Transcription

Cytoplasm

Steps of transcription (Prokaryotes)

Initiation

RNA polymerase

Binds to promoter

Helicase occurs (unwinds DNA strands

Polymerase initiate RNA synthesis at start point (start point = +1)

RNA transcript is released and detaches from DNA

mRNA made

Nucleus

Steps of transcription (Eukaryotes)

Initiation

RNA polymerase II

Binds to promoter

Helicase (unwinds DNA strands)

Polymerase initiate RNA synthesis at start point (start point = +1)

RNA transcript is released and detaches from DNA

Pre-mRNA made

RNA processing

mRNA made

Subtopic

Cytoplasm

Steps of Translation (Prokaryotes)

Initiation: The initiator tRNA carries the first amino acid F-Met (formyl- Methionine) to the small ribosomal subunit (30s)and scans the mRNA to find the start codon (AUG). Once found, the large subunit (50s) then joins the complex. The tRNA binds to the P site. Initiation factor 3(E) and initiation factor 1 (A) assist in the binding of the tRNA.

Elongation: Subsequent tRNA which carries the next amino acid binds at the A site. A peptide bond forms between the two amino acid. The enzyme that forms the bond is called peptidyl transferase. Next, the two tRNA's that occupy the P and A sites shift to occupy the E and P sites. Then the tRNA on the E site is released and a new tRNA comes onto the A site. This continues until a stop codon is found.

Termination: Once the stop codon is reached, a release factor arrives onto the A site and helps separate the complex.

Cytoplasm

Steps of Translation (Eukaryotes)

Initiation: The mRNA for eukaryotes differs in that it contains factors such as CAP on the 5' end and a poly A tail on the 3' end. This occurs only in eukaryotes because eukaryotes travel a longer distance from the nucleus to the cytoplasm for translation while transcription and translation for prokaryotes both occur in the cytoplasm.

The initiator tRNA carries the first amino acid Met (Methionine) to the small ribosomal subunit (40s)and scans the mRNA to find the start codon (AUG). Once found, the large subunit (60s) then joins the complex. The tRNA binds to the P site.

Elongation: Subsequent tRNA which carries the next amino acid binds at the A site. A peptide bond forms between the two amino acid. The enzyme that forms the bond is called peptidyl transferase. Next, the two tRNA's that occupy the P and A sites shift to occupy the E and P sites. Then the tRNA on the E site is released and a new tRNA comes onto the A site. This continues until a stop codon is found

Termination: Once the stop codon is reached, a release factor arrives onto the A site and helps separate the complex.

Mitochondria: powers and produces energy for the cell.

Cytoplasm: jelly-like, keeps everything in place, and protects cell organelles from getting damage.

Microtubules: move vesicles and organelles throughout the cell.

Lysosome: digests waste, and cleans up the cell

Smooth ER: makes lipids and steroids.

Centrosome: organizes microtubules

Chromatin: proteins and DNA

Nucleolus:creates ribosomes, is located around the nucleus

Nuclear Envelope: protein lined; allows movement in and out the nucleus

Ribosomes:help synthesizeprotein, carry genetic info, and helps repair damages.

Nucleus:conttrol center of the cell, houses DNA

Peroxisomes: metabolizes waste.

Rough ER: makes membrane proteins, waste, and has ribosomes.

Microfilaments: proteins (fibrous) that form the cellular cortex.

Plasma Membrane: protects, structures and detects transport in and out the cell.

Golgi apparatus: modifies proteins.

Vacuole: like a trash can, collects waste.

Organelles

Cytoplasm

Carries nutrients
Helps receive chemical signals
Translates chemical signals into intracellular functions

Mitochondria

Proteins break down sugars, and help produce cellular energy.

Perioxisomomes

Newly synthesized proteins are focused on degradation of lipids on the peroxisome surface.

Chloroplasts (plants)

Nucleus

Involved in transcription factors, RNA polymerase, DNA polymerase, and DNA binding proteins

Plastids (plants)

Carry transit peptides.

Rough ER

Golgi Apparatus makes lysosomes

Lysosomes carry proteins out using exocytosis

Membrane transport protein: translocates solutes, ions, nutrients, neurotransmitters, and drugs.

Translocase: Changes ATP for ADP in the intermembrans space.

Potassium Channel: Allows K+ to diffuse freely across the membrane, but not other ions, such as Na+ or Cl-

Ligand gated ion channel: allow for specified ions to pass through the membrane. (Like: Na+, K+, Ca2+, Cl-)

Cytochrome: An iron-containing protein that is a component of electron transport chains in the mitochondria and chloroplasts of eukaryotic cells and the plasma membranes of prokaryotic cells

ATP Synthase:
produces ATP

Glycoprotein:
initiate immune responses

Integrin:
links the cytoskeleton
to the extracellular matrix

Aquaporin:
transports water
across cell membranes

Receptor Tyrosine Kinase:
involved in cellular communication

Signaling molecule binds to the receptor

Relay molecule in signal transduction pathway

Activation of cellular response

Signaling molecule binds to Receptor

Relay molecule activates protein kinase 1

Kinase takes a phosphate group and inactivates protein kinase 1

Active Protein kinase 1 activates protein kinase 2 by converting ATP to ADP

Kinase removes a phosphate group from active protein kinase and results in a active protein kinase 2

Active protein kinase 2 phosphorylates a protein that brings about the cell's response to the signal

Active Protein kinase 2 is converted from a ATP to a ADP - active protein is formed

Protein phosphatases catalyze the removal of the phosphate groups from the proteins, making the proteins inactive again

The completion of this cycle results in a cellular response

Cellular response = Gene expression = mRNA = make protein

Signaling molecule binds to GPCR

G Protein is activated (GDP goes to GTP)

Activated G protein goes into the adenylyl cyclase

cAMP activates another protein and leads to a cellular response

Pathway of how proteins enter the endomembrane system

Eukaryotic Cell

Different scenarios based on G-protein signaling

Translation

Membrane proteins

Different scenarios based on G-protein signaling

Transcription

G-Protein signaling

Different scenarios based on G-protein signaling