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Cell Notes
Cell – the basic unit of life; 50,000 would fit into a typed letter “o”
Historical steps that led up to the Cell Theory:
1. In the 1600s, Dutch businessman Anton Van Leeuvenhock
described tiny living organisms in a drop of water using a single
magnifying lens
2. In 1665, Robert Hooke used a crude compound microscope
(series of lenses) to examine thin slices of cork. Hooke called the
tiny boxes found in the cork, “cells”.
3. In the 1830s, Schleiden concluded that all plants are composed
of cells. Schwann concluded that all animals were composed of
cells.
Cell Notes Continued
4. Virchow, in 1855, studied cell reproduction and stated that
where a cell exists, there must have been one before it
Cell Theory
1. All living things are composed of cells.
2. Cells are the basic units of structure and function in living
things
3. New cells are produced from existing cells.
Basic Cell Structures
Cells come in many shapes and sizes.
1. Cell membrane:
-thin
-flexible
-support
-protect
2. Cell wall:
-not found in animal cells
-support
-protect
Basic Cell Structures continued
3. Nucleus (plural – nuclei) “brain of the cell”
- contains genetic material
- controls cell’s activities
4. Cytoplasm
cytoplasm
cell wall
- surrounds the nucleus, inside the cell
membrane
- contains important structures
cell membrane
nucleus
Prokaryotes and Eukaryotes
1. Prokaryotes
-have a cell membrane and cytoplasm
-do not contain nuclei
-bacteria
2. Eukaryotes
- do contain nuclei
- have a cell membrane and cytoplasm
- have specialized structures (organelles)
-plants, animals, and fungi
Cell Structures
Cell Wall
- found in plants, algae, fungi, and nearly all prokaryotes
-animal cells do not have
-lie outside the cell membrane
- allow water, oxygen, carbon dioxide, and other substances
to pass through
- provide support and protection
- made from carbohydrates and proteins
- plant cell walls are made of cellulose (principal component
of both wood and paper)
Cell Structures
Cell Wall
- found in plants, algae, fungi, and nearly all prokaryotes
-animal cells do not have
-lie outside the cell membrane
- allow water, oxygen, carbon dioxide, and other substances
to pass through
- provide support and protection
- made from carbohydrates and proteins
- plant cell walls are made of cellulose (principal component
of both wood and paper)
Cell Structures continued
Nucleus
-controls most cell processes
-contains the hereditary information of DNA
-found in almost all eukaryotic cells
-contains chromatin (chromosomes)
-contain nucleolus which assemble ribosomes
-surrounded by a double-membrane layer called the Nuclear
Envelope which allows material to move into and out of the
nucleus (RNA)
Cytoskeleton
-a network of protein filaments that helps the cell to
maintain its shape
-aids in cell movement
Cell Structures continued
Important Structures of Cytoskeleton
1. Microtubules
- hollow protein tubes
- help maintain shape
-aid movement of organelles
(cilia and flagella)
- help in cell division
(centrioles in animal cells)
2. Microfilaments
-function in movement and support
Organelles in the Cytoplasm
Ribosomes
-place where proteins are assembled
Endoplasmic Reticulum (ER)
- where components of the cell membrane are assembled and
some proteins are modified
Organelles in the Cytoplasm continued
Types of Endoplasmic Reticulum (ER)
1. Rough Endoplasmic Reticulum
-ribosomes appear on the surface, hence the name “rough”
-newly made proteins move directly from the ribosomes into
the rough ER, where they may be chemically changed
Other cellular proteins are made by “free” ribosomes which are not
attached to any membrane.
2. Smooth Endoplasmic Reticulum
-does not have ribosomes
Organelles in the Cytoplasm continued
Golgi Apparatus
- proteins produced by the rough ER are received into the Golgi
-enzymes in the Golgi attach carbohydrates and lipids to the
proteins
-from the Golgi, proteins are sent to their final destinations
Lysosomes
-filled with enzymes
-break down lipids, carbohydrates, and proteins from food
-break down “old” organelles
-remove waste
Organelles in the Cytoplasm continued
Vacuoles
-place to store materials such as water, salts, proteins, and
carbohydrates
- saclike structures
- plant cells have a single large, central vacuole
-animal cells have many, smaller, vacuoles
Chloroplast
-found in plants
-not in animal and fungal cells
-use energy from sunlight to make energy-rich food molecules
(photosynthesis)
- contain green pigment chlorophyll
Organelles in the Cytoplasm continued
Mitochondria
- organelles that release energy from stored food molecules
- the energy is used to power growth, development, and
movement
-found in nearly all eukaryotic cells
Comparing Cells
Plant
Animal
Cell walls
no cell wall
Large vacuoles
small vacuoles
Chloroplasts
no chloroplasts
Cell membrane – regulates what enters and leaves the cell (food,
water, waste) and also provides protection and support
What makes up the cell membrane?
1. Lipids
-a double-layered (bilayer) sheet of lipids
-gives a cell membrane a tough, flexible structure
2. Proteins
-some form channels and pumps
Passive Transport
Passive transport does not require the cell to use energy.
Diffusion – movement of molecules from an area of high
concentration to an area of lower concentration (Fig. 7-16)
Osmosis – the diffusion of water through a selectively permeable
membrane (Figure 7-17)
Selectively permeable – some substances can pass through the
membrane and others cannot (or semi permeable)
the cell membrane is permeable to water but impermeable to
sugar/like other substances, water tends to diffuse from a region
where it is highly concentrated to one where it is less
concentrated
Passive Transport
Isotonic solution – a solution in which the concentration of
dissolved substances is the same as the concentration inside the
cell
•
In an isotonic solution, water molecules move into and out of the
cell at random
Hypotonic solution – a solution in which the concentration of
dissolved substances is lower than the concentration inside the
cell
•
In a hypotonic solution, water moves through the membrane into
the cell. HYPO
filled water balloon
Passive Transport
Hypertonic solution – a solution in which the concentration of
dissolved substances is higher than the concentration inside the
cell
•
If a cell is placed in a hypertonic solution, osmosis will cause
water to leave the cell Hype
exit
Facilitated diffusion – when molecules that cannot cross the cell
membrane’s lipid bilayer do so by moving throughprotein
channels instead; movement is from high to low concentration
•
Molecules that can cross the lipid bilayer include:
-water
-alcohol
-small lipids
Passive Transport
•
Molecules that cannot pass through the lipid bilayer include:
-ions
-sugars
-salts
Active Transport
Active transport – when the material moves from an area of lower
concentration to an area of greater concentration; requires the
input of energy
example: most animal cells have membrane proteins that pump
sodium ions (Na+) out of the cell and pump potassium ions (K)
in
Types of Active Transport:
1. pumps
2. endocytosis
3. exocytosis
Types of Active Transport continued
endocytosis – taking material into the cell by means of infoldings,
or pockets, of the cell membrane
exocytosis – the removal of large amounts of material from a cell
Cellular Organization
Cell
muscle cell
Tissue – group of cells that
muscle tissue
Function together
Organs – group of 2 or more
stomach (organ)
tissues that function together
Organ system – a group of organs
that work togther
digestive System
-mouth
-gall bladder
-esophagus
–pancreas
-small intestine
–large intestine