Luokat: Kaikki - signaling - enzymes - atp - phosphorylation

jonka Maya J Reed 1 vuosi sitten

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Membranes, Energy, and Cell Communication

Cells communicate over long distances by releasing signals that travel to distant receptors, initiating processes like depolarization. Depolarization occurs when ion channels reduce the negativity inside the cell, leading to action potential generation.

Membranes, Energy, and Cell Communication

Floating topic

Energy Changes

Chemical Reactions

Endergonic

accompanied by or requiring the absorption of energy, the products being of greater free energy than the reactants.

Energy required, nonspontaneous

products have more energy than the reactants

If the products have more energy than the reactants, then you can see that energy was absorbed through the process of the reaction

Delta G is positive

Exergonic

An exergonic reaction (such as cellular respiration) is a reaction that releases free energy in the process of the reaction.

energy released, spontaneous

The Overall delta G is negative

if the reaction proceeds with a net release of energy then the products have lower free energy than what the reactants started

Free energy

Energy in cells that is used for a cell to function

Non-Spontaneous Reaction

a reaction that does not favor the formation of products at the given set of conditions. In order for a reaction to be nonspontaneous, it must be endothermic,

Spontaneous Reaction

Only reactions with a negative ΔG are spontaneous, which means they occur with no net input of energy. Spontaneous reactions can be harnessed to perform cellular work

Thermodynamics

The study of energy transformations is called thermodynamics. Scientists use the terms system and surroundings in this field. System is the matter under study, while the rest of the universe is the surrounding

2nd Law

Every energy transfer or transformation increases the entropy of the universe

1st Law

Energy can be transferred and transformed, but it cannot be created or destroyed

plant cells

hypotonic - turgid/ normal (plants need a lot of water to survive)

hypertonic - plasmolyzed (loss of water/ cell can die)

isotonic - flaccid (not net movement of water and can cause plant to wilt)

animal cells

hypotonic - lysed

isotonic - normal

hypertonic - shriveled

Metabolism

Metabolic pathway

Anabolic Pathway

Anabolic and catabolic pathways: Anabolic pathways are those that require energy to synthesize larger molecules.

Pathways that consume energy to build larger, complicated molecules from simpler ones

Photosynthesis 6CO2 +6H20 + light-> C6H1206 + 6O2

Example is photosynthesis – where energy from the sun is used to combine carbon dioxide and water to form sugars.

Polymerization

Polymerization is a process through which a large number of monomer molecules react together to form a polymer.

Biosynthetic pathways

There are two known pathways for the biosynthesis of glycine.

Catbolic Pathway

Metabolism manages the material and energy resources of the cell

Pathways that release energy by breaking down complex molecules into simpler compounds

Celular resperation

Cellular respiration is a series of chemical reactions that break down glucose to produce ATP, which may be used as energy to power many reactions throughout the body.

C6H12O6+6O2->H2O + Energy

a complex molecule like glucose is broken down to carbon dioxide and water with the release of energy.

2. depolarization

Depolarization occurs when ion channels cause the inside of the cell to become less negative. It is a reduction in the magnitude of the membrane potential. This also triggers an action potential.

generation of action potential

4. falling phase/ repolarization

The inside of the cell becomes negative again.

3. rising phase

The voltage begins to increase until it reaches action potential.

1. resting state

Most voltage gated Na+ and K+ channels are closed.

5. undershoot

The K+ channels have to close up again and before this happens there is a slight overly negative charge in the cell before it is able to reach its resting state once again.

these pumps help maintain membrane potential

Energy transfer and transformation is critical to all aspects of biology from cells to ecosystems

Forms of Energy

Potential energy

An object that is not moving can also have energy – potential. This is due to location or structure.

Stored Energy

Happens Because of position, location, or arrangement

Electron in outer shell - more potential energy

Potential energy in foods is chemical energy

chemical energy stored in molecular structure

Kinetic energy

If energy is associated with the relative movement of objects it is called kinetic energy. An example is thermal energy – kinetic energy associated with random movement of atoms of molecules Light is a form of kinetic energy in the form of photons moving from one place to another.

