AP Biology - Unit 2: Cell Structure and Function All Topics

What are the basic structural and functional units of every organism?

Cells

What are the four common features of all cells?

1. Bound by a plasma membrane 2. Contain cytosol 3. Contain chromosomes 4. Contain ribosomes

What are the two main types of cells?

Prokaryotes and Eukaryotes

In which domains are prokaryotic cells found?

Bacteria and Archaea

Where is DNA located in prokaryotic cells?

In the nucleoid region

What distinguishes eukaryotic cells from prokaryotic cells?

Eukaryotic cells have DNA in the nucleus and membrane-bound organelles.

What is the function of organelles in eukaryotic cells?

They are membrane-bound structures that perform specific functions.

What is the endomembrane system?

A system of organelles and subcellular components that interact to modify, package, and transport materials in the cell.

Name two energy organelles in eukaryotic cells.

Mitochondria and Chloroplasts

What is compartmentalization in eukaryotic cells?

The presence of membrane-bound organelles that allow different metabolic processes to occur in separate locations.

What are unique cell components found in plant cells?

Chloroplasts, central vacuole, cell wall, and plasmodesmata.

What are unique cell components found in animal cells?

Lysosomes and centrosomes.

What surrounds the nucleus in eukaryotic cells?

The nuclear envelope, which is a double membrane with pores.

What is the function of the nucleolus?

It is the dense region of the nucleus where ribosomal RNA (rRNA) is synthesized.

What is the process by which DNA is transcribed into mRNA?

Transcription

What is the role of ribosomes in the cell?

They synthesize proteins.

Where can ribosomes be found in the cell?

In the cytosol (free ribosomes) or bound to the endoplasmic reticulum (bound ribosomes).

What is the function of the rough endoplasmic reticulum?

It compartmentalizes protein synthesis and contains ribosomes.

What is the function of the smooth endoplasmic reticulum?

It is involved in lipid synthesis and detoxification processes.

What is the primary function of vesicles in the cell?

To transport materials within the cell.

What is the process called that converts DNA to protein?

The central dogma: DNA → RNA → Protein.

What is the role of transport vesicles?

They carry proteins produced in the rough ER to their destinations.

What is the significance of ribosomal RNA (rRNA)?

It combines with proteins to form ribosomal subunits, essential for protein synthesis.

What is the primary function of the Smooth Endoplasmic Reticulum (Smooth ER)?

Synthesizes lipids and detoxifies the cell.

What type of membranes does the Golgi Complex contain?

Flattened membranous sacs called cisternae.

What is the role of the cis face of the Golgi Complex?

Receives vesicles from the Endoplasmic Reticulum (ER).

What does the trans face of the Golgi Complex do?

Sends vesicles back out into the cytosol or to the plasma membrane for secretion.

List the main functions of the Golgi Complex.

Receives, modifies, sorts materials, adds molecular tags, and packages materials into new transport vesicles.

What are lysosomes and their primary function?

Membranous sacs with hydrolytic enzymes that digest macromolecules.

What is autophagy in the context of lysosomes?

The process by which lysosomes recycle organic materials and organelles that are not functioning properly.

What role do lysosomes play in apoptosis?

They release enzymes into the cytoplasm to break down cellular components.

What are peroxisomes and their main function?

Membrane-bound compartments that catalyze reactions producing hydrogen peroxide (H2O2) and detoxify compounds.

What enzyme in peroxisomes breaks down hydrogen peroxide?

Catalase.

What are vacuoles and how do they differ in animal and plant cells?

Vesicles that store cellular materials; animal cells have small vacuoles, while plant cells have a large central vacuole.

What is the function of the central vacuole in plant cells?

Stores nutrients and water, important for turgor pressure.

What is the primary site of cellular respiration?

Mitochondria.

Describe the structure of mitochondria.

They have a smooth outer membrane and a highly convoluted inner membrane with folds called cristae.

What is located in the mitochondrial matrix?

Enzymes for the Krebs cycle, mitochondrial DNA, and ribosomes.

What is the role of chloroplasts in plant cells?

They are the site of photosynthesis and contain chlorophyll.

What are thylakoids in chloroplasts?

Membranous sacs where light-dependent reactions occur, organized into stacks called grana.

What is the stroma in chloroplasts?

The fluid around thylakoids where the Calvin cycle occurs.

What does the Endosymbiont Theory propose?

Mitochondria and chloroplasts evolved from free-living prokaryotic cells via endosymbiosis.

List the evidence supporting the Endosymbiont Theory.

Double membrane, ribosomes, circular DNA, and the ability to function independently.

What is the cytoskeleton?

A network of fibers throughout the cytoplasm providing structural and mechanical support.

What are the three types of fibers in the cytoskeleton?

Microtubules, microfilaments, and intermediate filaments.

What is the function of microtubules?

Provide structural support, assist in chromosome movement during cell division, and facilitate cell motility.

What are microfilaments made of and their primary functions?

Thin solid rods made of actin; they maintain cell shape, assist in muscle contraction, and aid in cell division.

What are intermediate filaments and their functions?

Fibrous proteins that maintain cell shape, anchor the nucleus and organelles, and form the nuclear lamina.

Why is cell size important for cellular metabolism?

Cellular metabolism depends on cell size, as waste must leave and nutrients must enter efficiently.

What happens when a cell exceeds a certain size?

