Concept 2 Anatomy and Physiology

Homeostasis

stability of the internal environment and the mechanisms that maintain the stability

Dynamic equillibrium

maintained when the rate of loss balances out the rate of gain

feedback mechanism

an input output loop to maintain homeostasis

positive feedback loop

the output/product of a system intensifies the response

examples of positive feedback loop

human child birth (hormones → contractions → pressure → more hormones→ more cotractions, more pressure, etc)

Fruit ripening (fruit ripes →, release ethylene →signals surrounding fruit to riper)

Negative Feedback loop

the output of a system causes a counter response to return to a stable point

examples of negative feedback loop

human body temperature (thermoregulation), water concentration (osmoregulation), blood sugar regulation

All feedback loops have:

recpetor, stimulus, effector

receptor

sensory organ that receives the stimulus

stimulus

an action that evokes a response

effector

an organ that does the response

when a mistake happens in the feedback loop,,,

homeostasis is thrown of (ex, type 1 diabetes)

Catalyst

substances that speed up the reactions without being permantly altered

catalysts CANNOT..

make a reaction that cannot occur otherwise

most biological catalysts are

proteins (enzymes)

How can cells regulate metabolism

by controlling the amount of an enzyme

what is feedback inhibition

output of a process is used as an input to control the behavior of the overall process itself, usually leading to inhibition of the process

chemical inhibitors can…

bind to enzymes and slow reaction rates

what can play a role in enzyme function too

enviornmental conditions (pH and tempture can lead to denaturation)

What is another way that cells maintain homeostasis

hhighly regulated signaling and transport mechanisms

Passive Transport

requires no extra energy, moves from area of high concentration to low

Active transport

Requires ATP, moves from areas of low concentration to high

Examples of passive transport

Simple diffusion

Facillitated diffusion

Osmosis

Simple diffusion

The spreading of molecules across the membrane until equilibrium is reached

ex: o2, co2, small non polar, lipid soluable molecules

Facilitated diffusion

a transport protein facilitates the diffusion of molecules that normally couldnt pass through the cell membrane (large polar molecules)
transport proteins act as chennels or carriers

Osmosis

the simple diffusion of water across the cel membrane

hypertonic solution

water inside the cell is more than the water outside the cell; cell shrivels

hypotonic solution

water inside the cell is less than water outside the cell

water rushes in and cell swells

isotonic solution

water is equal in and out the cell, it stays the same

Examples of active transport

Molecular pumps, exocytosis, endo cytosis

molecular pumps

pumps molecules across the membrane, against the gradient using a protein chanel

Endocytosis

uses vesicles to move large particles into the cell

ex, white blood cells engulf bacteria

Exocytosis

Uses vesicles to export materials outside of the cell

ex, when nerves sevrete neurotransmiters to send signals throughout the body

Cell signaling

allows cells to process information from their enviornemnt (stimuli) and communciate with other cells

Ligands

molecules that bind to other molecules (receptor proteins) for signaling proteins

what is the order of cell signaling

signal → message transduced →desired response

Autocrine signals

signals self - affect the same cell that releases them

paracrine signals

diffuse to NEARBY cells

Juxtacrine signals

require DIRECT CONTACT between signaling cell and the recieving cell

Hormones (endocrine signaling)

sugnals travels to distant cells

what is a receptor

a protein where the signal is received on the target cell

intracellular receptor

located inside the a cell

ligands for these signals are small and/or nonpolar

membrane receptors

located on the surface of a cell

ligands for these are large and/or polar

Recpetors are

highly specific, only certain ligands bind to certain receptors

what kind of bond is it when a ligand binds to a receptor protein

noncovalent (thereforer not strong) and is reverisble
this is so the signal can be regulated more easily

inhibitor

can block the normal ligand to prevent communication

ex caffeine

transduction

the passing along of the signal until the desired response is reached, can be short or long

when is a transduction longer

if a signal cascade of reactions is induced

how does the passing along of messages in transduction usually happen

changing the shape of a protein

phosphorylation

addition of phosphate groups by kinases

dephosphorylation

removal of phosphate groups by phosphates

second messenger

a small molecule that serves as an intermediate between the recpetor ands the cascade of responses after, key for regulation

what do seocond messengers typivally do

either distribute and/or amplify the initial signal recieved at the recpetor

The transduction pathway eventually triggers a…

response

what are some responses a signal can create

Opening of ion chennels (changing the balance of ion concentration inside and outside the cell)

ALteration in gene expression (genes may be switched on or switched off

Alteration of enzyme activity