CELL STRUCTURE AND FUNCTION. Despite the diversity among cells, three basic features are common to all cell types. All cells have outer boundary, an interior substance and a control region. CELL STRUCTURES. Composition: phospholipid bilayer with embedded proteins. Function:
CELL STRUCTURE AND FUNCTION
Despite the diversity among cells, three basic features are common to all cell types. All cells have outer boundary, an interior substance and a control region.
Composition: phospholipid bilayer with embedded proteins.
selective passage of molecules into and out of cell
Composition: nuclear envelope surrounding nucleoplasm, chromatin and nucleolus
Function: storage of genetic information, controls metabolic functioning and structural characteristics of the cell.
Composition: protein and RNA in two subunits
Function: Protein synthesis
Composition: membranous saccules and canals
Function: synthesis and /or modification of proteins and other substances, and transport by vesicle formation
Composition: stack of membranous saccules
Function: Processing, packaging, and distribution of molecules
Composition: membranous sac
Function: storage and transport substances
Composition: membranous vesicle containing digestive enzymes
Function: intracellular digestion
Composition: inner membrane (cristae) within outer membrane
Function: cellular respiration
Composition: microtubles, actin filaments
Function: shape of the cell and movement of its parts.
Composition: 9 + 2 pattern of microtubules
Function: movement of cell
Composition: 9 + 0 pattern of microtubules
Function: formation of basal bodies
Chromosomes are rod-shaped structures made of DNA and proteins.
Chromatid- the strand of a chromosome that becomes visible during meiosis or mitosis.
Chromatin – the less tightly coiled DNA-protein complex
Centromere – the region of the chromosome that holds the two sister chromatids together during mitosis.
Sex chromosomes are chromosomes that determine the sex of an organism, and they may also carry genes for other characteristics.
In humans, sex chromosomes are either X or Y.
XX for female
XY for male
The autosomes are all the other chromosomes in an organism except for sex chromosomes.
In humans two of the 46 are sex chromosomes, and the remaining 44 chromosomes are autosomes.
The DNA in eukaryotic cells wraps tightly around proteins called histones.
Histones help maintain the shape of the chromosomes and aid in the tight packaging of DNA.
Nonhistone proteins are generally involved in controlling the activity of specific regions of the DNA
The cell cycle is an orderly set of stages that take place between the time a cell divides and the time the resulting daughter cells also divide.
-the cell carries on its regular activities.
The three stages:
Stages of mitosis:
karyokinesis (division of the nucleus)
cytokinesis (division of the cytoplasm).
The old (parental) DNA strands unwind and “upzip”
New complementary nucleotides pair with the nucleotides in the old strands. A pairs with T and C pairs with G.
The enzyme DNA polymerase joins the new nucleotides forming new (daughter) complementary strands.
When replication is complete, the two double helix molecules are identical.
Is the formation of proteins by using information contained in DNA and carried by mRNA
is the process of forming a nucleic acid by using another molecule as a template; particularly the process of synthesizing RNA by using one strand of a DNA molecule as a template.
refers to the portion of protein synthesis that takes place at ribosomes and that uses the codons in mRNA molecules to specify the sequence of amino acids in polypeptide chains.
CONTROL OF CELL DIVISION
In eukaryotes, proteins regulate the progress of cell division at certain checkpoints.
1. Cell Growth Checkpoint.
Proteins at this checkpoint control whether the cell will divide.
Hint: if the cell is healthy and has grown to a suitable size during G1 phase, protein will initiate DNA synthesis (S phase). If conditions are not favorable for DNA synthesis, the cell cycle will stop at this point.
2. DNA Synthesis (G2) checkpoint.
DNA repair enzymes check the results of DNA replication. If this checkpoint is passed, proteins will signal the cell to begin the molecular processes that will allow the cell to divide mitotically.
3. Mitosis checkpoint.
If a cell passes this checkpoint, proteins signal the cell to exit mitosis. The cell enters into the G1 phase, the major growth phase of the cell cycle, once again.
PROKARYOTIC CELL DIVISION
Most prokaryotes reproduce by binary fission, in which two identical cells are produced from one cell.
EUKARYOTIC CELL DIVISION
In eukaryotic cell division, both the cytoplasm and the nucleus divide. There are two types of cell division in eukaryotes – mitosis and meiosis.