UNIT 2 pt. 2 - Transport, Compartmentalization, Size, Membrane | AP Biology

What is metabolism?

Collection of chemical processes within a cell

What are the advantages of cell compartmentalization?

Efficiency, Multi-functionality (many activities at once), and Increased Surface Area (double membranes w/ bends/folds)

What are disadvantages of cell compartmentalization?

Requires larger cells, barriers to movement, active movement o materials

What do cell membranes do?

Provide a boundary b/w interior of the cell and outside environment, and control transport materials in/out of a cell

What is the structure of a phospholipid? (ampipathic)

Polar, hydrophilic head and a non polar hydrophobic tail

What is a peripheral protein (embedded proteins)?

Proteins that are loosely bound to the surface area of the membrane, hydrophilic with charged and polar side groups (on the side of the heads)

What is an integral protein (embedded proteins)?

Span across the membrane, hydrophilic with charged/polar groups on the side of the heads, hydrophobic w/ nonpolar side groups on the inside of the bilayer

What are the 6 main roles of proteins?

Transport, cell-cell recognition, enzymatic activity, signal transduction, intercellular joining, attachment for extracellular matrix or cytoskeleton

What is the Fluid-Mosaic Model?

Structure as a mosaic of protein molecules in a fluid bilayer of phospholipids; structure is not static and is held together by hydrophobic interactions, which are weak covalent bonds

What do steroids/cholesterol do in the membrane? (Fluid-Mosaic Model)

Help regulate bilayer fluidity under environmental conditions, distributed and wedged b/w phospholipids

Where are carbohydrates, Glycoproteins specifically, placed in the membrane? (Fluid-Mosaic Model)

One or more carbohydrates attached to a membrane protein 

Where are carbohydrates, Glycolipids specifically, placed in the membrane? (Fluid-Mosaic Model)

Carbohydrate attached to a lipid in the bilayer

What substances can move freely across the membrane?

Small nonpolar/hydrophobic molecules, and some very small polar molecules such as H20 in minimal amounts

What substances can NOT move across the membrane?

Hydrophilic substances such as large polar molecules/ions

How does a cell wall work as a structural boundary?

Protects and maintains shape: prevents against cellular rupture when internal water pressure is high, helps plants stand up 

How does a cell wall work as a permeable barrier?

Plasomodesmata: small holes b/w plant cells that allow transfer of nutrients, waste, and ions 

What is a cell wall compromised of?

Complex Carbohydrates:

Plants - Cellulose, Fungi - Chitin, Prokaryotes - peptidoglycan (polymer)

What is a concentration gradient?

Membrane that separates two different concentrations of molecules

What is passive transport?

Net movement of molecules from an area of high concentration to low concentration w/o metabolic energy (NO ATP)

What is diffusion (passive transport)?

Free movement of smaller, non polar molecules from high concentration to low concentration

What is Facilitated diffusion (passive transport)?

Movement of molecules, such as hydrophilic molecules/ions, from high concentration to low concentration using transport proteins

What is active transport?

Movement of molecules against the concentration gradient using energy, such as ATP: from Low concentration to High concentration

What is endocytosis?

Uses energy to move LARGE molecules INSIDE, forms new vesicles derived from the plasma membrane to carry said molecules

What is Receptor-Mediated Endocytosis (endocytosis)?

Receptor proteins on the cell membrane are used to capture specific target molecules

What is Exocytosis?

Internal vesicles use energy to fuse with the plasma membrane and secrete large macromolecules OUT of the cell. 

What is osmosis?

The diffusion of free water across a selectively permeable membrane

What is Osmolarity?

Total solute concentration in a solution

What is tonicity?

Measurement of the relative concentrations of solute b/w two solutions (inside and outside of a cell)

What is hypertonicity?

More solute and less solvent

What is hypotonicity?

Less solute and more solvent

What is isotonicity?

Equal concentrations of solute and solvent

What direction does water move via osmosis in relation to solute concentration?

Hypotonic into Hypertonic

Water would move to the area with higher solute concentration; they are inversely related

What direction does solute concentration diffuse along the concentration gradient?

Hypertonic into Hypotonic

Solutes diffuse from higher to a lower concentration

What direction does water move via as an isotonic environment?

Equilibrium exists with equal movement of water in and out at equal rates; no net movement

What is environmental hypertonicity? How does it affect plants?

Less cellular solute, more cellular water; results in Plasmolysis: more water leaving OUT of the cell

What is an Isotonic solution? How does it affect plants?

Equal solute and water transaction; results in being flaccid: equal movement of water in and out

What is environmental hypotonicity? How does it affect plants?

More cellular solute and less cellular water; results in being Turgid: more water coming INTO the cell

What environmental condition is best for plants? (hyper, hypo, iso)

Hypotonicity; water flows into plant vacuoles, causing them to expand and press against cell wall, cell wall expands until it exerts pressure back onto cell (Turgor pressure!)

What environmental condition is best for animals? (hyper, hypo, iso)

Isotonic solution

What is environmental hypertonicity? How does it affect animal cells?

Less cellular solute and more cellular water, results in shrived appearance

What is environmental hypotonicity? How does it affect animal cells?

