Transcript Cell Structure and Function

Cell Structure and Function
Learning Target
I can discuss the history and
components of the cell theory.
Cells
• http://www.youtube.com/watch?v=RU5Ym
c00S4w
Cells
• A cell is the smallest
living unit of life
• Most are microscopic
Discovery of Cells
• Robert Hooke from England (1665)
– Observed sliver of cork
– Saw “row of empty boxes”
– Coined the term cell because it
reminded him of monk’s cells
Discovery of Cells
• Anton van Leeuwenhoek
– From Holland
– Observed tiny moving organisms in pond
water
– Animalcules
Cell theory
• (1838)Theodor Schwann, German biologist
• (1839) Matthias Schleiden, German botanist
“ all living things are made of cells”
• (1855) Rudolf Virchow
“all cells come from
pre-existing cells”
Principles of Cell Theory
• All living things are made of cells
• Cells are the basic units of structure
and function in living things.
• New cells are produced from
existing cells.
Cell Size
Cells Have Large Surface
Area-to-Volume Ratio
Characteristics of All Cells
• Cell (Plasma) membrane -- A
surrounding protective membrane
• Cytoplasm – cell contents in thick fluid
• Control center with DNA
Learning Target
I can discuss the history and
components of the cell theory.
Learning Target
I can analyze the similarities
and differences between
prokaryotic and eukaryotic
cells.
Cell Types
• Prokaryotic
• Eukaryotic
Review
• What are the characteristics of life?
Prokaryotic Cells
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First cell type on earth
Small with simple structure
Possess all characteristics of life
Cell type of Bacteria and Archaea
Prokaryotic Cells
• No membrane bound nucleus
• Nucleoid = region of genetic material (DNA)
• Organelles not bound by membranes
Eukaryotic Cells
• Nucleus bound by membrane;
contains genetic material (DNA)
• Include fungi, protists, plant, and
animal cells
• Possess many organelles
Protozoan
Learning Target
• I can analyze the similarities and
differences between prokaryotic and
eukaryotic cells.
Learning Target
• I can describe the functions of all major
cell organelles.
Composite Animal Cell
Composite Plant Cell
Cell Structure
• Eukaryotic cell is divided into two major
parts:
– Nucleus
– Cytoplasm
• the portion of the cell outside the nucleus;
organelles are suspended in this
Nucleus
• Control center of the
cell
• Found in plant and
animal cells
• Surrounded by a
double membrane
• Contains nearly all
cell’s DNA
• Chromatin
Nuclear Envelope
• Separates nucleus from rest of cell
• Double membrane
• Has nuclear pores
to allow movement
of materials into
and out of the nucleus
DNA
• Hereditary material stored in
the nucleus
• Chromosomes contain the
DNA which contain the
instructions for controlling the
cell’s functions
• Most of the time the DNA is
coiled into chromatin
• Chromosomes are seen as
coiled strands inside the
nucleus is the genetic
material seen in the nucleus
Nucleolus
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Found inside the nucleus
Most cells have 2 or more
Directs synthesis of RNA
Produces ribosomes
Ribosomes
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Small particles of RNA and protein
Located all over the cell
Site of protein synthesis
Assembles amino acids into proteins
Can be free or attached
Endoplasmic Reticulum
• Helps move substances within cells
• Network of interconnected membranes
• Two types
– Rough endoplasmic reticulum
– Smooth endoplasmic reticulum
Rough Endoplasmic Reticulum
• Has ribosomes attached to surface
– Manufacture proteins
– Not all ribosomes are attached to rough ER.
Some are free in the cytoplasm
• May chemically modify proteins from
ribosomes
Smooth Endoplasmic Reticulum
• No attached ribosomes
• Has enzymes that help build molecules
– Carbohydrates
– Lipids
Golgi Apparatus
• Involved in synthesis of plant cell wall
• Modifies, sorts and packages proteins and other
materials from the ER for storage in the cell or for
secretion outside of the cell.
