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Chapter 7: CELL STRUCTURE
pg. 151-171
Sec 1 : INTRODUCTION TO CELLS.
Microscope was used for the first time by Robert Hook in 1665. Microscope observations of organisms led to
the discovery of the basic characteristics common to all living things. The observations done by many different scientists
led to the formation of
CELL THEORY:
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All living things are made up of one or more cells
Cells are the basic unit of life
All cells come from preexisting cells
Cells vary greatly in size and shape. A cell’s shape reflect s its function. Cell size is limited by a cell’s surface area -to volume ratio .Cells with greater ratio are more efficient (can bring in all the nutrients they need and get rid of the waste
easier). The smaller is the cell the greater is the surface area-to-volume ratio. Smaller cells can perform their functions
better.
All cells have:
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Cell membrane
Cytoplasm
Ribosomes
DNA
Prokaryotic cells:
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Is simple in its organization
Have cell walls
May have lived on earth 3.5 billions years ago
Small in size 1-2 micrometers
Have no membrane bound organelles
No nucleus
Because are simple can reproduce faster
Bacteria are examples
Many have flagella – long thread-like structures that rotate to quickly move organisms
Some have pili – short thick outgrowth that allows them to attach to the surface.
Eukaryotic cells:
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Are complex and carry out more specialized functions
Are larger in size
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Have nucleus
Have many membrane-bound organelles
The root kary means “kernel” ( nucleus) , Eu- means “true” , pro- means “before” ( long time ago)
Sec 2 : INSIDE THE EUKARYOTIC CELL.
The cytoskeleton is a web of protein fibers and helps the cell move, keep its shape, and organize its parts.
Nucleus – a membrane-bound organelle that contains DNA and controls all cell’s activities.
Cytoplasm – the fluid that fills in the cell and everything suspended in it.
Cell membrane- a phospholipid (types of lipids) layer that covers a cell’s surface and acts as a barrier between the inside
and outside of the cell.
Ribosome- where protein synthesis formation of) occurs.
Endoplasmic Reticulum (ER) – a system of membranes that moves proteins and other substances through the cell.
(Transports). Rough ER has ribosomes attached to it. Smooth ER has no ribosomes.
Golgi apparatus (Golgi body) – a set of flattened membrane-bound sacks which modifies, sorts, and packages products
of the cells to be distributed.
Vesicles- store and release various substances as the cell needs them. Examples of vesicles:
1. Lysosomes - a vesicle that contains specific enzymes that break down large molecules.
2. Central Vacuoles - found in plant cells, stores water, nutrients, and waste.
3. Other vacuoles- contractile vacuoles (can contract or pump) pump excess water out of the
cell which helps to control the concentration of salts and other molecules and helps the cell
to maintain homeostasis.
Chloroplast- organelle found in plant cells only that uses light energy to make sugar molecules.
Mitochondria – organelles that use energy from organic compounds (glucose) to make ATP (an energy molecule that
cells can use for the reactions). Cells that have high energy requirements may contain hundreds of mitochondria.
(muscle cells)
Eukaryotic cells are either plant cells or animal cells.
Differences:
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Plant cells have cell wall around the cell membrane. Animal cells do not.
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Plant cells have chloroplast organelles. Animal cells do not
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Plant cells have central vacuoles filled with water. Animal cells do not.
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Plant cells have rectangular shape. Animal cells are rounder.
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Cell wall- lies outside the cell membrane, provides support and protection for the cell, and is made out
cellulose.
Sec 3: From Cells to Organisms
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Unicellular organisms consist of only one cell that carries out all functions.
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Colonial organism (unicellular) - cells that live in connected groups but do not depend on each other.
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Multicellular organisms made up of many cells that are specialized during the process called
differentiation.
Cellular organization
cell→ tissue→ organ→ organ system→ organism