BIOL300: Chapter 12

What are specialized membrane transport proteins responsible for?

Transferring small water-soluble molecules across the membrane.

What determines the selectivity of membrane transport proteins?

Each type of transport protein transfers a particular type of molecule based on size and electrical charge.

What is passive transport?

The spontaneous flow of molecules from a region of high concentration to a region of low concentration without the need for energy.

What is active transport?

The movement of a solute against its concentration gradient, requiring energy input.

What are the three main ways cells carry out active transport?

Coupled transporters, ATP-driven pumps, and light-driven pumps.

What role does the Na+-K+ pump play in cellular transport?

It transports Na+ out of the cell and K+ into the cell, maintaining ion balance.

What is an electrochemical gradient?

The driving force that moves an ion across the membrane, combining the concentration gradient and the voltage across the membrane.

What is the resting membrane potential of neurons?

Typically around -60 mV, indicating a negative charge inside the cell compared to the outside.

What triggers an action potential in a neuron?

depolarization of the membrane that opens voltage-gated Na+ channels.

What are ligand-gated ion channels?

Ion channels that open in response to the binding of a specific ligand

What is the role of K+ leak channels in resting membrane potential?

They allow K+ to move more freely out of the cell, contributing to the negative charge inside.

What is the function of the Ca2+ pump in muscle cells?

It returns Ca2+ to the sarcoplasmic reticulum, controlling muscle contraction.

What is the role of synapses in neuronal communication?

They convert electrical signals into chemical signals, allowing for excitatory or inhibitory transmission.

What is the effect of age on cognitive function according to recent studies?

Cognitive abilities peak in late middle age

How can exercise influence brain function?

Exercise-induced increases in blood volume and is correlated with neurogenesis.

What is the significance of the Na+/K+ pump in terms of energy?

It creates a large store of energy by maintaining a high concentration of Na+ outside the cell.

What is the role of voltage-gated ion channels?

They respond to changes in membrane potential and are crucial for action potentials.

What is the relationship between ion channels and signaling in nerve cells?

Ion channels are essential for generating and relaying electrical signals in neurons.

What is the outcome of ligand binding to the nicotinic acetylcholine receptor?

It causes depolarization and the initiation of an action potential.

What happens to K+ ions during the action potential?

K+ ions flow out of the cell to help repolarize the membrane after depolarization.

What is the role of the Na+-K+ pump in maintaining cellular homeostasis?

It regulates ion concentrations, crucial for maintaining the resting membrane potential.

what kind of molecules can get through the membrane on their own?

small, nonpolar molecules

Can ions diffuse across a membrane on their own?

They cannot diffuse on their own

What are the two classes of membrane transport proteins?

transporters and channels

Transporters

A transmembrane protein that changes its shape to transport molecules across the membrane. HAS TO CHANGE ITS SHAPE EVERY TIME A SPECIFIC ION WANTS TO PASS THROUGH.

Channels

passively move ions down their electrochemical gradient using voltage gates. GOES THROUGH ONE SHAPE CHANGE THAT ALLOWS MANY IONS TO PASS THROUGH

Passive transport goes from areas of

high to low concentration

In active transport, molecules are being moved.....

Against the concentration gradient

What does a coupled transporter do?

Transport solutes against gradient by linking one solute that goes down the gradient to another going against the gradient.

How does the ATP driven pump work

the movement of one molecule up its concentration gradient is coupled to the hydrolysis of ATP to ADP

Light driven transporters

Couple uphill transport to an input of energy from light

Electrochemical gradient

The combination of electric charge and the gradient forces that acts on membrane potential.

The outside of the cell is...

positive

The inside of the cell is...

negative

Which way does the Ca+ pump move calcium (into or out of)?

Out of the cell

Neurons "talk" to cells at a...

synapse

Synapses can transmit which two signals?

Excitatory and Inhibitory

What happens at an excitatory synapse?

