L14-Nucleus & Cell Cycle Flashcards
describe the nucleus.
its a rounded or elongated structure , usually found at the center of the cell contains genetic material and controls cell activity. It has 4 main components
- nuclear envelope
- nucleolus
- nuclear matrix
- chromatins
describe the nuclear envelope
the nucleus is surrounded ny 2 membranes called nuclear envelope that are separated by a small gap called perinuclear cisterna. it has polyribosomes attached to its outer surface showing that it is in continuity with the endoplasmic reticulum. it has small perforations that allow molecules to pass through and provide a controllable pathway between nucleus and the cytoplasm.
what size of molecules require energy to be transported into the nucleus?
any molecule larger than 9 micrometers require energy from ATP and carrier proteins to be transported other than that it can be passively transported into the nucleus
describe the chromatin
its mainly dan wrapped around or coiled around basic protein called histone protein. the basic structure of the chromatin is called a nucleosome which are 4 histone proteins with dan coiled around them.
what is linker dna?
a small segment of dan which joins together 2 nucleosomes.
name and explain the 2 types of chromatins
heterochromatin tightly coiled portion which is the non active part of the dan and is reserved in less active cells. and euchromatin which is the active part of the chromatin and less coiled.
what is a Barr body?
it is heterochromatin mass found in female cells of mammals. it is the 2nd X chromosome which is not active and it is the sex chromosome.
describe the nucleolus.
it has a spherical shape and rich in rRNA and proteins
what is the function of the nucleolus?
site of synthesis of the ribosomal RNA, ribosome al proteins synthesized in the ribosome are associated with the rRNA in the nucleolus and rRNA is synthesized and modified into 2 subunits small and large
what is the nucleoplasm/ nuclear matrix and define its components.
its the protoplasm of the nucleus and consists of fluid portion, proteinaceous matrix and variable ribonucleic protein particles.
what is the interphase?
it is along period where the cell increases its size and content and replicate its genetic material.
what are the 3 phases of interphase?
gap 1 phase synthesize phase and gap 2 phase.
describe the events during gap 1 phase.
the cell synthesize RNA, regulatory proteins and enzymes to carry out those activities and the cell growth to maintain its normal size and the centrioles begin to divide but finished on the G2 phase
describe the events that take place during the synthesize phase
the cell replicates its DNA and have 2 sets of DNA (4n)
describe the events that take place in the gap2 phase
the cell synthesize RNA and proteins required for cell division, energy required for mitosis is stored and centrioles and any other microtubules are created and the replicated DNA is analyzed and any errors are corrected
