Anatomy and Physiology I Final Exam Study Guide From Exam 1: Lesson 2 (slides 3-18, 21-31, 35-52) Introduction
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Anatomy and Physiology I
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Anatomy And Physiology I
Anatomy and Physiology I Final Exam Study Guide From Exam 1: Lesson 2 (slides 3-18, 21-31, 35-52) Introduction
• 1665 Robert Hooke inspected thin slices of cork and found they consisted of millions of small, irregular units
• This research produced the cell theory
o Cells are building blocks...
anatomy and physiology i final exam study guide from exam 1 lesson 2 slides 3 18
35 52 introduction • 1665 robert hooke inspected thin slices of cork and found they consisted of millions of
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Anatomy and Physiology I
Final Exam Study Guide
From Exam 1: Lesson 2
(slides 3-18, 21-31, 35-52)
Introduction
1665 Robert Hooke inspected thin slices of cork and found they consisted of millions of
small, irregular units
This research produced the cell theory
o Cells are building blocks of all plants and animals
o All cells come from division of preexisting cells
o Cells are smallest units that perform all vital physiological functions
o Each cell maintains homeostasis at cellular level
Cytology- the study of cellular structure and function; part of cell biology- integrates aspects
of biology, chemistry and physics
Two general classes of cells:
o Sex cells (germ/reproductive cells)-are either the sperm of males or oocytes of females
o Somatic cells- include all other cells in human body
3-1
Plasma membrane- outer boundary of a cell, also called cell membrane
o Physical isolation-physical barrier that separates inside of cell from
surrounding extracellular fluid
o Regulation of exchange with environment- plasma membrane controls entry of ions
and nutrients, eliminations of wastes and release of secretions
o Sensitivity to environment- first part of the cell affected by changes in the
composition, concentration or pH of extracellular fluid
▪ Contain receptors that allow cell to recognize and respond to specific molecules
in its environment
o Structural support- specialized connections between plasma membrane, or
between membranes and extracellular materials give tissues stability
Plasma membrane is extremely thin and contains lipids, proteins and carbohydrates
Membrane lipids-form most of the surface area of the plasma membrane but only make up 42%
of its weight
o Plasma membrane is called the Phospholipid bilayer-phospholipid molecules in it form
two layers
o Has hydrophilic end (phosphate portion) and hydrophobic end (lipid portion)
o In each half of bilayer, lie with hydrophilic heads at membrane surface and
hydrophobic tails in inside
o Also contains cholesterol and small quantities of other lipids
o Water and solutes cannot cross the lipid portion of the plasma membrane
Membrane proteins-account for about 55% of weight of plasma membrane
o Integral proteins-part of membrane structure and cannot be removed
with damaging/destroying the membrane
▪ Most span the width of the membrane one or more times, therefore known as
transmembrane proteins
▪ Greatly
, o Peripheral proteins-bound to the inner or outer surface of the membrane and
easily separated from it
Different types of functional proteins:
o Anchoring proteins-attach plasma membrane to other structures and stabilize its position
▪ Inside cell, membrane proteins are bound to the cytoskeleton
▪ Outside the cell, other membrane proteins may attach cell to extracellular
protein fibers or to another cell
o Recognition proteins (identifiers)-cells of immune system recognize other cells as
normal or abnormal based on presence or absence of characteristic recognition proteins
o Enzymes-may be integral or peripheral; catalyze reactions in extracellular fluid or
in cytosol, depending on location of the protein and its active site
o Receptor proteins- sensitive to the presence of specific extracellular molecules
called ligands
▪ Extracellular ligand will bind to appropriate receptor, causing changes in
the activity of the cell
o Carrier proteins-bind solutes and transport them across the plasma membrane
▪ May require ATP as energy source
o Channels-some integral proteins contain a central pore or channel that forms a
passageway across the plasma membrane
▪ Permits movement of water and small solutes across plasma membrane
▪ Many are highly specific and permit passage of only one ion
3-5
Permeability- property of plasma membrane that determines precisely which substances can
enter or leave the cytoplasm
Impermeable- membrane through which nothing can pass
Freely permeable-membrane through which any substance can pass without difficulty
The permeability of plasma membrane lies between these extremes, making it
selectively permeable
Distinction may be based on size, electrical charge, molecular shape, lipid solubility
Passive processes move ions or molecules across the membrane with no expenditure of
energy from the cell
Active processes require the cell to expend energy, in form of ATP (generally)
Types of transport include: diffusion (passive), carrier-mediated transport (passive or
active), vesicular transport (active)
1. Diffusion- when the net movement of a substance from an area of higher concentration to
an area of lower concentration
o Difference between high and low concentrations is called concentration gradient
o Diffusion tends to eliminate this gradient
o Described as proceeding down a concentration gradient or downhill
o Factors that influence diffusion rates:
▪ Distance-the shorter the distance, the more quickly concentration gradients
