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cell membrane
regulates the passage of substances into and out of the cell
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What molecules make up the cell membrane?
lipids and proteins
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types of lipids
- phospholipids
- cholesterol
- glycolipids
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phospholipids
bilayer with hydrophilic heads on the outside and hydrophobic heads on the inside
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amphipatic
both hydrophilic and hydrophobic
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integral proteins
span the cell membrane and can form channels, transporters, receptors, while others are enzymes
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peripheral proteins
attached to either the outer or inner surface of the cell membrane & form cytoskeletal anchors or act as enzymes
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functions of a cell membrane
- Communication
- Shape & protection
- Selective permeability
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maintenance of electrochemical gradient
the cell membrane creates both a chemical and electrical gradient across the membrane
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What kind of entities contribute to the development of the electrical gradient across the membrane?
ions and other charged molecules
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simple diffusion
Movement of molecules from a region of high concentration to an area of low concentration: does not require an input of energy, a cell membrane, or transport/carrier proteins
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facilitated diffusion
Movement of molecules from a region of high concentration to an area of low concentration: does not require an input of energy, but does require transport/carrier proteins in the cell membrane
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osmosis
Movement of water molecules or solvent molecules from a region of high water concentration to an area of low water concentration: does not require an input of energy, does not require pores in the cell membrane
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active transport
Movement of molecules from a region of low concentration to an area of high concentration: does require and input of energy & transport/carrier proteins in the cell membrane
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endocytosis
Transport of large molecules into the cell due to the “engulfing” action of the cell membrane & the subsequent formation of a membrane bound vesicle
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Phagocytosis
“cellular eating” of solid matter
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pinocytosis
“cellular drinking” of predominantly extracellular fluid
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Exocytosis
Reverse of endocytosis - secretory vesicles formed within the cell fuse with the cell membrane, emptying their contents into the extracellular environment
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Receptor-mediated endocytosis
specific pathway in which a molecule must bind to a specific receptor in the cell membrane to initiate an endocytotic event. Once within the cell, the receptors & molecules separate with the receptors returning to the cell membrane, while the specific molecules are processed
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cytoplasm
all cellular contents between the cell membrane & the nucleus - it includes the cytosol, organelles
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cytosol
thick fluid composed of 75% - 90% water with the remaining composed of soluble & insoluble molecules & ions
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organelles
"organs" of cells that have specific functions
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nucleus
- “Control center” of a cell, contains hereditary material (DNA) arranged as genes on chromosomes
- Surrounded by a double-membrane nuclear envelope which contain nuclear pores to allow the movement of molecules
- between the cytoplasm & nucleus
- Contain nucleoli for the assembly of ribosomes necessary for protein synthesis
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ribosomes
- Composed of ribosomal RNA (rRNA) & proteins
- Sites for protein synthesis
- May be free-floating in the cytoplasm or bound to endoplasmic reticulum
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endoplasmic reticulum
- Smooth ER is continuous with the nuclear envelope & is involved in Reticulum (ER) lipid metabolism & detoxification
- Rough ER has ribosomes attached to it & is involved in modification, storage, & transportation on proteins
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golgi complex
- Composed of flattened, stacked sacs called cisternae
- It processes, sorts, packages, & delivers proteins & lipids to the plasma membrane & forms lysosomes & secretory vesicles
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protein route for exocytosis
ribosomes, RER, transport vesicles, Golgi complex, secretory vesicles, exocytosis
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lysosomes
Contain digestive enzymes
Digestion includes processes such as autophagy - digestion of organelles & autolysis - digestion of their host cell
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peroxisomes
- Contain oxidizing enzymes, like catalase
- Detoxification function
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mitochondria
Site for cellular respiration, production of ATP
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cytoskeleton
Cellular shape & movement
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flagella
Long, whip-like structure for movement
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cilia
Short, hair-like structures for movement
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centrioles
Forms the mitotic spindle for cell division & is involved in the formation & regeneration of flagella & cilia
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cell cyle
interphase and mitosis
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interphase
- Composed of G1, S, & G2 phases
- Growth & preparation for division (mitosis) occur during the G phases
- DNA replication occurs during the S phase
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Mitosis
Prophase, Metaphase, Anaphase, & Telophase
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prophase
- chromosomal condensation, nuclear envelope
- disintegration, and spindle formation
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metaphase
“lining up” of the chromatid pairs on the metaphase (equatorial) plate
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anaphase
chromatid separation
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telophase
reverse of prophase
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