Cell Biology: Organelles, Membranes, and Surface Area-to-Volume

What is a ribosome?

Site of protein synthesis.

What are the three types of RNA involved in ribosome function?

mRNA, tRNA, rRNA.

What is the function of the ribosome?

Builds proteins.

How does the structure of the ribosome aid in function?

Its two subunits allow mRNA reading and protein assembly.

What is the endomembrane system?

Group of organelles that modify, package, and transport materials.

What are the components of the endomembrane system?

Nuclear envelope, ER, Golgi apparatus, vesicles, vacuoles, plasma membrane.

What are the two types of endoplasmic reticulum?

Rough ER and Smooth ER.

What is the function of rough ER?

Protein synthesis and processing.

What is the function of smooth ER?

Lipid synthesis and detoxification.

What is the Golgi apparatus?

Organelle that modifies, sorts, and packages proteins and lipids.

What is the function of the Golgi apparatus?

Processes and ships cellular products.

What are mitochondria?

Organelles that produce ATP through cellular respiration.

What is the function of mitochondria?

ATP production.

How does the structure of mitochondria aid function?

Cristaes increase surface area for ATP production.

What are lysosomes?

Organelles containing digestive enzymes.

What is the function of lysosomes?

Digest and recycle materials.

What is apoptosis?

Programmed cell death.

What are vacuoles?

Membrane-bound storage sacs.

What is the function of a central vacuole?

Stores water and maintains turgor pressure.

What are chloroplasts?

Photosynthetic organelles in plants and algae.

What is the function of chloroplasts?

Photosynthesis.

What are thylakoids?

Membrane sacs where light-dependent reactions occur.

What is the function of ribosomes?

Protein synthesis.

What is the cell theory of surface area to volume ratio?

Exchange efficiency depends on SA:V ratio.

What happens when surface area to volume ratio increases?

Material exchange becomes more efficient.

What type of SA:V ratio is best for cells?

High SA:V ratio.

How can cells increase surface area without increasing volume?

Folds, projections, or microvilli.

What is the effect of increased SA:V on heat exchange?

Faster heat exchange.

What is the relationship between organism size and SA:V ratio?

Smaller organisms have higher SA:V ratios.

What is the relationship between size and metabolic rate per unit mass?

Smaller organisms have higher metabolic rates per unit mass.

What are the components of the plasma membrane?

Phospholipids, proteins, cholesterol, carbohydrates.

What is the function of phospholipids?

Form a selective barrier.

What is the function of membrane proteins?

Transport, signaling, recognition.

What is the function of cholesterol?

Maintains membrane fluidity and stability.

What is the function of membrane carbohydrates?

Cell recognition and communication.

Describe a phospholipid.

Hydrophilic head and hydrophobic tails.

How are phospholipids oriented in a membrane?

Heads face water; tails face inward.

How does the phospholipid bilayer maintain homeostasis?

Controls movement into and out of the cell.

What are the two main types of membrane proteins?

Integral and peripheral proteins.

What are six functions of membrane proteins?

Transport, enzymes, signaling, recognition, adhesion, cytoskeleton attachment.

What makes part of a protein hydrophilic?

Polar or charged amino acids.

What makes part of a protein hydrophobic?

Nonpolar amino acids.

What is the fluid mosaic model?

Membrane components move freely within the bilayer.

Why is the plasma membrane selectively permeable?

The hydrophobic core blocks many substances.

Which molecules pass easily through membranes?

Small nonpolar molecules like O₂ and CO₂.

How does water move across membranes in large amounts?

Through aquaporins.

What are aquaporins?

Water channel proteins.

What are transport proteins?

Proteins that move substances across membranes.

What are the two major types of transport proteins?

Channel proteins and carrier proteins.

Why do ions need transport proteins?

They are charged and cannot cross the hydrophobic membrane core.

Which cells have cell walls?

Plants, fungi, and bacteria.

What is the function of the cell wall?

Support, protection, and shape.

How does the cell wall protect in hypotonic environments?

Prevents bursting from excess water.

What is a concentration gradient?

Difference in concentration across a space.

How are concentration gradients maintained?

Through passive and active transport.

What is passive transport?

Movement without energy from high to low concentration.

What are two examples of passive transport?

Diffusion and osmosis.

What is active transport?

Movement requiring ATP.

What direction does active transport move substances?

Low concentration to high concentration.

What are two examples of active transport?

Sodium-potassium pump and proton pump.

What is endocytosis?

Cell takes in materials using vesicles.

What are the three types of endocytosis?

Phagocytosis, pinocytosis, receptor-mediated endocytosis.

What is exocytosis?

Release of materials by vesicles fusing with the membrane.

Are endocytosis and exocytosis active transport?

Yes.

What is facilitated diffusion?

Passive transport through protein channels or carriers.

Does facilitated diffusion require proteins?

Yes.

How do ions cross the membrane?

Through transport proteins.

What is membrane potential?

The charge difference across a membrane.

How do large polar molecules cross the membrane?

Through carrier or channel proteins.

What is tonicity?

The relative solute concentration of a solution.

What is a hypotonic solution?

Lower solute concentration than the cell.

What is a hypertonic solution?

Higher solute concentration than the cell.

What is an isotonic solution?

Equal solute concentration to the cell.

What is water potential?

The tendency of water to move.

In what direction does water move?

From higher water potential to lower water potential.

What is homeostasis?

Maintaining stable internal conditions.

What is osmoregulation?

Control of water and solute concentrations.

How do cells maintain osmoregulation?

Transport proteins and osmosis.

How do organisms maintain osmoregulation?

Kidneys and excretory systems.

What is an electrochemical gradient?

A combination of concentration and charge differences.

How is an electrochemical gradient established?

By active transport of ions.

What is ATPase?

An enzyme that hydrolyzes ATP.

What is the function of the sodium-potassium pump?

Pumps 3 Na⁺ out and 2 K⁺ in using ATP.

What is cell compartmentalization?

Division of cellular functions into membrane-bound regions.

Why is compartmentalization important?

It increases efficiency and allows specialized reactions.

How do internal membranes aid cellular processes?

Separate reactions and create specialized environments.

What is the function of mitochondrial cristae?

Increase surface area for ATP production.

What is the function of thylakoid membranes?

Site of light-dependent photosynthesis reactions.

What is the function of ER folds?

Increase surface area for synthesis processes.

What is the function of Golgi sacs and membranes?

Modify, sort, package, and transport products.

How does increased membrane surface area affect reactions?

Allows more reactions to occur.

What is endosymbiosis?

Theory that organelles evolved from engulfed prokaryotes.

Which organelles originated through endosymbiosis?

Mitochondria and chloroplasts.

What evidence supports endosymbiosis?

Their own DNA and ribosomes.

How did mitochondria evolve?

From engulfed aerobic bacteria.

How did chloroplasts evolve?

From engulfed photosynthetic bacteria.

What is a prokaryote?

A cell without a nucleus or membrane-bound organelles.

What are three similarities between prokaryotic and eukaryotic cells?

DNA, ribosomes, plasma membrane.

What are three differences between prokaryotic and eukaryotic cells?

Nucleus, membrane-bound organelles, larger size in eukaryotes.

How do eukaryotic internal membranes maintain regions?

Separate cellular functions into compartments.