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What are all the constituents of body outside of cells?
the extracellular environment
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What water content of the body is divided into what two compartments?
- the intracellular compartment
- the extracellular compartment
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Extracellular water is found in what two substances?
- blood plasma (20%)
- tissue fluid (aka interstitial fluid, 80%)
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What is the material within of connective tissue, but outside of the cells?
extracellular matrix
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What term describes cells ability to allow some substances to cross the cell membrane while preventing others from doing so?
selective permeability
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What two types of mechanisms move substances across the cell membrane?
carrier-mediated transport and non-carrier-mediated transport
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Based on energy requirements what are the two types of membrane transport?
passive transport and active transport
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What type of membrane transport requires ATP?
active transport
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What is the movement of a substance from an area of high concentration to an area of low concentration?
diffusion
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If the concentration of a substance is different between two areas, what exists between the areas?
a concentration gradient
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What are water channels within a membrane?
aquaporins
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What is the diffusion of water across a membane?
osmosis
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What are proteins within the cell membrane that enable the passage of substance through the membrane?
carrier proteins
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What are proteins that allow the passage of ions through the cell membrane?
ion channels
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What are proteins may open or close to allow or prevent the passage of ions through the cell membrane?
gated ion channels
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What factors influence the rate of diffusion?
- the magnitude of the concentration gradient
- the permeability of the membrane
- the temperature of the solution
- the surface area of the membrane
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What is the amount of pressure that would have to be exerted to prevent osmosis?
osmotic pressure
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What term describes the effect of a solution on the osmotic movement of water?
tonicity
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What term describes a solution that has the same tonicity as plasma?
isotonic
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What term describes a solution that has a tonicity lower than plasma?
hypotonic
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What term describes a solution that has a tonicity greater than plasma?
hypertonic
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What happens to cells in a hypertonic solution?
They shrink (crenate).
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What happens to cells in a hypotonic solution?
They swell and will likely burst.
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What type of solution is used for irrigation of body cavities and wounds?
isotonic
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What is the concentration of an osmotic solution?
osmolality
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What type of sensors respond to osmolality?
osmoreceptors
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Where in the body are osmoreceptors found?
the hypothalamus
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What hormone is release in response to an increase in the osmolality of the blood?
antidiuretic hormone (ADH, also known as vasopressin)
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What is the function of ADH?
to decrease the production of urine
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What general category of structures transport large molecules such as glucose and amino acids through the cell membrane?
protein carriers
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Protein carriers cannot be directly observed. What three characteristics indicate that they exist?
- specificity
- competition
- saturation
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What limit is reached when the carrier proteins for a particular substance are saturated?
transport maximum (Tm)
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What type of transport across a cell membrane requires a protein carrier but does not require ATP?
facilitated transport
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The transport carriers for the facilitative diffusion of glucose are designated with what letters?
GLUT
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The protein carrier for glucose in skeletal muscles is GLUT4. Why is it necessary to designate the carriers for glucose with different numbers?
various isoforms exist
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Protein carriers do not remain in the cell membrane, but are inserted when the cell is stimulated as by exercise and insulin in skeletal muscle. What structures store the carriers within the cell?
vesicles
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What is the movement of molecules and ions against their concentration gradients, from lower to higher
concentrations and thus requires ATP?
active transport
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What type of transport across a cell membrane occurs when the hydrolysis of ATP is directly required for the function of the carriers?
primary active transport
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What four steps occur in primary active transport?
- the binding of the substance to be transported to the carrier
- the phosphorylation of the carrier
- a change in the configuration of the carrier
- a hinge-like action of the carrier releasing the substance on the opposite side of the membrane
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What term is often used to refer to primary active transport carriers?
pump
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What common and important primary carrier transports Na+ out of the cell and K+ into the cell?
the sodium/potassium pump (Na+/K+ pump)
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The steep concentration gradient across the cell membrane serves what three functions?
- to provide energy for coupled transport
- to produce electrochemical impulses
- to maintain proper ismotic pressure with the cell
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In what type of transport is the energy needed for the ìuphillî movement of a substance obtained from the downhill transport of Na+ into the cell?
secondary active transport (coupled transport)
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Two types of coupled transport exist. Which type occurs when the substance being moved goes in the same direction as Na+, that is into the cell?
cotransport (symport)
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Two types of coupled transport exist. Which type occurs when the substance being moved goes in the opposite direction as Na+, that is out of the cell?
countertransport (antiport)
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What is the transport of the products of digestion from the lumen of the intestine into the blood?
absorption
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What is the transport of molecules out of the filtrate in the kidneys back into the blood?
reabsorption
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In order for s substance such as glucose to be transported from the lumen of the intestine or kidney tubules, what type of transport occurs at the apical surface of epithelial cells?
cotransport (with Na+)
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In order for s substance such as glucose to be transported from the lumen of the intestine or kidney tubules, what two types of transport occur at the basal surface of epithelial cells?
- primary active transport of Na+ and K+
- facilitated diffusion of the substance crossing the cell
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Some molecules are too large to be moved by carrier proteins and are instead secreted from the cell when vesicles containing them fusion with the cell membrane. What is this process called?
exocytosis
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What process brings substances into the cell when those substances are too large to be moved by protein carriers?
endocytosis
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What term refers to endocytosis and exocytosis?
bulk transport
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What is the potential difference or voltage that exists between the two sides of cell membrane?
membrane potential
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What is the potential difference across a cell membrane when the cell is in an unstimulated state?
resting membrane potential
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What term refers to how cells communicate with each other?
cell signalling
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In what type of cell signaling do cells within an organ secret regulatory molecules that diffuse through the extracelluar matrix to nearby target cells?
paracine signaling
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In what type of cell signaling do cells by means of neurotransmitters through synapes?
synaptic signaling
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In what type of cell signaling to cells communicate through hormones?
endocrine signaling
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What molecules respond to the chemical signals produced by cells?
receptor proteins
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What substances allow a polar regulatory molecule binding with a receptor protein in the cell membrane to influence actions deep within the cell?
second messengers
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What derivative of ATP is an important second messenger?
cyclic AMP (cAMP)
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What four steps generally take place as a polar regulatory molecule binds to a receptor on the cell membrane?
- the regulatory molecule binds to a receptor
- this activates an enzyme which produces cAMP from ATP
- cAMP activates enzymes in the cytoplasm
- the activated enzymes change the activity of the cell
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What is an association of three membrane-associated protein subunits, designated alpha, beta, and gamma, that is regulated by guanosine nucleotides (GDP and GTP)? The protein subunits dissociate in response to a membrane signal and, in turn, activate other proteins in the cell.
G-protein
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What are the three subunits of a G-protein?
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When a receptor is not bound to a regulatory molecule, what molecule is attached to the alpha subunit of the Gprotein?
GDP (guanosine diphosphate)
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When a regulatory molecule attaches to a receptor associated with a G-protein, what happens to the G-protein?
The alpha subunit release GDP and attaches to GTP (guanosine triphosphate) and dissociates from the beta and gamma subunits.
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What happens when the alpha subunit of G-protein dissociates from the beta and gamma subunits and binds to
GTP?
Either the alpha subunit or the beta-gamma complex moves through the membrane and binds to the effector protein (an enzyme or ion channel).
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What happens when a subunit of a G-protein activates its effector protein?
The alpha subunit splits GTP into GDP and Pi causing the subunits of the G-protein to reaggregate and bind to the unstimulated receptor again
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