AP Bio unit 2

Structure of ribosomes

Two subunits (small and large), not membrane enclosed, made of rRNA and proteins.

Function of ribosomes

Synthesize proteins according to the mRNA sequence.

Role of mRNA

Travels to ribosomes in the cytoplasm to provide instructions for protein synthesis.

Structure of smooth ER

Network of membrane tubes without ribosomes attached.

Function of smooth ER

Lipid synthesis and detoxification.

Structure of rough ER

Network of membrane tubes with ribosomes attached.

Function of rough ER

Compartmentalizes the cell and packages newly synthesized proteins for export.

Structure of Golgi complex

Series of flattened, membrane-bound sacs in eukaryotic cells.

Function of Golgi complex

Modifies, folds, and packages proteins for trafficking.

Structure of mitochondria

Double membrane; outer smooth, inner folded into cristae.

Function of mitochondria

Production of ATP energy through cellular respiration.

Mitochondrial matrix

Location of Krebs cycle reactions.

Mitochondrial intermembrane space

Area between inner and outer membranes; site of processes contributing to ATP production.

Function of lysosomes

Digestion, recycling of materials, apoptosis (programmed cell death).

Contents of lysosomes

Hydrolytic enzymes to digest damaged parts or macromolecules.

Function of vacuoles

Storage of water/macromolecules, release of waste, maintain turgor pressure.

Photosynthesis

Production of sugar using sunlight in plant cells.

Structure of chloroplasts

Double outer membrane.

Function of chloroplasts

Capture sunlight to produce sugar by photosynthesis.

Structure of thylakoids

Highly folded membrane compartments in grana.

Function of thylakoids

Site of light-dependent reactions; folding increases efficiency.

Structure of stroma

Fluid between inner chloroplast membrane and thylakoids.

Function of stroma

Site of Calvin-Benson cycle (carbon fixation).

What do all cells contain?

Plasma membrane, cytoplasm, ribosomes, and DNA.

Functions of plant vacuoles

Store water, use turgor pressure for support, break down waste.

Processes in mitochondria

Cellular respiration to produce ATP.

How ER and Golgi work together

ER synthesizes proteins/lipids, Golgi modifies, sorts, packages them for transport or export.

How lysosomes and vesicles interact

Vesicles fuse with lysosomes; hydrolytic enzymes digest contents.

Why are cells small?

Higher surface area-to-volume ratio increases efficiency.

How surface area-to-volume ratio helps

More efficient material exchange across plasma membrane.

Examples of maximizing surface area

Mitochondrial cristae for ATP production; thylakoids for photosynthesis.

Plasma membrane

Selectively permeable barrier between internal and external environments.

Phospholipid structure

Hydrophilic head, hydrophobic tail; amphipathic.

Function of phospholipids

Form bilayer boundary of cell.

Amphipathic definition

Has both hydrophilic and hydrophobic regions.

Peripheral proteins

Loosely bound to membrane surface; hydrophilic.

Integral proteins

Span the membrane; hydrophilic and hydrophobic regions anchor them.

Functions of membrane proteins

Transport, recognition, enzymatic activity, signal transduction, joining, attachment.

Fluid mosaic model

Membrane of phospholipids and proteins; flexible and dynamic.

Role of cholesterol in membranes

Regulates fluidity under different conditions.

Function of carbohydrates in membranes

Serve as cell recognition markers.

Glycoproteins

Carbohydrates attached to membrane proteins.

Glycolipids

Carbohydrates attached to lipids in membrane.

Selectively permeable membrane

Small nonpolar molecules pass freely; ions and large polar molecules need transport proteins.

Channel proteins

Provide hydrophilic tunnel for specific molecules.

Carrier proteins

Change shape to move molecules across the membrane.

Which small molecules pass freely

O₂, CO₂, N₂.

Molecules that cannot pass freely

Large polar molecules and ions.

Can water pass through membranes?

Yes, minimally through bilayer or via aquaporins.

Cell wall functions

Structural support, protection, prevents rupture, permeable barrier.

Plant cell wall composition

Cellulose.

Fungal cell wall composition

Chitin.

Prokaryotic cell wall composition

Peptidoglycan.

Plasmodesmata

Small holes between plant cells for exchange of materials.

Concentration gradient

Difference in solute concentration between areas.

Passive transport

Movement from high to low concentration without energy.

Diffusion

Movement of molecules from high to low concentration.

Facilitated diffusion

Diffusion through transport proteins; allows ions/hydrophilic molecules to pass.

Active transport

Movement from low to high concentration using ATP.

ATP in transport

Provides energy for active transport and gradient maintenance.

Endocytosis

Cell takes in materials by forming vesicles from plasma membrane.

Phagocytosis

Endocytosis of large particles.

Pinocytosis

Endocytosis of extracellular fluid.

Receptor-mediated endocytosis

Receptors capture specific molecules for endocytosis.

Exocytosis

Release of large molecules by vesicles fusing with plasma membrane.

Purpose of plasma membrane

Controls transport, allows gradients, supports diffusion.

Electrochemical gradient

Combination of concentration gradient and membrane voltage.

Phospholipid bilayer organization

Heads face outward/inward (hydrophilic); tails inside (hydrophobic).

How integral proteins stay in membrane

Hydrophobic regions interact with bilayer interior; hydrophilic regions interact with water.

Functions of lipids in membranes

Maintain structure and fluidity.

Functions of carbohydrates in membranes

Serve as identification markers.

Na⁺/K⁺ pump

Uses ATP to pump 3 Na⁺ out, 2 K⁺ in, maintains potential.

Cotransport

Active transport of two substances by one protein.

Symport

Two substances move in same direction.

Antiport

Two substances move in opposite directions.

Membrane potential

Voltage difference across membrane due to ion distribution.

Osmosis

Movement of water across selectively permeable membrane.

Aquaporins

Proteins that allow large amounts of water transport.

Osmolarity

Total solute concentration in solution.

Tonicity

Relative solute concentration inside vs outside cell.

Hypotonic solution

Lower solute outside; water enters cell.

Hypertonic solution

Higher solute outside; water leaves cell.

Isotonic solution

Equal solute inside and outside; no net water movement.

Plasmolysis

Water leaves plant cell, cytoplasm shrinks.

Flaccid

Plant cell in isotonic environment.

Turgid

Plant cell in hypotonic environment; optimum state.

Turgor pressure

Water pressure pushing against plant cell wall.

Osmoregulation in plants

Maintains water balance via vacuoles and cell walls.

Osmoregulation in animals

Maintains water balance via solute regulation.

Contractile vacuole

Pumps water out of freshwater protists to maintain balance.

Solvent vs solute

Solvent = dissolving substance; solute = dissolved substance.

Water potential (Ψ)

Ψ = ΨP + ΨS; water moves from high to low potential.

Effect of solutes on Ψ

More solute = more negative ΨS, lower water potential.

Solute potential equation

ΨS = –iCRT.

Endocytosis vs exocytosis

Endocytosis takes in material, exocytosis releases it.

Facilitated diffusion vs active transport

Facilitated: passive, down gradient, no energy. Active: requires energy, moves against gradient.

Effective graph components

Title, labeled axes.

Box-and-whisker plot

Graph showing variability and distribution of data.

Compartmentalization in eukaryotes

Membranes and organelles isolate processes to increase efficiency.

Role of lysosome compartmentalization

Maintains acidic pH for enzyme function while protecting cytoplasm.