Complete Test Bank Molecular Biology of the Cell 6th
Edition Alberts Questions & Answers with rationales
(Chapter 1-24)
Eukaryote - ANSWER An organism whose cells contain complex structures
enclosed within membranes. The defining membrane bound structure thats sets
them apart from prokaryotic cells is the nucleas or nuclear envelope within which the
genetic material is carried. All species of large complex species are eukaryotes,
including animals, plants and funghi.
Euchromatin - ANSWER This shows as pale areas in the nucleas under electro
magnification. It is a less densly packed form of chromatin; 10% is even less
condensed and in this form it can be actively transcribed to produce RNA.
Heterochromatin - ANSWER This shows as dark areas on the eukaryotic nucleas;
it is densly packed chormatin (DNA and protein complex) which cannot be
transcribed.
Histones - ANSWER Special proteins around which DNA is wrapped.
Lamins - ANSWER Intermediate filament proteins which protect the structure of the
nucleas, they polymerize to from a network of filaments that lie just within the nuclear
membrane. The network of these filament proteins is called the nuclear lamina.
Nuclear Lamina - ANSWER The network of intermediate nuclear filament proteins
(Lamins) which is located just below the nuclear membrane and is linked to the
membrane and chromatin.
Nuclear Pores - ANSWER 9nm (approx) gaps in the nuclear envelope that allow
the passage of RNA and ribosomes out of the nucleas and the entry of selected
small proteins and small water soluble molecules.
Prokarayotes - ANSWER An organism of the kingdom of Monera, comprising the
bacteria and cyanobacteria. Characterised by the abscence of a distinct, membrane
bound nucleas or membrane bound organelles and by DNA that is not organised in
to chromosomes. Also called moneran.
Protoctist - ANSWER Any of various unicellular eukaryotic organisms and their
multicellular, coenocytic or colocial descendants that belong to the kingdom of
Protocista according to some taxonomic systems. The protoctists include
protozoans, slime moulds, various algae and other groups. In many new
classification systems, all proctists are considered protists.
,Signal Sequence - ANSWER Affectionately known as the 'address label' of a
polypeptide. A short (3-60 amino acids long) peptide chain that directs the transport
of a protein. These may also be called targeting signals, signal peptides, transit
peptides, or localization signals.
The amino acid sequences of these direct proteins (which are synthesized in the
cytosol) to certain organelles such as the nucleus, mitochondrial matrix, endoplasmic
reticulum, chloroplast, apoplast and peroxisome. Some signal peptides are cleaved
from the protein by signal peptidase after the proteins are transported.
Endoplasmic Reticulum - ANSWER The endoplasmic reticulum (ER) is a
eukaryotic organelle that forms an interconnected network of tubules, vesicles, and
cisternae within cells. Rough endoplasmic reticula synthesize proteins, while smooth
endoplasmic reticula synthesize lipids and steroids, metabolize carbohydrates and
steroids (but not lipids), and regulate calcium concentration, drug metabolism, and
attachment of receptors on cell membrane proteins. Sarcoplasmic reticula solely
regulate calcium levels.
Smooth endoplasmic reticulum - ANSWER Cell organelle responsible for
attachment of receptors on cell membrane proteins, synthesizing lipids and steroids,
metabolizing carbohydrates and steroids (but not lipids) and regulating calcium
concentration and drug metabolism.
Rough endoplasmic reticulum - ANSWER Cell organelle responsible for
synthesizing proteins.
Catalytic site - ANSWER In molecular biology this site is part of an enzyme where
substrates bind and undergo a chemical reaction.The majority of enzymes are
proteins but RNA enzymes called ribozymes also exist. The active site of an enzyme
is usually found in a cleft or pocket that is lined by amino acid residues (or
nucleotides in ribozymes) that participate in recognition of the substrate. Residues
that directly participate in the catalytic reaction mechanism are called active site
residues.
Vesicles - ANSWER Small lipid-bounded spheres which transport proteins, glyco
proteins and newly synthesized lipids (which are imbedded in the sphere itself) from
the endoplasmic reticulum to the Golgi Apparatus or from the Golgi apparatus to
another destination. They move short distances by the process of difussion, moving
long distances requires the assistance of proteins associated with microtubules.
Golgi apparatus - ANSWER This is an organelle found in all eukaryotic cells.It was
identified in 1897 by the Italian physician Camillo Golgi, after whom it is named. It
processes and packages proteins after their synthesis and before they make their
way to their destination; it is particularly important in the processing of proteins for
secretion. Its size varies in different types of cells depending on cell function; a
hormone secreting cell will contain a far larger version of this organelle than a
muscle cell for example. It also forms a part of the cellular endomembrane system.
Constitutive release - ANSWER The constant release of small amounts of a
substances from the cell membrane.
