Unit 2 – Cell Structure and Function

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Unit 2 Cell Structure and Function

• Cell Theory The concept was formally
  articulated in 1839 by Schleiden Schwann and
  has remained as the foundation of modern biology.
  
• 6 main components of cell theory 
• All known living things are made up of cells.
• The cell is structural functional unit of all
  living things.
• All cells come from pre-existing cells by
  division. (Spontaneous Generation does not
  occur).
• Cells contains hereditary information which is
  passed from cell to cell during cell division.
• All cells are basically the same in chemical
  composition.
• All energy flow (metabolism biochemistry) of
  life occurs within cells.

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Types of cells

• Two main types of cells exist prokaryotes and
  eukaryotes
• Prokaryotes (pro before, kary nucleus)
• lack a membrane bound nucleus
• No organelles (mitochondrion, chloroplast, etc.
• Bacteria and cyanobacteria (monerans)
• Primitive structure
• Reproduce by simple fission (division)
• Smaller than eukaryotes

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Types of Cells - continued

• Eukaryotes (eu true, kary nucleus)
• Plants, animals, protists, and fungi
• Possess a nucleus and membrane bound organelles
• Larger and more advanced than prokaryotic cells
• more complex cellular division

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Questions 1-3, p 72

• How did improvements in the microscope help
  scientists form the cell theory?
• Improvements allowed scientists to see cells in
  greater and greater detail and enabled them to
  discover cells in all types of living matter.
• How do prokaryotic and eukaryotic cells differ?
• Eukaryotic cells have a nucleus and
  membrane-bound organelles, prokaryotic cells do
  not.
• Analyze Today, scientists can study human cells
  grown in petri dishes. Explain how this
  technique builds on the work of early scientists.
• Once it was understood that cells were the basic
  building block of living matter, scientists could
  concentrate on describing different types of
  cells and discovering the relationships between
  cell type and cell function. One way to do this
  is too isolate the cell itself.

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Questions 4 5, p72

• Compare In what ways are cells similar to
  atoms?
• Both are basic units, or building blocks. The
  atom is the basic unit of matter the cell is the
  basic unit of living organisms.
• Medicine Suppose a certain poison kills human
  cells by blocking pores in the nuclear membrane.
  Explain why it would or would not kill bacteria.
• It would not kill bacteria because bacteria do
  not have a nucleus, so there are no nuclear pores
  to be blocked.

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• Cell Components
• 1. Cytoplasm
• The cytoplasm is the region outside the nucleus
  and is the location where nutrients are absorbed,
  transported, and processed including the cytosol
  (fluid soup of the cell) and the organelles.
• The cytoplasm stores the waste until proper
  disposal can be carried out.
• Both the nucleus and the cytoplasm are
  collectively referred to as the protoplasm.
• The cytoplasmic organelles are the parts of the
  cell found in the cytoplasm.

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• 2. Plasma Membrane (Cell membrane)
• The cell membrane is the outer most edge of the
  cell. It is also referred to as the plasma
  membrane.
• It holds the contents of the cell in place and
  regulates the movement of molecules in and out of
  the cell.
• The plasma membrane is composed of a double layer
  of lipid molecules with protein molecules
  embedded in it.
• A lipid molecule consists of two parts, a polar
  head and a non-polar chain tail. The polar end
  is hydrophilic, an attraction with water, while
  the non-polar tail is hydrophobic, repels water.
  
• Like molecules (polar / non-polar) attract while
  unlike molecules repel.

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• 3. Nucleus
• The nucleus is the cells control centre.
• It is round and surrounded by a double membrane
  called the nuclear envelope.
• The nucleus contains most of the genes (genetic
  material).
• The dark region found in the nucleus is called
  the nucleolus.
• The nucleolus is responsible for the formation of
  ribosomes.

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• 4. Mitochondria (pl) mitochondrion (s)
• Tiny oval shaped organelles called mitochondria
  are often referred to as the power plant of the
  cell.
• They provide the body with needed energy through
  a process called respiration. The equation for
  respiration is ???
• Mitochondria are found in both plant and animal
  cells.
• In respiration, chemical bond energy is converted
  into other forms of energy. Mitochondria are
  found where energy is most often needed
  (muscles).
• Special enzymes that assist the breaking down of
  sugar molecules are found within the
  mitochondria.
• When a sugar molecule is broken up, 36 of the
  energy is converted to ATP, while the remaining
  64 is heat.
• Mitochondria have two separate membranes a
  smooth outer membrane and a folding inner
  membrane.
• The inner membrane consists of finger-like
  projections called cristae.

