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Eukaryote - ACCURATE ANSWERS 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...
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Eukaryote - ACCURATE ANSWERS✔✔ 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 - ACCURATE ANSWERS✔✔ 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 - ACCURATE ANSWERS✔✔ This shows as dark areas on the
eukaryotic nucleas; it is densly packed chormatin (DNA and protein complex)
which cannot be transcribed.
,Histones - ACCURATE ANSWERS✔✔ Special proteins around which DNA is
wrapped.
Lamins - ACCURATE ANSWERS✔✔ 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 - ACCURATE ANSWERS✔✔ 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 - ACCURATE ANSWERS✔✔ 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 - ACCURATE ANSWERS✔✔ 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 - ACCURATE ANSWERS✔✔ 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 - ACCURATE ANSWERS✔✔ 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 - ACCURATE ANSWERS✔✔ 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 - ACCURATE ANSWERS✔✔ 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 - ACCURATE ANSWERS✔✔ Cell organelle
responsible for synthesizing proteins.
Catalytic site - ACCURATE ANSWERS✔✔ 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 - ACCURATE ANSWERS✔✔ 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 - ACCURATE ANSWERS✔✔ 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 - ACCURATE ANSWERS✔✔ The constant release of small
amounts of a substances from the cell membrane.
Regulated release - ACCURATE ANSWERS✔✔ 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 - ACCURATE ANSWERS✔✔ The process by which substances are
exported from a cell.
Phagocytosis/Endocytosis - ACCURATE ANSWERS✔✔ The process by which
substances or pathogens are taken in to a cell by engulfment by a vesicular
structure surrounded by cell membrane.
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