phloem part 1

The accumulation of nutrients into plant tissues is the source for

Almost all nutrients in humans

What elements are essential for structure or metabolism in plants

N, P, K - the limiting nutrients

What happens if plants don’t have the essential nutrients

Abnormal growth, development, or reproduction

What forces drive movement

1. Hydrostatic pressure

2. Gravity

3. Concentration

4. Electric field for ions

What sums up all of the forces that drive movement

Chemical potential

What is the driving force for a neutral molecule?

The concentration gradient

What impacts the chemical potential for ions?

Concentration gradient, and any electrical potential (Electrochemical potential)

Passive transport

Occurs spontaneously when one solute concentration is higher than the other and goes down a chemical potential gradient

Active transport

Occur against a chemical potential gradient

Membrane permeability

The extent to which a membrane permits the movement of a substance

Diffusion of salts across the membrane can produce

An electrical membrane potential

Diffusion potential

Ions crossing a membrane at different rates, causing separation of charge

When does the diffusion potential form an ion speed up or slow down?

as potassium diffuses along its concentration gradient, it slows down and the diffusion of chlorine speeds up. Ultimately, both diffuse at the same rate, but a diffusion potential exists

What if only K was passing through the membrane instead of KCl

K, would diffuse across the membrane until the membrane potential balanced the concentration gradient

Do all cells have a membrane potential?

Yes, due to selective ion movement across their plasma membranes

Equilibrium

When ions electrochemical potential is equal for an ion across a membrane- No extra energy is needed

Steady state

Active transporters to maintain equilibrium for ions- Extra energy required

What ion has the greatest concentration of any ion in plant cells and the greatest membrane permeability

Potassium

What is the predicted diffusion potential for cells?

-80 to -50 mV Because it’s close to the theoretical diffusion potential of potassium since it’s the most permeable and abundant ion in most eucaryotic cells

What is the actual resting membrane potential for plants?

-200 to -100 mV

Why is the actual membrane potential more negative than predicted?

H+ ATPase electrogenic pumps that transport protons out of the cell without an accompanying ion making the inside more negative

Plant membrane potential consist of

1. Diffusion potential

2. Active electrogenic ion transport

More permeability for ions and water, suggesting other things that move these in or out other than the membrane

Porsche in channel proteins can be opened or closed by gate regions in response to

Membrane potential changes, ligands, hormones, light, post translational protein modifications, mechanical stress- thigmomorphogenesis

Two types of potassium

1. Inwardly opening to allow inward diffusion of potassium from the apoplast

2. Outwardly opening to release potassium from membrane to apoplast

Carrier proteins

Bond to an organic or inorganic cell to transport it across a membrane. Slower than a channel protein

In what kind of diffusion are carrier proteins used

Passive facilitated diffusion or secondary active transport

Primary active transport- H+ ATPase

Proton binds to pump and energy is needed to change conformation and move proton across cell membrane. Pumping protons out, causes the outside to be lower in pH and inside more neutral

secondary active transport

Move solute against their concentration gradient which requires energy. Energy is delivered by protons, moving with their concentration gradient, generating proton motive force. as protons move inside it carries the solute against its concentration with it