Exam 2 Flashcards
Membrane protein functions
-Transport (stuff in and out of cell)
-Enzymatic activity (activity between enzymes)
-Signal transduction (signaling molecules and receptors)
-Cell-cell recognition (hey this is me)
(Ex: HIV can only enter in cell if CD4 proteins and co-receptor CCR5 are there (needs coreceptor to recognize))
-Intercellular joining (combine two cells)
-Attachment to cytoskeleton (stability of cell)
Diffusion
movement from [high] to [low]
Osmosis
-Movement of water through membrane from [high] to [low]
-moves through aquaporins
-passive transport
Isotonic
Solution around cell has same solute concentration
Hypotonic
Solution around cell has lower solute concentration, so water moves into cell
Hypertonic
solution around cell has higher solute concentration, so water leaves cell
Equilibrium
net movement of molecules is the SAME on both sides of the membrane
Selective Permeability
small hydrophobic molecules move the fastest through membranes (hydrophilic molecules have a hard time passing across because they are hydrophilic like the exterior of the membrane, so have a hard time passing through)
Types of Transmembrane Proteins
Channel and Carrier proteins
Channel proteins
- passive transport only
-hydrophilic pores
-may be gated to control diffusion
Types of gated channel proteins
-Ligand
-Electrically
-Mechanically
Carrier proteins
-specific binding of a solute
-slower than channel proteins
-passive or active transport
-can be fully saturated
Passive Transport
- no energy required
-[high] to [low]
-driving force is electrochemical gradient
-channel and carriers
Active transport
- requires energy like ATP
-[low] to [high]
-only by carriers
-can create an electrochemical gradient
Symport
molecules move through in same direction
Antiport
molecules move through in different direction
Primary active cotransport
-energy put in to actively move two substances across membrane
-Ex: Na+/ K+ ATPase Pump
-creates gradient
Secondary active cotransport
-fueled by gradient
-Ex: secondary active glucose pump to pump glucose from [low] to [high]
Bulk transport definition and types
Moves large molecules
Types:
-Phagocytosis: cell engulfs food
-Pinocytosis: cell engulfs fluid
-Receptor-Mediated Endocytosis: ligands bin to receptors to bring in specific molecules
Juxtacrine signaling
adjacent cell signaling
Paracrine signaling
nearby cell signaling
Synaptic signaling
electrical signal triggers release of neurotransmitter
Endocrine signaling
distant cells (bloodstream)
cell response
change in cellular activity:
-gene expression
-enzyme activity
-cell division
-cytoskeletal structure
-motor activity
Lipid-soluble signals
-hydrophobic- so can move through membrane
-binds to intracellular signals
-commonly steroids, thyroid hormone, NO
Water soluble signals
-hydrophobic
-needs help of receptors
-activates signal transduction pathway
Ligand-gated ion channel
ACh (signal) molecule binds to gated channel to allow Na+ through
G protein- coupled receptor
signal binds to receptor to dissociate G-protein and then activate effector protein that starts cell responses
Enzyme linked receptor
Insulin links to insulin receptor, which then binds phosphates to insulin receptor inside cell and carries out cellular responses
Phosphorylation
addition of a phosphate group to a molecule or ion
-protein kinase adds
-phosphatase removes
Second Messenger
-carry instructions from first messenger throughout cell
-most important is cAMP
G-protein –> adenylyl cyclase –> cAMP –> protein kinase A –> cellular response
Signal Transduction Pathway
-reception
-transduction
-cellular response
Amplification
small signal= large response
Regulation/ specificity
Cells responds to same signals differently
Ex: epinephrine in heart increases rate, but relaxes smooth muscle
Termination
-cell responses are limited
-balances kinase and phosphatase activities
Reduction
gaining electron
Oxidation
losing electron
reducing agent
gets oxidized
makes other molecule get reduced
oxidizing agent
gets reduced
makes other molecule get oxidized
Electrons move with what ion?
Hydrogen ions!
Do redox reactions release energy?
Yes! They are exergonic!
