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cell theory
1st unifying theory of biology
- Cells are the fundamental units of life.
- All organisms are composed of cells.
- All cells come from preexisting cells.
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Why are cells so small?
- A small diameter allows for a high surface area-to-volume ratio. (which is essential)
- Volume determines the amount of chemical activity in the cell per unit time.
- Surface area determines the amount of substances that can pass the cell boundary per unit time.
(page 4 on slide)
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The __ is the outer surface of every cell, & has more or less the same structure in all cells.
plasma membrane
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functions of the plasma membrane
- selectively permeable barrier
- allows cells to maintain a constant internal environment
- is important in communication & receiving signals
- often has proteins for binding & adhering to adjacent cells
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The plasma membrane is made up of a __ bilayer with __ & other molecules embedded.
phospholipid; proteins
It is not rigid, but more like an oily fluid in which the proteins & lipids are in constant motion.
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proteins in the the plasma membrane
- glycoprotein (has carb side chain)
- integral protein
- transmembrane protein (goes through the bilayer)
(page 11 on slide)
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2 types of cells
- prokaryotic cell: in bacteria & archaea, DNA is contained in the nucleoid
- eukaryotic cell: DNA is in a membrane-enclosed nucleus
(page 12 on slide)
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found in both cells of prokaryotes & eukaryotes
- ribosomes (float freely in prokaryotic cells)
- plasma membrane
- cytoplasm
- DNA
(page 12 on slide)
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Cytoplasm consists of __ (water & dissolved material) & suspended particles.
cytosol
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ribosomes
sites of protein synthesis
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nucleus
- usually the largest organelle
- contains the DNA
- site of DNA replication
- site where gene transcription is turned on & off
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nucleolus
- center of nucleus
- where assembly of ribosomes begin
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The nucleus is surrounded by 2 membranes - the __
nuclear envelope
(page 16 on page)
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function of nuclear pores
control movement of molecules between nucleus & cytoplasm
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Some large molecules (e.g., proteins) must have a certain amino acid sequence known as a __ to cross the nuclear envelope.
nuclear localization signal (NLS)
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The endomembrane system includes the __
- plasma membrane
- nuclear envelope
- endoplasmic reticulum
- golgi apparatus
- lysosomes
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network of interconnected membranes in the cytoplasm
endoplasmic reticulum
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function of rough endoplasmic reticulum (RER)
synthesis of new proteins
New synthesized proteins are transported into the RER lumen, modifies, folds, & transports the proteins
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function of smooth endoplasmic reticulum (SER)
synthesis of lipids, oils, phospholipids, steroids
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ribosomes
- consist of more than 50 different protein molecules
- noncovalently bonded to ribosomal RNA
- considered little factories for proteins
- not considered an organelle
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Where can ribosomes be found in eukaryotic cells?
- free in cytoplasm or attached to the ER
- inside mitochondria & chloroplasts
- in neurons found over a meter from the cell body
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The golgi apparatus is composed of __
- flattened sacs (cisternae)
- small membrane-enclosed vescicles
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functions of the golgi apparatus
- receives proteins from the RER - can further modify them
- concentrates, packages, sorts proteins
- adds & modifies carbs to proteins
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The __ region of the golgi apparatus receives vesicles form the ER.
cis
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At the __ region, vescicles bud off from the golgi apparatus & are moves to the plasma membrane or other organelles.
trans
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