Chapter 6-AP Biology

Microtubules are hollow rods made of a globular protein called tubulin. Each tubulin protein is a dimer made of two subunits. These are easily assembled and disassembled. What are four functions of microtubules?

1. Maintenance of cell shape 2. Cell motility 3. Chromosome movement in cell division 4. Organelle movement

What are the three roles of the cytoskeleton?

1. Maintenance of cell shape 2. Mechanical support 3. Cell motility (movement) both of the cell as a whole and more limited movement of parts of the cell

What are three functions of the cell wall?

1. Protects the plant cell 2. Maintains its shape 3. Prevents excessive uptake of water

List and describe three major functions of the smooth ER

1. Synthesis of lipids: Enzymes of the smooth ER are important in the synthesis of lipids, including oils, phospholipids, and steroids. 2. Detoxification of drugs and poisons: Detoxification usually involves adding hydroxyl groups to drug molecules, making them more soluble and easier to flush from the body. 3. Storage of calcium ions: In muscle cells, the smooth ER membrane pumps calcium ions from the cytosol into the ER lumen.

What is a lysosome? What do they contain? What is the pH range inside a lysosome?

A lysosome is a membranous sac of hydrolytic enzymes that an animal cell uses to digest (hydrolyze) macromolecules. The pH range inside a lysosome is acidic.

One function of lysosomes is intracellular digestion of particles engulfed by phagocytosis. Describe this process of digestion. What human cells carry out phagocytosis?

Amoebas and many other protists eat by engulfing smaller organisms or food particles, a process called phagocytosis. The food vacuole formed in this way then fuses with a lysosome, whose enzymes digest the food. Digestion products, including simple sugars, amino acids, and other monomers, pass into the cytosol and become nutrients for the cell. Some of the human cells that carry out phagocytosis are macrophages, a type of white blood cell that helps defend the body by engulfing and destroying bacteria and other invaders.

Animal cells have a centrosome that contains a pair of centrioles. Plant cells do not have centrioles. What is another name for centrosomes? What is believed to be the role of centrioles?

Another name for centrosome is "microtubule-organizing center." The centrioles function as compression-resisting girders of the cytoskeleton.

Where are bound ribosomes and what do they produce?

Attached to the outside of the ER or nuclear envelope. Membrane proteins.

Which two domains consist of prokaryotic cells?

Bacteria and Archaea

Why are cells so small?

Cells are small because a high surface-to-volume ratio facilitates the exchange of materials between a cell and its environment. As a cell (or any other object) increases in size, its volume grows proportionally more than its surface area. (Area is proportional to a linear dimension cubed.) Thus, a smaller object has a greater ratio of surface area to volume.

What is the function of the chloroplasts?

Chloroplasts are sites of photosynthesis. These organelles convert solar energy to chemical energy by absorbing sunlight and using it to drive synthesis of organic compounds such as sugars from carbon dioxide and water.

Found within the nucleus are the chromosomes. They are made of chromatin. What are the two components of chromatin? When do the thin chromatin fibers condense to become distinct chromosomes?

Chromatin is composed of proteins and DNA. Chromatin fibers condense to become distinct chromosomes as a cell prepares to divide.

A second function of lysosomes is to recycle cellular components in a process called autophagy. Describe this process.

During autophagy, a damaged organelle or small amount of cytosol becomes surrounded by a double membrane, and a lysosome fuses with the outer membrane of this vesicle. The lysosomal enzymes dismantle the enclosed material, and the organic monomers are returned to the cytosol for reuse. With the help of the lysosomes, the cell community renews itself. A human liver cell, for example, recycles half of its macromolecules each week.

A major difference between prokaryotic and eukaryotic cells is the location of their DNA. Describe this difference.

In a eukaryotic cell, most of the DNA is in an organelle called the nucleus, which is bounded by a double membrane. In a prokaryotic cell, the DNA is concentrated in a region that is not membrane enclosed, called a nucleoid.

What is the composition of the cell wall?

Microfibrils made of the polysaccharide cellulose are synthesized by an enzyme called cellulose synthase and secreted to the extracellular space, where they become embedded in a matrix of other polysaccharides and proteins.

There are three main types of fibers that make up the cytoskeleton. Name them.

Microtubules, Microfilaments, Intermediate Filaments

What is the function of the mitochondria?

Mitochondria are the sites of cellular respiration, the metabolic process that uses oxygen to generate ATP by extracting energy from sugars, fats, and other fuels.

List all the structures of the endomembrane system.

Nuclear envelope Endoplasmic reticulum Golgi apparatus Lysosomes Vesicles Vacuoles Plasma membrane

Use this figure to explain how the elements of the endomembrane system function together to secrete a protein and to digest a cellular component.

Nuclear envelope is connected to rough ER, which is also continuous with smooth ER. Membranes and proteins produced by the ER flow in the form of transport vesicles to the Golgi apparatus. Golgi apparatus pinches off transport vesicles and other vesicles that give rise to lysosomes, other types of specialized vesicles, and vacuoles. Lysosome is available for fusion with another vesicle for digestion. Transport vesicle carries proteins to plasma membrane for secretion. Plasma membrane expands by fusion of vesicles; proteins are secreted from cell.

Explain the important role played by peroxisomes.

Peroxisomes contain enzymes that remove hydrogen atoms from various substrates and transfer them to oxygen, thus producing hydrogen peroxide as a by-product.

What is the function of ribosomes? What are their two components?

Ribosomes are the cellular components that carry out protein synthesis. Their two components are a large subunit and a small subunit.

Explain the difference between smooth and rough ER

Smooth ER is so named because its outer surface lacks ribosomes. Rough ER is studded with ribosomes on the outer surface of the membrane and thus appears rough through the electron microscope.

Where is a free ribosome and what does it produce?

Suspended in the cytosol. Proteins that function within the cytosol.

Explain the lumen

The ER lumen is the cavity, or cisternal space. Because the ER membrane is continuous within the nuclear envelope, the space between the two membranes of the envelope is continuous with the lumen of the ER.

Besides packaging secretory proteins into transport vesicles, what is another major function of the rough ER?

The rough ER grows membrane proteins and phospholipids for the cell by adding them to its own membrane. The ER membrane expands, and portions of it are transferred in the form of transport vesicles to other components of the endomembrane system.

Explain transport vesicles

Transport vesicles bud off from a region of the rough ER called transitional ER and travel to the Golgi apparatus and other destinations.

What is the functions of organelles in a prokaryotic cell?

cell wall: rigid structure outside the plasma membrane plasma membrane: membrane enclosing the cytoplasm bacterial chromosome: carries genes in the form of DNA nucleoid: region where the cell's DNA is located (not enclosed by a membrane) cytoplasm: interior of cell flagella: locomotion organelles of some bacteria