AP Biology Unit 2: Cell Structure, SA:V, and Compartmentalization

What is the normal function of ribosomes?

Translate mRNA into polypeptides. Synthesis of proteins

What happens if ribosomes are disrupted?

Protein production decreases or becomes faulty, especially affecting secreted and membrane proteins.

What is the role of the rough endoplasmic reticulum (rough ER)?

Supports synthesis, folding, and initial processing of many secreted and membrane proteins.

What are the consequences of disrupted rough ER function?

Proteins may fold/process incorrectly or fail to enter the normal transport pathway.

What is the primary function of the smooth endoplasmic reticulum (smooth ER)?

Lipid synthesis, detoxification, and calcium storage in specialized cells.

What can occur if the smooth ER is disrupted?

Lipid production, detoxification, or calcium regulation may be impaired.

What does the Golgi apparatus do?

Packages, modifies, sorts proteins and lipids for transport and storage.

What happens if the Golgi apparatus is not functioning properly?

Proteins may be produced but modified, sorted, packaged, or delivered incorrectly.

What is the main function of mitochondria?

Site for cellular respiration; the matrix hosts the citric acid cycle.

What are the effects of mitochondrial dysfunction?

Reduced ATP production and impaired energy metabolism.

What is the role of lysosomes?

Digest macromolecules, aid in apoptosis, and help with the immune system.

What occurs if lysosomes are disrupted?

Digestion/recycling decreases, waste may accumulate, and apoptosis may be impaired.

What is the function of vacuoles in plant cells?

Storage and maintenance of turgor pressure.

What happens if vacuoles are not functioning properly?

Loss of turgor pressure can lead to wilting.

What is the primary function of chloroplasts?

Conducts photosynthesis, converting sunlight and water into oxygen and glucose.

What are the effects of damage to chloroplasts?

Impaired light reactions and carbon fixation.

What does the nucleus do?

Stores most eukaryotic DNA and regulates gene expression.

What can happen if the nucleus is damaged?

Disruption of gene expression and movement of RNA and proteins.

What is the function of the nucleolus?

Where rRNA is made and ribosomal subunits are assembled.

What are the consequences of nucleolus disruption?

Reduced ribosome production, affecting protein synthesis.

What is the role of the cytoplasm?

Gives the cell shape, holds organelles, and is the site for metabolic reactions.

What can occur if the cytosol is disrupted?

Impaired cell shape, movement, and organelle positioning.

What is the function of the cytoskeleton?

Supports cell shape, movement, and intracellular transport.

What happens if the cytoskeleton is disrupted?

Impaired cell shape, movement, and chromosome separation during division.

What is the role of centrioles/centrosome?

Organizes microtubules and supports formation of cilia and flagella.

What can occur if centrioles are damaged?

Cells may lose structural support and chromosome separation may be less reliable.

What is the function of the cell wall?

Provides support and prevents excessive expansion in plants and fungi.

What happens if the cell wall is compromised?

Mechanical attachment and cell-to-cell communication may weaken.

What are cell junctions?

Connections between neighboring cells, including tight junctions and desmosomes.

What is the function of peroxisomes?

Breakdown fatty acids and detoxify harmful substances.

What can happen if peroxisomes are not functioning?

Impaired fatty-acid processing and accumulation of harmful substances.

What is the role of the cell membrane?

Regulates movement of substances in and out of the cell.

What occurs if the cell membrane is disrupted?

Cargo may not reach the correct destination, affecting secretion and transport.

What are transport/secretory vesicles?

Membrane-bound sacs that carry cargo between organelles.

What structures produce or form vesicles?

Rough and smooth ER, Golgi apparatus, and plasma membrane.

What is the role of vesicles in the secretory pathway?

Vesicles are membrane-bound carriers that transport proteins from the ER to their destination.

What happens when protein is made but not secreted?

Translation may be working, but issues may arise in rough ER processing, vesicle transport, Golgi sorting/packaging, or vesicle fusion with the plasma membrane.

What causes old organelles to accumulate in a cell?

Impaired lysosomal digestion/recycling can lead to the accumulation of old organelles.

What occurs in a plant cell when it loses water?

The central vacuole loses volume, turgor pressure falls, and the cell becomes less rigid.

What is the effect of damaged cristae on ATP production?

Damage reduces the inner-membrane area available for electron transport and ATP synthase, decreasing oxidative phosphorylation.

What are some important components of a cell that are not membrane-bound organelles?

Cytoplasm, cell wall, cytoskeleton, and cell junctions.

What is the function of plasmodesmata in plant cells?

Plasmodesmata connect adjacent plant cells and facilitate communication and transport.

Where does the citric acid (Krebs) cycle occur?

In the mitochondrial matrix.

What damage can affect the respiratory electron transport chain?

Damage to the inner mitochondrial membrane can weaken the proton gradient and reduce ATP synthesis.

What is the location of light-dependent photosynthesis reactions?

