BIOLOGY 235 HUMAN PHYSIOLOGY
TEST #1
Endoplasmic0reticulum0-
0ans✔The0endoplasmic0reticulum0(ER)0is0a0membranous0organelle0that0shares0part0of
0its0membrane0with0that0of0the0nucleus.0Some0portions0of0the0ER,0known0as0the0roug
h0ER,0are0studded0with0ribosomes0and0are0involved0with0protein0manufacture.0The0re
st0of0the0organelle0is0referred0to0as0the0smooth0ER0and0serves0to0produce0vital0lipids0
(fats).
Mitochondria0-0ans✔The0"powerhouses"0of0the0cell,0mitochondria0are0oval-
shaped0organelles0found0in0most0eukaryotic0cells.0As0the0site0of0cellular0respiration,0m
itochondria0serve0to0transform0molecules0such0as0glucose0into0an0energy0molecule0kn
own0as0ATP0(adenosine0triphosphate).0ATP0fuels0cellular0processes0by0breaking0its0hi
gh-
energy0chemical0bonds.0Mitochondria0are0most0plentiful0in0cells0that0require0significant
0amounts0of0energy0to0function,0such0as0liver0and0muscle0cells.
Golgi0apparatus0-
0ans✔If0the0proteins0from0the0rough0ER0require0further0modification,0they0are0transpor
ted0to0the0Golgi0apparatus0(or0Golgi0complex).0Like0the0ER,0the0Golgi0apparatus0is0co
mposed0of0folded0membranes.0It0searches0the0protein's0amino0acid0sequences0for0sp
ecialized0"codes"0and0modifies0them0accordingly.0These0processed0proteins0are0then0
stored0in0the0Golgi0or0packed0in0vesicles0to0be0shipped0elsewhere0in0the0cell.
peroxisome0-
0ans✔They0are0small0vesicles0found0around0the0cell.0They0have0a0single0membrane0t
hat0contains0digestive0enzymes0for0breaking0down0toxic0materials0in0the0cell.0They0diff
er0from0lysosomes0in0the0type0of0enzyme0they0hold.0Peroxisomes0hold0on0to0enzymes
0that0require0oxygen0(oxidative0enzymes).0Lysosomes0have0enzymes0that0work0in0oxy
gen-poor0areas0and0lower0pH.0
Peroxisomes0absorb0nutrients0that0the0cell0has0acquired.0They0are0very0well0known0fo
r0digesting0fatty0acids.0They0also0play0a0part0in0the0way0organisms0digest0alcohol0(eth
anol).0Because0they0do0that0job,0you0would0expect0liver0cells0to0have0more0peroxisom
es0than0most0other0cells0in0a0human0body.0They0also0play0a0role0in0cholesterol0synthe
sis0and0the0digestion0of0amino0acids.
, Plasma0membrane0-
0ans✔a0fluid0combination0of0phospholipids,0cholesterol,0and0proteins.0Carbohydrates0a
ttached0to0lipids0(glycolipids)0and0to0proteins0(glycoproteins)0extend0from0the0outward-
facing0surface0of0the0membrane.
Desmosomes0(cell0junctions)0-0ans✔Adds0to0structural0rigidity0between0cells0
-skin
-cervix
-cardiac0muscle
*extreme0cell0membrane0rigidity
Gap0junctions0(cell0junctions)
*A0gap0junction0is0a0specialized0cell0junction0that0directly0connects0the0cytoplasm0of0t
wo0cells.0-0ans✔-
Gap0junctions0allow0various0molecules0and0ions0to0pass0freely0between0cells.
-
A0gap0junction0channel0is0composed0of0two0connexons,0also0known0as0hemichannels,
0which0line0up0across0the0intercellular0space.
-
Most0gap0junction0hemichannels0are0composed0of0a0complex0of0six0connexin0proteins,
0each0characterized0by0four0transmembrane0domains.0Six0connexin0sub-
units0assemble0to0create0one0connexon,0or0hemichannel.
Channel0composition0influences0the0function0of0the0gap0junction.
-
Gap0junctions0allow0for0electrical0communication0between0cells,0they0also0allow0they0p
assage0of0small0second0messengers.
-
Gap0junctions0are0expressed0in0virtually0all0tissues0and0cells,0but0most0notably0in0cell0
types0that0are0involved0in0direct0electrical0communication,0such0as0neurons0and0cardia
c0muscle.
Tight0junctions0(cell0junctions)
*Tight0junctions0serve0as0selectively0permeable0seals0in0our0body's0internal0and0extern
al0surfaces.0-0ans✔-
Tight0junctions0are0the0closely0associated0areas0of0two0cells0whose0membranes0join0t
ogether0forming0a0virtually0impermeable0barrier0to0fluid.
-
Tight0junctions0perform0vital0functions0including0holding0cells0together,0and0forming0pr
otective0and0functional0barriers.
-
Tight0junctions0are0composed0of0a0branching0network0of0sealing0strands0with0each0str
and0acting0independently0from0the0others.
-The0major0types0of0proteins0in0junctions0are0the0claudins0and0the0occludins.
