Unit 3 - Cells and Cellular Transport

What functions do the organelles provide for the cell?

Some examples:

Explain how dehydration can disrupt osmoregulation in an organism.

With less water in the body, water tends to exit the cells into the hypertonic surroundings, and the body cells will shrivel and die. Water is necessary to be in an ideal amount to sustain an isotonic environment.

How does each of the components function in the membrane?

-Phospholipid bilayer: main structure, selectively permeable

Why are cells small?

As a cell's dimensions are increased, volume increased much more quickly than surface area. The surface is where reactions and transport takes place, and if the volume is too large relative to the surface area, the surface will not be able to keep up with and supply the cell. Thus cells tend be small to maximize the ratio of surface area to volume.

Describe the components of a cell membrane.

Components:

How are chloroplasts and mitochondria same and different?

Chloroplasts and mitochondria both contain tightly coiled membranes for reactions, and were likely once prokaryotes that assimilated with larger eukaryotic cells. Chloroplasts, however, provide for photosynthesis, while mitochondria provide for the reverse, respiration.

How do the processes of endocytosis and exocytosis move large molecules?

Both move large particles (or cells) using a portion of the plasma membrane and then splits off either out of (exocytosis) or into (endocytosis) the cell.

How are prokaryotic and eukaryotic cells similar and different?

Both types of cells have an outer membrane, ribosomes, cytosol, and a region of nuclear material. Prokaryotic cells, however, have no membrane-bound organelles. They contain only nucleoid region, as opposed to the nucleus in eukaryotes. Prokaryotic cells are much smaller than eukaryotic cells.

How can cells increase surface area without increasing volume dramatically

By constructing inner membranes, and then tightly coiling these membranes (as in the mitochondria, the ER, and the chloroplasts), cells can greatly increase the surface area for reactions with minimal increase in volume.

In general, how are cell walls different from ECM of animal cells? Consider all forms of life that have cell walls.

Cell walls are very rigid, and serve a protective purpose for the cells. The extracellular matrix (ECM) in animal cells is much more of a loose connection between cells, and serves a primarily communicative/coordination purpose.

Why are eukaryotic cells compartmentalized?

Compartmentalization allows a cell to perform many functions that may require specific/unusual conditions (such as pH) without interfering with other cell functions. An example is the lysosome, which is able to digest unwanted material without releasing its digestive enzymes into the rest of the cell.

What structures are components of cytoskeleton and what is their function?

Components:

Describe how the specialization of organs contributes to the functioning of an organism in terms of cellular transport (exchange of gases, circulation of fluids, digestion of food, excretion of wastes).

Ex: The separate kidneys allow a separate organ to regulate the excretion of wastes and maintenance of ideal concentrations in blood solutions, without interfering with the function of other organs.

Explain the differences of environmental tonicity to internal environments of cells.

If an exterior solution is:

How does the electrochemical gradient of a cell affect the movement of ions across a membrane?

If the direction of an electrochemical gradient of an ion is into the cell, there is a lower concentration of the ion within the cell, and the membrane more will flow into the cell through the membrane. If the direction is outward, more ions will leave the cell.

How is passive transport different from active transport?

Passive transport does not require energy input, while active transport does.

How are plant cells different from animal cells?

Plant cells are surrounded by a rigid cell wall. They typically have a large central vacuole for storage, and plasmodesmata that act as channels between cell walls. They also have chloroplasts, the organelle in which photosynthesis takes place (and gives green color).

What do they look like?

Prokaryotic cells are much smaller than eukaryotic cells. Prokaryotic cells may have a flagellum or pili on their sides, and are encased in a capsule. Eukaryotic cells are much larger and more complex, containing many sophisticated inner membranes/organelles.

Describe the structure of the cell membrane.

The cell membrane is composed primarily of a phospholipid bilayer. It is interspersed with many other molecules that assist in structure and transport.

What are the roles of the cytoskeleton?

The cytoskeleton plays a major role in providing support, motility, and regulation to the cell.

Describe what the endomembrane system is of a cell.

The endomembrane system is a system of many inner cell membranes that are related either by direct physical connection or transfer through vesicles. Its parts include the nuclear envelope, the endoplasmic reticulum, the Golgi apparatus, lysosomes, and vacuoles.

How do the components of the endomembrane system work together?

The endomembrane system's components work together through continuity and vesicles. An example is protein synthesis and transport. The nuclear envelope sends out ribosomes and mRNA, and proteins are synthesized in the rough ER. These proteins are then sent through vesicles to the Golgi apparatus. The Golgi then sends them through vesicles either to the plasma membrane or elsewhere in the cell.

Explain why the membrane is "selectively permeable."

The membrane is designed to only allow certain substances to pass through it. The phospholipid bilayer is a major factor in this, as are various transport proteins.

How do the nucleus and ribosomes work together?

The nucleolus within the nucleus synthesizes ribosome subunits, which are assembled into ribosomes outside the nucleus. The nucleus then supplies mRNA to the ribosomes to code for protein construction.

How do membranes show fluidity?

The phospholipid bilayer, as well as the various proteins and other molecules embedded in it, are not completely packed together, allowing the membranes layers to move laterally in the membrane plane, but keep the two layers together vertically.

How is water potential related to osmosis?

The water potential of a division in an osmotic situation determines the direction in which water will flow. If positive, water leaves this section. If negative, it gains water. Water potential is equal to the sum of solute (osmotic) potential (equal to -iCRT) and pressure potential (physical pressure on solution, if any)