cellular perspectives exam 2

Features shared by both prokaryotes & eukaryotes?

Plasma membrane, cytosol, ribosomes, DNA.

Role of vesicles?

Transport sacs; bud and fuse; maintain membrane orientation.

Types of vacuoles?

Food (digestion), Contractile (water balance), Central (plants: storage, turgor).

What regulates membrane fluidity?

Fatty acid saturation (unsaturated ↑ fluidity, saturated ↓), cholesterol (prevents melting at warm temps, freezing at cold temps).

What is active transport?

ATP-powered movement of ions/molecules against gradient.

Plasma membrane model?

Fluid mosaic (regulated by FA saturation + cholesterol).

What is anabolism? Give an example.

Build-up reactions that require energy. Ex: glycogen synthesis, muscle growth. Memory trick for anabolism: Anabolic steroids → build muscle.

What is catabolism? Give an example

Breakdown reactions that release energy. Ex: glycogen → glucose, digestion. Memory trick for catabolism Cats break things → catabolism breaks down molecules

What is homogenization?

Blending tissues/cells → makes a homogenate (cell contents).

What is centrifugation used for?

Spins homogenate to separate cell parts by size/density.

What pellets at low, medium, and high centrifuge speeds?

Low → nuclei, Medium → mitochondria, High → vesicles & ribosomes.

Key difference between prokaryotes and eukaryotes?

Prokaryotes: no nucleus; Eukaryotes: nucleus with double membrane.

Size range of prokaryotes vs eukaryotes?

Prokaryotes: 1-5 µm; Eukaryotes: 10-100 µm.

What is selective permeability?

Some molecules pass freely; others need proteins.

What is metabolism?

All chemical reactions in the cell.

What is the endomembrane system (EMS)?

Interconnected system of membranes that traffic proteins, lipids, and cargo.

Members of EMS?

Nuclear envelope, ER, Golgi, lysosomes, vesicles/vacuoles, plasma membrane.

Function of Rough ER?

Makes proteins for secretion or EMS (has ribosomes).

Function of Smooth ER?

Synthesizes lipids, metabolizes carbs, detoxifies, stores Ca²⁺.

What is unique about the Golgi apparatus?

Stacks of unconnected cisternae; modifies proteins; cis face = receive, trans face = ship.

Lysosome functions?

Digest food, destroy pathogens, recycle damaged organelles (autophagy).

What is the cytoskeleton?

Dynamic protein network for structure, transport, motility.

Microtubule size & functions?

Largest (~25 nm). Resist compression, tracks for kinesin/dynein, form cilia/flagella.

What motors move along microtubules?

Kinesin → + end (outward), Dynein → - end (inward).

Microfilament size & functions?

Smallest (~7 nm). Actin filaments; resist tension, muscle contraction, cell shape, movement, cytokinesis.

Intermediate filament size & functions?

Medium (~8-12 nm). Strong, rope-like, stable; reinforce shape, anchor organelles, form nuclear lamina.

What is the plasma membrane made of?

Phospholipid bilayer with proteins & carbs → fluid mosaic.

What are integral vs peripheral proteins?

Integral: embedded in bilayer; Peripheral: loosely attached.

Functions of membrane proteins?

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

What do membrane carbohydrates do?

Act as identity markers (e.g., blood type).

Examples of simple diffusion?

Small, nonpolar molecules (O₂, CO₂).

Examples of facilitated diffusion?

Polar molecules (H₂O via aquaporins).

Direction of diffusion?

High → low concentration.

What is equilibrium in diffusion?

Balanced distribution, but molecules keep moving.

Do substances diffuse independently?

Yes.

Real-life example of diffusion?

Perfume spreading across a bus.

Microtubules main roles?

Resist compression, tracks for motors, cilia/flagella movement.

Microfilaments main roles?

Actin + myosin → resist tension, motility.

Intermediate filaments main roles?

Strong, permanent support (keratin, lamina).

Transport types across membranes?

Diffusion, facilitated diffusion, active transport.

Function of carbs on glycoproteins/glycolipids?

Identity markers (e.g., blood types).

What is diffusion?

Movement of molecules from high to low concentration, down their concentration gradient, without energy.

What molecules can pass through the plasma membrane by simple diffusion?

Small, nonpolar molecules (like O₂ and CO₂).

What is passive transport?

Transport across the membrane that requires no energy, powered by concentration gradients.

What is facilitated diffusion?

Passive transport using transport proteins (channels or carriers), still moving down concentration gradient.

Give an example of a molecule that requires facilitated diffusion.

Water (via aquaporins) or glucose (via glucose transporter).

What is osmosis?

Diffusion of free water molecules across a semi-permeable membrane.

Why is osmosis considered facilitated diffusion?

Because water needs aquaporins (transport proteins) to cross the hydrophobic membrane interior.

Which direction does water move during osmosis?

From areas of high free water (low solute) to low free water (high solute).

What happens at equilibrium in osmosis?

Water molecules still move, but equal amounts cross in both directions (no net change).

What does tonicity describe?

The ability of a solution to cause a cell to gain or lose water, based on solute concentration.

What is an isotonic solution?

Equal solute concentration inside and outside the cell → no net water movement.

What happens to an animal cell in a hypertonic solution?

Water moves out → the cell shrinks and shrivels.

What happens to a plant cell in a hypertonic solution?

The membrane pulls away from the wall (plasmolysis).

What is a hypotonic solution?

Lower solute outside → more free water outside → water moves into cell.

What happens to an animal cell in a hypotonic solution?

Cell swells and may burst (lysis).

What happens to a plant cell in a hypotonic solution?

Cell becomes turgid (firm), which is its normal state.

Why don't plant cells burst in hypotonic solutions?

Their rigid cell wall pushes back against excess water.

How do single-celled freshwater organisms (like Paramecia) prevent bursting?

They use contractile vacuoles to pump out excess water.

Why are animal body fluids (like blood) isotonic?

To keep water balance stable and prevent cells from swelling or shrinking.