Passive Transport• Diffusion refers to a natural phenomenon caused by the tendency of small particles to spread out evenly within any given space.• Dialysis is a form of diffusion in which the selectively permeable nature of a membrane causes the separation of smaller solute particles from larger solute particles.• Osmosis is the diffusion of water through a selectively permeable membrane.• Facilitated Diffusion is when the movement of molecules of molecules is facilitated or made more efficient by the action of carrier mechanisms in a cell membrane.• Filtration involves the passing of water and permeable solutes through a membrane by the forces of hydrostatic pressure.
Active Transportation• One type of active transport pump, the sodium- potassium pump, operates in the plasma membrane of all human cells. • it actively transport sodium ions and potassium ions but in opposite directions. it actively transport sodium ions and• In endocytosis the plasma membrane “traps” potassium ions but in opposite directions. some extra cellular material and brings it into the cell• Exocytosis is the process by which large molecules notably proteins, can leave the cell even though they are too large to move through the plasma membrane.
Cell Metabolism• Catabolism includes – Cellular respiration – Glycolysis – Citric acid cycle – Electron transport system• Anabolism – DNA – RNA – mRNA – tRNA
Cell Metabolism• Enzymes are classified as functional proteins; they regulate cell functions by regulating metabolic pathways. – Enzymes are proteins and have the chemical properties of proteins – Enzymes are usually teritary or quanternary proteins of complex shapes. – The active site is the portion of the emzyme molecule that chemically “fits” the sunstrate molecule(s). – Enzymes fall into several groups • Oxidation-reduction enzymes • Hydrolyzing enzymes • Phosphorylating enzymes • Enzymes that add or remove carbon dioxide • Enzymes that rerange atoms within a molecule • Hydrases
Protein Synthesis• Transcription 1. A strand of RNA forms along a segment of one strand of a DNA molecule 2. Uracil attaches to adenine and guanine attaches to cytosine (Complementary paring). mRNA is formed. 3. Introns , of mRNA, are removed by enzymatic process; which leaves behind segments that are copies of the DNA’s exon. 4. The mRNA leaves the nucleus therefore completing transcription.
Protein Synthesis• Translation 1. In the cytoplasm, the edited mRNA molecule attracts ribosome subunits that come together around the mRNA molecule.
DNA Transcription• DNA must be copied to messenger RNA (mRNA)• mRNA goes from nucleus to the ribosomes in cytoplasm• mRNA complements known as codons – Only 3 nucleotide “letters” long• Remember RNA has uracil (U) instead of thymine (T)!
Transcription – Step IA C G T A T C G C G T AT G C A T A G C G C A T Template DNA Strands
Transcription – Step IIA C G T A T C G C G T AU G C A U A G C G C A UTemplate DNA is Matched Up withComplementary mRNA Sequences
Transcription – Step IIIA C G U A U C G C G U AU G C A U A G C G C A U mRNA leaves nucleus and goes to ribosomesA new complementary RNA strand ismade (rRNA)
Protein Translation• Modified genetic code is “translated” into proteins• Codon code is specific, but redundant! – 20 amino acids – 64 triplet (codon) combinations
tRNA in cytoplasm has a codon attached to an amino acid
tRNA structure• 3-base code (triplet) is an “anticodon”• Protein molecule• Attached amino acid that is carried from cytoplasm to ribosomes
Protein Synthesis• Start: Ribosome binds to mRNA at start codon (AUG)• Elongation: – tRNA complexes bind to mRNA codon by forming complementary base pairs with the tRNA anticodon – The ribosome moves from codon to codon along the mRNA. – Amino acids are added one by one• Release: release factor binds to the stop codon
Growth• Mitosis is the process of organizing and distributing nuclear DNA during cell division. 1. Interphase is when a cell is not experiencing mitosis. 2. Prophase (“before phase”) is when the cell begins to divide, usually before cytokines( “pinching in half”) become apparent. The nucleus envelope falls apart as the paired chromatids coil up to form dense, compact chromosome. 3. Metaphase is when the chromosomes are lined along a plane at the “equator” of the cell. 4. Anaphase is when the centromere of each chromosome splits to form two chromosomes, each consisting of a single DNA molecule. 5. Telophase is the end phase and during this phase that the DNA is returned to its original form and location within the cell.
Growth• Meiosis is the type of cell division that occurs only in primitive sex cells during the process of their becoming mature sex cells. –