TEST #1
Endoplasmic0reticulum0-
0ans✔The0endoplasmic0reticulum0(ER)0is0a0membranous0organelle0that0shares0part0of
0its0membrane0with0that0of0the0nucleus.0Some0portions0of0the0ER,0known0as0the0roug
h0ER,0are0studded0with0ribosomes0and0are0involved0with0protein0manufacture.0The0re
st0of0the0organelle0is0referred0to0as0the0smooth0ER0and0serves0to0produce0vital0lipids0
(fats).
Mitochondria0-0ans✔The0"powerhouses"0of0the0cell,0mitochondria0are0oval-
shaped0organelles0found0in0most0eukaryotic0cells.0As0the0site0of0cellular0respiration,0m
itochondria0serve0to0transform0molecules0such0as0glucose0into0an0energy0molecule0kn
own0as0ATP0(adenosine0triphosphate).0ATP0fuels0cellular0processes0by0breaking0its0hi
gh-
energy0chemical0bonds.0Mitochondria0are0most0plentiful0in0cells0that0require0significant
0amounts0of0energy0to0function,0such0as0liver0and0muscle0cells.
Golgi0apparatus0-
0ans✔If0the0proteins0from0the0rough0ER0require0further0modification,0they0are0transpor
ted0to0the0Golgi0apparatus0(or0Golgi0complex).0Like0the0ER,0the0Golgi0apparatus0is0co
mposed0of0folded0membranes.0It0searches0the0protein's0amino0acid0sequences0for0sp
ecialized0"codes"0and0modifies0them0accordingly.0These0processed0proteins0are0then0
stored0in0the0Golgi0or0packed0in0vesicles0to0be0shipped0elsewhere0in0the0cell.
peroxisome0-
0ans✔They0are0small0vesicles0found0around0the0cell.0They0have0a0single0membrane0t
hat0contains0digestive0enzymes0for0breaking0down0toxic0materials0in0the0cell.0They0diff
er0from0lysosomes0in0the0type0of0enzyme0they0hold.0Peroxisomes0hold0on0to0enzymes
0that0require0oxygen0(oxidative0enzymes).0Lysosomes0have0enzymes0that0work0in0oxy
gen-poor0areas0and0lower0pH.0
Peroxisomes0absorb0nutrients0that0the0cell0has0acquired.0They0are0very0well0known0fo
r0digesting0fatty0acids.0They0also0play0a0part0in0the0way0organisms0digest0alcohol0(eth
anol).0Because0they0do0that0job,0you0would0expect0liver0cells0to0have0more0peroxisom
es0than0most0other0cells0in0a0human0body.0They0also0play0a0role0in0cholesterol0synthe
sis0and0the0digestion0of0amino0acids.
, Plasma0membrane0-
0ans✔a0fluid0combination0of0phospholipids,0cholesterol,0and0proteins.0Carbohydrates0a
ttached0to0lipids0(glycolipids)0and0to0proteins0(glycoproteins)0extend0from0the0outward-
facing0surface0of0the0membrane.
Desmosomes0(cell0junctions)0-0ans✔Adds0to0structural0rigidity0between0cells0
-skin
-cervix
-cardiac0muscle
*extreme0cell0membrane0rigidity
Gap0junctions0(cell0junctions)
*A0gap0junction0is0a0specialized0cell0junction0that0directly0connects0the0cytoplasm0of0t
wo0cells.0-0ans✔-
Gap0junctions0allow0various0molecules0and0ions0to0pass0freely0between0cells.
-
A0gap0junction0channel0is0composed0of0two0connexons,0also0known0as0hemichannels,
0which0line0up0across0the0intercellular0space.
-
Most0gap0junction0hemichannels0are0composed0of0a0complex0of0six0connexin0proteins,
0each0characterized0by0four0transmembrane0domains.0Six0connexin0sub-
units0assemble0to0create0one0connexon,0or0hemichannel.
Channel0composition0influences0the0function0of0the0gap0junction.
-
Gap0junctions0allow0for0electrical0communication0between0cells,0they0also0allow0they0p
assage0of0small0second0messengers.
-
Gap0junctions0are0expressed0in0virtually0all0tissues0and0cells,0but0most0notably0in0cell0
types0that0are0involved0in0direct0electrical0communication,0such0as0neurons0and0cardia
c0muscle.
Tight0junctions0(cell0junctions)
*Tight0junctions0serve0as0selectively0permeable0seals0in0our0body's0internal0and0extern
al0surfaces.0-0ans✔-
Tight0junctions0are0the0closely0associated0areas0of0two0cells0whose0membranes0join0t
ogether0forming0a0virtually0impermeable0barrier0to0fluid.
-
Tight0junctions0perform0vital0functions0including0holding0cells0together,0and0forming0pr
otective0and0functional0barriers.
-
Tight0junctions0are0composed0of0a0branching0network0of0sealing0strands0with0each0str
and0acting0independently0from0the0others.
-The0major0types0of0proteins0in0junctions0are0the0claudins0and0the0occludins.