Golgi Apparatus Function
1. Molecules come in vesicles
2. Vesicles fuse with Golgi membrane
3. Molecules may be modified by Golgi
4. Molecules pinched-off in separate vesicle
5. Vesicle leaves Golgi apparatus
6. Vesicles may combine with plasma
membrane to secrete contents
Lysosomes
• Contain digestive enzymes
• Functions
– Aid in cell renewal
– Use enzymes to break down
food and worn out cell parts
– Digests invaders
Vacuoles
• Membrane bound storage sacs
• More common in plants than animals
• Store
– Water
– Food
– Wastes
Mitochondria
• Have their own DNA
• Bound by double membrane
Mitochondria
• Produces the energy a cell needs to carry
out its functions
• Break down fuel molecules (cellular respiration)
– Glucose
– Fatty acids
• Release energy
– ATP
Chloroplasts
• Capture energy from the sun and convert it into
chemical energy
• Photosynthesis
Microfilaments/Microtubules
• Located all over the
cell
• 3 functions:
– mechanical support
– anchor organelles
– help move
substances
A = actin, IF = intermediate filament, MT = microtubule
Cilia & Flagella
• Provide motility
• Cilia
– Short
– Used to move substances
outside human cells
• Flagella
– Whip-like extensions
– Found on sperm cells
Cilia & Flagella Structure
• Bundles of microtubules
• Continuous with plasma
membrane
Centrioles
• Pairs of microtubular structures
• Play a role in cell division
Learning Target
• I can describe the functions of all major
cell organelles.
Learning Target
• I can explain how the cell membrane
controls movement of substances both
into and out of the cell and within the cell.
Cell Membrane
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Also known as the plasma membrane
Contains cell contents
Double layer of phospholipids & proteins
Controls what enters or exits the cell
Phospholipids
• Polar
– Hydrophilic head
– Hydrophobic tail
• Interacts with water
Cell Walls
• Found in plants, fungi, & many protists
• Surrounds plasma membrane; provides support
and protection for the cell
Cell Wall Differences
• Plants – mostly cellulose
• Fungi – contain chitin
Cytoplasm
• Viscous fluid containing organelles
• components of cytoplasm
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Interconnected filaments & fibers
Fluid = cytosol
Organelles (not nucleus)
Storage substances
Learning Target
• I can explain how the cell membrane
controls movement of substances both
into and out of the cell and within the cell.
Learning Targets
• I can describe and contrast these types of
cell transport: osmosis, diffusion,
facilitated diffusion and active transport.
• I can predict the effect of osmosis within
cells based on the type of solution
surrounding the cell.
Movement Across the Plasma Membrane
• Materials move through the plasma
membrane in two ways:
– Passive transport
– Actively transport
Passive Transport
• No energy required
• Move due to gradient
– differences in concentration, pressure, charge
• Move to equalize gradient
– Materials move from areas of high
concentration to areas low concentration
(downhill)
Types of Passive Transport
1. Diffusion
2. Osmosis
3. Facilitated diffusion
Diffusion
• Molecules move to equalize concentration
Osmosis
• Special form of diffusion
• Fluid flows from lower solute concentration
• Often involves movement of water
– Into cell
– Out of cell
Solution Differences & Cells
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solvent + solute = solution
• Hypotonic
– Solutes in cell more than outside
– Outside solvent will flow into cell
– Cell will swell
• Isotonic
– Solutes equal inside & out of cell
• Hypertonic
– Solutes greater outside cell
– Fluid will flow out of cell
– Cell will shrink
Facilitated Diffusion
• Selectively permeable membrane
• Channels (are specific) help molecule
or ions enter or leave the cell
• Channels usually are transport proteins
(aquaporins facilitate the movement of
water)
• No energy is required
Process of Facilitated Transport
• Protein binds with molecule
• Shape of protein changes
• Molecule moves across membrane
Membrane Proteins
1. Channels or transporters
– Move molecules in one direction
2. Receptors
– Recognize certain chemicals
Membrane Proteins
3. Glycoproteins
– Identify cell type
4. Enzymes
– Catalyze production of substances
Active Transport
• Molecular movement
• Requires energy (against gradient)
• Example is sodium-potassium pump
Endocytosis
• Movement of large molecules
– Particles
– Organisms
• Movement is into cells
• Types of endocytosis
– bulk-phase (nonspecific)
– receptor-mediated (specific)
Process of Endocytosis
• Plasma membrane surrounds material
• Edges of membrane meet
• Membranes fuse to form vesicle
Forms of Endocytosis
• Phagocytosis – cell eating
• Pinocytosis – cell drinking
Exocytosis
• Reverse of endocytosis
• Cell discharges material
Process of Exocytosis
• Vesicle moves to cell surface
• Membrane of vesicle fuses
• Materials expelled
End Chapter 5
Learning Targets
• I can describe and contrast these types of
cell transport: osmosis, diffusion,
facilitated diffusion and active transport.
• I can predict the effect of osmosis within
cells based on the type of solution
surrounding the cell.