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126 Cards in this Set
- Front
- Back
Cells of the human body exhibit a broad diversity of morphologies (shapes)
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According to the Cell Theory, cells are the basic structural and functional unit of living organisms.
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Plasma membranes of human cells are non-selectively permeable.
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Peripheral proteins of plasma membranes are imbedded in the lipid bilayer.
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Plasma membranes are rigid, inflexible lipid-protein sheets.
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Peripheral proteins can be used as transmembrane transport molecules.
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The lipid bilayer of the plasma membrane is hydrophobic.
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Amphipathic molecules have both hydrophobic and hydrophilic regions.
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Cholesterol is primarily a
A. hydrophobic B. hydrophilic compound. |
A
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Passive membrane processes A. require
B. do not require input of energy. |
B
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Ions diffuse through solution from a region of
A. higher concentration to a region of lower concentration B. lower concentration to a region of higher concentration. |
A
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Membrane cholesterol is found associated with
A. phosphate heads B. lipid tails of the lipid bilayer. |
B
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The membrane transport process that requires a change in shape of the transport molecule is
A. channel-mediated diffusion B. carrier-mediated diffusion |
B
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Membrane-spanning proteins
A. are B. are not amphipathetic. |
A
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Osmosis refers to the simple diffusion of
A. solutes B. water |
B
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Water diffuses to a region of
A. higher solute concentration B. lower solute concentration. |
A
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Lipid-soluble solutes
A. can B. cannot cross membrane layers via simple diffusion. |
A
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Cell Theory (4)
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1. A cell is the basic structural and functional unit of living organisms.
2. The activity of an organism depends on both the indl and the collective activities of its cells. 3. According to the principle of complementarity of structure and function, the biochemical activities of cells are dictated by the relative number of their specific subcellular structures. 4. Continuity of life from one generation to another has a cellular basis. |
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Cells are composed of:
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carbon, hydrogen, nitrogen, oxygen and trace amounts of several other elements.
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Human cells have three main parts:
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plasma membrane
cytoplasm nucleus |
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Plasma Membrane
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a fragile barrier, outer boundary of the cell.
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Cytoplasm
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the intracellular fluid of cell that is packed with organelles, small structures that perform specific cell functions.
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Nucleus
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controls cellular activities and typically lies near the cell's center.
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Fluid Mosaic Model
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The FMM of membrane structure depicts the plasma membrane as an exceedingly thin structure composed of a double layer, or bilayer, of lipid molecules with protein molecules plugged in it. The proteins, many of which float in the fluid lipid bilayer, form a constantly changing mosaic pattern.
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Lipid Bilayer is composed of:
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mostly phospholipids
cholesterol glycolipids |
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Phospholipids
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Two parts:
- charged, polar head, hydrophobic (water-loving) - uncharged, nonpolar tail, hydrophobic (water hating) made up of two fatty acid chains |
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Glycolipids
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- lipids with attached sugar groups.
- found only on the outer plasma membrane surface and account for about 5% of the total membrane lipid. |
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Membrane Proteins (64)
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proteins make up about half of the plasma membrane
- integral proteins - peripheral proteins |
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Integral Proteins
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- firmly imbedded in the lipid bilayer
- most are transmembrane proteins wihch span entire width altho some can protrude from one side only - have both hydrophobic and hydrophilic regions - some are enzymes but most are involved in transport |
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Peripheral Proteins
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- not embedded in the lipid
- attach loosely to integral proteins |
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Glycocalyx
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"sugar covering"
- fuzzy, sticky, carbohydrate-rich area at the cell serface. Enriched by glycolipids and glycoproteins secreted by the cell. - provides highly specific biological markers by which approaching cells recognize each other. |
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Membrane Junctions
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- tight junctions
- desmosomes - gap junctions |
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Tight Junctions
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- impermeable junctions that prevent molecules from passing through the intercellular space.
- however, some TJ's are somewhat leaky and may allow certain types of ions to pass. - E.g.: TJ's bt epithelial cells lining the digestive tract keep digestive enzymes and microorganisms in the intestine from seeping into the bloodstream. |
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Desmosomes
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" binding bodies"
- are anchoring junctions - mechanical couplings scattered like rivets along the sides of abutting cells that prevent their separation. - bind neighboring cells together and contribute to a continuous internal network of strong "guy-wires" - distributes tension throughout a cellular sheet and reduces the chance of tearing when it is subjected to pulling forces. - abundant in tissues subjected to great mechanical stress, such as skin and heart muscle. |
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Gap Junctions
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"bond"
- a communicating junction bt adjacent cells that allow ions and small molecules to pass from one cell to the next for intercellular communication. - present in electrically excitable tissues, such as the heart and smooth muscle, where ion passage from cell to cell helps synchronize their electrical activity and contraction. |
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Selective/Permeable Barrier
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the plasma membrane allows some substances to pass while excluding others.
