Transcript Cells

Cells
What is Life?
• Before we tackle this question, it is
important to consider what qualifies
something as “living”
Characteristics of Living Things
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Cellular organization
Growth and development
Require energy to survive
Cells have DNA
Reproduction- all living things reproduce
Sense and respond to change in
environment
Living things include animals, plants, protists, fungi
and bacteria
Homeostasis
• An organism’s outside environment may
change, but conditions inside its body
must remain the same
• Many chemical reactions keep an
organism alive
• These reactions can only take place when
conditions are exactly right
• An organism’s ability to maintain a
stable, internal condition to survive is
called homeostasis
• Homeostasis is the maintenance of a
stable internal environment
• For example:
• Your body maintains a temperature of
about 37 degrees Celsius
• When you get hot, your body responds by
sweating
• When you are cold, your muscles twitch in
an attempt to warm you up
• Some living things maintain homeostasis
by changing their environment
• A tissue is a group of cells that work
together to perform a certain job
Ex: blood, muscle, bone, fat, nerves
• An organ is a structure that is made of two
or more tissues working together to
perform a specific function
Ex: liver, heart, kidneys, lungs, brain
• An organ system is a group of organs
working together to perform a certain job
Examples: circulatory system, digestive
system, nervous system
Robert Hooke
• In 1665, Hooke, a
physicist and inventor,
became the first person
to view cells using a
slice of cork under a
microscope
• He named what he
saw cells because they
reminded him of tiny
rooms in a monastery
Anton van Leeuwenhoek
1632-1723
• First scientist to view living
cells
• Using a compound microscope
that he invented, he
discovered one-celled protists
in pond water samples which
he named animacules (little
animals)
• He also saw bacteria (1676)
from teeth scrapings, as well
as sperm from dogs and other
animals (1677)
The Cell Theory
A. All cells come from pre-existing cells
B. All organisms are either unicellular or
multi-cellular
C. Cells are the basic unit of structure of life
What are some benefits to
being multicellular?
Unicellular
• An organism made up of
one cell (bacteria and
some protists)
Multicellular
• Organisms that are
composed of many cells
(animals, plants, fungi, and
some protsists)
Benefits to being multi-cellular
• Larger size
• Longer Life
• Specialization- each type of cell has a
different job, making multi-cellular
organisms more efficient than unicellular
organisms
Five similarities of all Cells
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Require energy
Produce proteins
Have a cell membrane
All cells divide to make new cells
All have DNA (genetic material)
Eukaryotes
• These are plant and
animal cells
• These cells have
enclosed membranebound organelles that
carry out specific
functions in the cell
• Multi-cellular
• DNA is stored in a
nucleus
Prokaryotes
• These are bacterial
cells
• Do not have
membrane-bound
organelles
• Unicellular
• Lacks a nucleus;
instead it has a
circular DNA region
Prokaryote
Prokaryotes are bacteria
They are unicellular
organisms
They lack a nucleus,
Instead, the DNA is
coiled as a long, circular
strand in the center of
the cell
Some bacteria have a
flagellum that provides
them with movement
Biological Molecules Our Body
is Built on
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Carbohydrates (glucose)
Lipids (fats)
Proteins
Nucleic Acid
Cells rely on these to do their job, and in the
cell you will soon learn that proteins and
lipids are even manufactured there!
Organelles
• Tiny cell structures that carry out
specific jobs
• They are membrane-bound
• Found in both plant and animal cells
(eukaryotes), but not in bacterial cells
As you will soon see, the cell is like a
factory- different organelles working together
to make important materials for the cell
The cell membrane is semi-permeable (only some things
pass through it)- it controls what goes in and out of the
cell-allows certain molecules to pass through
Nucleus
• The “control center” of the cell, because it
contains DNA, it directs all the cell’s
activities
• The nucleus is protected and surrounded
by a nuclear membrane
Stores DNA….It is the control
center of the cell!!
Nucleolus
• This small structure is located inside the
nucleus
• It is the site for the production of
ribosomes
Ribosomes
• Attached to the surface of some
endoplasmic reticulum, but also free
floating in the cytoplasm
• Makes (synthesizes) proteins
• Proteins are made here and then sent to
the golgi bodies via vesicles
• Proteins are responsible for thousands of
different chemical reactions that keep us alive
and are also responsible for traits we are born
with , like eye color and lip shape, etc
The Protein Factories!
Chromatin
Chromatin are very
thin strands of
genetic material
(DNA) that float
around in the
nucleus (the purple
lines)
These strands are
the reason the
nucleus is the
“control center” of
the cell
Lysosomes
Small round
structures that
contain chemicals
that break down
large food parts and
old, worn-out cell
materials
They also release
enzymes, so that
they may be used
again
More common in
animal cells than
plant cells
Mitochondria
Rod shaped structures
with a double- layer
membrane
The “power houses” of
the cell because they
produce energy the cell
needs to do its work
Unlike other organelles,
they have their own
DNA so they can divide
and make more of
themselves in the cell!