Light energy

Kinetic energy of movement of photons

Thermal energy

Kinetic energy of molecular motion

signal molecule/ligand and a receptor

How does a signal work using cAMP?

Messenger binds to GPCR to activate it | Activated GPCR binds to G protein then binds to GTP which activates G protein | Activated G protein/GTP binds to adenylyl cyclase, GTP is hydrolyzed which activates adenylyl cyclase | Activated adenylyl cyclase converts ATP to cAMP | cAMP, a second messenger activates another protein leading to a cellular response

Stage 1: Reception Stage 2: Transduction Stage 3: Response

Signal Transduction

Cells communicate using rather physical contact or releasing a signal to a target cell

use

Active transport

Needed protein to transfer molecules
Exocytosis

Some inside cells are gotten rid out membrane

Endocytosis

eat outside cells through membrane

Pumps

Protien=ATD

Contractile Vacuole

NA+/K+ pump

Requires energy
From low concentration to high concentration

long distance signaling - if the cell is releasing the signal from a far distance to a receptor

local signaling - exchanging of signals within close proximity

paracrine or synaptic

Enzymes

enzymes lower the energy of activation barrier: exergonic reaction to change in the presence of enzyme

If a reaction is spontaneous/exergonic then it doesn’t require any energy input

Environmental Factors Affecting Enzyme Activity
pH

cell’s neutral pH is 7.2 and this is where most enzymes function, there are some exceptions as seen here.

Enzyme Regulation

Allosteric regulation

Regulatory molecule: Inhibitor or Activator

Regulator molecule binds to a protein at one site and affects the protein’s function at another site. Allosteric regulation may either inhibit or stimulate an enzyme’s activity

Allosteric Regulation

Allosteric regulation occurs when a regulatory molecule (inhibitor, activator) binds to a protein at one site and affects the protein’s function at another site. Allosteric regulation may either inhibit or stimulate an enzyme’s activity

Cooperativity

type of allosteric regulation. In cooperativity, the binding of one substrate molecule to the active site of one subunit locks all other subunits into the active shape. Cooperativity amplifies the response of enzymes to substrates

Inhibition of Enzyme Activity

Noncompetitive inhibition

A noncompetitive inhibitor binds to the enzyme away from the active site, altering the shape of the enzyme so that even though the substrate can still bind, the active site functions much less effectively, if at all.

Competitive inhibition

A competitive inhibitor mimics the substrate, competing for the active site.

Temperature

rate or speed of a reaction increases with increase in temperature

The ATP Cycle

ATP becomes ADP and the energy which is stored is released to help out some biological function. Later when a phosphate group is added, ADP is recharged back to ATP. This cyclic transformation from ATP to ADP and again back to ATP is called as ATP cycle.

ATP is a renewable resource that is regenerated by addition of a phosphate group to ADP. The energy to phosphorylate ADP comes from catabolic reactions in the cell.

Both endergonic and exergonic reactions occur in cells

couple these two by using coupling agents like ATP

ATP

ATP is called the energy coupler or the currency of the cell.

Mechanical work

ATP binds noncovalently to motor proteins and then is hydrolyzed

Transport work

ATP phosphorylates transport proteins

Energy coupler in cells:cellular work

Chemical reactions powered by ATP

formation of glutamine (amino acid)

this reaction is coupled with ATP hydrolysis,

Pi formed is added to one of the reactants glutamic acid
makes it unstable (high free energy).

its attempt to be more stable reacts with ammonia to form glutamine and the Pi group is released in the process

Coupling is favored

Flow of Electrons

Cyclic

Anaerobic Conditions
Synthesis of ATP

Non-Cyclic

Aerobic Conditions
Produces NADPH in addition to ATP

Facilitates the synthesis of organi moelcules and extended storage of energy

Photosystems

Photosystem 2

The reaction - center chlorophyll 'a' absorbs at 680 nm

Photosystem 1

The reaction - center chlorophyll 'a' absorbs at 700 nm

Output: 6 NADH, 2 FADH, 2 ATP

Output: 2 Pyruvate, 2 NADH, 4 ATP

Creation of ATP

Substrate level phosphorylation

Becoming Reduced

Becoming Oxidized

Fermentation

Alcohol Fermentation

Converts sugars into cellular energy producing ethanol and carbon dioxide as by products.

