Chem Definitions - Module 2-5

active transport

 the movement of molecules across a membrane through the use of cellular energy, against a concentration gradient

passive transport

the movement of molecules across a membrane along their respective concentration gradient (from a region of high concentration to a region of low concentration) where energy is not required

simple diffusion

the passive movement of molecules across a membrane along a concentration gradient without the assistance of membrane proteins

facilitated diffusion

the passive movement of molecules across along a concentration gradient with the help of transport proteins in the plasma membrane

ion channels

Are integral membrane proteins that allow the passage of ions from one side of the membrane to the other

Transporters / Carrier Proteins

Are integral membrane proteins that assist in the movement of certain molecules (ions, peptides, small molecules, lipids and macromolecules) across a membrane

osmosis

the passive movement of water molecules across a semipermeable membrane from an area of high concentration to an area of low concentration (across a concentration gradient)

osmolarity

the concentration of molecules in a solution

expressed as the total number of solute particles per litre

hypoosmotic

total number of solutes is lower than that of another solution

isoosmotic

two solutions having the same osmolarity

hyperosmotic

total number of solutes is higher than that of another solution 

pump/s

transmembrane proteins that actively transport a solute/molecule/substance against its electrochemical gradient

electrochemical gradient

*An electrochemical gradient is a gradient of electrochemical potential, usually for an ion that can move across a membrane. The gradient consists of two parts, the chemical gradient, or difference in solute concentration across a membrane, and the electrical gradient, or difference in charge across a membrane*

Primary active transport

directly uses chemical energy (such as ATP) to move molecules across a membrane against their electrochemical or concentration gradient

Secondary active transport

the transport of a solute in the direction of its increasing electrochemical potential coupled to the facilitated diffusion of a second solute (usually an ion) in the direction of its decreasing electrochemical potential

* ATP is not used in the primary delivery of the molecule


* Indirect use of ATP to transport molecules from an area of low concentration to an area of high concentration

Antiporters

carry two substances/molecules across the membrane in opposite directions

Symporters/Cotransporter

carry two substances/molecules across the membrane in the same direction

Peptide bonds

are covalent bonds formed between two amino acids

primary structure

amino acids bonded together to form a polypeptide chain → has peptide bonds

secondary structure

hydrogen bonding of polypeptide chain causes amino acids to twist and fold into a repeating pattern

tertiary structure

3-dimensional arrangement of a polypeptide chain

quaternary structure

arrangement of two or more polypeptide chains

contractile proteins

Proteins that generate force during muscle contractions

regulatory proteins

Proteins that help switch the muscle contraction process on and off

myosin

Contractile protein that makes up the thick filament of a sarcomere.

A myosin molecule consists of a tail and two myosin heads, which bind to myosin binding sites on actin molecules during muscle contraction.

actin

Contractile protein that is the main component of the thin filament of a sarcomere.

Each actin molecule has a myosin binding site where the myosin heads bind to during muscle contraction.

tropomyosin

Regulatory protein that is a component of the thin filament.

When skeletal muscle fibre is relaxed, tropomyosin covers myosin-binding sites on actin molecules, preventing myosin heads from binding to actin,

troponin

Regulatory protein that is a component of the thin filament.

When Ca2+ ions bind to troponin, it changes the shape of the regulatory protein. This conformational change moves tropomyosin away from myosin binding sites on actin, which allow myosin heads to bind to actin so that muscle contraction can occur

sarcoplasmic reticulum (SR)

a specialised form of endoplasmic reticulum found in skeletal muscle, which is dedicated to Ca2+ ion handling for muscle contraction and relaxation

sarcoplasm

the cytoplasm of a muscle fibre

pre synaptic neuron

transmits a signal towards a synapse

post synaptic neuron

transmits a signal away from a synapse

synaptic cleft / synapse

the space located between the presynaptic and postsynaptic endings, where nerves impulses are transferred from axons of presynaptic neuron to dendrites of postsynaptic neuron through a neurotransmitter/s

synaptic/axon terminal

the part of the axon that releases the neurotransmitters that relay signals across the synapse/synaptic cleft

motor end plate

a synaptic connection that is formed at the sites where the terminal branches of the axon contact a muscle target cell

average reaction rate

the change in concentration over a selected period of time

mol L^-1 s^-1

unit for average reaction rate

Instantaneous rate

Can find the reaction rate at an **exact point of time**

(Can only be done by finding the rate law)

Rate Laws

Are the mathematical expressions that describe the relationship between the rate of a chemical reaction and the concentration of the reacting substances

Rate constant

expresses the relationship between the rate of a chemical reaction and the concentrations of the reacting substances

order/s of reaction

describe how the rate of reaction depends on the concentration of the reactants

Reaction intermediates

molecules that are produced by the reactants (or preceding intermediates), but then are used/consumed during the elementary steps

Catalysts

are substances that are not consumed during a reaction

they are reactants in the first elementary step, and in the final elementary step, they are unchanged as a product

amphoteric

contains both acidic and basic properties / behaves as both an acid and base

semi permeability

something that is selectively permeable, will only allow certain molecules/substances to pass through

absolute refractory period

when the neuron will not respond to any stimuli (regardless of strength or threshold being reached)

occurs during an action potential

relative refractory period

when in most situations there is no response to a stimulus, except when there is a higher than normal stimulus, action potential can occur

can occur during hyperpolarisation

acid

species that acts as a proton donor

base

species that acts as a proton acceptor

dissociation

the separation of ions that occurs when a solid ionic compound dissolves

The higher the dissociation \[constant\] the stronger the acid or base

Ka

acid dissociation constant that measures the extent of dissociation

pKa

the -log of Ka

pH

a measure of how acidic or basic a substance or solution is

a pH below 7 indicates an acidic solution: more H+ than OH-

a pH above 7 indicates a basic/alkaline solution: more OH- than H+

equivalence point

the point where the chemical reaction comes to an end → all acid has reacted & conjugate base has formed

end-point

endpoint is the point where the colour change occurs in a system (used as an approximation of the equivalence point)

buffer

a mixture of a weak acid and its conjugate base → that resists changes in pH when small amounts of strong acid or base are added

1/2 equivalence point

the region in which half of the acid has reacted