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Passive Processes
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- substances cross the plasma membrane without any energy input from the cell.
- two main types of passive transport: diffusion and filtration |
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Active Processes
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the cell provides the metabolic energy (ATP) needed to move substances across the membrane.
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Diffusion
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- the tendency of molecules or ions to move from an area of higher concentration to an area of lower concentration, down their concentration gradient.
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While the plasma membrane is a physical barrier to free diffusion because of its hydrophobic core, a molecule will diffuse through the membrane if the molecule is:
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1. lipid soluble
2. small enough to pass through membrane channels, or 3. assisted by a carrier molecule. |
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Simple Diffusion
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- unassisted diffusion of lipid-soluble or very small particles
- nonpolar and lipid-soluble substances diffuse directly thru the lipid bilayer - substances that diffuse thru include oxygen, carbon dioxide, and fat-soluble vitamins. - bc oxygen concentration is higher in the blood, it diffuses into the cells - carbon dioxide concentration is higher in cell so it diffuses into the blood. |
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Facilitated Diffusion
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- assisted diffusion
- the transported substance either: (1) binds to protein carriers in the membrane and is ferried across, or (2) moves through water-filled protein channels - certain molecules such as glucose, other sugars, some amino acids and ions are transported this way |
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Carriers
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- transmembrane integral proteins that show specificity for molecules of a certain polar substance or class of substances too large to pass through membrane channels, such as sugars and amino acids
- carrier changes shape to facilitate transport - is a protein carrier specific for one chemical, binding of substrate causes shape change in transport protein - the substance moves down its concentration gradient like in simple diffusion - glucose has higher concentration in blood so goes into cells - carrier-mediated transport is limited by the number of protein carriers present, so if all are engaged, said to be saturated |
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Channels
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- transmembrane proteins that transport substances, usually ions or water, through aqueous channels
- mostly ions selected on basis of size and charge - like carriers, channels can be inhibited by certain molecules, show saturation and tend to be specific - moves down its concentration gradient |
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Osmosis
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- diffusion of a solvent such as water through a specific channel protein (aquaporin) thru the lipid bilayer.
- occurs whenever the water concentration differs on the two sides of a membrane - if distilled water is present on both sides, no net osmosis occurs - if solute concentration differs, water concentration differs (as solute concentration increases, water concentration decreases). - extent to which water's concentration is decreased by solutes depends on the number, not the type of solute particles. |
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Osmolarity
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the total concentration of all solute particles in a solution
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Tonicity
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the ability of a solution to change the shape or tone of cells by altering their internal water volume
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Isotonic Solutions
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- cells retain their normal size and shape (same solute/water concentration as inside cells; water moves in and out)
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Hypertonic Solutions
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- cells lose water by osmosis and shrink in a hypertonic solution (contains a higher concentration of solutes than are present inside the cells)
- cells immersed in hypertonic solutions lose water and shrink, or crenate |
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Hypotonic Solutions
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Cells take on water by osmosis until they become bloated and burst (lyse) in a hypotonic solution is more dilute (contains a lower concentration of solutes than are present in cells)
- cells placed in a hypotonic solution pump up rapidly as water rushes into them - e.g.: distilled water contains no solutes, so water continues to enter cells until they finally burst or lyse - |
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Uses of hyper- and hypo-tonic Solutions
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Hypertonic: used intravenously into the bloodstream of edematous patients (those swollen because water is retained in their tissues) to draw excess water out of that extracellular space and move it into the bloodstream to be eliminated by kidneys
- hyptonic solutions: may be used to rehydrate tissues of extremely dehydrated patients; can drink colas, apple juice, sports drinks |
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Energy source for Simple Diffusion, Facilitated Diffusion and Osmosis
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kinetic energy
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Active Transport
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- like carrier-mediated facilitated diffusion, requires carrier proteins that combine specifically and reversibly with the transported substances
- transports substances against its concentration gradient |
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Two Active Transport Processes
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- processes are distinguished according to their source of energy
- primary active transport - secondary active transport |
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Primary Active Transport
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- energy comes directly from hydrolysis of ATP
- performed across the plasma membrane by a solute pump, directly using energy of ATP hydrolysis - hydrolysis of ATP results in the phosphorylation of the transport protein which causes the protein to change shape in such a manner that it pumps the bound solute across the membrane. - ex moved: Na+, K+, H+, Ca2+, and others |
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Sodium-Potassium Pump
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- ex of a primary active transport system
- K+ concentration is higher in cell - Na+ concentration is higher outside of cell - SP pump drives Na+ out of the cell against a steep concentration gradient and pumps K+ back in |
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Secondary Active Transport
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- transport is driven indirectly by energy stored in ionic gradients created by operation of primary active transport pumps.