Lactic Acid Fermentation

A process in which sugars are converted into cellular energy in which lactic acids is a part of the solution.

Gibbs Free energy

G > 0

A reaction/process cannot occur spontaneously. An input of free energy is required to drive the reaction. Reaction is endergonic.

G = 0

A system is at equilibrium: no net change occurs

G < 0

A reaction/process can occur spontaneously. Reaction is exergonic

Gfinalstate – G initialstate or Gproducts – G reactants

Membranes, Energy, and Cell Communication

Energy transfers and transformations in cells

Subtopic
Cell Signaling

components of membranes

membrane potential

Membrane potential is the amount of voltage in the cell. When there is no net movement of certain ions across the membrane then equilibrium potential is reached.

ion channels

Ion channels are membrane proteins that allow for transport of ions across membranes. They are always open but can be closed at times. This would depend on the voltages within the membrane.

gated

Ion channels are able to open and close in response to stimuli.

stretch gated - open when membrane is deformed

ligand gated - open and close when a neurotransmitter binds to channel

voltage gated - open and close in response to changes in membrane potential

ungated

Ion channels are always open and allow for ions to move through.

selective permeability

A cell has to regulate transport of substances across the cellular membrane. This is important because it helps manage and separate different materials traveling throughout the cell. Small nonpolar molecules and small uncharged polar molecules have higher permeability and can travel through the bilayer. Large uncharged polar molecules and ions have low permeability and cannot pass through the membrane on its own.

active transport

Active transport moves substances from low to high concentration, against concentration gradients, requiring energy (ATP).

bulk transport

Large molecules cross the membrane in bulk in vesicles.

endocytosis

Endocytosis takes in molecules. There are three types: phagocytosis, pinocytosis, receptor-mediated endocytosis

phagocytosis takes in large food particles/ other cells by extending its membrane out

pinocytosis takes in extracellular fluid from outside in vesicles

receptor mediated endocytosis is a specialized type of pinocytosis that allows for the cell to acquire bulk quantities of specific substances even if they may not be concentrated in the extracellular fluid

exocytosis

Transport vesicles move towards the membrane, fuse with it and release their contents. Exocytosis is used to export products.

cotransport

Cotransport occurs when active transport of a solute indirectly drives transport of other substances. For example, plant cells use the H+ generated from proton pumps to drive active transport of nutrients into the cell.

NA+/ K+ pump

The sodium potassium pump aids in the transport of sodium and potassium ions in a cell. There is usually in abundance of sodium outside the cell and abundance of potassium inside the cell. 3 Na+ are transported out of the cell for every 2 K+ ions transported in.

types of electrogenic pump

Electrogenic pumps are proteins that generate voltage across a membrane. These also help store energy used for cellular work.

proton pumps

A positive charge leaves the cell, and a slight negative charge develops inside the cell and a positive charge outside the membrane.

passive transport

Passive transport is a movement across a membrane that does not require any energy. It is moving down the concentration gradient, from an area of high concentration to low concentration.

osmosis

Osmosis is the diffusion of water across a selectively permeable membrane. Water diffuses from an area of lower solute concentration to an area of higher solute concentration until the concentrations are equal on both sides.

water balance in cells

tonicity

tonicity is the ability of a surrounding solution to cause a cell to gain or lose water

hypotonic

solute concentration is less than that inside the cell with respect to the cell/ solute concentration is less than that outside of the cell with respect to the environment

hypertonic

solute concentration is greater than inside the cell with respect to the cell/solute concentration is greater than that outside of the cell with respect to the environment

isotonic

solute concentration is the same as inside the cell; no net water movement

diffusion

Diffusion is the tendency for molecules to spread out evenly into available space. They always move from areas of high concentration to low concentration.

