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Cells – Key Ideas
•
Unicellular organisms perform the same basic functions as multicellular
organisms
•
Cells are specialized to carry out specific functions
•
Cells are generally more efficient when they work together to perform a specific
function
•
Cells in the human body are organized into tissues
•
Groups of tissues are organized into organs.
•
Groups of organs are reffered to as organ systems
•
Some diseases are caused when cells are invaded by microscopic living things
•
Your health depends on how well your cell systems work together
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Cell Organization
TISSUE – a group of cells that are similar in shape and
function
Tissues are often organized into larger structures called
organs
ORGAN – a structure composed of one or more different
types of tissues; specialized to carry out a specific
function
Many organs are made up of several different types of
tissues.
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Organ (see fig.1 p.41)
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Cellular Organization
•
Organ Systems – groups of
organs that have related
functions
•
See Table 1 p.42
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Unicellular Organisms
•Many organisms are composed of
just ONE cell
•These are called micro-organisms
or microbes
•These single cells are also
responsible for feeding, digesting,
excreting, and reproducing
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The Importance of Micro-organisms
Not all cause disease
Some are useful to create foods that we like such
as cheese and yogurt
We have many micro-organisms in our bodies
that are either harmless or beneficial
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BACTERIA (fig.2 p44)
•Some can make their own food
•Some are parasitic
•Bacteria can be found in every
environment on Earth
•Are PROKARYOTIC
•No nucleus
•No mitochondria
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Protists (fig.4 p45)
•
Protists – a unicellular organisms
that are neither plant nor animal; is
a eukaryotic cell
•
Anywhere there is water you will
find protists
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Plant-Like Protists Diatoms
• found in both fresh water and salt
water
• Contain chlorophyll
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Plant-Like Protists Euglena
• Similar to both plant and animal
cells
• Can feed upon smaller cells
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Animal-Like Protists Amoeba
• Changes its shape as it moves
• It moves by stretching out a
branch of cytoplasm called a
pseudopod
• Pseudopod is anchored to an
object and the rest of the amoeba
is dragged towards it
• Pseudopod is also used to eat
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Animal-Like Protists Paramecia
• Cilia help move it
• Cilia beat to create a current that
draws food into its mouth
• Eats bacteria and other small cells
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Fungi
multicellular or unicellular
•
• Examples include
•
Bread mould
•
Mushrooms
•
Puff balls
• Harmful effects
•
Cause ringworm
•
Dutch elm disease
•
Athlete’s foot
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Yeast
• unicellular fungi
• Must rely on other organism as a source of food
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Is Smaller Better?
• The bigger a cell is, the longer messages take to
reach the nucleus, or for the rest of the cell to
receive instructions
• Cells must be small for information to travel
quickly
• See fig.1 p.49
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Is Smaller Better?
• Small cells are needed so waste can be removed
quickly and nutrients received quickly
• Cells that do a lot of work are usually smaller so
that the nutrients and wastes can enter or leave
more quicker
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Cell Specialization
Multicellular organisms benefit from cell
specialization
Cell Specialization – the development of cells to
perform a specific function
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Specialized Plant Cells
Thin-walled plant cells
are found in the flexible
tissues of leaves, flowers
etc..
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Specialized Plant Cells
Thick-walled plant cells are
specialized for support
Thick cell walls are
stretchable and flexible
E.g. celery stalk
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Specialized Plant Cells
Very thick-walled cells
provide rigid support
Cell usually dies because
cell walls are too thick for
nutrients to pass in and
out of
E.g tree trunk
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Specialized Animal Cells –
Nerve Tissue
Conduct electrical
signals in the body
Tend to be long and thin
Coated by fatty material
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Respiratory Cells
Lung Cells are very thin- Why?
Some cells produce mucus
Mucus – a slippery substance that
coats the cells lining the cavities
open to the air
Mucus traps particles that enters
the lungs
Cilia move the particles and
mucus out
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Blood Tissue
Red Blood Cells
White Blood Cells
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Stomach tissue
Cells are covered by
mucus to protect them
from the strong acid
Cells have many Golgi
Apparatuses to produce
and store the proteins
that break down food
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Fat Tissue
Most of the cyctoplasm is
occupied by vacuoles
Nutirents are converted
to fat and stored in the
cells
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Small Intestine
Absorb nutrients from food
Finger-like projections called
villi – increase surface area
for absorption
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Cell Wars – The Invaders
Disease – any condition that is harmful or
interfers with the well-being of an organism
Infection- the action of disease-producing
organisms, which invade the body and interfer
with the normal activities of the cell
Can rob nutrients or produce waste products
that are poisonous
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Bacteria
Tetanus, strep throat and
pneumonia are examples
Spoil food and
contaminate water
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Fungi
Several disease are
caused by fungi eg.
Athlete’s foot
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Protists
Plasmodium- causes malaria
Giardia lamblia – causes beaver
fever
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Viruses
Virus – a small strand of genetic information
covered by a protein coat; invade living cells and
uses it to make more viruses
Viruses are not true cells
They do not contain a nucleus, cytoplasm,
organelles or a cell membrane
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Viruses
Cause colds
Cold sores
Influenze
AIDS
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The Defenders
Some white blood cells ingest the invader directly where
lysosomes will destroy them and the WBC
Pus – a creamy white substance made of strands of
protein and cell fragments that remain after invaders have
been attacked by white blood cells
White blood cells also kill cells that have been damaged
the intruders
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Antibodies
Antibody – a large molecule produced by a special type of
white blood cell; aids the immune system
Invading cells have Markers, on their cell membranes or
protein coats.
These markers have a specific shape
Antibodies are designed to fit the shape and lock onto
them
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Antibodies