Chapter 6 Homework

What is the Golgi Apparatus?

stacks of membranous sacs whose functions include packaging, storing and modifying proteins produced in rough ER

What are vacuoles?

different types of sacs with different functions

What is a nuclear envelope?

double membrane the is reinforced with intermediate filaments that surrounds the nucleus; pores allow movement of substances in/out of the nucleus

What is a lysosome?

membranous vesicles (sacs) that such as food digestion in Amoeba, recycle cell components contain hydrolytic enzymes for intraceldigest such as old worn out organelles , and programmed cell destruction for metamorphosis and development

What are the major differences between prokaryotic and eukaryotic cells? Be sure to include size

Prokaryotic cells have no true nucleus, lack nuclear envelope, and their genetic material floats freely in the nucleoid region. One of the distinguishing characteristics of prokaryotes is the lack of internal organization with no membrane bound organelles, so that the prokaryotic cytoplasm is bounded by the plasma membrane. The prokaryotic cell is generally less than 10 microns, and includes bacteria from Domain Bacteria and Domain Archaea. // Eukaryotic cells have a true nucleus surrounded by a nuclear envelope and containing genetic material inside. These cells contain numerous organelles, including membrane bound organelles, and results in the cytoplasm identified as the area between the plasma membrane and the nucleus. They are usually significantly larger than prokaryotic cells, ranging from about 10 to 100 microns, and includes members of Domain Eukarya (protists, fungi, plants, and animals.

Describe the structure and function of a eukaryotic ribosome.

The ribosome is composed of rRNA & proteins. It is composed of two subunits, a large subunit which received the tRNA, & a small subunit, which holds mRNA. Free ribosomes are suspended in the cytosol, and produce proteins that will function within cell. Bound ribosomes are attached to the rough ER and wil synthesize proteins that either become part of a membrane, or are exported to other cells

What is a plasma membrane?

boundary for the cell that is composed of phospholipid bilayer with embedded proteins (as as cholesterol): also regulates selective permeability

What is the ER?

series of membranous tubules and canals (cisternae) with the rough ER having ribosomes attached and the smooth ER absent of ribosomes. The rough ER functions in protein synthesis, while the smooth ER carries out lipid synthesis, detoxification, calcium ion storage, carbohydrate metabolism

Name several types of vacuoles and explain how their functions differ

Central vacuoles in plants store water, have pigments, have toxins, absorb water & function in cell elongation: contractile vacuole pump excess water from cell and food vacuole involved digestion

How can impaired lysosomal functions cause disease?

If a lysosome lacks any one of active hydrolytic enzymes normally present, the organelle becomes engorged with indigestible substrates which can then interfere with function. For example, Tay Sachs disease is caused by a missing lipid digesting enzyme, and the accumulating lipids cause interference in nervous system activity, eventually resulting in the death of the afflicted child

Explain the characteristics of the mitochondria and chloroplasts that place them in a separate category from organelle in the endomembrane system

Membranes in both mitochondria and chloroplasts, like most membranes, are dynamic structures always changing. However, unlike other membrane bound organelles with a single phospholipid bilayer mitochondria and chloroplast membranes have a double membrane with smooth outer membrane and convoluted inner membrane (foldings are called cristae). In the mitochondria, the inner compartment (matrix) and inner membrane contain specific enzymes for the metabolic steps of cellular respiration, and the cristae gives the inner mitochondrial membrane a large surface area that enhances the productivity of cellular respiration. In the chloroplasts, the double membrane separates a narrow intermembrane space, and then inside the chloroplast is another membranous system arranged into flattened sacs called thylakoids. The thylakoids can be stacked into grana with fluid outside thylakoids called the stroma in which the synthesis of glucose during the process of photosynthesis occurs. In addition, both mitochondria and chloroplasts are considered to be semiautonomous. Unlike all other organelles, they have their own DNA and ribosomes, and thus are capable of reproducing independently. In fact, they closely resemble prokaryotes, with a circular DNA molecules attached to their inner membrane. It is widely accepted that these organelles originated as an endosymbiont (cell living within another cell) of early ancestral cells

Explain the role of peroxisomes in eukaryotic cells.

Peroxisomes contain special sets of enzymes for specific metabolic pathways. They transfer hydrogen from various substrates to oxygen producing hydrogen peroxide, are can be used to detoxify alcohol, or break down fatty acids for fuel in cellular respiration. Glyoxysomes are a special type of peroxisome that initiates the conversion of fatty acids into sugar in seeds so the emerging seedling has a source of energy

Describe the structure and functions of the nucleus. Be sure to include an explanation of how the nucleus controls proteins synthesis in the cytoplasm.

The nucleus is a spherical organelle enclosed by a nuclear envelope which is composed of a double membrane (lipid bilayer with proteins). The nuclear shape is stabilized by a network of protein filaments, and the membrane is perforated by pores to allow movement of molecules in and out of the nucleus. Within the nucleus are the chromatin and nucleoli. The primary function of the nucleus is to store and transmit genetic instructions for cell . This function is carried out by the chromatin , which condense into chromosomes during the cell division process. The nucleolus is the site of ribosome subunit synthesis. The nuclear pores serve as conduits for materials to move into and out of the nucleus as needed. The chromatin, with its genetic instructions (DNA) always remains within the nucleus. However, the DNA will be transcribed into mRNA, which in turn leaves through the nuclear pores, into the cytoplasm to direct protein synthesis.

Explain why compartmentalization is important in eukaryotic cells

The size of a cell is limited by the surface area to volume ratio, since as a cell grows, its surface area increases by n2, but its volume increases by a factor of n'. This means that the exchange of materials with the environment through the surface area is not increasing as quickly as the internal volume whose needs must be met. Compartmentalization compensates for a limited plasma membrane size by having internal membranes that increase the available surface area of the membrane for exchange to take place. In addition, the compartmentalization also sets up localized conditions so that specific chemical reactions are sequestered, allowing them to occur without interference from incompatible metabolic processes elsewhere