6. Many groups of tissues work together as an organ. Each muscle in body is individual organ.
Within a muscle, there is more than muscle tissue-there are nerve tissues and connective
tissues. Each type of tissue performs essential task to help organ function.
7. Organ completes series of specialized tasks. Group of organs that work together to
perform specific function is organ system. Organization of body’s cells into tissues, organs,
and organ systems creates division of labor among those cells that makes multicellular life
possible. Specialized cells like nerve and muscle cells able to function b/c other cells are
specialized to obtain food and oxygen needed by those cells.