0.0(0)

Chat with Kai

Feedback Loops

CLASS PRESENTATIONS

Positive vs. Negative Feedback Loops

Positive	Negative
Results in amplification	Results in stabilization

Graphic by Tanisha Kurani

Feedback Loop Examples

Example	Information
Blood Clotting	Group of blood cells, platelets, and protein clumped together over a wound to stop bleedingNegative loopBleeding (input) is stopped by clot (output), reverses direction of blood
Ice-Albedo	Albedo - Amount of sunlight or radiation reflected by a surface Positive loopIce is highly reflective, it reflects some sunlight back to space, heating the ocean up and melting more and more ice.
Body Temperature	Receptors are stimulated by a discrepancy from the normal 98.6 degrees F and send a signal to control centerControl center decides whether to vasodilate (cool down) or vasoconstrict (heat up) and sends a signal to effectors w/ decisionEffectors execute the decision w/ sweat glands or muscle contractionNegative loopThe body loses or retains heat to stabilize yourself to a particular temperature
Labor/Giving Birth	More pressure on cervix stimulates receptor cells that releases oxytocinOxytocin goes back to cervix and simulates contractionsPositive loop - Contractions go back to more pressure on the cervix until baby is born
Fruit Ripening	Acidic levels rise and amount of simple sugars increase, activating fruit ripening enzymesEnzymes cause the ripened fruit to ripen more fruit
Guard Cells/Stomata	Guard cells = 2 epidermal cells that open and close stomatal poresStomata = Tiny substance essential to photosynthesis, made up of guard cellsTakes in CO2, releases O2 Stomata must open to release water, but when it opens, leads to water going in and needing to refillNegative loop

Transport

BIGELOW SLIDES PARAMECIUM GIZMOS __OSMOSIS PRACTICE PROBLEMS__STUDY BOOKLET (HANDED OUT IN CLASS) OSMOSIS GIZMOS PRACTICAL APPLICATION PRACTICAL APPS WORKSHEET

Factors that influence diffusion:

Concentration
Temperature
Size
Charge
Pressure

Concentration

Concentration gradient - adjacent regions with different concentrations

When a cell goes through passive transport or diffusion, it tries to travel from a high concentration gradient to a low concentration gradient.

KEY VOCAB:

Solute: The thing being dissolved
Solvent: The thing dissolving the solute
Solution: The product once it’s dissolved

Passive Transport

Diffusion - The movement of atoms/molecules from an area of high concentration to low concentration
Osmosis - Diffusion relating to water
Facilitated diffusion - Diffusion where molecules pass through protein channel

Hypertonic - Outside > InsideIf the solvent is hypertonic, the solute is hypotonicEnds in shriveling up	Isotonic - Outside=InsideIf the solvent is isotonic, the solute is tooThe end goal of all diffusion	Hypotonic - Inside > OutsideIf a solvent is hypotonic, the solute is hypertonicEnds in swelling and ruptures

Turgor Pressure - Plants fill themselves with water to preserve structure
- If it loses that water, it stops pushing and becomes soft
Osmotic Pressure - The amount of turgor needed to stop osmosis
Plasmolysis - Cell membrane pulling away from cell wall (opposite of turgor)

Active Transport

Active transport moves against the concentration gradient (low to high) and requires energy.

Protein pump - A pump that moves molecules across the membrane

Endocytosis	Exocytosis
Into the cell - uses cell membrane to engulf materials Phagocytosis - The cell eats the particles and uses them for stuffPinocytosis - The cell drinks up the particles and uses it for stuffReceptor-Mediated - The cell uses receptors to target specific molecules	Fuses with cell

Examples

Bioenergetics

BIGELOW SLIDES

Energy - The ability to do work

Entropy - Unusable dispersed energy

Laws of Thermodynamics

First Law of Thermodynamics: Energy cannot be created or destroyed
Second Law of Thermodynamics: Energy tends to disperse spontaneously, always increasing entropy in a system

Potential vs. Kinetic Energy, Endergonic Exergonic

Potential energy - Energy that is stored in a fixed position or motion
- Chemical energy - form of potential energy due to arrangement of atoms within the molecules
Kinetic energy - Energy of motion

Endergonic	Exergonic
Reactions that store energy into the moleculeCondensation, photosynthesis	Reactions that have a release of free energyCellular respiration

Metabolic Control + Enzymes

Most enzymes not only have an active site, but also an Allosteric Regulation

Allosteric Regulation - Cofactors/Coenzymes bind to atom and change active site of enzymes

Allosteric Activation - Changes shape of active site so enzyme is turned on and works
Allosteric Inhibition - Changes shape of active site so the enzyme is turned off and doesn’t work

Coenzyme - Allows redox reactions to proceed

Ex: ATP - provides activation energy to start reactions whenever needed
- Breaks bonds between 2nd and 3rd phosphate groups, giving off the potential energy, can spend and refill
- Stores (Endergonic) and releases (Exergonic)

Feedback Inhibition - Final product of a process decreases/stops the process once the product is made

Negative loop

Electron Transfer Chains and Redox Reactions

Metabolic reactions may be Redox reactions, Redox reactions transfer electrons between atoms.

REMEMBER: The electron that has a charge is being reduced

Electron Transfer Chains - Can be formed with many Redox reactions over and over, releases energy in small amounts (slow) and fuels many reactions in a cell

Homeostasis Study Guide (Chapter 5, Cengage Biology Honors)

ALL REVIEW Q’S HOMEOSTASIS GIZMOS