Topic 5 - The Working Cell

plasma membrane

a phospholipid bilayer that selectively allows (semipermeable) for the diffusion of small, nonpolar molecules (e.g. oxygen, carbon dioxide) and lipid molecules

What's embedded within the plasma membrane?

cholesterol, proteins (peripheral & integral), glycoproteins, glycolipids

What is the fluid mosaic model?

a model that represents the cell membrane as a fluid “mosaic” of components

What properties affect membrane fluidity?

phospholipid type (saturated v. unsaturated fatty acids), cholesterol, temperature

passive transport

cell doesn’t expend energy for this, specifically, relying on diffusion

diffusion

a form of passive transport that represents molecular movement from a region of high concentration to low concentration (requires a concentration gradient)

active transport

cell must expend energy

bulk transport

involves membranous vesicles moving large substances

endocytosis

when a cell takes in materials from its outside environment into their membrane by engulfing them in the plasma membrane, forming a vesicle.

exocytosis

where a cell expels large molecules and/or waste products by fusing a vesicle with the plasma membrane

What cannot pass through the hydrophobic core of the plasma membrane?

polar and charged molecules

Facilitated passive transport

requires integral proteins aka “transport proteins” 

Channel Proteins 

specific to the transported substance which are sometimes open all the time and sometimes only open when a signal is received (e.g. aquaporin)

Carrier Proteins

specific to the transported substance and some are used in active transport (e.g. GLUT)

Osmosis

the diffusion of water across a semi-permeable membrane (molecular movement moves from high solvent to an area of low solvent concentration)

Water moves from…

an area of low osmolarity to an area of high osmolarity

osmolarity

describes the solution’s total solute concentration

hypertonic solution

net movement of water OUT of the cell, leading to cell shrinking

hypotonic solution

net movement of water INTO the cell, leading to cell swelling and burst due to excessive water intake

isotonic solution

no net movement IN or OUT of the cell due to equal solute concentration

Active transport

utilizes energy to move substances from low to high concentration, requiring the using integral carrier proteins known as pumps

What are the 3 types of carrier proteins used for active transport?

uniporters, symporters, and antiporters

Uniporters

move a SINGLE type of molecule/ion down a concentration gradient

Symporter

moves TWO types of molecules/ions in the SAME direction

Antiporter

moves TWO types of molecules/ions in OPPOSITE directions

Primary Active Transport

energy is directly provided by ATP hydrolysis

Secondary Active Transport

energy stored in electrochemical gradient that relies on the flow of another ion to provide energy to move another molecule against its gradient

energy

the capacity to do work

kinetic energy

energy in motion

potential energy

stored energy

How can PE be transformed into KE?

as energy conversion generates heat byproduct

What type of energy do hydrocarbons contain?

chemical energy

How does the structure & function of ATP allow for it to function as a battery?

stores energy obtained from food and releases it later as needed

Metabolism

sum of all chemical reactions within an organism

Anabolism

process that assemble/build larger molecules from smaller ones (requires energy)

Catabolism

process that break down larger molecules to smaller ones (requires energy)

What is the change in G (available energy)  in exergonic reactions?

delta G < 0

What is the change in G in endergonic reactions?

delta G > 0

Enzymes

proteins that function as biological catalysts by decreasing activation energy 

Enzyme-Substrate Complex

enzymes have a highly specific active site to fit the shape + chemistry of a substrate (the entry of a substrate enables shape change of the enzyme to further perfect the fit in which products are released afterwards) 

Enzyme Inhibitor

molecules that binds to an enzyme and reduces the rate of enzymatic reactions

Competitive Inhibition

compete with substrates to bind at an enzyme’s active site

Noncompetitive Inhibition

bind at the allosteric site of an enzyme

What are forms of enzyme regulation?”

enzyme inhibitor, allosteric regulators

Allosteric Regulator

molecule that binds at a site other than an enzyme’s active site that leads to a change in the active site

How do cells communicate with each other?

signaling molecules, receptor proteins, signal transduction pathway

Membrane Proteins

proteins embedded in the cell membrane that receive external signals like hormones and neurotransmitters

Receptor Proteins

a specialized class of proteins that recognize and bind to a specific ligand

Signal Transduction Pathway

a sequence of chemical reactions that lead to cellular response

What are 3 types of membrane receptors?

G-Protein coupled receptor, enzyme-linked, ion channel gated receptor

What are the 3 types of signaling molecules?

hormones, neurotransmitters, pheromones (can be hydrophobic or hydrophilic)

How doe membrane receptors receive signaling molecules to start the process of cellular response?

a signaling molecule attaches to the receptor protein and the receptor protein accelerates the creation of product from substrate (signaling molecule), upon reaction completion, the signaling molecule upon creating necessary products