More cellular solute and less cellular water; results in cell being Lysed: cell bursts

What is an isotonic solution? How does it affect animal cells?

Equal solute and water, normal for animal cells

What does water potential measure?

Tendency of water to move by osmosis

What is the directionality of water in regards to water potential?

Water moves from high to low 

What is Active Transport?

Movement of molecules AGAINST a concentration gradient - like going uphill! Requires membrane proteins such as integral proteins

What are some examples of cell compartmentalization (open answers allowed, you can ignore question!)

Mitochondria folding, Chloroplast folding, Lysosome membrane for Hydrolytic Enzyme enclosure

What are similarities between prokaryotic cells and eukaryotic cells? (membranes)

Cell membrane, cytoplasm, ribosomes, and DNA

How was the nucleus theorized to form?

Formed from the infoldings of the plasma membrane

How was the mitochondria/chloroplast theorized to form?

Via endosymbiosis: free-living aerobic prokaryote engulfed by anaerobic cell through endocytosis, was mutually beneficial until engulfed cell lost independent functionality and evolved into an organelle

What is the relationship b/w functions of endosymbiotic organelles and their ancestors?

Both mitochondria and chloroplasts have double-membranes; prokaryotic cells also have own circular DNA and can reproduce similar to process in prokaryotes, both contain own ribosomes than synthesize proteins

What are aquaporins and what do they do?

Water transport proteins that regulate water transport across cell membranes, enabling rapid movement of water and maintaining homeostasis

What is an antiport and what does it do?

Membrane proteins that transport two different molecules in opposite directions across a cell membrane

What is cotransport and what does it do?

Type of secondary active transport where a transport proteins moves two different substances across a membrane at the same time; the energy from moving one down the gradient powers the other moving against

What is the electrochemical gradient?

The combined effect of the concentration gradient and an electrical gradient (based on charge) across a membrane, creating a form of stored potential energ

What are electron transport proteins?

Protein complexes and carrier molecules in the inner mitochondrial membrane that transfers energy from electrons to oxygen, creating a proton gradient used to produce ATP via chemiosmosis

What are embedded/integral/membrane proteins?

Permanently embedded and acts as transport channels/pumps for ions

What is Endosymbiosis?

Origin of eukaryotic cells, where a larger host cell engulfed a smaller prokaryotic cell, resulting in a mutually beneficial, integrated relationship

What is membrane potential?

Voltage difference across a cells’ plasma membrane; acts like a battery, enabling cells to function and process signals.

What are microvilli?

Finger-like projections that extend from the cell membrane of some cells, particularly in the small intestine, to increase surface area for absorption

What is peptidoglycan?

A vital polymer in bacterial cell walls, providing structural rigidity and protection from osmotic pressure

What is phagocytosis?

Membrane absorbs particle, enveloping it in a vesicle, then transporting to a lysosome for digestion

What is pinocytosis?

Cell takes in small amounts of extracellular fluid and dissolved substances by forming vesicles pinched off from the membrane

What is a plasmodesmata?

Channels that pass through the cell walls of plant cells, connecting the cytoplasm of adjacent cells and allowing for direct communication and the transport of various ions.

What is pressure potential?

Pressure exerted by a solution or cell contents against its container, such as a cell wall

What is receptor-medicated endocytosis?

Cell specifically targets and envelopes a molecule using receptor proteins, then forming a vesicle which is transported to the cell

What are receptor proteins

Proteins that bind to specific signal molecules to initiate a cellular response

What is symport?

Symporter protein moves two different molecules or ions across a cell membrane simultaneously in the same direction

What is a vacuole?

Membrane-bound, fluid-filled sac that functions primarily for storage of water, nutrients, ions, and waste products. (Turgor pressure maintenance)

What is a vesicle?

Small, membrane-bound sac that acts as a transportation vehicle within a cell or for exporting substances from the cell

What is the endomembrane system?

Endoplasmic reticulum, Golgi apparatus, lysosomes, and vacuoles; works together to synthesize, modify, package, and transport proteins/lipids, and manage cellular waste.

What do glycolipids do?

Cell recognition for immune responses, cell adhesion/fusion, signaling, protection, stability

What do glycoproteins do?

cell recognition, cell signaling, cell adhesion, stability, and immune response

Why does the surface area to volume ratio play a role in mediating size?

As a cell grows, volume increases faster than its surface area, reducing this ratio and hindering the efficient diffusion of nutrients and gases in and waste products out

What is a stomata?

Tiny pores on the surface of plants, controlling the exchange of gases for photosynthesis and regulating water loss

What are three pieces of evidence that support the endosymbiotic theory?

Presence of circular DNA within mitochondria and chloroplasts, which resembles bacterial DNA, their reproduction via binary fission, similar to prokaryotes, and the existence of a double membrane surrounding each organelle, consistent with a host cell engulfing a prokaryotic cell

How is the concentration gradient maintained?

Active transport and continuous flow, which use energy or physical movement to counter the tendency for substances to move from high to low concentration; example is ion pumps

Why is water potential important in transpiration?

Creates the water potential gradient that drives the movement of water from the soil, up the plant, and out into the atmosphere