Download Osmosis/Diffusion

Cell Structure
& Function
http://koning.ecsu.ctstateu.edu/cell/cell.html
Learning Targets
I can…
- Discuss the parts of the Cell Theory
- Explain the function of the nucleus
- Explain the function of the cell membrane
Discovery of the Cell
• Mid-1600s scientists began using microscopes
to observe living things
• 1665, Robert Hooke looked at cork with early
compound microscope
• Thousands of tiny empty chambers called
“cells”
• 1674 Anton van Leeuwenhoek used singlelens scope to look at pond water
• What did he see?
The Cell Theory
• More observations confirmed that CELLS were
the basic units of life
• 1838, Matthias Schleiden-all plants made of
cells (pg. 170, Fig. 7-2)
• 1839, Theodore Schwann, all animals made of
cells
• 1855, Rudolf Virchow, new cells produced only
from division of existing cells
Discoveries Summarized in The Cell
Theory
1. All living things are made up of
cells
2. Cells are the smallest working
units of all living things.
3. All cells come from preexisting
cells through process of cell
division.
Definition of Cell
A cell is the smallest
unit that is capable of
performing life
functions.
Exploring the Cell
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Fluorescent labels
Light microscopy
Confocal light microscopy
High-resolution video technology
TEM
SEM
Scanning probe microscope
Examples of Cells
amoeba
Plant
Bacteria
Nerve cell
Red
Blood cell
Definition of Cell
A cell is the smallest
unit that is capable of
performing life
functions.
Cells are composed of …
• key chemical elements
-carbon
-hydrogen
-oxygen
-nitrogen
-phosphorus
-sulfur
Cells carry out life functions
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Grow/reproduce
Homeostasis
Energy transformation
Dispose of wastes
Make new molecules
Two Categories of Cells
•Prokaryotic
•Eukaryotic
Prokaryotic
• One-celled organisms, EX:
bacteria
• Smaller/simpler (some
exceptions)
• Few internal structures
• No nucleus for DNA
• Carry out all life funtions
-grow
-reproduce
-respond to environment
Eukaryotic
•
•
•
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Contain organelles surrounded by membranes
Most living organisms are eukaryotic
DNA contained in nucleus
Bigger and more variety
“Typical” Animal Cell
“Typical” Plant Cell
7.2 Eukaryotic Cell Structure
• The eukaryotic cell is like a factory
• Many structures in the cell act like specialized
organs…ORGANELLES
• Eukaryotic cell divided into 2 parts:
1. nucleus
2. cytoplasm (outside the nucleus)
They work together
Nucleus
• Control center of cell, “main office, boss”
• Contains nearly all the cell’s DNA and coded
instructions for making proteins and other
important molecules
• Surrounded by nuclear envelope (made up of
2 membranes)
• Membrane separates it from cytoplasm
• Nuclear pores so material can move in and out
of nucleus (ex. Proteins, RNA)
Nucleus (cont.)
• Chromatin- granular material made of
DNA bound to protein
• Most of time it is spread throughout
nucleus
• During division it condenses and forms
CHROMOSOMES (threadlike, contain
genetic info that’s passed to next
generation)
Nucleolus
• Inside nucleus
• Contains RNA
to build
proteins
• ribosome
assembly
begins
Nuclear Membrane (envelope)
• Surrounds nucleus
• Made of TWO
layers
• Openings allow
material to enter
and leave nucleus
Ribosomes
• **PROTEINS are put together on the
ribosomes (cell is “protein-making machine”)
• Small particles of RNA and protein found
throughout the cytoplasm
• They follow coded instructions from the
nucleus
• Many ribosomes in cells which are active in
protein synthesis
• Free ribosomes can make proteins
Just a reminder…
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Proteins are macromolecules
They contain N, C, H, O
They are made up of amino acids
Some control rate of reactions
Some regulate cell processes
Some carry substances into/out of
cells
• Some help fight disease
Endoplasmic Reticulum, ER
• Moves materials
around in cell
(transportation)
• Smooth type: no
ribosomes
• Rough type (pictured):
ribosomes embedded
in surface (involved in
making proteins)
ER (cont.)
• Lipid components of the cell
membrane are assembled
• Proteins and other materials
exported from cell are also
assembled here
• New proteins leave the ribosomes
• Some are inserted into the rough ER
and are chemically modified
Smooth ER
• No ribosomes on surface
• Can hold collections of enzymes
that carry out certain jobs:
-synthesis of membrane lipids
-detox of drugs
**liver cells contain a lot of
smooth ER
Golgi Apparatus
• Protein “packaging
plant”
• Move materials
within the cell
• Move materials out
of the cell
• Receives the
proteins produced in
rough ER
Golgi Apparatus (cont.)