NADH
oxidized form NAD+ is an electron acceptor during cellular respiration (NADH has the electron (tell by H+))
Cellular Respiration steps
- Glycolysis
- Pyruvate Decarboxylation
- Citric Acid Cycle
- Oxidative Phosphorylation
Glycolysis Purpose
-Split glucose into pyruvate
- C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy (exergonic redox)
Glycolysis Problem and Solutions
Problem: Glycolysis needs NAD+ to function
Solution: Fermentation under anaerobic conditions or aerobic respiration
Glycolysis location in cell
Cytosol
Glycolysis steps
-First, 2 ATP broken down in order to break down 1 glucose into 1 fructose
Secondly, fructose cleaved into 2 G3P
Thirdly, 2 G3P converted into 2 pyruvates by removing phosphates and other bonds. The removal of these bonds fuels energy to convert 2 NAD+ + 2 Pi into 2 NADH, as well as 4 ADP + 4 Pi into 4 ATP (substrate level phosphorylation)
(No O2 consumed and no carbon oxidized)
Glycolysis input and output
Input:
1 6C glucose
2 NAD+
2 ADP
2 Pi
Output:
2 pyruvates
2 NADH and 2 H+
2 ATP (4 formed, but 2 used up)
Lactate Fermentation
-generates NAD+ for glycolysis
-pyruvate reduced to lactate
-NADH from glycolysis oxidized to NAD+
-no consumption of ATP, O2, no oxidation of CO2
Alcoholic Fermentation
-generates NAD+ for glycolysis
-1 pyruvate converted to 1 acetaldehyde (toxic) and 1 CO2
-NADH from glycolysis converted to NAD+ and converts acetaldehyde to ethanol (dehydrates)
problem with anaerobic fermentation
Lots of energy still trapped in reduced organic molecules (pyruvate, ethanol, lactate)
How does pyruvate enter mitochondria
passively transported through porin in outer mitochondria membrane.
Actively transported via H+ pyruvate cotransporter (symport) into inner membrane
Pyruvate Decarboxylation
-step in-between glycolysis and citric acid cycle
-transport protein removes carboxyl group, producing CO2
-converts NAD+ to NADH
-combines with coenzyme A to form Acetyl CoA!!!
Location of citric acid cycle
matrix of mitochondria
How many cycles of citric acid cycle to oxidize 1 glucose molecule?
2 cycles
Steps of Citric Acid Cycle
- Acetyl-CoA (2C) + Oxaloacetate (4C) → Citrate (6C) + CoA (leaves)
- 2 decarboxylations (removal of CO2)
- 1 substrate level phosphorylation (take a phosphate group away and convert GDP to GPT)
- 4 oxidations/ reductions of:
3 NAD+ → 3 NADH + 3 H+ (6 electrons)
1 FAD → 1 FADH2 (2 electrons)
Overall regenerates Oxaloacetate (4C) to start over again
End products from citric acid cycle and pyruvate decarboxylation
-6 carbons converted to 6 CO2
-2 ATP
-8 NADH
-2 FADH2
(90% energy stored in NADH and FADH2)
Reduced all carbons and stored energy in reduced coenzymes
Problem at end of Citric Acid Cycle + solution
Problem: Energy is stored in energy carriers!
Answer: Oxidative Phosphorylation
Oxidative Phosphorylation 2 processes
Electron Transport Chain and Chemiosmosis
ETC location
inner mitochondria membrane
Point of ETC
extract electrons from electron carriers, reducing energy levels to level of water, regenerate NAD+ for glycolysis, and creating electrochemical gradient
Respiratory Complex I
-pumps H+ ions
-converts NADH to NAD+
Respiratory Complex II
- does NOT pump H+
-converts FADH2 to FAD
Coenzyme Q or CoQ
accepts electrons from complexes I and II and transports to III
Respiratory Complex III
-pumps H+ ions
Cytochrome C
transports electrons from complex III to IV
Respiratory Complex IV
-pumps H+ ions across membrane
-oxygen combines with end electrons and H+ to form water
(reason we breathe O2!!)
End of ETC
electrons reduced and combined with O2 to make water, gradient formed, NAD+ (glycolysis and citric acid cycle!) and FAD regenerated
ATP Synthase Complex
converts ADP to Pi by using energy creating from electrochemical gradient
ATP degenerated from NADH and FADH2
NADH- 2-3 ATP
FADH2- 1-2 ATP
Total ATP generated from Cellular respiration
32!