facilitated diffusion

Facilitated diffusion is passive transport aided by proteins. They help move hydrophilic substances across membranes as they cannot diffuse on their own.

carrier proteins

Carrier proteins undergo subtle changes that help transport proteins from on side to another. Sort of like an elevator, it takes in a few molecules at a time, closes, and opens up on the other side.

channel proteins

Channel proteins provide channels that allow a specific molecule or ion to cross the membrane.

aquaporin

Aquaporin are types of proteins that aid in the transport of water across membranes.

mosaic plasma membrane
two different types of proteins present in membranes

integral

Integral proteins are partially or fully inserted into the membrane. If they are fully inserted than they are called transmembrane proteins.

transmembrane proteins/ transport proteins

peripheral

Peripheral proteins are anchored to the membrane

phospholipid bilayer
membrane fluidity

presence of cholesterol in animal cells

the presence of cholesterol regulates the movement of phospholipids in membranes; at moderate temperatures it helps to reduce movement while in low temperatures, it prevents packing between phospholipids

types of fatty acids present

unsaturated fatty acids provide a bend in the structure of the phospholipid bilayer, allowing for more fluidity; the presence of unsaturated fatty acids also helps the membrane withstand low temperatures

temperature

each phospholipid has a specific phase transition temperature; above this temperature, the lipid is in liquid crystalline phase and fluid; below this temperature, the lipid is in a gel phase and is rigid

Production of ATP using organic molecules through cell respiration.

Cellular Respiration
Oxidative Phosphorylation

Location: Mitocondria

Chemiosmosis

Comparison

Chloroplast Strucutre

Thylakoid Space

Thylakoid Membrane

Stroma

Mitochondrion Structure

Intermembrane Space

Inner Membrane

Matrix

Transporting of Proton through channels in the membrane of mitochondria from the inner and outer compartments.

The constructing of a proton (H+) gradient

Protons diffuse down the gradient though a protein

Coupled to ATP Synthase

Electron Transport Chain

The electrons go through the chain higher to lower energy levels.

The energy released in the ETC is then used as a proton gradient,

Citric Acid Cycle

Location: Mitochondrial Matrix

Input: 2 Acetyl CoA

Malate is Oxidizde, NAD+ is reduced

Succinate is oxidized, FAD is reduced.

ATP formation

Once CO2 is released, the 4 carbon molecule is oxidized, then reactive due to additional CoA

Isocitrate is oxidized, NAD+ is reduced

The Acetyle CoA+Oxaloacetate from Citrate.

Pyruvate Oxidation

Location: Initial - Cytosol; Final - Mitochondria Matrix

Input: 2 Pyruvate

A carboxyl group is removed from pyruvate, NAH+ is reduced, then a acetyl groups is transferred to coenzyme A.

Output: 2 Acetyl CoA, 2 NADH

Glycosis

Location: Cytosol

Order of Events

Input: 1 Glucose, 2 ATP

Energy Payoff Phase

Step 10

The phosphate group is transferred from PEP to ADP forming pyruvate

Step 9

The enolase removes a water molecule from 2-phosphoglycerate, yielding phosphoenolpyruvate.

Step 8

The enzyme relocates the remaining phosphate group

Step 7

The phosphate group is transferred to ADP, to form ATP and 3-phosphoglycerate

Step 6

Energy from the exergonic reaction is used to attach a phosphate group to the oxidized substrate.

G3P is oxidized by the transfers of electrons to NAD+, creating NADH

Energy Investment Phase

Step 5

Conversion between DHAP and G3P

Step 4

Aldolase cleaves the sugar molecule into 2 difference (3) carbon sugars

Step 3

Phosphofructokinase transfers a phosphate group from ATP to the opposite side of the sugar, investing a ATP.

Step 2

Glucose - 6 phosphate us converted to frutose 6 phosphate

Step 1

Hexokinase transfers a phosphate group from ATP to glucose