, Regulated release - ANSWER The release of substances from a cell membrane
only when specific conditions exist. A good example is the release of gastrointestinal
hormones and digestive enzymes in response to food.
Exocytosis - ANSWER The process by which substances are exported from a cell.
Phagocytosis/Endocytosis - ANSWER The process by which substances or
pathogens are taken in to a cell by engulfment by a vesicular structure surrounded
by cell membrane.
Lysosomes - ANSWER Small organelles which contain digestive enzymes with an
internal pH of around 5. They are responsible for breaking down large molecules
taken in to the cell by phagocytosis and also for the breaking down of old organelles.
Peroxisomes - ANSWER Organelles that are plentiful in liver cells and adipocytes,
responsible for breaking down fatty acids and amino acids in to hydrogen peroxide
(among other things) via the action of an enzyme known as catalayse.
MItochondrian - ANSWER Sausage shaped organelles with a double membrane.
The inner membrane folds in to cristae. This organelle plays a fundamental role in
the production of ATP in eukarayote cells and they are abundant in cells which
require high amounts of energy such as muscle cells.
Cristae - ANSWER Internal compartments formed by the inner membrane of a
mitochondrion. They are studded with proteins, including ATP synthase and a variety
of cytochromes. The maximum surface for chemical reactions to occur is within the
mitochondria. This allows cellular respiration (aerobic respiration since the
mitochondrion requires oxygen) to occur.
Mitochondrial DNA - ANSWER The DNA located in mitochondria
It can be regarded as the smallest chromosome, and was the first significant part of
the human genome to be sequenced. In most species, including humans, mtDNA is
inherited solely from the mother. The DNA sequence of mtDNA has been determined
from a large number of organisms and individuals (including some organisms that
are extinct), and the comparison of those DNA sequences represents a mainstay of
phylogenetics, in that it allows biologists to elucidate the evolutionary relationships
among species. It also permits an examination of the relatedness of populations, and
so has become important in anthropology and field biology.
Mitochondrial Matrix - ANSWER This matrix contains soluble enzymes that
catalyze the oxidation of pyruvate and other small organic molecules.
It also contains the mitochondria's DNA and ribosomes. The word "matrix" stems
from the fact that this space is viscous, compared to the relatively aqueous
cytoplasm.
Cell Wall - ANSWER An extracellular structure in plants which is rigid and
surrounds the cell membrane giving it shape and support, like playtex for plants lol! It
is primarily composed of cellulose which is a polysaccharide.
Edition Alberts Questions & Answers with rationales
(Chapter 1-24)
Eukaryote - ANSWER An organism whose cells contain complex structures
enclosed within membranes. The defining membrane bound structure thats sets
them apart from prokaryotic cells is the nucleas or nuclear envelope within which the
genetic material is carried. All species of large complex species are eukaryotes,
including animals, plants and funghi.
Euchromatin - ANSWER This shows as pale areas in the nucleas under electro
magnification. It is a less densly packed form of chromatin; 10% is even less
condensed and in this form it can be actively transcribed to produce RNA.
Heterochromatin - ANSWER This shows as dark areas on the eukaryotic nucleas;
it is densly packed chormatin (DNA and protein complex) which cannot be
transcribed.
Histones - ANSWER Special proteins around which DNA is wrapped.
Lamins - ANSWER Intermediate filament proteins which protect the structure of the
nucleas, they polymerize to from a network of filaments that lie just within the nuclear
membrane. The network of these filament proteins is called the nuclear lamina.
Nuclear Lamina - ANSWER The network of intermediate nuclear filament proteins
(Lamins) which is located just below the nuclear membrane and is linked to the
membrane and chromatin.
Nuclear Pores - ANSWER 9nm (approx) gaps in the nuclear envelope that allow
the passage of RNA and ribosomes out of the nucleas and the entry of selected
small proteins and small water soluble molecules.
Prokarayotes - ANSWER An organism of the kingdom of Monera, comprising the
bacteria and cyanobacteria. Characterised by the abscence of a distinct, membrane
bound nucleas or membrane bound organelles and by DNA that is not organised in
to chromosomes. Also called moneran.
Protoctist - ANSWER Any of various unicellular eukaryotic organisms and their
multicellular, coenocytic or colocial descendants that belong to the kingdom of
Protocista according to some taxonomic systems. The protoctists include
protozoans, slime moulds, various algae and other groups. In many new
classification systems, all proctists are considered protists.
,Signal Sequence - ANSWER Affectionately known as the 'address label' of a
polypeptide. A short (3-60 amino acids long) peptide chain that directs the transport
of a protein. These may also be called targeting signals, signal peptides, transit
peptides, or localization signals.
The amino acid sequences of these direct proteins (which are synthesized in the
cytosol) to certain organelles such as the nucleus, mitochondrial matrix, endoplasmic
reticulum, chloroplast, apoplast and peroxisome. Some signal peptides are cleaved
from the protein by signal peptidase after the proteins are transported.
