Download Cell Structure & Function

Cell Structure
& Function
http://koning.ecsu.ctstateu.edu/cell/cell.html
Discovery of the Cell
• Mid-1600s scientists began using microscopes
to observe living things
• 1665, ______________looked at cork with
early compound microscope
• Thousands of tiny empty chambers called
______________
• 1665(-ish) Anton van Leeuwenhoek used
single-lens scope to look at ______________
• What did he see?
The Cell Theory
• More observations confirmed that CELLS were
the ___________________
• 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
__________
2. Cells are the smallest working
units of all living things.
3. All cells come from ___________
through process of
________________.
Definition of Cell
A cell is the smallest
unit that is capable of
performing life
functions.
Exploring the Cell
• Fluorescent labels
• Light microscopy
• Confocal light microscopy
• High-resolution video technology
• TEM
• SEM
• Scanning probe microscope
**See page 172 for some nice images!
Examples of Cells
amoeba
Plant
Bacteria
Nerve cell
Red
Blood cell
Two Types of Cells
Prokaryotic
• Do not have
structures
surrounded by
membranes
• Few internal
structures
• One-celled
organisms, EX:
bacteria
• No nucleus for DNA
http://library.thinkquest.org/C004535/prokaryotic_cells.html
Eukaryotic
• Contain organelles surrounded by membranes
• Most living organisms
• DNA contained in nucleus
Plant
http://library.thinkquest.org/C004535/eukaryotic_cells.html
Animal
“Typical” Animal Cell
http://web.jjay.cuny.edu/~acarpi/NSC/images/cell.gif
“Typical” Plant Cell
http://waynesword.palomar.edu/images/plant3.gif
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 the cell’s DNA and instructions for
making proteins and other
important molecules
• Surrounded by nuclear
envelope or membrane
(made of 2 membranes)
• 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 here
http://library.thinkquest.org/12413/structures.html
Ribosomes
• **PROTEINS are put together on the
ribosomes (cell is “protein-making
machine”) Protein synthesis
• Small particles of RNA and protein
found throughout the cytoplasm
Endoplasmic Reticulum, ER
• Extension of nucleus
• Moves materials
around in cell
(transportation)
• Rough type shown:
ribosomes on surface
• Site of protein
synthesis
ER (cont.)
• Proteins and other materials
exported from cell are 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”
• Material traveling on
ER is modified,
sorted, packaged
and labeled for
intra- and
extracellular
transportation
Golgi Apparatus (cont.)
“customization shop”, finishing
touches are put on proteins
before they are “shipped” to
other places in or outside the
cell
Lysosomes are produced here
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
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”
-Enclosed by two membranes
—outer and
inner
membrane
• The inner membrane folds over many
times (cristae) Where chem. Rxns.
Happen
• In humans, mitochondria come from
Mom
Chloroplasts
• Found in plant cells
• Capture the energy from sunlight and
convert it into chemical energy during
photosynthesis
• “Solar power plants”
• Surrounded by two membranes
• Inside are large stacks of other
membranes, which contain the green
pigment chlorophyll.
Organelle DNA
Chloroplasts and mitochondria
contain their own small DNA
molecules
• Lynn Margulis, an American
biologist, suggested
mitochondria and chloroplasts
are the descendants of ancient
prokaryotes.
•
Cytoskeleton
• Network of protein filaments
• Structure , support, maintain shape of cell
• Involved in movement
Microfilaments
Microtubules
Microfilaments
• Threadlike
• Made of actin
• Tough, flexible framework
that gives support
• movement
Microtubules
Hollow, made of proteins
called tubulins
Help build cilia and flagella
allowing cells to move
Form centrioles
Centrioles
• Found only in animal cells
• Set up the framework that moves the
chromosomes to opposite sides of the cell
during cell division.
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
Diffusion
• Particles move from an area of high
concentration to an area of low
concentration
• Diffusion depends on random particle
movements so substances diffuse across
membranes without using energy
• Equilibrium- when the concentration of
the solute is the same throughout a
system
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.
http://library.thinkquest.org/12413/structures.html
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)
living cells exist in a liquid
environment
One of the most important functions
of the cell membrane- regulate the
movement of dissolved molecules
from the liquid on one side of the
membrane to the liquid on the other
side
• Cytoplasm contains a solution of many
different substances in water
• A solution is a mixture of two or more
substances
• Solute dissolved in solvent
• The concentration of a solution is the mass of
solute in a given volume of solution, or
mass/volume
• Ex. 12 g of salt dissolved in 3 liters of water
Osmosis
• 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
• Osmosis is the diffusion of water through
a selectively permeable 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.
• cell contains salts, sugars, proteins, and other
molecules making it hypertonic to fresh water
• Osmotic pressure should produce 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 like an
overinflated balloon
• 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