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SOMB II Practice Test.
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SOMB II Practice Test.
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USABOEukaryote - 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.
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.
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, 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 substrate. Residues that directly participate in the catalytic
reaction mechanism are called active site residues.
Vesicles - correct 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 - correct 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 - correct answer-The constant release of small amounts of a substances
from the cell membrane.
Regulated release - correct 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 - correct answer-The process by which substances are exported from a cell.
Phagocytosis/Endocytosis - correct 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 - correct 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 - correct 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 - correct 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 - correct 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 - correct 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 - correct 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 - correct 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.
Plastids - correct answer-These are major organelles found in the cells of plants and algae.
They are the site of manufacture and storage of important chemical compounds used by the
cell, often containing pigments used in photosynthesis. The types of pigments present can
change or determine the cell's color.These organelles are responsible for photosynthesis,
storage of products like starch and for synthesis. All types are derived from proplastids
, (formerly "eoplasts", eo-: dawn, early), which are present in the meristematic regions of the
plant. Proplastids and young chloroplasts commonly divide, but more mature chloroplasts
also have this capacity.
Chloroplasts - correct answer-These plant organelles have their own DNA like mitochondria.
They are normally larger than mitochondria though and they also have a three membrane
system.
Thylakoid - correct answer-A thylakoid is a membrane-bound compartment inside
chloroplasts and cyanobacteria. They are the site of the light-dependent reactions of
photosynthesis. Thylakoids consist of a thylakoid membrane surrounding a thylakoid lumen.
Chloroplast thylakoids frequently form stacks of disks referred to as grana (singular:
granum). Grana are connected by intergrana or stroma thylakoids, which join granum stacks
together as a single functional compartment.
Stroma - correct answer-Stroma (fluid), the fluid in between grana, where carbohydrate
formation reactions occur in the chloroplasts of plant cells photosynthesizing
Glycosaminoglycans (GAG's) - correct answer-Also known as mucopolysaccharides these
are long unbranched polysaccharides consisting of a repeating disaccharide unit. The
repeating unit consists of a hexose (six-carbon sugar) or a hexuronic acid, linked to a
hexosamine (six-carbon sugar containing nitrogen). These are the major component of the
'gel' found in the extracellular matrix of tissue. They are negatively charged and thus attract
ions, especially sodium which aids diffusion of water in to the tissue, giving tissue it's
compression resistance.
Extracellular Matrix - correct answer-This matrix is secreted by cells and laid down externally
and it's properties vary enormously depending on it's chemical composition and which tissue
is being examined. In some cells it acts as cement or scaffolding. In plants it can be
associated with individual cells.
Elastin - correct answer-An flexible protein found in the extra cellular matrix of blood vessels.
Collagen - correct answer-A strong protein which can provide strength and/or flexibility found
in animal tissue.
Connective Tissue - correct answer-The name often given to tissue that contain a large
proportion of extracellular matrix. In this tissues the cells that are secreting the materials are
often quite far from each other.
Gap junction - correct answer-A specialised type of cell junction, an example of which is the
smooth muscle of the intestine. The gap's allow for effective transmission of molecules and
electrical activity between the cells.
Tight junctions - correct answer-These cell junctions are linked very closely and prevent
movement of membrane proteins, in the skin for example or in the role mainting the polarity
of the cells of the intestine.
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