CH. 3 ~ CELLS
Robert Hooke
1665
• Looked at thin
slices of cork under
a microscope
• Did not know at
the time about
their structure and
function.
• What IS a cell?
1670’s Van Leeuwenhoek….hand lens
A cell is the smallest unit of life
that can carry out all the
activities necessary for life.
THE CELL THEORY
One of the foundations of modern biology. It states:
1. All living things are made up of one or more cells
2. Cells are the most basic unit of structure and function
in an organism
3. Cells originate only from pre-existing cells
4. Energy Flow (metabolism) occurs within cells;
must maintain an internal balance (homeostasis)
5. Cells contain DNA (hereditary information) -reproduce.
Schleiden + Schwann + Virchow
VIRCHOW
“Omnis cellula e cellula”
• 1855: New cells arise from pre-existing cells
• Tremendous controversy….against the prevailing
theory at the time
• “Spontaneous Generation” aka Vitalism
• Ponds dry up…..teeming with life again
• Rotting meats ‘spontaneously’ give rise to maggots
“Spontaneous Generation”
(Life evolves from non-life)
(Francesco Redi 1688)
• Spallanzani 1700’S
• Still did not believe….Blocking the “vital force”…..
Who ultimately disproved spontaneous generation?
PASTEUR 1860’S
TYPES
OF
CELLS
Cell Size
• 1 meter = 1000 millimeters (mm)
• 1 mm = 1000 micrometers (um)
• 1 um = 1000 nanometers (nm)
Why are cells so different?
1m
Specialized
Functions!
What Limits the Size of a Cell?
• Human Body consists of
about 100 trillion cells
• (A string 100 trillion
inches long could be
wrapped around Earth
more than 63,000
times)
• Cell grows- needs to
take in food and get rid
of waste through the
cell membrane.
• Cell cannot grow so
large that their surface
area becomes too small
to take in enough food
and remove enough
wastes
• Cells volume increases
faster than its surface
area.
• Surface area = 6s2
• Volume = l x w x h
DEFINITIONS/DESCRIPTION
PROKARYOTIC CELL
EUKARYOTIC CELL
SIZE
Very small .2-10 um
ORGANISMS
Bacteria, cyanobacteria
Varies, generally much
larger 5-100 um
Plants, animals and fungi
CILIA AND FLAGELLA
Yes (pili)
Yes
CELL WALL
Yes
PLAMA (CELL) MEMBRANE
Yes
Yes (Plants and Fungi)
No (Animals)
Yes
CYTOPLASM
Yes
Yes
CHROMOSOMES, DNA
Strand of DNA
(nuceloid,plasmid)
Yes
Yes
No
Yes
RIBOSOMES
MEMBRANE BOUND
ORGANELLES
Yes
Every bacterial cell
– Eubacteria
– Archeabacteria
Every organisms that is not bacteria:
Animals – Plants – Fungus - Protists
Inner Life of the Cell Animation 3.12
Cell Membrane
• Surrounds ALL cells
• Semi-permeable – Selective; only allows
certain substances to pass through
• Contains proteins that help to pass materials
through, for identification, anchoring.
• “Phospholipid bilayer”
• Flexible and “fluid”
Cytosol/Cytoplasm
• Semi fluid portion of the cell; contains the
organelles and allows reaction to occur
• Composed mostly of water and plays a role in
diffusion of materials across the cell membrane.
Amoeba Cytoplasmic Streaming 1.52
Elodea Cytoplasmic Streaming 1.12
Nucleus
• Membrane-bound organelle;
Surrounded by the nuclear envelope aka membrane
• Found only in Eukaryotes
• Controls the cell functions
and processes
• Contains DNA that directs the formation of
necessary proteins. (genetic blueprint)
Nucleolus
• An organelle within the nucleus that produces
ribosomes and RNA
Ribosomes
• small organelles that are
sites of protein synthesis
• Made by the nucleolus
• Take information from the
DNA (delivered to the
ribosome by RNA) and use it
to make protein
• Sometimes found on the ER
(or the rough endoplasmic
reticulum), but also found in
the cytoplasm of ALL cells
Endoplasmic reticulum (ER) –
• detoxification and transport; works closely with the golgi apparatus
• Attached to the nuclear membrane and zigzags through the cell
• Rough or smooth
– Rough = has ribosomes
*protein synthesis & folding
– Smooth = no ribosomes
*Lipids/detox
Golgi Apparatus (Bodies)
• Packaging and distribution “UPS center”
• Flattened, layered, sac-like organelles which are located near
the nucleus.
• Works w/ ER….receives proteins, lipids- modifies and
packages into vesicles for transport to:
– Lysomes
– Plasma membrane
– Other organelles
lysosome
T
R
A
N
S
P
O
R
T
ER and Golgi
MITOCHONDRIA
• “Powerhouse” of the cell
• Converts food into energy (ATP)
(Site of cellular respiration)
• Inner and outer membrane
• Has it’s own DNA (endosymbiotic theory)
• Found in Eukaryotes Only
•
•
•
•
VACUOLE
Contains water
(Can also store nutrients, waste products)
Large in plants, small in animals
Controls “turgor pressure”
in plants.
Lysosomes
• Contain hydrolytic enzymes to break down old organelles (may
also play a role in programmed cell death….apoptosis)
Peroxisomes
• Contain enzymes (catalase) that produce (for detox purposes) or
degrade (if needed- so not released into the cell) hydrogen peroxide
Centrioles
• Only in animals cells. Two structures
near the nucleus, give rise to the
spindle apparatus needed for cell
reproduction.
• 9/3 Triplet Microtubule arrangement
• Flagella – long whip-like tail for movement
• Cilia – short hairs for movement
• Microtubule
“9 + 2” arrangement
PLANT CELL
CHLOROPLASTS
• Converts sunlight, water and carbon dioxide to sugar
and oxygen through photosynthesis
– Has chlorophyll – pigment that captures the sun’s
light.
• Inner and outer membrane
• Found in Eukaryotes only
• Found only in plants
(producers/autotrophs)
Cell Wall
• A rigid structure found on the outside of plant,
fungal and bacterial cells
• Permeable – allows most substances to enter
freely
• Composed of cellulose and protein
• Located OUTSIDE of the cell membrane
• Structure relates to function:
– The rigid structure of the cell wall provides support
and structure for the organisms
– Allows for turgor pressure in plants
Animal
• No cell wall
• No chloroplast
• Small vacuoles
• Has centrioles
Plant
• Cell wall
• Chloroplasts
• Large vacuole
• No centrioles