are eliminated
▪ Molecule size- the smaller the molecule size, the faster concentration gradients
are eliminated
, ▪ Temperature- the higher the temperature, the faster the diffusion rate
▪ Concentration gradient- the larger the concentration gradient, the faster
diffusion will proceed
▪ Electrical forces-opposite electrical chargers attract each other, and like
charges repel
Interior of membrane has net negative charge due to high concentration
of proteins; pulls positive ions from extracellular fluid into the cell, while
opposing entry of negative ions
The net result of the chemical and electrical forces acting on any ion is
called the electrochemical gradient
o An ion or molecule can diffuse across plasma membrane only by crossing the lipid
portion of the membrane or passing through a membrane channel
o Simple diffusion- alcohol, fatty acids, steroids, lipid soluble drugs, dissolved gases;
can enter cells easily because they can diffuse through lipid portions of membrane
o Channel mediated diffusion- whether an ion can cross a membrane channel depends on:
size and charge of ion, size of hydration sphere, interactions between ion and channel
walls
▪ Leak channels- (passive channels), remain open and allow passage of ions across
plasma membrane
o Osmosis-special case of diffusion, net diffusion of water across a membrane (osmosis
for movement of water, diffusion for movement of solutes)
▪ Each solute in a solution diffuses as though it were the only material in solution-
concentration gradient of another ion has no effect on rate of another ion’s
diffusion
▪ Water molecules tend to flow across a membrane toward the solution containing
the higher solute concentration- because this movement is down the concentration
gradient for water
▪ Osmosis is diffusion of water molecules across selectively permeable membrane
▪ Occurs across a selectively permeable membrane that is freely permeable to
water but not to solutes
▪ Water flows across selectively permeable membrane toward solution with
higher concentration of solutes, where concentration of water is lower
o Osmolarity and tonicity
▪ Total solute concentration in an aqueous solution is it’s Osmolarity, or
osmotic concentration
▪ When we describe effects of various osmotic solutions on cells we use term
tonicity instead of Osmolarity because the nature of solutes is often as important as
the total Osmolarity
▪ Isotonic- solution that does not cause an osmotic flow of water into or out of
the cell
▪ Osmolarity refers to the solute concentration of the solution while tonicity is
a description of how the solution affects a cell
▪ Hypotonic solution-water will flow into the cell, causing it so swell; may burst
and release contents, known as hemolysis
▪ Hypertonic solution-causes cell to lose water by osmosis, causing the cell to
shrivel known as crenation
, ▪ Normal saline- NaCl, given to patients to combat sever blood loss or
dehydration; isotonic to the body cells
▪ Dextran-carbohydrate that cannot cross membrane, elevate the Osmolarity of the
blood, and as osmosis draws water into the vessels from the extracellular fluid,
blood volume increases
3-6
2. Carrier-mediated transport-integral proteins bind specific ions or organic substrates and
carry them across the plasma membrane
o Specificity- each carrier protein in plasma membrane will bind and transport only
certain substances
o Saturation limits- availability of substrate molecules and carrier proteins limits the rate
of transport into or out of cell
▪ When all available carrier proteins operate at max speed, carriers are called
saturated; rate of transport cannot increase regardless of size of
concentration gradient
o Regulation- hormones provide an important means of coordinating carrier protein activity
▪ Co transport (symport)- carrier transports two substances in same direction at
same time, either into or out of the cell
▪ Counter transport (antiport)- one substance moves into cell and other moves out
o Two examples:
o 1. Facilitated diffusion-molecule to be transported first binds to a receptor site on
carrier protein, shape of protein then changes, moving the molecule across the
membrane and releasing it into the cytoplasm
▪ No ATP is expended, molecules move from area of higher to lower concentration
(once carriers are saturated, rate of transport cannot increase, regardless of further
increases in gradient)
▪ All cells move glucose by facilitated diffusion
o 2. Active transport- high energy bond (ATP or another compound) provides energy
needed to move ions or molecules across membrane
▪ Not dependent on concentration gradient- cell can import or export specific
substrates, regardless of their intracellular or extracellular concentrations
▪ Carrier proteins called ion pumps actively transport cations sodium
NA+, potassium K+, calcium Ca 2+ and magnesium Mg2+ across
membranes
▪ Specialized cells transport additional ions, such as iodide I-, chloride Cl- and
iron Fe2+
▪ Sometimes one carrier protein will move more than one kind of ion at the same
time; if counter transport occurs, the carrier protein is called an exchange
pump
▪ Sodium-Potassium exchange pump: sodium and potassium are the principle
cations in body fluids
Sodium concentrations are high in extracellular fluids but low in
cytoplasm while potassium is low in the extracellular fluid and high in
cytoplasm
Exchanges intracellular sodium for extracellular potassium- for each ATP
consumed, three sodium ions are ejected and two potassium ions
reclaimed
If ATP is available, rate of transport depends on concentration of sodium
in cytoplasm
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