- secondary active transport systems are all coupled systems; that is, they move more than one substance at a time. |
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Symport System
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- when two transported substances are moved in the same direction
e.g.: when Na+ moves down its gradient, it drags along glucose against its gradient into the cell |
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Antiport System
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- move transported substances in opposite directions across the membrane
- e.g.: Ca2+, H+ (out of cells via antiporters) |
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Vesicular Transport
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- fluids containing large particles and macromolecules are transported across cellular membranes inside membranous sacs called vesicles
e.g.: exocytosis, endocytosis, transcytosis |
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Exocytosis
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- "out of the cell"
- vesicular transport processes that eject substances from the cell interior into the extracellular fluid |
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Endocytosis
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- "within the cell"
- those in which the cell ingests small patches of the plasma membrane and moves substances from the cell exterior to the cell interior |
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Transcytosis
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- moving substances into, across, and then out of the cell
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Substance, or Vesicular, Trafficking
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- moving substances from one area (or organelle) in the cell to another
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Energy for Vesicular Transport
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- energized by ATP (or in some cases another energy-rich compound, GTP - guanosine triphosphate)
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What are three types of Endocytosis that use clathrin-coated vesicles?
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- phagocytosis
- pinocytosis - receptor-mediated endocytosis |
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Phagocytosis
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"cell eating"
- the cell engulfs a large or solid material |
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Phagosome
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- endocytotic vesicle formed when a particle binds to receptors on the cell's surface, cytoplasmic extensions called pseudopods form and flow around the particle and engulf it
- phagosome fuses with a lysosome and its contents digested or any indigestible content is ejected from the cell by exocytosis |
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Phagocytes
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- cells that help police and protect the body by ingesting and disposing of bacteria, other foreign substances, and dead tissue cells
- move about by amoeboid motion |
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Pinocytosis
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- "cell drinking"
- also called fluid-phase endocytosis - infolding plasma membrane surrounds a very small volume of extracellular fluid containing dissolved molecules |
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Receptor-mediated Endocytosis
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- the main mechanism for the specific endocytosis and transcytosis of most macromolecules by body cells
- receptors are plasma membrane proteins that bind only certain substances |
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Exocytosis
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- process of E is typically stimulated by a cell-surface signal such as binding of a hormone to a membrane receptor or a change in membrane voltage, accounts for hormone secretion, neurotransmitter release, mucus secretion, and ejection of wastes
- substance to be removed from the cell is first enclosed in a protein-coated membranous sac, called a vesicle. - vesicle migrates to the plasma membrane, fuses with it, and then ruptures, spilling the sac contents out of the cell |
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Membrane Potential
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voltage across the membrane
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Plasma Membrane
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membrane made of a double layer of lipids (phospholipids, cholesterol, etc.) within which proteins are embedded. Proteins may extend entirely thru the lipid bilayer or protrude on only one face. Externally facing proteins and some lipids have attached sugar groups.
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Plasma Membrane Functions
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serves as an external cell barrier, and acts in transport of substances into or out of the cell. Maintains a resting potential that is essential for functioning of excitable cells. Externally facing proteins act as receptors (for hormones, neurotransmitters, and so on) and in cell-to-cell recognition
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Cytoplasm
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cellular region between the nuclear and plasma membranes. Consists of fluid cytosol containing dissolved solutes, organelles (the metabolic machinery of the cytoplasm), and inclusions (stored nutrients, secretory products, pigment granules)
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Cytoplasmic Organelles
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mitochondria
ribosomes rough endoplasmic reticulum smooth endoplasmic reticulum golgi apparatus lysosomes peroxisomes microtubules intermediate filaments centrioles |
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Mitochondria
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- rodlike, double-membrane structures; inner member folded into projections called cristae
- contain own DNA, RNA and ribosomes and can reproduce themselves. |
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Mitochondria Functions
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site of ATP synthesis
powerhouse of the cell |
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Ribosomes
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- dense particles consisting of two subunits, each composed of ribosomal RNA and protein. Free or attached to rough endoplasmic reticulum.
- free ribosomes make proteins that function in the cytosol and imported into mitochondria; membrane-bound ribosomes synthesize proteins for cell membranes or for export. |
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Ribosome Functions
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the sites of protein synthesis
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Rough Endoplasmic Reticulum
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- membrane system enclosing a cavity, the cisterna, and coiling thru the cytoplasm; ER is continuous with the nuclear membrane.
