concept 7.4: active transport uses energy to move solutes against their gradients

facilitates diffusion

passive because the solute move down its concentration gradient and the transport requires to energy

active transport

requires energy usually in the form of ATP hydrolysis to move substances against their concentration gradients

describe active transport

requires energy, not spontaneous, +delta G

what proteins are involved in active transport

carrier proteins

why is active transport good for cells

it enables cells to maintain solute concentrations that differ from the environment

example of active transport

the concentration of potassium ions is higher and concentration of sodium ions is lower inside animal cells than their surroundings so sodium is taken out through a pump while potassium is taken in

membrane potential

the voltage across a membrane

how is a voltage created in a membrane

by differences in the distribution of positive and negative ions across the membrane

what is the normal resting membrane potential of a human cell

the inside of the cell is negative relative to the outside

what is the benefit of having a negatively charged cell

it favors passive transport of cations into the cell and anions out of the cel

what two forces make up if electrochemical gradient

a chemical force and an electrical force

what does the electrochemical gradient do

drives the diffusion of ions across a membrane

what is an electrogenic pump

a transport protein that generates voltage across a membrane and stores energy that can be used for cellular work

what electrogenic pumps do animals use

sodium/potassium pump

what electrogenic pump do plants, fungi, and bacteria have

proton pump

why is proton pump important

in the generation of ATP by the mitochondria in cellular respiration and chloroplasts in photosynthesis

cotransport

occurs when active transport of a solute indirectly drives transport of other substances

what do plant cells use proton pumps do to

they use the pumps to generate an H+ gradient across the cell membrane

how does a cotransporter go with a proton pump

a cotransporter couples the movement of H+ that is generated from the pumps back down its concentration gradient to the active transport of sucrose into the cell

how do plants load sucrose to their veins for transport

with a cotransporter

how do cotransporters differ in animal cells

they are used to couple the active transport of glucose to the diffusion of Na+ into cells lining the intestine

what role does sodium play in human bodies

sodium in waste is reabsorbed in the colon to maintain a constant level in the body and a rapid drop in sodium (like after diarrhea) it can be life threatening