USABO Exam Questions & Answers
(Grade A+)
Eukaryote -
correct 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 -
correct 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 -
correct answer ✅This shows as dark areas on the eukaryotic
nucleas; it is densly packed chormatin (DNA and protein complex)
which cannot be transcribed.
Histones -
correct answer ✅Special proteins around which DNA is wrapped.
,USABO Exam Questions & Answers
(Grade A+)
Lamins -
correct 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 -
correct 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 -
correct 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 -
correct 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.
,USABO Exam Questions & Answers
(Grade A+)
Protoctist -
correct 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 -
correct 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 -
correct answer ✅The endoplasmic reticulum (ER) is a eukaryotic
organelle that forms an interconnected network of tubules,
, USABO Exam Questions & Answers
(Grade A+)
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 -
correct 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 -
correct answer ✅Cell organelle responsible for synthesizing
proteins.
Catalytic site -
correct 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
(Grade A+)
Eukaryote -
correct 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 -
correct 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 -
correct answer ✅This shows as dark areas on the eukaryotic
nucleas; it is densly packed chormatin (DNA and protein complex)
which cannot be transcribed.
Histones -
correct answer ✅Special proteins around which DNA is wrapped.
,USABO Exam Questions & Answers
(Grade A+)
Lamins -
correct 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 -
correct 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 -
correct 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 -
correct 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.
,USABO Exam Questions & Answers
(Grade A+)
Protoctist -
correct 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 -
correct 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 -
correct answer ✅The endoplasmic reticulum (ER) is a eukaryotic
organelle that forms an interconnected network of tubules,
, USABO Exam Questions & Answers
(Grade A+)
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 -
correct 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 -
correct answer ✅Cell organelle responsible for synthesizing
proteins.
Catalytic site -
correct 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
