Cell Structure and Function

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Cell Structure and Function

• Chapter 7

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Early Cell Scientists

• The microscope has made the study of cells
  (cytology) possible.
• Robert Hooke first observed dead cork cells and
  published his findings in Micrographia.
• He coined the word cell
• Anton Van Leeuwenhoek developed the microscope
  for biological use and studied bacteria protists

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Cell Theory

• Matthias Schleiden stated that all plants were
  made of cells
• Theodor Schwann stated all animals are made of
  cells.
• Rudolf Virchow said cells come from preexisting
  cells through division.
• These 3 statements are called The Cell Theory.
• All living things are composed of cells
• Cells are the basic unit of structure and
  function of living things
• All cells come from preexisting cells.

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Exploring the Cell

• Advancement in technology has made following
  material in a living cell possible.
• Electron microscopes allow us to see very small
  parts but they must be cut in thin slices or in a
  vacuum.
• Scanning Tunneling Microscopes can trace the
  surface of a single atom.

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Prokaryotes Eukaryotes

• All cells contain a cell membrane DNA
• Prokaryotes do not have a nucleus are smaller
  and simpler
• Genetic material is in a loop.
• Eukaryotes have a nucleus are larger with
  specialized organelles.
• Eukaryotes may be unicellular or multicellular
• Their DNA is kept separate by the nuclear envelope

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Eukaryotic Cell Structure

• Eukaryotic cells contain tiny specialized
  structures called Organelles.
• The cell is divided into 2 parts The nucleus and
  the cytoplasm

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Figure 7-5 Plant and Animal Cells
Section 7-2
Animal Cell
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Figure 7-5 Plant and Animal Cells
Section 7-2
Plant Cell
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The Nucleus

• The nucleus controls the cell processes by using
  the DNA stored there to make proteins. Proteins
  control nearly all chemical reactions in the
  organism
• The Nuclear Envelope surrounds the nucleus.
• Two layers inner and outer membranes
• Nuclear pores are small holes allowing things in
  and out. (similar to a balloon)
• The dark material in the nucleus is called
  chromatin. It is DNA and a protein called
  histones
• As the cell divides the chromatin forms
  individual chromosomes.
• The Nucleolus begins ribosomes assembly

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Cytoplasmic Organelles

• Ribosomes are protein factories made of RNA and
  Protein
• Ribosomes use info (mRNA) from the nucleus to
  make proteins
• Some ribosomes are attached to membranes
  (endoplasmic reticulum) while others are free
• Among the smallest organelles
• Endoplasmic Reticulum (ER) assemble the lipid
  portions of the cell membrane
• ER transports materials through the inside of the
  cell
• Smooth ER channels look smooth, stores chemicals
  and enzymes
• Rough ER involved in the process of protein
  synthesis, ribosomes are attached
• Golgi Apparatus modifies proteins by adding
  carbohydrates lipids on them and storing them.

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Organelles Continued Again

• Lysosomes are vacuoles which contain enzymes to
  digest materials in a cell. Cleanup crews or
  suicide packets
• Tay-Sachs causes lysosomes to work improperly.
• Vacuoles are saclike structures that are used for
  storage of water, salts, protein, carbohydrates
• Large single vacuoles are used to support heavy
  plant cells
• Plastids are vacuole type organelles in plants.
• Chloroplast- contains chlorophyll conducts
  photosynthesis
• Leukoplast- store starch (sugars) like in
  potatoes
• Chromoplast- store pigments for color (flowers)

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Mitochondria Chloroplasts

• Mitochondria Chloroplasts are the power
  stations. Changing energy from one form to
  another.
• Cells needing more energy have more mitochondria.
• Mitochondria change the chemical energy stored in
  food (glucose) into compounds that are more
  convenient for the cell to use (ATP)
• contain 2 layers. One surrounds the organelle the
  other (Cristae) increases the surface area where
  chemical reactions occur.
• Mitochondria have DNA inherited from the mother.
• Chloroplasts trap the energy of light and convert
  it into chemical energy (glucose). These are
  green.
• Contains 3 layers two surround and one traps
  sunlight.
• Both Mitochondria and Chloroplasts contain DNA
• Lynn Margulis suggests the endosymbiot hypothesis