 Modifies, sorts, and packages proteins and
other materials from the ER for storage in the
cell or secretion out of cell
 “customization shop”, finishing touches are
put on proteins before they are “shipped” to
other places in or outside the cell
 Material for membranes of the cell is
packaged and distributed by Golgi
 Lysosomes are products of the Golgi
Lysosomes
• “Digestive plant” for
proteins, lipids, and
carbohydrates
• Filled with enzymes
• Transports undigested
material to cell
membrane for removal
• Cell breaks down if
lysosome explodes
Lysosomes (cont.)
• Clean-up crew
• They remove junk (organelles that are no
longer useful)
• Tay-Sachs disease and lysosomes not
working properly
• Paramecia digest food by surrounding it
in a vacuole. Lysosomes fuse with
vacuole and release acids
Vacuoles
• Sac-like structures, storage area
• Store water, salts, proteins, CHOs
• Plants can have one large Central Vacuole
filled with liquid
• Allows plants to support leaves, flowers
• Contractile vacuole in paramecium
pumps water out of cell (homeostasis)
Mitochondria
• Convert the chemical energy stored in food
into compounds that the cell can use
“Powerhouse of the cell”
• Most of the chemical reactions
involved in cellular respiration
happen in the
mitochondria
• The inner membrane folds are
where chem. rxns. happen
• Folding increases the surface
area inside the mitochondria
which allows the small
organelle to do as much work
as possible.
Chloroplasts
• Found in plant cells
• Capture the energy from sunlight and
convert it into chemical energy during
photosynthesis
• “Solar power plants”
• Inside are large stacks of other
membranes, which contain the green
pigment chlorophyll.
Cytoskeleton
• Network of protein filaments
• Give structure and support, maintain shape of
cell
• Movement
cytoskeleton
microfilaments
microtubules
Microfilaments
• Threadlike
• Made of actin
• Tough, flexible framework
that gives support
• movement
Microtubules
Hollow, made of proteins
Maintain cell shape
In cell division, they form a mitotic spindle
which helps separate chromosomes
In animal cells, form centrioles that help
organize cell division
Centrioles are NOT found in plant cells
Microtubules (cont.)
•Help build cilia and
flagella
•Enable cells to swim
through liquids
•Like oars of a boat
Surrounding the Cell
Cell Membrane
• Outer membrane of cell
that controls movement in
and out of cell
• nearly all cell membranes
made of double-layered
sheet called a lipid bilayer
• flexible structure and
strong barrier between
the cell and its
surroundings.
Cell Membrane (cont.)
• two layers of lipids
• protein molecules embedded in
the lipid bilayer
• Carbohydrate molecules attached
to many of the proteins
• Structure of cell membrane
Osmotic Pressure
• Cells need a way to balance the
intake and loss of water
• Osmosis exerts a pressure (osmotic
pressure) on the hypertonic side of a
selectively permeable membrane
• Osmotic pressure can cause serious
problems for a cell.
Functions of proteins and CHOs
• Some of the proteins form channels
and pumps that help to move
material across the cell membrane
• Many of the CHOs act like chemical
identification cards and allow
individual cells to identify each
another
Cell Wall
• provide support and
protection for the cell.
• plants, algae, fungi, and
many prokaryotes
• outside the cell membrane
• porous enough to allow
water, oxygen, carbon
dioxide, and certain other
substances to pass
through easily.
Cell Wall (cont.)