In the thylakoid membrane.

What is the role of the chloroplast stroma?

It is where the Calvin-Benson cycle occurs, and damage to its enzymes reduces CO₂ fixation.

What is apoptosis?

Programmed cell death, which involves regulated pathways and may include lysosomal breakdown.

How does the rough ER contribute to protein synthesis?

It supports protein synthesis and initial processing before proteins are sent to the Golgi.

Why is a Golgi defect significant for protein secretion?

It can prevent modification, sorting, packaging, and delivery of proteins, even if ribosomes are functioning normally.

Why is a lysosome's membrane important?

It maintains an acidic environment for digestive enzymes and separates those conditions from the cytosol.

Why does ATP synthase depend on a membrane?

It relies on a proton gradient across a membrane; if the gradient dissipates, less energy is available to make ATP.

Do all cells have every organelle?

No, cell structures vary with cell type and function; for example, animal cells do not have chloroplasts.

What is the significance of surface area-to-volume ratio (SA:V) in cells?

As cells grow, volume increases faster than surface area, leading to a lower SA:V which can limit nutrient uptake and waste removal.

How do microvilli and root hairs assist cells?

They increase surface area for exchange without a corresponding increase in volume.

What is compartmentalization in cells?

It separates processes into specialized spaces using membranes, allowing for different conditions and simultaneous reactions.

What happens if the inner mitochondrial membrane leaks H⁺?

The proton gradient dissipates, reducing the driving force for ATP synthase and decreasing oxidative phosphorylation.

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

SA:V = surface area ÷ volume.

What is the effect of increasing the side length of a cube on its SA:V?

Doubling the side length multiplies surface area by 4 but volume by 8, halving the SA:V.

How can experimental design test the effect of cell size on diffusion?

By comparing penetration depth or fraction reached in cubes of the same material but different sizes.

What should be considered if actual data contradicts expected trends?

Report the data, consider measurement error, and do not force the expected result onto the evidence.

What happens to ATP production in light-dependent reactions if the thylakoid membrane cannot maintain a proton gradient?

ATP production decreases.

What effect does a loss of acidic interior in lysosomes have on digestion?

Hydrolytic enzymes work less effectively, reducing digestion and recycling.

What may be impaired if Golgi stacks are disrupted?

Protein/lipid modification, sorting, packaging, or delivery may be impaired.

Why is compartmentalization important for larger eukaryotic cells?

It organizes processes into specialized environments, improving efficiency.

What is a key function of a cell membrane beyond being a boundary?

It selectively controls movement and maintains different conditions on its two sides.

What are the main features of prokaryotic cells?

Plasma membrane, cytoplasm, DNA, ribosomes.

What distinguishes eukaryotic cells from prokaryotic cells?

Eukaryotic cells have a membrane-bound nucleus and typical membrane-bound organelles.

What is the membrane infolding hypothesis?

It proposes that infolding of the ancestral plasma membrane led to the nucleus and endomembrane system.

What does the endosymbiotic theory suggest?

Mitochondria and chloroplasts descended from prokaryotes engulfed by an ancestral host cell.

What evidence supports the endosymbiotic theory?

Own DNA, bacterial-like ribosomes, division resembling binary fission, and double membranes.

Why is a single piece of evidence not absolute proof for the endosymbiotic theory?

A single feature may have multiple explanations; multiple observations strengthen the theory.

Which organelle is considered to have originated first, mitochondria or chloroplasts?

Mitochondria are generally considered to have originated before chloroplasts.

Do mitochondria and chloroplasts function independently now?

No, they depend on the host cell for many proteins and functions.

What happens to a protein made in a cell with a Golgi defect?

The protein may still be synthesized, but modification, sorting, packaging, or delivery is disrupted.

What is the effect of fewer cristae in mitochondria?

Less inner-membrane area is available for electron transport and ATP synthase, potentially lowering oxidative phosphorylation.

What process is first affected if thylakoid membranes are damaged?

Light-dependent reactions are first affected.

What does a cell with DNA, ribosomes, cytoplasm, and a membrane but no nucleus classify as?

Prokaryotic cell.

Why might ATP production slow if a cell cannot maintain a proton gradient?

The gradient stores potential energy; if it dissipates, ATP synthase has less driving force.

What happens to a plant cell that loses water?

The central vacuole volume and turgor pressure fall, making the cell limp.

How does having multiple independent features support the endosymbiotic theory?

It strengthens the explanation by converging on prokaryotic ancestry.

What is the relationship between surface area and volume as cell size increases?

Surface area increases at a lower rate than volume, causing SA:V to decrease.

What is a fair test to study cell size and diffusion?

Change size; measure penetration depth/fraction reached while keeping other variables constant.

What is the role of compartments in cells?

They maintain specialized conditions and proton gradients, allowing for organized reactions.

What is the significance of the SA:V ratio in cells?

A higher SA:V ratio improves resource uptake and waste removal per unit of cell contents.