BIO Midterm 2
Nuclear pore complexes: control what enter/exits nucleus
Nuclear lamina: gives structure to nucleus
Chromatin: DNA + protein, contains genetic material
Nucleolus: makes ribosomes from RNA and protein from cytoplasm
ER Lumen: where substances are made
ER encloses ER lumen
Rough ER processes many proteins synthesized there by adding carbohydrates by glycosylation
Glycosylation: protein + sugar = glycoprotein
Smooth ER has many enzymes embedded in membrane involved in building marcomolecules
Synthesis of most lipids, including phospholipid + cholesterol in Smooth ER
Smmoth ER contains enzymes that detoxify harmful substances
Liver cells have lots of Smooth ER
Smooth ER stores calcium ions
Lysosomes contain acid hydolases
Lyosomes contains enzymes that are active at low pH
Cell movements due to flagella and cilia are due to microtubules
Autocrine: cell targets itself
Signaling across gap junctions: cell targets a cell connected by gap junctions/cytoplasmic bridges, sometimes chemical selectivity
Paracrine: cell targets nearby cell, the closer the cells the better it works
Endocrine: cell targets a distant cell via bloodstream
Nuerons use a special form of paracrine signaling
Cell signaling involves reception, transduction, response.
Signaling transduction: group of proteins that forma signal transduction pathway carry the message away from the cell surface
Sometimes cell receptors are in the cell
Sensitivity to external signals is determined by: number of receptors present on target cell, percent of receptors bound by ligand, affinity of ligand for receptor
Abnormal HER2+: causing cells to grow too quickly
Ion Channel Receptors: one way channels, gated channels open and close in response to a signal, such as a ligand binding
Heterotrimeric G protein: Alpha, Betta, Gamma
G-protein coupled receptors: ligand binds to G-protein coupled receptor, which causes the alpha part of the heterotrimeric G protein to exchange GTP for GDP
GTP(inactive)
GDP(active)
GDP causes Betta and Gamma subunits to separate from the Alpha subunit → this triggers a cellular response
GTP is hydrolyzed to form GDP
Enzyme-linked receptors: ligand binding site combines w/another receptor when both receptors have a signaling molecule, making a dimer
then the activated tyrosine kinase regions form unphosphorylated ATP and transforms it into ADP,
the relay proteins pick up the message then carry it to another relay protein
Steroid receptors are mostly inside the cell and bind directly to DNA
they influence protein production in the target cel by increasing/decreasing transcription of specific genes (slow process)
Signaling pathways contain dozens of second messengers
Enzyme-catalyzed chemical reactions can activate/inactivate second messengers rapidly, many second messengers when activated have their own enzymatic activity
Cytoplasmic response (fast - less than a second)
Nuclear response (slow- hours/days)
Different responses:
Pathway leads to a single response
Pathway branches → two response
Cross-talk occurs b/w 2 pathways
Different receptor leads to different response
Affect of ACH on cells:
Heart Muscle: decreased rate and force of contraction
Skeletal muscle: contraction
Salivary gland: secretion
Cells that die by apoptosis shrink/collapse/condense - “blebbing” of the plasma membrane occurs and eventually cell is engulfed by another cell
Apoptosis can occur due to extracellular signal and by the mitochondria
Entropy (S): disorder happens naturally/spontaneously, organization requires energy
Chemical energy: the PE stored in chemical bonds
Free energy (G): energy available to do work
Enthalpy (H): energy contained in a molecule’s chemical bonds
Chemical reactions can create changes in free energy
ΔG=ΔH-TΔS (t=temp.)
Endergonic = uses energy
Exergonic = releases energy
When products contain more free energy than reactants ΔG is positive - endergonic
When reactants contain more free energy than products, ΔG is negative - exergonic
ATP has a high amount of enthalpy
Hydrolysis of ATP is a common exergonic reaction used to power: chemical work, transport work, and mechanical work
Activation energy: energy needed to get a reaction started
Cells can regulate enzyme activity by regulating production and degradation of enzymes (slow) good for long-term
Competitive inhibitors: compete with the substrate for binding to the same active site
Noncompetitive inhibitors: bind to sites other than the enzymes active site
Allosteric enzymes: exist in either an active or inactive state and use non-competitive inhibitors to regulate activity
Allosteric inhibitors are non-competitive inhibitors that bind to the allosteric site to inactivate the enzyme
Allosteric activators bind to the allosteric site to activate the enzyme
Oscillation: going between active form and inactive form
Feedback inhibition: when the end product of the pathway is an allosteric inhibitor of an earlier enzyme in the pathway
Oxygen helps us break down glucose and other food molecules to power cellular reactions
Oxidative phosphorylation: use of ATP snythase and energy derived from a proton (H+) gradients to make ATP (happens in ETC)
Glycolysis converts glucose into 2 pyruvate
Glycolysis occurs in cytoplasm
Glycolysis does not require oxygen
Glycolysis has a net production of 2 ATP molecules by substrate-lvl phosphorylation and 2 NADH produced by the reduction of NAD+
NAD+ accepts 2 electrons and 1 proton to become NADH
NAD+: oxidized form
NADH: reduced form
When oxygen is present, pyruavte is converted to Acetyl-CoA which enters the citric acid cycle
When oxygen is absent, pyruvate is fermented which is coupled to oxidation of NADH back to NAD+
Pyruvate Oxidation:
produces CO2 and NADH
occurs in mitochondrial matrix
multi enzyme complex, coenzyme A, completes the reaction in 3 steps
Citric Acid Cycle:
Krebs cycle oxidizes the Acetyl-CoA to completely break it down into CO2
occurs in mitochondrial matrix
many electrons are transferred to the electron carriers NAD+ and FAD
After glycolysis, pyruvate oxidation, and citric acid cycle, 1 glucose molecule has been oxidized to produce: 6 CO2, 4 ATP, 10 NADH, 2 FADH2
ETC
Enzymes remove electrons from NADH and FADH2 and pass them along the chain
Energy released from the ETC pumps protons into the inter membrane space
Creates a concentration gradient: protons are more abundant in the inter membrane space than the mitochondrial matrix
Chemiosmosis
uses energy from the proton gradient to generate ATP
protons pass through ATP synthase, releasing energy that is used to make ATP
ATP synthase uses the mitochondrial proton gradient to make ATP
produces 34 ATP
Fermentation reduces organic molecules in order to regenerate NAD+
Ethanol fermentation occurs in yeast + some bacteria
CO2, ethanol, and NAD+ are produced
Lactic Acid Fermentation
occurs in animal cells (especially muscles)
electrons are transferred from NADH to pyruvate to produce lactic acid