Neurotransmitters depolarise the postsynaptic membrane, making it fire an action potential if the threshold is reached. -> influx of positive ions such as Na+

What happens at an inhibitory synapse?

a neurotransmitter is released that decreases the likelihood of postsynaptic neurons firing an action potential. -> influx of negative ions (Cl-)

Around how many V is action potential?

~40V

What is electrophysiology?

the study of neurons

What are three ways we can take care of our neurons?

1. stimulation through exercise

2. certain foods/ flavonoids such as blueberries, fish, nuts

3. practicing/ using your brain

what is neurogenesis?

the formation of new neurons -> neurons SOMETIMES divide

In an effort to increase neurogenesis in elderly patients a study was done where the elders were taken to a local school and..

taught underprivileged students to read

At what age range do we mentally peak

60's

True or False: Anxiety increases as we age

False- anxiety decreases

True or false: we get happier as we age

True

what is the driving force of passive transport?

the concentration gradient

What are some possible energy sources for active transport?

1. coupled reactions

2. light

3. energy carriers (ATP, GDP, NADH)

Sodium is higher inside or outside of the cell?

outside

for sodium, the driving force is massive because...

the voltage and concentration work in the same direction

When voltage and concentration work in opposite directions, the net movement is ...

small

what is an example of voltage and concentration working in opposite directions?

Potassium

Is there more potassium outside or inside the cell?

inside

How does the sodium potassium pump work?

1 - pump first binds to Na+.

2 - ATP comes along, "phosphorylates" pump, pumo changes shape.

3 - pump then releases Na+ to outside

4 - pump now open out, only has configuration to fit K+. Pump binds K+.

5 - Pump reverts back to original conformation (like a spring bottle, no atp needed this way) and releases K+ into cell, ready to start again.

glucose-Na+ symport

uses the electrochemical Na+ gradient to drive the active import of glucose

What kind of transporters can we find in the gut?

Glucose transporters

The Ca2+ pump is constantly on and pumping calcium inside or outside the cell?

Outside

What is the most controlled ion in the cell?

Calcium (Ca2+)

Ion channels are specific when it comes to... ?

size and charge of an ion they let pass through

Are ion channels turnstiles or gateways?

gateways

True or false: ion channels are always open

False -> they are gated and carefully controlled

What are the three ways that ion channels are controlled?

1. voltage-gated (membrane potential)

2. ligand-gated (ligand binding)

3. mechanically-gated (mechanical force applied to channel)

example of stress/ mechanical gated ion channels

hair cells of the ear (stress is sound)

what is considered the most complex object in the universe?

The human brain

Why are the inside of neurons/ cells negative?

Positive ions leave the cell.

Which channel "flickers" and contributes to the negative charge inside the cell?

Potassium

Potassium slowly leaves the cell through

the leaky potassium channel

The leaky potassium channel sets the...

resting membrane potential

how did we discover neurons?

through giant squids

What is action potential?

change in the membrane voltage over time

The fire of the action potential is called an

upstroke

The repolarization of a neuron is also called a

downstroke

Which protein does the upstroke of the action potential?

the voltage gated sodium channel

the voltage gated sodium channel opens at the

action potential threshold

True or False: neurons depolarize for a long time

FALSE -> they only depolarize for like half a second or else they may die

What prevents too much sodium from entering the cell?

the ball and chain

Action potentials are propagated along the neurons'

axons

True or false: action potential can travel both up and down an axon

FALSE: can only travel one way

What channels open in order to release neurotransmitters?

Voltage-gated Ca2+ channels

When calcium enters a neuron, it sends a signal ____ the neurotransmitters

to release

What opens up the voltage-gated ion channels in nuerons?

The change in voltage of the cell

What do neurotransmitters bind to on the postsynaptic cell?

receptors

An excitatory synapse causes other neurons to__

fire as well

an inhibitory synapse causes other neurons to ____

not fire

Benzodiazepines are drugs that cause neurons to (fire or not fire)?

not fire -> letting chloride into the neuron