the cell theory · 2013-10-29 · • cell organelles structure and function • the cell membrane...
TRANSCRIPT
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Cells • 2 Basic Cell Types:
• Prokaryotes • Eukaryotes
• Cell Organelles Structure and Function • The Cell Membrane
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The Cell Theory 1. All living things are composed of cells.
2. Cells are the basic unit of structure and function
in living things.
3. All cells are produced from other cells.
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Two Basic Cell Types:
Prokaryotic vs. Eukaryotic
Cells
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Two Basic Types
• Remember….cells are the basic unit of life
for ALL living things.
• There are two basic types of cells:
1. Prokaryotic cells – found in bacteria
2. Eukaryotic cells – found in protists, fungi,
plants and animals
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Characteristics Shared
• Perform the same basic functions
• Surrounded by plasma membrane to control
what enters and leaves the cell
• “Filled” with cytoplasm
• Contain ribosomes to make protein
• Contain DNA to give the general
instructions for the cell’s life
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What Makes Eukaryotic Cells
Different?
• Much larger • Much more complex
• Contain a true nucleus to house the genetic material (DNA)
• Linear DNA packaged into chromatin found inside the nucleus
• Contains specialized structures in the cytoplasm called organelles to carry out various functions
• Not all have a cell wall
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Eukaryotic Cells
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What Makes Prokaryotic Cells
Different?
• Much smaller
• Less complex
• No true nucleus
• Circular DNA that is found in the cytoplasm
• No organelles found in the cytoplasm
• Surrounded by a cell wall
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Prokaryotic Cell
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What does size have to do with
it? • Prokaryotic cells are much smaller than
eukaryotic cells. Why?
– Smaller surface area to volume allows nutrients to
easily and quickly reach inner parts of the cell.
– Eukaryotic cells are larger and can not pass
nutrients as quickly. They require specialized
organelles to:
• carry out metabolism
• provide energy
• transport chemicals throughout the cell
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Prokaryotic Cell
http://www.cellsalive.com/cells/bactcell.htm#top
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Cell Organelles
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Review
• No organelles in prokaryotic cells
• Both plants and animals are eukaryotic
cells!
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Animal Cell
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Plant Cell
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Organelles Found in Plant and
Animal Cells
• Cell Membrane
• Nucleus
• Nucleolus
• Mitochondria
• Endoplasmic reticulum
• Ribosomes
• Golgi apparatus
• Vacuoles (small in animals; large in plants)
• Lysosomes
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The Cell Membrane • Location: Around the outside of the cell
• Function: Controls what substances enter and
leave the cell
• Aka: “plasma membrane”
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Nucleus • Location: In the cytoplasm
• Function: Directs all of the cell’s activities; stores
the chromatin
• Aka: “control center”
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Nucleolus • Location: In the nucleus
• Function: Makes ribosomes
• Aka: “little nucleus”
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Mitochondria
• Location: In the cytoplasm
• Function: Produces energy
• Aka: “Powerhouse” or “Mighty
Mitochondria”
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Ribosomes • Location: In the cytoplasm and on the
rough ER
• Function: Makes protein
• Aka: “Protein packs”
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Endoplasmic Reticulum (ER)
• Location: In the cytoplasm around the nucleus
• Function: Modifies materials needed in the cell
• Aka: “Fashion designers”
Rough ER (has ribosomes)
Smooth ER (no ribosomes)
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Golgi Apparatus
• Location: In the cytoplasm
• Function: Sorts and ships materials to the correct
parts of the cell
• Aka: “the post office”
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Vacuoles • Location: In the cytoplasm (large in plants;
small in animals)
• Function: Storage
• Aka: “the closet”
Animal Cell Vaculole = small Plant Cell Vaculole = large
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Lysosome • Location: In the cytoplasm
• Function: Destroys worn out cell parts
• Aka: “the death chamber:
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Cilia / Flagella
• (*animal cells only: not all cells have one of
these)
• Location: on the cell membrane
• Function: help the cell move
• AKA: the “motor”
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Organelles Found in Only Plant
Cells
• Cell Wall
• Chloroplast
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Cell Wall • Location: Around the cell membrane of
plant cells
• Function: Gives the cell shape and
protection
• Aka: “plant cell armor”
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Chloroplast • Location: In the cytoplasm
• Function: Photosynthesis: Makes sugar
from sunlight (also takes in carbon dioxide
and gives off oxygen)
• Aka: “mean green sugar machine”
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See the Cell in Action!
• http://www.youtube.com/watch?v=1Z9pqST72is
&feature=related (14 min.)
• Visit this link to see the cell in action, just click
on the various organelles to get a better idea of
how they work!
http://www.johnkyrk.com/CellIndex.html
http://www.cellsalive.com/cells/cell_model.htm
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Prokaryotic Cell
http://www.cellsalive.com/c
ells/bactcell.htm#top
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Plant Cell http://waynesword.palomar.edu/lmexer1a.htm
Name_________________
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Animal Cell • http://waynesword.palomar.edu/lmexer1a.htm
Name_________________
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Prokaryotic Cell
http://www.cellsalive.com/c
ells/bactcell.htm#top
Name_________________
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Movement Through
the Cell Membrane
http://programs.northlandcollege.edu/biology/biology1111/animations/passive1.swf
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Selectively-Permeable Membranes
• A selectively-permeable membrane will allow
certain molecules to pass through it, but not
others.
