BSC 2010 EXAM 2 QUESTIONS AND
ANSWERS
What factors influence membrane fluidity? - Answer- -temperature
-ratio of saturated vs. unsaturated fats
Where are proteins of the cell membrane constructed? - Answer- -endoplasmic
reticulum
-Golgi apparatus
In what way are membranes 'asymmetrical'? - Answer- membranes have distinct inside
and outside faces that can not be switched w/o harming the cell because it changes the
function of the membrane and the flow of substances facilitated by the proteins.
List the functions performed by membrane proteins. - Answer- -transport
-enzymatic activity
-signal transduction
-cell-cell recognition
-intercellular joining
-attachment to the cytoskeleton and extracellular matrix (ECM)
What are cell junction proteins and why are they important for multicellular organisms? -
Answer- Cell junction proteins are membrane proteins that "hook" together with the cell
junction protein of another cell to cause intercellular joining over a gap.
It's important for multicellular organisms because this is how cells come together to form
tissues, which form an organ, then organ systems and then the organism and allows the
organism to function and grow in ways that are impossible if all the cells in the body did
not work together.
Explain how water diffuses across membranes. - Answer- The diffusion of water is
called osmosis. Water diffuses from the area of low solute concentration (high water
concentration) to high solute concentration (low water concentration).
What makes prokaryotic and eukaryotic cells different from one another? What features
do all cells have? - Answer- Eukaryotic cells: membrane-enclosed organelles, nucleus,
generally larger, DNA contained in nucleus
Prokaryotic cells: organelles are not membrane-enclosed, no nucleus, generally smaller
in size, DNA contained in nucleoid
, All cells: cell (plasma) membrane, cytosol, chromosomes, ribosomes
Why does the surface area-to-volume ratio place a limit on the size of cells? - Answer-
The surface area determines how much can pass through the boundary of the cell at
once, so if the volume is too large for the surface area then not enough nutrients,
oxygen, and waste will be able to pass in and out of the cell which will eventually lead to
cell death.
Explain the structure and function of the nucleus. Include a description of the nuclear
envelope and nuclear pores. - Answer- Nucleus is made up of 3 parts:
-chromatin=material consisting of DNA and proteins
-nucleolus=non-membranous structure involved in production of ribosomes; a nucleus
has one or more
-nuclear envelope=double membrane enclosing the nucleus; perforated by nuclear
pores which allow substances in and out of nucleus; continuous with the ER
Function of nucleus: contains most of the genes of a cell, protein synthesis
Name 2 places genes are found in animal cells. - Answer- -nucleus
-mitochondria
-(chloroplasts in plant cells)
What do ribosomes do in cells? What 2 types of macromolecules are ribosomes
constructed from? - Answer- -protein synthesis
Ribosomes are constructed from: nucleic acid (rRNA) and protein
What is the difference between free and bound ribosomes? - Answer- Free ribosomes:
suspended in the cytosol, most proteins formed by these function within the cytosol
Bound ribosomes: attached to the outside of endoplasmic reticulum or nuclear
envelope, generally make proteins that are used for insertion into membranes, for
packaging within certain organelles, or for export from the cell
Where in a cell are the proteins made by free ribosomes found? - Answer- cytosol
Where are all proteins made by bound ribosomes (RER) found? - Answer- Rough
Endoplasmic Reticulum (RER) (?)
List all organelles whose membranes are considered part of the endomembrane
system. What functions does the EMS serve for the cell? - Answer- EMS: nuclear
envelope (nucleus), endoplasmic reticulum, Golgi apparatus, lysosomes, various
vesicles and vacuoles, plasma membrane
Function of EMS: synthesis of proteins, transport of proteins into membranes and
organelles or out of the cell, metabolism and movement of lipids, detoxification of
poisons
ANSWERS
What factors influence membrane fluidity? - Answer- -temperature
-ratio of saturated vs. unsaturated fats
Where are proteins of the cell membrane constructed? - Answer- -endoplasmic
reticulum
-Golgi apparatus
In what way are membranes 'asymmetrical'? - Answer- membranes have distinct inside
and outside faces that can not be switched w/o harming the cell because it changes the
function of the membrane and the flow of substances facilitated by the proteins.
List the functions performed by membrane proteins. - Answer- -transport
-enzymatic activity
-signal transduction
-cell-cell recognition
-intercellular joining
-attachment to the cytoskeleton and extracellular matrix (ECM)
What are cell junction proteins and why are they important for multicellular organisms? -
Answer- Cell junction proteins are membrane proteins that "hook" together with the cell
junction protein of another cell to cause intercellular joining over a gap.
It's important for multicellular organisms because this is how cells come together to form
tissues, which form an organ, then organ systems and then the organism and allows the
organism to function and grow in ways that are impossible if all the cells in the body did
not work together.
Explain how water diffuses across membranes. - Answer- The diffusion of water is
called osmosis. Water diffuses from the area of low solute concentration (high water
concentration) to high solute concentration (low water concentration).
What makes prokaryotic and eukaryotic cells different from one another? What features
do all cells have? - Answer- Eukaryotic cells: membrane-enclosed organelles, nucleus,
generally larger, DNA contained in nucleus
Prokaryotic cells: organelles are not membrane-enclosed, no nucleus, generally smaller
in size, DNA contained in nucleoid
, All cells: cell (plasma) membrane, cytosol, chromosomes, ribosomes
Why does the surface area-to-volume ratio place a limit on the size of cells? - Answer-
The surface area determines how much can pass through the boundary of the cell at
once, so if the volume is too large for the surface area then not enough nutrients,
oxygen, and waste will be able to pass in and out of the cell which will eventually lead to
cell death.
Explain the structure and function of the nucleus. Include a description of the nuclear
envelope and nuclear pores. - Answer- Nucleus is made up of 3 parts:
-chromatin=material consisting of DNA and proteins
-nucleolus=non-membranous structure involved in production of ribosomes; a nucleus
has one or more
-nuclear envelope=double membrane enclosing the nucleus; perforated by nuclear
pores which allow substances in and out of nucleus; continuous with the ER
Function of nucleus: contains most of the genes of a cell, protein synthesis
Name 2 places genes are found in animal cells. - Answer- -nucleus
-mitochondria
-(chloroplasts in plant cells)
What do ribosomes do in cells? What 2 types of macromolecules are ribosomes
constructed from? - Answer- -protein synthesis
Ribosomes are constructed from: nucleic acid (rRNA) and protein
What is the difference between free and bound ribosomes? - Answer- Free ribosomes:
suspended in the cytosol, most proteins formed by these function within the cytosol
Bound ribosomes: attached to the outside of endoplasmic reticulum or nuclear
envelope, generally make proteins that are used for insertion into membranes, for
packaging within certain organelles, or for export from the cell
Where in a cell are the proteins made by free ribosomes found? - Answer- cytosol
Where are all proteins made by bound ribosomes (RER) found? - Answer- Rough
Endoplasmic Reticulum (RER) (?)
List all organelles whose membranes are considered part of the endomembrane
system. What functions does the EMS serve for the cell? - Answer- EMS: nuclear
envelope (nucleus), endoplasmic reticulum, Golgi apparatus, lysosomes, various
vesicles and vacuoles, plasma membrane
Function of EMS: synthesis of proteins, transport of proteins into membranes and
organelles or out of the cell, metabolism and movement of lipids, detoxification of
poisons
