BIOL 4/5

What defines a eukaryotic cell?

A cell with a nucleus and membrane-bound organelles

What is an organelle?

A membrane-bound structure with a specific function

What is the main advantage of organelles?

Compartmentalization of cellular functions

What organelle stores DNA?

The nucleus

What is chromatin?

DNA + proteins (histones)

What happens to chromatin during cell division?

It condenses into chromosomes

What is the nuclear envelope?

Double membrane surrounding the nucleus

What are nuclear pores?

Protein complexes controlling entry/exit of molecules

What is the nucleolus?

Site of rRNA synthesis and ribosome assembly

What is a nuclear localization signal (NLS)?

A sequence directing proteins to the nucleus

What amino acids are common in NLS?

Lysine and arginine

What happens if a protein lacks an NLS?

It remains in the cytoplasm

What are ribosomes made of?

rRNA and proteins

Where are ribosomes assembled?

In the nucleolus

What do ribosomes do?

Synthesize proteins

Where are free ribosomes located?

In the cytosol

What proteins do free ribosomes make?

Cytosolic or organelle-targeted proteins

Where are bound ribosomes located?

On rough ER

What proteins do bound ribosomes make?

Secreted or membrane proteins

What is the endomembrane system?

A network of membranes for protein/lipid processing

What organelles are part of the endomembrane system?

ER, Golgi, lysosomes, vacuoles, plasma membrane, nuclear envelope

What is the rough ER?

ER with ribosomes; synthesizes proteins

What is the smooth ER?

ER without ribosomes; lipid synthesis and detox

What does smooth ER store?

Calcium ions (Ca2+)

What is the Golgi apparatus?

Organelle that modifies and sorts proteins

What are the cis and trans faces of Golgi?

Cis receives; trans ships products

What is the secretory pathway?

ER → Golgi → vesicles → membrane/secretion

What is a signal peptide?

Sequence directing proteins to ER

What is SRP?

Signal recognition particle guiding ribosome to ER

What is a lysosome?

Organelle with digestive enzymes

What pH do lysosomes maintain?

About pH 5 (acidic)

What is autophagy?

Recycling of damaged organelles

What is a vacuole?

A storage and digestion vesicle

What is the central vacuole?

Large plant vacuole maintaining turgor pressure

What are contractile vacuoles?

Remove excess water in protists

What is the function of mitochondria?

ATP production via cellular respiration

What is the outer mitochondrial membrane?

Smooth and permeable

What is the inner mitochondrial membrane?

Folded into cristae for ATP production

Where does the ETC occur?

Inner mitochondrial membrane

What is the mitochondrial matrix?

Contains enzymes, DNA, ribosomes

What is the intermembrane space?

Area for proton gradient

What is the function of chloroplasts?

Photosynthesis

What are thylakoids?

Membrane sacs containing chlorophyll

What are grana?

Stacks of thylakoids

What is the stroma?

Fluid where carbon fixation occurs

What is endosymbiosis?

Origin of organelles from engulfed bacteria

Which organelles came from endosymbiosis?

Mitochondria and chloroplasts

What evidence supports endosymbiosis?

Double membranes, circular DNA, ribosomes

What are peroxisomes?

Organelles that detoxify and break down fatty acids

What harmful molecule is produced in peroxisomes?

Hydrogen peroxide (H2O2)

What enzyme breaks down H2O2?

Catalase

What is the cytoskeleton?

Network of protein fibers in the cell

What are the three cytoskeleton components?

Microtubules, microfilaments, intermediate filaments

What are microtubules made of?

Tubulin dimers

What is the function of microtubules?

Support, transport, cell division, cilia/flagella

What are microtubules’ diameter?

~25 nm

What is the centrosome?

Microtubule organizing center

What are centrioles?

Structures with 9×3 microtubule arrangement

What motor proteins move on microtubules?

Kinesin and dynein

What direction does kinesin move?

Toward + end

What direction does dynein move?

Toward - end

What is the structure of cilia/flagella?

9+2 microtubule arrangement

What powers cilia/flagella movement?

Dynein and ATP

What are microfilaments made of?

Actin

What is the diameter of microfilaments?

~7 nm

What is the function of microfilaments?

Shape, movement, contraction

What motor protein works with actin?

Myosin

What is the role of actin in cell division?

Forms cleavage furrow

What are intermediate filaments?

Strong, stable fibers for support

What proteins are examples of intermediate filaments?

Keratin

What is the function of intermediate filaments?

Anchor organelles and resist tension

What is polymerization?

Addition of monomers to form filaments

What is depolymerization?

Removal of monomers from filaments

What is dynamic instability?

Rapid growth and shrinkage of microtubules

Why are eukaryotic cells larger than prokaryotes?

They have organelles for energy and organization

What is surface area-to-volume ratio (SA:V)?

Ratio affecting diffusion efficiency

How does size affect SA:V?

Larger size decreases SA:V

Why is low SA:V a problem?

Reduced nutrient/waste exchange efficiency

What is the solution to SA:V limitations?

Multicellularity

What are advantages of multicellularity?

Specialization, efficiency, protection

What structures help cells stick together?

Cell junctions and extracellular matrix

What is the difference between plant and animal cells?

Plants have cell wall, chloroplasts, vacuole

What do animal cells have that plants don’t?

Centrosomes and many lysosomes

What is the plasma membrane?

Boundary controlling cell environment

What is exocytosis?

Release of substances outside the cell

What is insulin?

Hormone regulating blood glucose

Where is insulin produced?

Pancreatic beta cells

How is insulin secreted?

Through ER → Golgi → vesicles → exocytosis

What is preproinsulin?

Initial polypeptide with signal peptide

What is proinsulin?

Processed form before final insulin

What is C-peptide?

Segment removed to form active insulin