• Generally, small
particles can pass
through…
Partially permeable
membrane
…but large
particles
cannot
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Structure of the Plasma/Cell
Membrane
• Plasma Membranes consist of 2 types of
molecules – phospholipids and proteins
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Diagram of a Phospholipid
Phospholipids have 2 regions:
• Polar head region:
– attracts water molecules (hydrophilic)
– Phosphorous group
• Non-polar tail region:
– nonpolar tails repel water molecules
(hydrophobic).
– Made of long carbon chains (fatty acids)
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Phospholipid bilayer
• Due to the hydrophobic and hydrophilic nature of the
phospholipid, a double layer is formed where the heads
protect the tails from the water. This is called the
phospholipid bilayer. The bilayer is fluid, not a hard shell.
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Proteins are Embedded Within the Bilayer
• Proteins act as passageways for nonpolar
(hydrophobic) molecules to pass through.
• Without proteins embedded in the bilayer, essential
molecules needed for communication, energy, etc.,
would not reach the interior of the cell.
• Carbohydrates are attached to the proteins.
– Allow for cell recognition and communication.
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Proteins are Embedded Within the
Bilayer (continued)
• The model of the lipid bilayer with embedded
proteins is called the Fluid Mosaic Model.
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TWO Types of Transport Through a
Cell Membrane
1. Active Transport – the movement of molecules
through a cell membrane using energy
2. Passive Transport – the movement of molecules
through a cell membrane without the expenditure
of energy
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3 Types of Passive Transport
1. Diffusion - Movement of molecules from areas
of high concentration to low concentration
2. Osmosis - Diffusion of water molecules from
higher concentration of water to lower
concentration of water
3. Facilitated Diffusion - Diffusion through pores
or channel proteins
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DIFFUSION
• Molecules tend to move from areas where there is more
of them to where there is less
high concentration low concentration
– This is called moving WITH the concentration gradient.
• Diffusion continues until equilibrium is reached, or
where molecules are equally distributed.
– Some solutes will be able to move through when others will
not.
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Diffusion (continued)
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OSMOSIS
• Water passes through cell membranes rapidly.
• Osmosis is a specialized form of diffusion that moves water molecules through membranes.
• Osmotic pressure – when more water molecules accumulate inside a cell, pressure increases. This pressure is called osmotic pressure.
– when osmotic pressure is high inside the cell, water will want to leave the cell.
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OSMOSIS
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3 Types of Solutions
hypertonic solution -solute concentration is HIGHER in
the solution than in the cell.
• Water will move out of the cell- cell will shrivel
hypotonic solution - solute concentration is LOWER in
the solution than in the cell.
• Water will move into the cell- cell will swell
isotonic solution - EQUAL solute concentrations in the
solution and in the cell.
• Water will move in and out of the cell at equal rates.
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FACILITATED DIFFUSION
– some molecules cannot diffuse through on their own
(membrane is impermeable to them), and will need
assistance (facilitate).
– Passive transport aided by proteins. Each are very
specific to the size/shape/polarity of solute.
-transport proteins
-channel proteins
*aquaporins- facilitated diffusion of water
*ion channels- open and close in
response to a stimulus (gated channels)
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Active Transport
• Some molecules exist in low amounts on one side of a
membrane and need to be moved to areas of high
amounts
• active transport- the use of energy to move molecules
from LOW concentration to HIGH concentration
(against or opposite the concentration gradient)
• Cell membranes have mechanisms to move these
molecules against their concentration gradients:
1. ion/molecular pumps
2. endocytosis
3. exocytosis
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Types of Active Transport
1. ion/molecular pumps
-Molecules can be moved through the membrane by specific proteins embedded in the membrane
-Na, K, Ca ions are transported in this manner
-sodium-potassium pump is the major pump of animal cells
-proton pump is main pump of plants, fungi, and bacteria
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2. endocytosis- process of cells engulfing large particles by forming a vesicle around them
-different names for different sizes of particles:
pinocytosis (cell drinking)
-occurs if the particles have been partially broken down into a liquid of tiny dissolved molecules
phagocytosis (cell eating)
- If the particles are cell fragments or organic matter
3. exocytosis -process by which wastes or secretions (hormones) are brought to the cell membrane, packaged into vesicles and sent out of the cell
– the reverse of endocytosis
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Unicellular vs. Multicellular
• Unicellular organisms – single celled.
• Include both prokaryotes and eukaryotes.
• Maintain homeostasis by growing, responding to the environment, transforming energy, and reproducing.
• Multicellular organisms – many cells working together to create an organism.
• Cells are specialized – different cell types play different roles.
• Ex. Move, respond, communicate, substance production.
• Cells communicate with one another to maintain homeostasis for the organism.
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• The organization allows them to divide labor in order to maintain homeostasis.
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Cellular communication
• Cells in large organisms must communicate with one another in order to work together to maintain homeostasis!
• Occurs via chemical signals that influence the behavior of the cells receiving the signals.
• Receptors are often found on the outside of cells where they bind chemical signaling molecules and influence cellular activity.