Pretty cool, huh?
Energy Center of the Cell! Uses energy
released from glucose molecules
Mitochondria
• You eat and the
intestines break down
food into small
molecules
• A cell eats and the
mitochondria breaks
down the molecules
for the cell using
oxygen and glucose
from food.
Structure of the Mitochondria
• In which type of cells would you expect to
find a lot of mitochondria?
Muscle cells contain many mitochondria
because our muscles require lots of
energy to perform the tasks they do.
Cytoplasm
• The cytoplasm is the clear, gel-like fluid
that is inside the cells between the cell
membrane and the nucleus
• It is constantly moving
The jelly-like fluid in the cell that the
organelles sit in is the cytoplasm
Endoplasmic
Reticulum
A passageway through
which proteins and other
materials move within the
cell
Spots on the endoplasmic
reticulum are called
ribosomes
Rough E.R. (has
ribosomes)- so it makes
proteins
Smooth E.R.-(lacks
ribosomes) it makes lipids
The E.R. is always next to
the nucleus
Rough Endoplasmic Reticulum
Proteins are transported by vesicles that bud off the E.R.
and are sent to the golgi body and from the golgi body they
bud off and are sent to other parts of the cell
Golgi Bodies (Golgi Complex)
• Structures within the cell that look like a
flattened stack of pancakes
• This structure is like the “post office”
• It sorts, packages, modifies proteins and
other material, then distributes throughout
the cell and out
Golgi Body
Plant cells have mostly the same organelles as
animal cells, but a few differences do exist..
Plant Cell Wall
Cell Wall
• Found only in plant cells and bacterial
cells
• It forms the outer most layer of the cell
• It protects and supports the plant cell
• It is rigid and made up of a carbohydrate
called cellulose
The Outer Most Layer of a Plant
Cell is the Cell Wall
All cells have a cell membrane!!!
• In animal cells, the cell membrane forms the outer layer
• In plant and prokaryote cells, the cell wall forms the outer
most layer and the cell membrane is just inside of it
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Animal Cell
Plant Cell
Chloroplasts
• Large green structures found only in plant
cells
• Chloroplasts capture energy from sunlight
and use it to make food for the plant cell
• Chlorophyll in the chloroplasts are
responsible for the plant’s green color and
is the main pigment used in
photosynthesis
Photosynthesis takes place in
the stack of thylakoids
Central (large)
Vacuoles
A sac like structure
found in plant cells
Storage area-stores
food and other
important materials
When the vacuole is full
of water the plant is
plump and healthy
Without much water,
the plant wilts because
the vacuole shrivels, no
longer supporting the
cell wall
Similarities Among Cells
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All cells require energy to survive
All cells make proteins (even prokaryotes)
All cells have a cell membrane
All cells contain DNA
All cells come from a pre-existing cell
Warm-up
1. What three structures are only found in
the plant cell?
2. What is the function of the nucleus? Of
the mitochondria?
Prokaryote cells
• Prokaryote cells are bacteria cells
Cell Comparison
Eukaryote cell
• More modern cell
• Contains DNA in an
enclosed organelle called
a nucleus
• Has membrane- bound
organelles
• Larger than prokaryotes
Prokaryote cell
• The earliest and simplest
cells on earth
• Does not contain a
nucleus; DNA floats freely
in the cytoplasm
• Lacks organelles
• Smaller than eukaryotes
Microscopes
• Until the 1500’s, there was no way to see
cells. The first microscope was invented in
1590
• An instrument that makes small objects
look larger
• A simple microscope uses only one lens,
an example is a hand lens
• A compound microscope uses more than
one lens (curved lenses) to focus light and
can magnify an object up to 1000 times its
size
Light Microscopes
• Works by magnifying an object by bending
the light that passes through the curved
convex lens
• The light passing through the lens bends
inward, when this light hits the eye, the
eye sees the object as larger than it really
is
Electron Microscopes
• These microscopes send a beam of
electrons over the surface of a specimen,
rather than through it
• This results in a detailed, threedimensional image of the specimen’s
surface
• Electron microscopes can magnify an
object up to 150,000 times its size!
The plasma membrane is made up of a phospholipid
bilayer embedded with proteins
• The heads of the phospholipids are hydrophilic (water loving) and
the tails facing inward are hydrophobic (water fearing)
• The lipid bilayer is called a fluid mosaic model because it has a fluid
consistency comparable to light oil
One way that molecules pass through the cell membrane is
by diffusion, a method of transfer that is passive and does
not require energy. In the picture- water is the solvent and
the green substance is the solute
Facilitated Transport
Active Transport
Photosynthesis
Cellular Respiration