Week 9

Membrane Transport ppt

Osmosis: the movement of water

Water will move through a membrane from a hypotonic solution to a hypertonic solution to try to dilute it

Solute transport:

  • Diffusion is the transport of solutes through the membrane freely - from high to low

  • Facilitated diffusion is when a solute needs the assistance of a transport protein to move through the membrane - from high to low

  • Active transport is when energy is required to move solutes through a membrane with a transport protein - from low to high

We need to know the process of the O2 and CO2 diffusion, but don’t have to know all the chemistry involved

Carrier proteins:

  • Capable of binding one or more molecules to an active site

  • each protein is highly specific for certain molecules

  • Transport molecules across a membrane by undergoing a conformational change

  • The need for a conformational change makes facilitated diffusion slower than with channel proteins and much slower than simple diffusion

  • Can transport either one solute, or two solutes simultaneously

  • These processes include:

    • uniport: the movement of a single solute molecule (ie. glucose)

    • Coupled transport: movement of two solutes

      • Symport: solutes move in the same direction

      • Antiport: solutes move in opposite directions

Uniport carrier protein: GLUT1 Transporter example

  • Glucose binds to the inside of a transport protein

  • The transport protein changes to be open to this inside of the cell instead

  • Glucose enters the cell

  • Insides of transport cell closes, and outside open

Insulin receptors need to activate GLUT4 transporter to move glucose in

  • Type II DM is when the receptor stops working, and the GLUT4 can’t be stimulated to do their job

  • This process:

    • When the insulin receptor binds insulin, the activated receptor phosphorylates the IRS-1 protein. IRS-1 can lead to recruitment of GRB2, activating the Ras pathway

    • IRS-1 activates PI 3-kinase which catalyzes the addition of a phosphate group to the membrane lipid PIP2. thereby converting it to PIP3. PTEN can convert PIP3 back to PIP2

    • PIP3 binds a protein kinase called Akt, which is activated by other protein kinases.

    • Akt catalyzes phosphorylation of key proteins, leading to an increase in glycogen synthase activity and recruitment of the glucose transporter, GLUT4, to the membrane

Antiport carver proteins

  • anion exchange protein

    • Situated in the erythrocyte plasma membrane

    • Mediates the reciprocal exchange of chloride and bicarbonate ions in opposite directions

Cystic FIbrosis Transmembrane Conductance Regulator (CFTR)

  • Normal lungs have mucus lining the airways

  • Cystic fibrosis is caused beta defect in the secretion ions in cells linking the lungs, leading to insufficient hydration, thick mucus, and the promotion of bacterial growth

  • Proposed structure and orientation of CFTR in the long cell membrane

Active transport:

  • similar to facilitated transport in that is requires a transport Poe in, but this process requires energy (ATP) to proceed

  • The energy requirement is due to the need to transport (pump) solutes against a gradient (ie. from low concentration to high concentration)

  • Active transport is typically unidirectional

  • Can be direct (primary)

    • Movement of solutes against a gradient using ATP

    • The Sodium Potassium Pump is an example of this

      • When sodium entrees the pump, ATP is broken creating ADP and a phosphate. This phosphate is what closes the pump inside the cell, to open the outside and release the sodium. When the outside is open, potassium enters the pump to be brought into the cell

        • Moves 3 sodium out, brings 2 potassium in

      • That extra phosphate is left in the cell to form back into ATP to repeat the process

  • Can also be Indirect (secondary)

    • The symport movement of 2 solutes, one that’s been moved by direct active transport along with another solute (ie. a specific indirect transport is reliant on a specific direct transport process).

    • The energy driving system is from the original direct process

  • When the direct active transport has pumped too much out of the cell, the indirect transport will pump that back in, as well as pumping in a solute

Membrane potential:

  • positive charge on the outside of the membrane, negative change on the inside of the membrane

    • With enough of the sodium potassium pump changing the levels of each within the cell, this can reverse.

  • If cell at rest is -70mV and you get Sodium rushing in, the cell will be at +30mV (Depolarization)

  • The amount of sodium then drops as the cell regulates it (depolarization)

  • At rest, the cell is polarized

  • Voltage gates change with the membrane potential voltage

Peritubular Capillary:

  • blood from artery enters Glomerular capsule

  • The travels through the convoluted tubule

  • The blood is filtered in this process, and then reabsorbs what is needed, then sent to the veins

  • What is filtered out is the solutes (filtrate) and water that your body didn’t need (urine)

  • Then filtrate is is sent into the peritubular capillary to potentially be reabsorbed.

    • This process involved simple diffusion, active transport, and

Water also moves through filtration which is forced through with pressure

  • High BP can cause this, which is why people with higher BP need to pee more often. The pressure is forcing the water out so the blood can dehydrate slightly, so te heart isn’t working so hard

    • Chronic HTN wears out the left side of the heart in years

  • Blood clots also cause this

    • The right side of the heart is a lot weaker, and a blood clot can stop is quickly (hours to days)

Metabolism- Glycolysis ppt

Metabolism:

  • all chemical reactions that occurs within a cell

Metabolic pathways:

  • a series of chemical reactions each of which accomplishes a specific task. 2 general types

    • Catabolic

    • Anabolic

Catabolic pathways:

  • degradative reactions that breakdown cellular components (digesting food)

  • Exergonic (release energy used to drive cellular function)

  • Often involve the hydrolysis of macromolecules or Biological oxidation

  • Proceeds with or without oxygen (aerobic vs anaerobic)

  • Products may become building blocks for biosynthesis

Anabolic pathways:

  • synthetic reactions that build cellular components (ie. glycogen, muscle proteins, etc.)