- externally studded with ribosomes |
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Rough ER Functions
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- sugar groups are attached to proteins within the cisternae
- proteins are bound in vesicles for transport to the Golgi apparatus and other sides - external face synthesizes phospholipids |
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Smooth ER
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- membranous system of sacs and tubules
- free of ribosomes |
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Smooth ER Functions
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- site of lipid and steroid (cholesterol) synthesis, lipid metabolism,a nd drug detoxification
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Golgi Apparatus
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- a stack of smooth membrane saces and associated vesicles close to the nucleus
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Golgi Apparatus Functions
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- packages, modifies, and segregates proteins for secretion from the cell, inclusion in lysosomes, and incorporation into the plasma membrane
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Lysosomes
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- membranous sacs containing acid hydrolases
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Lysosomes Functions
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sites of intracellular digestion
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Peroxisomes
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- membranous sacs of oxidase enzymes
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Peroxisomes Functions
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- the enzymes detoxify a number of toxic substances
- the most imp enzyme, catalase, breaks down hydrogen peroxide |
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Microtubules
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- cylindrical structures made of tubulin proteins
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Microtubules Functions
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- support the cell and give it shape
- involved in intracellular and cellular movements - form centrioles and cilia and flagella, if present |
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Microfilaments
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- fine filaments composed of the protein actin
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Microfilaments Functions
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- involved in muscle contraction and other types of intracellular movement, help form the cell's cytoskeleton
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Intermediate Filaments
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- protein fibers; composition varies
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Intermediate Filaments Functions
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- the stable cytoskeletal elements
- resist mechanical forces acting on the cell |
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Centrioles
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- paired cylindrical bodies, each composed of nine triplets of microtubules
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Centrioles Functions
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- organize a microtubule network during mitosis to form the spindle and asters. Form the basis of cilia and flagella.
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Inclusions
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- varied
- includes stored nutrients such as lipid droplets and glycogen granules, protein crystals, pigment granules |
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Inclusions Functions
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- storage for nutrients, wastes, and cell products
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Cellular Extensions
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cilia
flagella microvilli |
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Cilia
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- short cell-surface projections; each cilium composed of nine pairs of microtubules surrounding a central pair
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Cilia Functions
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- coordinated movement creates a unidirectional current that propels substances across cell surfaces
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Flagella
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- like a cilium, but longer; only example in humans is sperm tail
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Flagella Functions
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- propel the cell
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Microvilli
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- tubular extensions of the plasma membrane; contain a bundle of actin filaments
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Microvilli Functionis
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- increase surface area for absorption
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Nucleus - What is Found?
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nuclear envelope
nucleoli chromatin |
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Nucleus
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- largest organelle
- surrounded by the nuclear envelope - contains fluid nucleoplasm, nucleoli and chromatin |
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Nucleus Functions
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- control center of the cell
- responsible for transmitting genetic information and providing the instructions for protein synthesis |
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Nuclear Envelope
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- double-membrane structure pierced by pores
- outer membrane continuous with the ER |
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Nuclear Envelope Functions
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- separates the nucleoplasm from the cytoplasm and regulates passage of substances to and from the nucleus
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Nucleoli
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- dense, spherical (non-membrane bounded) bodies, composed of ribosomal RNA and proteins
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Nucleoli Functions
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- site of ribosome manufacture
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Chromatin
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- granular, threadlike material composed of DNA and histone proteins
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Chromatin Functions
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- DNA constitutes the genes
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Cytoskeleton (87)
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- cell skeleton: an elaborate network of rods running thru the cytosol
- supports cellular structure and provides the machinery to generate various cell movements. |
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3 Types of Rods in Cytoskeleton
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In order of increasing size:
- microfilaments - intermediate filaments - microtubules None are membrane covered |
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Centrosome
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- cell center
- acts as a microtubule organizing center - contans paired centrioles |
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Centrioles
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- small, barrel-shaped organelles oriented at right angles to each other
- the centrosome matrix is best known for generating microtubules and organizing the mitotic spindle in cell division |
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Cell Life Cycle
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series of changes a cell goes through from the time it is formed until it reproduces.
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Two Major Periods of Cell Cycle
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1. Interphase - cell grows and carries on its usual activities.
2. Cell Division or Mitotic Phase - divides into two cells. |
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Cell Division - Mitosis
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see pps. 97-99: 4 phases:
1. prophase 2. metaphase 3. anaphase 4. telophase |
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Protein Synthesis
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pps. 100-107
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Developmental Aspects of Cells
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pps. 108-109
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