It becomes difficult for the cell to regulate what comes in and out of the plasma membrane.

What is the ideal surface area-to-volume ratio for cells?

Cells need a high surface area-to-volume ratio to optimize the exchange of materials through the plasma membrane.

What is the formula for the total surface area of a cuboidal cell?

Total SA = height x width x number of sides x number of boxes (or SA = 6S² if only 1 box).

What is the formula for the volume of a cuboidal cell?

Total V = height x width x length x number of boxes (or V = S³ if only one box).

What is the formula for the surface area of a spherical cell?

SA = 4πr².

What is the formula for the volume of a spherical cell?

V = 4/3πr³.

How do you calculate the surface area-to-volume ratio for cells?

SA:V ratio = SA/V.

In the example of a cuboidal cell with dimensions 1x1x27, what is the SA:V ratio?

SA = 162 units², V = 27 units³, so SA:V = 6.

In the example of a cuboidal cell with dimensions 3x3x1, what is the SA:V ratio?

SA = 54 units², V = 27 units³, so SA:V = 2.

Which cuboidal cell has the best exchange of material through the plasma membrane?

The cell with the higher SA:V ratio (Option 1).

How does the radius of a spherical cell affect the SA:V ratio?

As the radius increases, the SA:V ratio decreases.

For a spherical cell with radius 5, what is the SA:V ratio?

SA = 314 units², V = 523.3 units³, so SA:V ≈ 0.6.

For a spherical cell with radius 8, what is the SA:V ratio?

SA = 803.8 units², V = 2143.6 units³, so SA:V ≈ 0.37.

Which spherical cell has the best exchange of material through the plasma membrane?

The cell with the higher SA:V ratio (Option 1).

What is the general trend regarding cell size and efficiency in exchanging materials?

Smaller cells have a high SA:V ratio, optimizing material exchange, while larger cells have a lower SA:V ratio, losing efficiency.

What happens to the cellular demand for resources as cell size increases?

The cellular demand for resources increases, while the rate of heat exchange decreases.

What is the primary component of the plasma membrane?

Phospholipids

What are the two main regions of phospholipids?

Hydrophilic heads and hydrophobic tails

What is the orientation of hydrophilic heads in the plasma membrane?

They are oriented toward aqueous environments.

What is the orientation of hydrophobic tails in the plasma membrane?

They face inwards, away from aqueous environments.

What model describes the structure of cell membranes?

Fluid Mosaic Model

What does 'fluid' refer to in the Fluid Mosaic Model?

The membrane is held together by weak hydrophobic interactions and can move and shift.

How do unsaturated hydrocarbon tails affect membrane fluidity?

They prevent tight packing of phospholipids, maintaining fluidity at low temperatures.

What role does cholesterol play in membrane fluidity?

It helps maintain fluidity at high and low temperatures.

What are the two major categories of proteins in the plasma membrane?

Integral proteins and peripheral proteins.

What are integral proteins?

Proteins embedded into the lipid bilayer.

What distinguishes peripheral proteins from integral proteins?

Peripheral proteins are not embedded in the lipid bilayer and are loosely bonded to the surface.

What is the function of membrane carbohydrates?

They are important for cell-to-cell recognition.

What are glycolipids?

Carbohydrates bonded to lipids.

What are glycoproteins?

Carbohydrates bonded to proteins; they are the most abundant.

What is selective permeability?

The ability of membranes to regulate the substances that enter and exit.

What types of molecules can easily pass through the plasma membrane?

Small nonpolar, hydrophobic molecules like hydrocarbons, CO2, O2, and N2.

What types of molecules have difficult passage through the plasma membrane?

Hydrophilic polar molecules, large molecules, and ions.

What is the function of cell walls in certain organisms?

They provide structural boundary, permeability barrier, and protection from osmotic lysis.

What is the composition of plant cell walls?

Cellulose.

What are plasmodesmata?

Hole-like structures in the cell wall filled with cytosol that connect adjacent cells.

What is the significance of membrane lipid composition for the Channichthyidae fish?

It helps maintain membrane fluidity in extremely low temperatures.

How does temperature affect membrane fluidity?

Temperature changes can alter the movement and packing of phospholipids.

What is the role of hydrophilic regions in integral proteins?

They make up the interior of channels or pores and are exposed to the cytosol.

What is the role of hydrophobic regions in integral proteins?

They interact with fatty acids on the interior of the membrane.

What is selective permeability?

The regulation of what enters and exits the cell due to the hydrophobic interior of the membrane.

What are the two main types of transport across a membrane?

Passive transport and active transport.

What is passive transport?

Transport of a molecule that does not require energy because it moves with its concentration or electrochemical gradient.

What are the three examples of passive transport?

Diffusion, osmosis, and facilitated diffusion.

Define diffusion.

A spontaneous process where substances move from a high to low concentration, down the concentration gradient.

What is osmosis?

The diffusion of water down its concentration gradient across a selectively permeable membrane.

What is facilitated diffusion?

The diffusion of molecules through the membrane via channel or carrier proteins without requiring energy.

What are channel proteins?

Proteins that form an open pore in the membrane to move charged ions, which can open or close in response to stimuli.

What are aquaporins?

Specialized channel proteins for the transport of water.

What are carrier proteins?

Proteins that alternate between two conformations to transport large polar molecules like glucose and amino acids.

What is active transport?

Transport of a molecule that requires energy because it moves a solute against its concentration gradient.