• made from fibers
of carbohydrate
and protein
• Plant cell walls are
composed mostly
of cellulose (a
tough CHO fiber)
• Wood and paper
(cellulose)
Diffusion
• Particles move from high
concentration to low concentration
• Equilibrium- when the concentration
of the solute is the same throughout
a system
• diffusion depends on random particle
movements, so substances diffuse
across membranes without using
energy
living cells exist in a liquid
environment (adult body=50-65%
water)
One of the most important
functions of the cell membraneregulate movement of dissolved
molecules on one side of the
membrane to the other side
• If a substance can diffuse
across a membrane, the
membrane is permeable
• Impermeable to substances
that cannot cross it
• Most biological membranes
are selectively permeable
• Cytoplasm contains a solution of different
substances in water
• A solution is a mixture of two or more
substances
• Solute is dissolved in solvent
• The concentration of a solution = mass of
solute in a given volume of solution
(mass/volume)
• Ex. 12 g of salt dissolved in 3 liters of water
Osmosis
• Osmosis is the diffusion of
water through a selectively
permeable membrane
• cells contain salts, sugars, proteins,
and other molecules making them
hypertonic to fresh water
• Osmotic pressure produces a net
movement of water into a typical cell
that is surrounded by fresh water
• If that happens, volume of a cell will
increase until the cell becomes
swollen…eventually, the cell may
burst
• Most cells in large organisms do not
come in contact with fresh water
• Cells are in fluids like blood that are
isotonic
• Isotonic fluids have concentrations of
dissolved materials roughly equal to
those in the cells themselves
• plant cells and bacteria do come into
contact with fresh water but have
tough cell walls
• Cell walls prevent the cells from
expanding
• Increased osmotic pressure makes
the cells more likely to experience
injuries to their cell walls
Facilitated Diffusion
• cell membranes have protein channels
• make it easy for certain molecules to cross the
membrane
• Red blood cells have a cell membrane protein
with an internal channel that allows only
glucose to pass through it
• It facilitates, or helps, the diffusion of glucose
across the membrane -facilitated diffusion
Active Transport
• Requires energy to move cells against a
concentration gradient
• Small molecules, ions can be moved
using transport proteins or pumps in the
membrane
• Larger molecules can be moved across
membrane by endocytosis and exocytosis
Molecular Transport
• Ca, K, Na moved across membrane by proteins
that act like pumps
Endo/Exocytosis
• Larger molecules, solid clumps of material
• Endocytosis-materials taken into the cell by
infoldings, pockets, of cell membrane
Phagocytosis
• “cell eating”
• Extensions of cytoplasm surround particle and
package it in a food vacuole
• Cell engulfs it
• Ex. Amoebas
• Uses a lot of energy
Pinocytosis
• Cells take up liquid
from environment
• Pockets form along
cell membrane and
fill with liquid
• Then pinch off and
form vacuoles in the
cell
Exocytosis
• Release material from the cell
• Membrane of vacuole surrounding the
material fuses with the cell membrane and
forces contents out of cell
• Ex. Contractile vacuole removes water
7.4 Diversity of Cellular Life
• Multicellular-organisms made up of many cells
• all multicellular organisms depend on
communication and cooperation among
specialized cells
• Cells within an organism can develop in
different ways to perform different tasks in a
process called cell specialization
Specialized Animal Cells
• Red blood cells-specialized to
transport oxygen
• contain a protein that binds to
oxygen in the lungs and
transports the oxygen throughout
the body where it is released
• Cells specialized to produce proteins are found
in the pancreas
• Pancreas- a gland that produces enzymes that
make it possible to digest food
• Pancreatic cells are packed with ribosomes
and rough ER
• Pancreatic cells also have a well-developed
Golgi apparatus and clusters of storage
vacuoles loaded with enzymes
• human ability to move is due to
specialized structures of muscle cells
• They generate force by using an
overdeveloped cytoskeleton
• Skeletal muscle cells are packed with
fibers arranged in a tight, regular pattern
• The fibers are actin microfilaments and a
cytoskeletal protein called myosin
Specialized Plant Cells
• exchange carbon dioxide, oxygen, water vapor,
and other gases through tiny openingsstomata (on the undersides of leaves)
• Specialized cells called guard cells regulate
the exchange
• Guard cells monitor the plant's
internal conditions and change their
shape according to the conditions
• When the plant can benefit from gas
exchange, the stomata open
• The stomata close tightly when the
plant's internal conditions change
Levels of Organization
• in a multicellular organism
individual cells
tissues
organs
organ systems.
• Similar cells are grouped into units called
tissues
• Tissue is a group of similar cells that perform a
certain function
• The collection of cells that produce digestive
enzymes in the pancreas makes up one kind of
tissue
• Most animals have four main types of tissue:
muscle, epithelial, nervous, and connective
tissue
• Many groups of tissues work together as an
organ
• Each muscle in your body is an individual
organ
• Within a muscle there are nerve tissues and
connective tissues
• Each type of tissue performs an important
task to help the organ function
• A group of organs that work together to
perform a specific function is called an organ
system
• Example: Digestive system
• Muscle cells make up smooth muscle tissue
and along with other tissues makes up the
stomach (organ). The stomach is part of
digestive system (organ system) pg. 193
Inside the Cell
Chromosomes
• In nucleus
• Made of DNA
• Contain instructions for
traits & characteristics
http://library.thinkquest.org/12413/structures.html
Cytoplasm
• Gel-like mixture
• Surrounded by cell membrane
• Contains hereditary material
Mitochondria
• Produces energy through
chemical reactions – breaking
down fats & carbohydrates
• Controls level of water and
other materials in cell
• Recycles and decomposes
proteins, fats, and
carbohydrates
http://library.thinkquest.org/12413/structures.html
Vacuoles
• Membrane-bound sacs
for storage, digestion,
and waste removal
• Contains water solution
• Help plants maintain
shape
http://library.thinkquest.org/12413/structures.html
Chloroplast
• Usually found in plant
cells
• Contains green
chlorophyll
• Where photosynthesis
takes place
http://library.thinkquest.org/12413/structures.html