  • Endergonic (requires energy)

Classification of organisms:

  • Based on need for oxygen

  • Obligate Aerobes

    • An absolute requirement for oxygen

  • Obligate anaerobes:

    • Cannot use oxygen

    • Oxygen may be toxic to these organisms (some types of bacteria)

    • Can be treated using a hyperbaric chamber

  • Facultative organisms:

    • Can function under aerobic or anaerobic conditions, and can switch back and forth based on oxygen availability

    • Include some types of bacteria and fungi

ATP:

  • energy released from catabolic reactions is stored in the chemical bonds of other molecules

  • energy released from the breaking of these bonds is used to perform work

  • Adenosine triphosphate (ATP) is the molecule most commonly used to store energy for cellular work

  • the 3 phosphate groups of ATP are united by phosphoanhydride bonds

  • Energy released form ATP by breaking the outermost phosphoanhydride bond

  • The products of this reaction are ADP and inorganic phosphate (Pi)

  • In the outer phosphonanhydride bond (where the energy is stored from the food that you eat)

    • Gives you 7.3 kcal/mol of energy when broken

    • ATP can be reformed by adding the same amount of energy to ADP and (Pi)

  • Other high-energy molecules (like GTP, creatine phosphate, etc, giving you short bursts of energy) That can store energy that can be used to form ATP

Chemotrophic energy metabolism:

  • Pathways by high cells catabolize nutrients and conserve the released energy in ATP

  • Types of metabolic reactions

    • Oxidation (removal of electrons)

    • Reduction (addition of electrons)

    • Hydrogenation (Addition of protons)

    • Dehydrogenation (removal of protons)

  • In bio chemistry:

    • Oxidation reactions often include dehydrogenation

      • Many of the enzymes I circled in this proves are called Dehydrogenases

    • Reduction reaction often include hydrogenation

    • Oxidation and reduction (redox) reactions always take place simultaneously

Coenzymes:

  • in biochem, electrons and hydrogen atoms removed by oxidizing a substrate are transferred to one of several coenzymes

  • The partial oxidation of glucose incvovles the coenzyme: nicotinamide adenine dinucleotide (NAD+)

  • Nicotinamide is a derivative of niacin (B vitamin)

Glucose metabolism:

  • glucose is the main energy source for most cells in the body

  • It is denied from dietary carbs (starch, sucrose, etc)

  • The metabolism of glucose, regardless of the presence or absence of oxygen, begin with a 10-step reaction sequence called “Glycolysis”

    • Step 1: Glycolysis:

      • phase 1: preparations dn cleavage. Use 2 ATP to break the bonds, creating 2 ADP and 2 glyceraldehyde-3-phosphate

      • Phase 2: Oxidation and ATP generation. The two glyceraldehyde-3-phosphate are oxidized to 3-phosphoglycerate. Some energy from this oxidation is conserved as 2 ATP and 2 NADH are produced

      • Phase 3: Pyruvate formation and ATP generation. 2 3-phsophglycerate molecules are converted to Pyruvate with accompanying synthesis of 2 more ATP

      • Pyruvate is the final product of glycolysis. It’s fate depends on the presence or absence of oxygen

  • Step 2: Follow glycolysis, glucose metabolism proceeds along one of two major pathways

    • Aerobic respiration

      • Results in the complete oxidation of glucose

      • End products are carbon dioxide and water

      • Results in the conversion of pyruvate to an activated form of acetate known as acetylene CoA, which becomes the substrate for aerobic respiration, where NADH is oxidized back into NAD+ by molecular oxygen

      • Glucose is a good source of energy because its complete oxidation releases 686 kcal/mol

      • The complete oxidation of glucose requires oxygen and yields carbon dioxide and water as final products:

        • C6H12O6+6O2 → 6CO2+6H2O

      • Not all of the energy release from this reaction is available for work. Some of it is released as heat

    • Anaerobic respiration

      • Results in the partial oxidation of glucose

      • Yields less energy than by aerobic respiration

      • In an anaerobic environment, pyruvate will be chemically reduced by a process called “fermentation”

      • Yeast ferments pyruvate into ethanol+CO2

      • Animals ferment pyruvate into lactate

      • ADH contains zinc

      • Pyruvate to Acetaldehyde to Ethanol

Gluconeogenesis:

  • the process by which cells synthesize glucose from 3- and 4- carbon precursors that are usually noncarbohydrate in nature

  • This process usually occurs in the liver and kidneys

  • The kidneys delaminate (remove NH2) amino acids excrete the amino group as ammonia (NH3), and synthesize glucose forms the rest of the molecules

  • After your body has used its glucose and fat storage, and starts breaking down protein for energy