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• 5. Ribosomes
• Ribosomes are the organelles responsible for the
  synthesis of proteins.
• They are one of the smallest organelles found in
  the cytoplasm.
• A ribosome is made up of two parts. The mRNA
  molecule attaches between the two parts and is
  fed through the ribosome in protein synthesis.
• The ribosomes are located on the endoplasmic
  reticulum (ER).

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• 6. Endoplasmic Reticulum (ER)
• The ER is a series of canals that carry material
  throughout the cytoplasm.
• The canals, composed of flattened parallel
  membranes are referred to as ER.
• There are two types of ER
• 1. Smooth ER No ribosomes appear flat
• 2. Rough ER Has ribosomes attached to it
  appears bumpy
• Rough ER is found mostly where enzymes are needed
  since the ribosomes make enzymes (which are a
  type of protein).
• Smooth ER is found where lipids are synthesized.

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• 7. Golgi Apparatus
• The Golgi apparatus appears like a stack of
  pancakes, but is actually a bunch of membranous
  sacs piled on one another.
• In the Golgi apparatus, protein molecules are
  stored after being produced by the ribosomes.
• The Golgi apparatus will move to the plasma
  membrane and then fuse or stick to it. At this
  point, small packages called vesicles are
  released out of the cell. For more information
  refer to transport of molecules.

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• 8. Lysosomes
• Lysosomes are vesicles containing a variety of
  digestive enzymes that help break down large
  molecules and worn-out cell parts.
• They are formed by the Golgi apparatus.
• They play an important role in the defence
  mechanism of the human body by destroying harmful
  substances that find their way into the cell.
• They also release digestive enzymes that break
  down bacteria.

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• 9. Centrioles
• Centrioles are paired cylindrical structures that
  play an important role in cell division.
• They are responsible for separating the
  chromosomes into two different cells.
• Are only found in animal cells.
• The centrioles are produced by the centrosomes
  (make microtubules centrosomes are found in
  both plant and animal cells).

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• 10. Vacuole
• A large part of the cytoplasm in plant cells is
  composed of a fluid-filled space called a
  vacuole.
• The vacuole serves as a storage space for sugars,
  minerals, and proteins.
• It may be referred to as a contractile vacuole
  when it increases and decreases in size.
• It will change its size for two reasons
• 1. To change the pressure of the cell
• 2. To regulate the rate of absorption of
  minerals

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• 11. Chloroplast
• Chloroplasts are the location for photosynthesis.
• They contain a green pigment called chlorophyll.
• They are not found in animal cells.

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• 12. Cell Wall
• Most plant cells are surrounded by a non-living
  cell wall.
• Cell walls are composed of cellulose.
• Their main function is to protect and support the
  plant.
• Some plants will have a secondary cell wall that
  is used for additional support.

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Cool Cells website

• http//www.wiley.com/legacy/college/boyer/04700037
  90/animations/cell_structure/cell_structure.htm

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Questions 1-3, p 79

• What are the functions of the cytoskeleton?
• The cytoskeleton supports and shapes a cell,
  helps position and transport organelles, provides
  strength, assists in cell division, and aids cell
  movement.
• Describe the structure of the nucleus.
• The nucleus is surrounded by a double membrane
  with pores that connect its interior to the
  cytoplasm. DNA and the nucleolus are located
  inside the nucleus.
• Explain the structure and function of the
  mitochondrion.
• A mitochondrion supplies energy to a cell by
  releasing the energy stored in food molecules.
  The outer membrane surrounds a highly folded
  inner membrane where chemical activity occurs.
  It has its own ribosomes and DNA.

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Questions 4-6, p 79

• What function does the cell wall perform in a
  plant?
• The cell wall protects, supports, and shapes a
  plant cell, and regulates what moves into the
  cell. The cell walls of multiple cells can help
  support the entire plant.
• Compare What similarities do mitochondria and
  chloroplasts share?
• Both membranes-bound organelles have their own
  DNA and help make energy available to the cell.
• Compare Describe how the endoplasmic reticulum,
  mitochondrion, and Golgi apparatus are
  structurally similar.
• All are composed of membrane-enclosed chambers.
  The surface area of each is greatly increased by
  folds and layers.

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Question 7, p 79

• Health Medicine, alcohol, and many drugs are
  detoxified in liver cells. Why do you think the
  liver cells of some people who abuse alcohol and
  drugs have an increased amount of smooth ER?
• Increased amounts of smooth ER in the livers
  cells suggests that the cells have responded to
  increased amounts of toxins by producing more
  smooth ER to handle the processing.