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Cytoskeleton

• Cytoskeleton is the cells framework made of a
  variety of filaments and fibers which provide
  structure movement
• Microfilaments- made of actin support move the
  cell
• Microtubules- hollow tubes made of protein
  tubulin used for structure support.
• Centrioles- made from microtubules and are found
  in animal cells for cell division
• Cilia are hair-like projections used in movement
  of the organism and of substances along the
  surface of the cell.
• Flagella are whip-like structures used for
  locomotion
• Cilia Flagella both have a 2 wrapped by 9
  arrangement of fibers

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Cytoskeleton
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Cell Boundaries

• The Cell Membrane surrounds the cell providing
  protection and support, regulating what enters
  leaves
• The cell membrane is composed of several
  molecules
• Lipids (phospholipids) make a double layer called
  the bilayer.
• Proteins act as channels and pumps on the surface
  of the cell
• Carbohydrates act as chemical identification
  cards.
• The cells processes take place through the
  membrane
• The Cell Wall sturdy structure outside the cell
  membrane.
• The cell wall is made of three layers (plants and
  bacteria)
• Gluey layer- space formed between two cells.
  Contains Pectin
• Primary layer- composed of cellulose. Wall is
  elastic.
• Secondary layer- composed of cellulose and
  lignin. Found in woody stems, provides rigidity.

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The Lipid Bilayer
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Diffusion Through Cell Boundaries

• Concentrations are a ratio of mass of solute to
  volume of solvent. 12g salt / 6 l H2O
• Diffusion is the movement of molecules of a
  substance which move from an area of higher
  concentration of that substance to an area of
  lower concentration. (with the Concentration
  Gradient)
• Diffusion stops when equilibrium has been reached
• Membrane must be permeable
• Selectively permeable membranes allow some things
  in while restricting others
• Requires no energy outside of molecular motion.

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Osmosis of water
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Osmosis

• Osmosis is the diffusion of water molecules
  through a selectively permeable membrane.
• If a molecule is to large to move then water will
  move to reach equilibrium.
• Isotonic solutions have the same concentration on
  both sides of a membrane.
• Hypertonic solutions have a higher concentration
  on the outside of the membrane. Cell shrinks.
  H2O out.
• Hypotonic solutions have a higher concentration
  on the inside of the membrane. Cell bulges. H2O
  in.
• All conditions above refer to the concentration
  of the solute (dissolved material) and not the
  concentration of the solvent.
• Osmotic pressure is the force exerted by osmosis
• Contractile vacuoles remove excess water.

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Hypertonic, Hypotonic, and Isotonic Solutions
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Move Cell Membrane Movement

• Facilitated Diffusion is the movement of
  molecules by specific protein channels which
  requires no energy.
• Passive Transport requires no energy. I.e.
  diffusion, osmosis, facilitated diffusion.
• Active Transport is an energy requiring process
  enables materials to move across a membrane
  against the concentration gradient.
• Molecular Transport is active transport useing
  transport proteins to pump smaller molecules
  through the membrane by proteins changing shape.
• Large molecules are moved by Cell Membrane shifts
• Endocytosis takes materials into the cell.
  Phagocytosis large solid particle, Pinocytosis
  for large amounts of liquids.
• Exocytosis removes large molecules from the cell.

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Facilitated Diffusion
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Sodium-Potassium Pump
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Endocytosis and Exocytosis
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Endocytosis and Exocytosis
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Cell Specialization Levels of Organization.

• Unicellular organisms have all the
  characteristics of life in one cell
• Multicellular organisms cells develop
  differently to perform a special function.
• Cell specialization is the evolution of cells
  from common stem cells to a cell suited for one
  function.
• Red Blood cells contain hemoglobin, a protein to
  carry oxygen
• Muscle cells have actin microfilaments and myosin
  a cytoskeleton protein which slide past one
  another causing muscle contraction.
• Organization LevelsCells, Tissues, Organs, Organ
  System
• Tissues are groups of similar cells performing
  the same function
• Organs are groups of tissues working to perform a
  specific act
• Organ systems are organs working to perform a
  specific function.

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Chapter 7 Is Finished!

• How can you tell if a redneck is married?
• He has dried tobacco juice on both side of the
  pickup.
• Did you hear that they have raised the minimum
  drinking age in West Virginia to 32.
• They want to keep alcohol out of the high
  schools.
• A new law recently passed in West Virginia
  states
• When a couple gets divorced, theyre STILL
  brother and sister.