BIO 3 - Week 6 Content

Trace a K⁺ ion from a clay particle to the xylem, naming what drives it across each membrane.

• Cation exchange

• Root entry

• Crosses the root

• Enters the xylem

Trace a glucose molecule from the gut lumen to the blood, naming what drives it across each membrane.

• Breaks down

• Enters apical

• Exits basolateral

Describe how different types of pumps contribute to uptake of cations, anions, and glucose

• Plant H⁺ pump: spends ATP to pump H⁺ and makes root cell negative to pull cations

• Animal Na⁺/K⁺ pump: spends ATP to keep Na⁺ low and pulls glucose

Breaking down food in the open

• Fungi grow directly into their food and secrete enzymes to absorb monomers

• Tradeoff: digested nutrients can diffuse or be stolen

Breaking down food in an enclosed gut

Animals digest food in gut to prevent nutrient theft and allow processing

Breaking down food by outsourcing to partners

Organisms rely on mutualists for missing enzymes or surface area

Features shared as homology

• Pumps

• Digestive enzymes

Features shared as convergence

• Seals between cells and cell polarity

• Microbial partners and high surface area

Cation / exchange

• Cation: positively charged ion

• Cation exchange: occurs when plant roots pump out hydrogen to displace cations

H+ co-transport / proton pump

Proton pump uses ATP to create an electrochemical gradient and import anions

Root hair

Extensions of root epidermal cells that increase SA

Casparian strip

Impermeable band of lignin that seals cell walls

Xylem

Vascular pipes that transport water and dissolved minerals from roots to leaves

Digestive enzyme

Enzymes that make macromolecules into absorbable monomers

Lignin

A rigid polymer

Gut

Used for digestion

Cell polarity

Having different transport proteins on opposite faces of a cell

Tight junctions

Strands of proteins that seal the spaces between adjacent cells

Lumen

Hollow interior cavity of the gut

Mycorrhizae

Symbiotic fungi living with plant roots that can expand

Xylem

Powered by the sun which evaporates water from leaves and creates tension

Phloem

Powered by ATP and loads sugar at a source to draw water in by osmosis

Animal circulation

Powered by cellular ATP driving muscular contractions to make a pressure difference

Explain why vascular networks use a few wide pipes for distance and many narrow ones near cells.

• Wide pipes minimize friction and move large volumes over large distances

• Narrow tubes provide enough time and SA for slow diffusion

Leaving capillaries

• Molecules dissolve straight through cells

• Small solutes slip through gaps

• Large proteins stay inside to hold fluid

• Fats are cleaved

• White blood cells squeeze between cells

Tuning leakiness

• Tissues adjust gap size

• Brain capillaries are sealed by tight junctions

Local cell uptake

• Cells tag incoming glucose with a phosphate

• Control intake rate

• Resting muscle moves to surface

Identify convergent transport solutions in plants and animals.

• Branching pipe networks

• Selective border seals + polarized cells

• Molecular trapping

Cytoplasmic streaming

Internal mixing inside cells where proteins move interior membranes and drag the cytoplasm

Vascular system

Intercellular pipes that overcome the diffusion limit

Properties of water

Water stays liquid over a temperature range, is a good solvent, holds heat, and sticks to itself and the walls

Non-vascular plants

Lack pipes, rely on osmosis, and have a limited height

Vascular plants

Use lignin reinforce xylem against collapse

Transpiration

Evaporation of water vapor out of stomata, which creates negative pressure

Phloem

Living tubes that transport sugars from sources to sinks

Open circulation

A heart pumps into an open body cavity bathing organs

Closed circulation

A heart pumps blood inside vessels with exchange at capillaries

Poiseuille’s law

small changes in vessel radius can cause huge changes in blood flow

Endothelial cells

Thin layer of cells forming walls that are selective

Phosphate trap

Enzymes immediately attach a phosphate group to incoming glucose to maintain a diffusion gradient

What goes in and out of cells and organsisms

• Energy in & heat out

• Nutrients in & waste and metabolic byproducts out

Homeostasis

managing extracellular solutes by getting what you need and getting rid of what you don’t

What happens if a cell or organisms has zero outflow?

• Reactions stall

• pH shifts

• Solutes pile up

• Metabolic byproducts become toxic

Toxicology

Essential molecules can become toxic at too high a concentration

How do organisms get wastes and toxins out compared to getting nutrients in?

Organisms use the same ways in reverse or in special organs to move unwanted molecules out

Strategies organisms use to avoid toxicity?

• Exclude

• Sequester

• Convert

• Excrete

Serpentine Soil

Low ratio and high concentration of toxic heavy metals

How do serpentine excluders keep nickel out of their leaves?

• Membrane proteins: take up less at root and use pump inside root vacuoles

• Vascular system: load into xylem