Endoplasmic Reticulum - ANSWER The endoplasmic reticulum (ER) is a
eukaryotic organelle that forms an interconnected network of tubules, vesicles, and
cisternae within cells. Rough endoplasmic reticula synthesize proteins, while smooth
endoplasmic reticula synthesize lipids and steroids, metabolize carbohydrates and
steroids (but not lipids), and regulate calcium concentration, drug metabolism, and
attachment of receptors on cell membrane proteins. Sarcoplasmic reticula solely
regulate calcium levels.
Smooth endoplasmic reticulum - ANSWER Cell organelle responsible for
attachment of receptors on cell membrane proteins, synthesizing lipids and steroids,
metabolizing carbohydrates and steroids (but not lipids) and regulating calcium
concentration and drug metabolism.
Rough endoplasmic reticulum - ANSWER Cell organelle responsible for
synthesizing proteins.
Catalytic site - ANSWER In molecular biology this site is part of an enzyme where
substrates bind and undergo a chemical reaction.The majority of enzymes are
proteins but RNA enzymes called ribozymes also exist. The active site of an enzyme
is usually found in a cleft or pocket that is lined by amino acid residues (or
nucleotides in ribozymes) that participate in recognition of the substrate. Residues
that directly participate in the catalytic reaction mechanism are called active site
residues.
Vesicles - ANSWER Small lipid-bounded spheres which transport proteins, glyco
proteins and newly synthesized lipids (which are imbedded in the sphere itself) from
the endoplasmic reticulum to the Golgi Apparatus or from the Golgi apparatus to
another destination. They move short distances by the process of difussion, moving
long distances requires the assistance of proteins associated with microtubules.
Golgi apparatus - ANSWER This is an organelle found in all eukaryotic cells.It was
identified in 1897 by the Italian physician Camillo Golgi, after whom it is named. It
processes and packages proteins after their synthesis and before they make their
way to their destination; it is particularly important in the processing of proteins for
secretion. Its size varies in different types of cells depending on cell function; a
hormone secreting cell will contain a far larger version of this organelle than a
muscle cell for example. It also forms a part of the cellular endomembrane system.
Constitutive release - ANSWER The constant release of small amounts of a
substances from the cell membrane.
, Regulated release - ANSWER The release of substances from a cell membrane
only when specific conditions exist. A good example is the release of gastrointestinal
hormones and digestive enzymes in response to food.
Exocytosis - ANSWER The process by which substances are exported from a cell.
Phagocytosis/Endocytosis - ANSWER The process by which substances or
pathogens are taken in to a cell by engulfment by a vesicular structure surrounded
by cell membrane.
Lysosomes - ANSWER Small organelles which contain digestive enzymes with an
internal pH of around 5. They are responsible for breaking down large molecules
taken in to the cell by phagocytosis and also for the breaking down of old organelles.
Peroxisomes - ANSWER Organelles that are plentiful in liver cells and adipocytes,
responsible for breaking down fatty acids and amino acids in to hydrogen peroxide
(among other things) via the action of an enzyme known as catalayse.
MItochondrian - ANSWER Sausage shaped organelles with a double membrane.
The inner membrane folds in to cristae. This organelle plays a fundamental role in
the production of ATP in eukarayote cells and they are abundant in cells which
require high amounts of energy such as muscle cells.
Cristae - ANSWER Internal compartments formed by the inner membrane of a
mitochondrion. They are studded with proteins, including ATP synthase and a variety
of cytochromes. The maximum surface for chemical reactions to occur is within the
mitochondria. This allows cellular respiration (aerobic respiration since the
mitochondrion requires oxygen) to occur.
Mitochondrial DNA - ANSWER The DNA located in mitochondria
It can be regarded as the smallest chromosome, and was the first significant part of
the human genome to be sequenced. In most species, including humans, mtDNA is
inherited solely from the mother. The DNA sequence of mtDNA has been determined
from a large number of organisms and individuals (including some organisms that
are extinct), and the comparison of those DNA sequences represents a mainstay of
phylogenetics, in that it allows biologists to elucidate the evolutionary relationships
among species. It also permits an examination of the relatedness of populations, and
so has become important in anthropology and field biology.
Mitochondrial Matrix - ANSWER This matrix contains soluble enzymes that
catalyze the oxidation of pyruvate and other small organic molecules.
It also contains the mitochondria's DNA and ribosomes. The word "matrix" stems
from the fact that this space is viscous, compared to the relatively aqueous
cytoplasm.
Cell Wall - ANSWER An extracellular structure in plants which is rigid and
surrounds the cell membrane giving it shape and support, like playtex for plants lol! It
is primarily composed of cellulose which is a polysaccharide.
