Bio chapter 2

Diffusion of Uncharged Particles

Substances in solution tend to move down their concentration gradient for uncharged particles, each substance moves independently

Fick’s law of diffusion

describes the rate of diffusion of uncharged particles in a solution down their concentration gradient. F=kA(c1-c2)/d

Diffusion with charged particles

depends on combination of concentration and electrical gradient

Osmosis

The movement of water down its concentration gradient across a semipermeable membrane.

Lower H2O concentration means…

Higher solute concentration

Osmolarity

determined by the combined concentration of all solutes in a solution

Osmotic pressure

the pressure required to prevent the flow of water across a semipermeable membrane due to osmosis. Proportional to the difference in solute concentrations on either side of the membrane.

isosmotic

two solutions have the same osmolarity

Hyperosmotic

a solution has a higher concentration than another

Hyposmotic

a solution has a lower concentration than another

Water potential

the overall tendency of water to move

Hydrostatic pressure (pressure potential) ΨP

the pressure exerted by a fluid against the walls of its container, influencing water movement in plants. (normally positive)

Osmotic pressure (solute potential) ΨS

the pressure required to prevent the flow of water into a solution due to its solute concentration. It affects the movement of water across cell membranes. (normally negative)

Water cohesion and adhesion (matrix potential) ΨM

refers to the properties of water molecules that enable them to stick to each other and to other substances, playing a crucial role in water transport in plants. (normally negative)

Water potential equation

Ψ = ΨP + ΨS + ΨM

Water will move from to

an area of higher water potential to an area of lower water potential.

Phospholipid Bilayer surface/ core

Hydrophilic lipophobic surface/ hydrophobic lipophilic core

Phospholipid bilayer diffusion constants

Hydrophobic molecules (02, co2, ), Small uncharged polar molecules (h2, o glycerol, urea), large uncharged polar molecules (glucose), ions (cl-, k+, na+)

Passive transport

Examples: Simple diffusion, channel protein (permeation), Carrier protein (facilitated diffusion),

Move: With electrochemical gradient

Primary active transport

Examples: Uniport pump, antiport pump,

move: up and down electrochemical gradient

Secondary active transport

Uses ATP

Example: symporter,

Moves: up and down electrochemical

movement of solute _ its gradient doesn’t need energy

down

movement of a solute _ its gradient required energy from:

up, ATP powered pump (primary active transport), or contransport with another solute moving down its gradient, which must then be moved back with ATP (secondary active transport)

geometric consequences of getting bigger

increased distance betweens urface and center

decreased surgace area to volume ratio

as an organism gets larger, it’s center is further from it’s surface which causes

increased distance for diffusion

total surface area=

6 * length ²

Total volume

length ³

surface change is proportional to

change in length squared

Volume change is proportional to

change in length cubed

claude bernard

french scientist- conducted experiments on digestion and thermoregulation in 1850

internal environment is composed of

interstitial fluid, and blood regulated to maintain specific conditions hospitable to body’s cells

Negative feedback loops

regulated variable→control center→Effector→Regulated variable

young actively growing cells have a flexible __ cell wall

Primary

__ content is higher in young actively growing primary cell walls

Pectin

Some older cells form a rigid __ cell wall

secondary

secondary cell walls have more _ which makes them rigid

lignin

three components plants cells have that are not found in animal cells

cell walls, vacuoles, chloroplasts

Cells are glued together by a pectin layer called the __

middle lamella

cell walls are mostly composed of __

cellulose

cellulose is interconnected by __

hemicellulose

Plasmodesmata

openings between adjacent primary cell walls

symplast

continuous cytoplasm within plasmodesmata

central vacuole contains mostly water and __

enzymes, salts, pigments, alkaloids

vacuoles store needed ions and create __ to keep cells rigid

tugor pressure

root hairs

absorb water and nutrients

root cap

Protects growing tip, releases lubricating slime, perceives gravity

growth is __ and occurs via __ and __

irreversible, cell duplication, cell expansion

differentiation

cells assume a particular identity & function

cell duplication occurs via

mitosis

new cells arise in regions of specialized tissue called

meristem

new meristematic cells are totipotent which means

they have the potential to differentiate into any cell type

apical meristem

produce primary tissues at stem and root tips to increase length of plant

EX: Shoot apical meristem (SAM), Root Apical meristem (RAM)

Lateral meristems

produce secondary tissues that increase the width of the plant

ex: vascular cambium, cork cambium

cells expand by __

loosening cell walls, generating turgor pressure (hydrostatic pressure)

turgor pressure is generated by

transported solutes into vacuoles, water moves in via osmosis

primary growth

usually occurs at apical meristem

secondary growth

occur in lateral meristem produces wood and increases width

Lateral meristem occurs in two regions

Vascular cambium, cork cambium

vascular cambium

produces secondary xylem (wood) on inner edge, and secondary phloem on outer edge

cork cambium

produces cork cells, present in place of epidermal cells

Bark is made of

Cork cells + cork cambium + secondary phloem. Outer cork cells are typically dead

dermal tissue

outer covering: epidermis and periderm in woody plants

vascular tissue

xylem (water conduction) and phloem (food conduction)

ground tissue

simple bulk of plant body, can be specialized for many functions

epidermal cells

barrier cells, form an outer protective layer, secrete cuticle to protect from water loss and pathogens but prevent gas exchange

Parenchyma

Most common cell type, leaves are photosynthetic, roots provide storage, thin cell walls, remain totipotent

collenchyma

provide support to shoots, thicker primary cell walls and long shape, can continue to lengthen in growing regions

sclerenchyma

very thick secondary cell walls with lignin, do not change shape once mature, most die.

fibers strengthen shoots, sclereids protect surfaces like seeds

xylem is the conduit for

water and nutrients

phloem is the conduit for

sugars, amino acids and hormones,

xylem has two conducting cells

Tracheids, Vessel elements

Tracheids are found in

all vascular plants

vessel elements are found in

angiosperms and gnetophytes

phloem has two major cell types

sieve tube elements, companion cells (parenchyma)

Sieve tube elements

transport vessels, lack most cell organelles, connect to companion cells via plasmodesmata

companion cells (parenchyma

metabolic support for sieve tube elements

Stomata

pores that allows gas exchange, part of dermal tissue

guard cells

open and close depending on water and co2 levels

water potential is measured in

megapascals

1 atm= __ Megapascal

.1

hydrostatic potential

tendency of water to move due to compression due to pump, gravity, or containment

turgid

cells with enough turgor pressure to induce wall pressure

flaccid

cells without enough pressure to induce wall pressure

How do plants control water flux of cells?

they alter ion concentrations in different fluid spaces

matrix potential

attraction between water molecules and other objects bia hydrogen bonds

surface tension

water molecules cohere to eachother at the surface

cohesion-tension system

water is pulled up by evaporation at leaves

transpiration

evaporation from leaves that creates negative water potential

water uptake at roots

water enters at root hairs, moves to xylem via three routes, casparian strip controls entry into xylem

soil water potential

not zero because of solutes and adhesion to particles, water in soil: -.2MPa, water in roots: -.6 MPa

Transport in xylem is __

passive

when sunlight and temperature increases the stomata __

opens

transpiration is expensive in terms of __ use

water

water loss is reduced by:

Reduced leaf surface area, thickened cuticle, reduced stomata, derived forms of photosynthesis

translocation

the movement of sugars by bulk flow in sap

where are sugars made (source)?

Photosynthesizing organs, primarily mature leaves

where are sugars sent (sinks)?

organs that don’t photosynthesize, young leaves, flowers, roots

sugars move from sources to sinks __ water potential gradient

along