Biology - Chapter 22 - Cells
Cells - the units of structure and function of living things on earth.
Cytology – The study of cells (also known as cell biology)
Organelles - little organs within a cell
Robert Hook – first observed cork under microscope and thought of cells.
Cell Theory (Principle) - All living things are composed of living units called cells and of
cell products and that all cells come from preexisting cells.
(German botanist Matthias Schleiden and German physiologist Theodor Schwann)
The size of an organism is determined by the NUMBER if its cells, not the SIZE of
its cells.
70% of the cell of water. Other substances are carbohydrates (sugars, starches), lipids
(fatty acids, cholesterol), nucleic acids, and proteins.
Three parts of the cell:
1. The Nucleus - “the control center of the cell” - A spherical body located near the
center of the cell which contains the genetic code of the cell and serves as the
cell’s master control center. Contains DNA
2. The Cytoplasm - jellylike fluid which serves as the fluid medium for many
molecules and organelles the cell contains. The busy factory of the cell where
many actions take place.
3. The Cell Membrane - the outer boundary layer that separates the cell from its
environment and controls what enters and leaves the cell.
Refer to table 22.1 in the book for the following details:
Nucleus:
Main function is to store DNA - deoxyribonucleic acid - the “blueprints” used to
construct the cell’s machinery.
Nuclear envelope - separates the nucleus from the rest of the cell. It is a double
membrane with a narrow water-filled space between the layers.
Nuclear pores - porthole like proteins in the nuclear envelope that serve as gates to
regulate transport of large molecules in and out of the nucleus.
Nuclear matrix - scaffold of protein attached to the inside of the nuclear envelope
bythin girders. Contains enzymes needed for cell’s DNA replication.
Nucleolus - Inside the nucleus - produces ribosomes (protein factories of the cell - they
produce proteins in the cytoplasm of the cell but are made in the nucleolus).
Cytoplasm:
Cytoskeleton - The skeleton of a cell which maintains cell shape, made of microtubules
(hollow tubes made of a protein called tubulin). It’s a mass transit system in the cell
which can change shape and be moved.
Mitochondria - Sausage shaped structure of the cell which serves as the power plant
of the cell by burning carbohydrates and producing ATP. Plant cells have chloroplasts
for photosynthesis (production of their food energy) instead of mitochondria found in
animal cells.
Ribosomes - Protein factories - make proteins by assembling amino
acids. Ribosomes are the smallest of all organelles.
Endoplasmic Reticulum - A system of folded membranes that attaches to the outside
of the cell’s nucleus and extends throughout the cell. (the industrial complex for
ribosome factories). ER also breaks down toxins and wastes and manufactures fat
molecules.
Rough ER - near the nucleus, has ribosomes attached so looks like bumps.
Smooth ER - further from the nucleus, no ribosomes so smoother appearance.
Golgi Complex - stacks of flattened membrane-enclosed compartments that serve as
“shipping centers” of the cell. It receives proteins made in the rough endoplasmic
reticulum, packages them, and ships them to their final destinations.
Lysosomes - recycling centers of the cell - breaks down proteins with acid and
enzymes. Can also attack bacteria that invades body cells.
Vacuole - Storage containers of the cell. Very large in plant cells. Smaller but more
numerous in animal cells..
Cell Membrane - (plasma membrane) - thin barrier that separates the cell from its
surrounding environment. It is self-sealing and self-repairing. There are strict regulations
of material traveling through this membrane into and out of the cell. Made up of a
phospholipid bilayer.
Cell Wall - the rigid, boxlike structure outside the cell membrane of a plant cell that
provides support and protection for the plant. This is made of cellulose and gives plants
their structure, even though they have no skeleton.
Homeostatsis: Maintaining a stable internal environment. The most pressing task of
any living cells is to simply stay alive in order to keep functioning.
Cell Movement:
Cilia - Tiny, hair-like projections from the bottom of the cell membrane for movement.
Flagella - A large, moveable, whiplike tail that extends from the cell for movement.
Note differences in Cellular Respiration and Photosynthesis
Cellular Respiration
Photosynthesis
Used by animals and some plants
Used by plants only
Uses food (glucose) to produce energy
(ATP)
Uses energy (sunlight) to produce food
(glucose)
Breaks down glucose to CO2 and O2
Uses CO2 and O2 to produce glucose
Occurs in mitochondria of cells
Occurs in chloroplasts
Cell Transportation:
Passive Transport - requires little or no energy.
Diffusion - Movement of molecules from high concentration to low concentration.
Osmosis - One way diffusion through a semipermeable membrane.
Active Transport - requires energy to move molecules across a cell membrane.
Endocytosis - cell takes in solid particles (nourishing products go into cell)
Phagocytosis - cell eating - cell takes in solid particles by surrounding with cell
membrane.
Pinocytosis - cell drinking - cell takes in water by surrounding with cell
membrane.
Exocytosis - cell eliminates waste products (waste products out of cell).
Cell Reproduction - also known as cell cycle
Mitosis - Cell division which results in the division of one cell into two new daughter
cells, which are genetically identical to the cell from which they were formed with the
same number of chromosomes.
Five stages of the cell cycle:
Interphase, Prophase, Metaphase, Anaphase, Telophase
(next chapter) Meiosis - Cell division which results in the division of one cell into two
new daughter cells, in which the number of chromosomes in the daughter cells is
reduced to half the number in the parent cell.