Versatility of Cellular Respiration
-catabolic pathways funnel electrons from many different organic molecules (proteins, carbs, fats) which can enter into different steps in cellular respiration
-lots of carbs accepted
Regulation of cellular respiration
Based on feedback inhibition. If not enough ATP, processes speed up. If enough ATP, processes slow down. Done by regulating enzymes along metabolic pathway
Photosynthesis vs Aerobic respiration
AR:
-C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + energy
-Electrons removed from carbs and added to oxygen
-Exergonic- electrons lose energy (ETC)
P:
-6 CO2 + 6 H2O + energy → C6H12O6 + 6 O2
-Electrons from water added to CO2 to form carbohydrates and release oxygen
-Endergonic- electrons gain energy! (excitement stage)
Two Parts of Photosynthesis
Light Dependent and Light Independent (Calvin cycle)
Why are plants green
-Green light wavelength is reflected/ transmitted, while all other wavelengths are absorbed
-Green wavelengths are the least productive for photosynthesis
-Many plants have chlorophyll pigment (green)
Location of Light-dependent processes
-Chlorplast
-Specifically photosystems imbedded inside thylakoid membranes
Photoexcitation process
- Light protons hit photosystem II, taking electrons from the oxidation of H2O (creates oxygen as byproduct)
- electron goes through electron transport creating ATP (Able to happen because electrochemical gradient formed by passing electron)
- Electron goes to photosystem I, and is re-excited by photons
- Electron goes to NADP+ reductase to convert NADP+ to NADPH
PSII vs PSI
PSII- wavelength 680
(electron from water)
PSI- wavelength 700
(electron from ETC)
End of Light-Dependent reactions
-Energy stored in NADPH and ATP for Calvin cycle
-O2 byproduct
Light Independent Location
-chloroplast
-Specifically stroma (like cytoplasm)
Input of Light Independent
-3 CO2
-9 ATP
-6 NADPH
Output of Light Independent
G3P! (precursor to glucose)
Needed organic carbon for start of Calvin cycle
Ribulose Bisphosphate (RuBP)
Steps of Calvin cycle (3)
- Carbon fixation to RuBP
(RuBP) (5C) + CO2 (1C)→ 1 3-Phosphoglycerate (2 x 3C) (happens 3 times) - Reduction: addition of electrons to create carbohydrate
(6 ATP + 6 NADPH –> 6 G3P)
1 G3P released! - Reorganization: 3 ATP help convert 5 G3P to 3RuBP
G3P purpose
-Energy storage (becomes glucose)
-Energy transport (sucrose synthesis)
-Oxidation of G3P in cytosol and mitochondria for ATP
Rubsico problem?
It can fix CO2 or O2, but the fixation of O2 is toxic. So cells must limit O2 in presence of Rubisco. Solution is C4 plants and CAM plants
(or enzyme is CO2 specific)
C4 plants
-C4 plants separate carbon fixation from where rubisco is (different place- separate cell)
-Carbon fixation happens twice
-Rubisco avoids O2
CAM plants
-Fix carbon at night (stored in vacuole)
-Complete cycle during the day with sun
Genetic material
-material used to store info for a cell, organelle or virus to carry out activities and replicate
-needs to be stored
-read in a way cells can understand
-transferred to next generations
T/F: Proteins can store genetic material that can be transferred back to DNA.
False
DNA and RNA transferrable, but once it’s given to protein it cannot be transferred back
Mendel
Purpose: Traits inherited independently
Experiment: dominant and recessive traits through peas
Morgan
Purpose: Genes located on chromosomes
Experiment: mapped gene expression in fruit flies
Griffith
Purpose: “transforming principles” passed down from dead to living cells
Experiment: found that when dead virulent (S) cells were combined with live benign cells, virulent material was passed down
Avery, McCarty and MacLeod
Purpose: Transforming principle is DNA
Experiment:
-Had 3 mixtures with either no proteins, no RNA, or no DNA
-Mixed with non living S cells
-Whichever did not make living S cells is the transforming factor!! (DNA)
Hershey and Chase
Purpose: genes composed of DNA
Experiment:
-Two separate cultures tracking radioactive isotopes spreading to infected cells through bacteriophage
-S= Protein, P= DNA
-The culture that had no radioactivity in solutions and only in cells was the one that held genetic material (DNA)
Chargaff
organism has equal ratio of A:T and G:C nucleotides in all cells
Rosalind Franklin
Used XRays and found that shape of DNA is a double strand helix
James Watson
Goldilocks principle: determined position of A+T, G+C
Why did scientist not believe DNA was genetic material
believed it was too simple! Thought proteins were more structurally and functionally diverse
