AP Biology Unit 2: Cellular Organelles and Membrane Transport

Flashcards reviewing key concepts, organelle structures, membrane transport mechanisms, and practice AP Biology exam questions from Unit 2.

What are the primary functions of the cell nucleus?

It stores genetic information (DNA), synthesizes RNA, and assembles ribosome subunits.

What structural feature surrounds the nucleus?

A double membrane known as the nuclear envelope, which contains pores.

What is the structure and main function of the rough endoplasmic reticulum (rough ER)?

It consists of a membrane studded with ribosomes attached to the nuclear envelope, and serves as the site of membrane-bound and secreted protein synthesis, cell compartmentalization, mechanical support, and intracellular transport.

What are the key functions of the smooth endoplasmic reticulum (smooth ER)?

Detoxification, calcium storage, and lipid synthesis.

What is the structure and main function of the Golgi complex?

It is composed of flattened sacs called cisternae, and functions in the folding, chemical modification, and packaging of synthesized proteins.

What are ribosomes composed of and what is their primary function?

They are composed of rRNA and protein (consisting of large and small subunits) and function in protein synthesis.

What are the primary metabolic functions of the mitochondria and where do they occur?

Oxidative phosphorylation occurs on the cristae or inner membrane, and the Krebs Cycle occurs in the matrix.

What are the key structures of a chloroplast and where do the reactions of photosynthesis occur?

Chloroplasts have a double outer membrane containing thylakoids stacked into grana (site of Light Reactions) and fluid stroma (site of Calvin-Benson Cycle).

What is the structure and function of lysosomes?

They are membrane-enclosed sacs containing hydrolytic enzymes used for intracellular digestion, recycling cell organic materials, and programmed cell death (apoptosis).

What are the functions of central, contractile, and food vacuoles?

Central vacuoles store water to maintain turgor pressure; contractile vacuoles perform osmoregulation in protists; and food vacuoles form during phagocytosis to fuse with lysosomes.

How does cell size affect the surface area-to-volume ratio and efficiency of material exchange?

Smaller cells typically have a higher surface area-to-volume ratio, allowing for more efficient exchange of materials with the environment.

Which components make up the structure of the plasma membrane?

Phospholipids, membrane proteins, glycolipids, glycoproteins, and cholesterol.

What are the characteristics of simple diffusion across a membrane?

It is a passive transport process requiring no energy that moves small, nonpolar molecules (such as $\text{CO}_2$, $\text{O}_2$, $\text{N}_2$, and steroids) down their concentration gradient without transport proteins.

How does facilitated diffusion function across the plasma membrane?

It is a passive process requiring no energy that moves small molecules or ions (such as water, $\text{Na}^+$, $\text{K}^+$, and $\text{Ca}^{2+}$) down their concentration gradient using channel or carrier transport proteins.

What defines active transport across a cell membrane?

It requires energy input to move molecules or ions (such as $\text{Na}^+$, $\text{K}^+$, $\text{Ca}^{2+}$, and $\text{H}^+$) against their concentration gradient using carrier transport proteins.

What are the three forms of endocytosis shown in cellular transport?

Phagocytosis (cellular eating), pinocytosis (cellular drinking), and receptor-mediated endocytosis.

What sequence of organelles is involved in exocytosis of synthesized proteins?

Rough ER (synthesis) \rightarrow Golgi complex (packaging and modification) \rightarrow Plasma Membrane (export).

What defines a hypertonic solution and how does water move relative to it?

A hypertonic solution has a high solute concentration and low free water concentration, causing it to gain water from a hypotonic solution.

What defines a hypotonic solution and how does water move relative to it?

A hypotonic solution has a low solute concentration and high free water concentration, causing it to lose water to a hypertonic solution.

What happens to water movement when a cell is placed in an isotonic solution?

The solution has equal solute and free water concentration relative to the cell, resulting in equal movement of water into and out of the cell.

In paramecia, why does the rate of contractile vacuole contraction decrease as environmental osmolarity increases?

As osmolarity increases, the osmotic gradient decreases so less water enters the paramecia by osmosis, requiring a lower rate of contraction to remove excess water.

Where are the ribosomes that synthesize the membrane-bound CFTR protein located?

On the (Rough) Endoplasmic Reticulum / ER.

Where is a mutant CFTR protein located if it has an amino acid substitution in its ATP-binding site?

In the cellular/plasma membrane.

In Mexican morning glory petal cells, what cellular component causes the vacuole pH to increase during flower opening and how?

The $\text{K}^+/\text{H}^+$ transport protein moves $\text{H}^+$ ions out of the vacuole.

Why does the activation of the $\text{K}^+/\text{H}^+$ transport protein cause the vacuole of morning glory petal cells to swell?

It transports $\text{K}^+$ into the vacuole, increasing the solute concentration (lowering water potential) inside the vacuole so that water enters by osmosis.