Chapter 6

Name the three well-defined kingdoms within domain Eukarya.

1. Plantae 2. Animalia 3. Fungi

The large size of the typical eukaryotic genome appears to make it necessary to split the genome into pieces, each a separate linear DNA molecule, termed a(n) ....

Chromosome

True or false. There is a membrane separating the nucleolus from the rest of the nucleus.

False. There is no membrane separating the nucleolus from the rest of the nucleus.

Surrounding the nucleus and separating it from the cytoplasm is the..., Composed of two lipid bilayer membranes.

Nuclear envelope

Each eukaryotic chromosome also has special structures at both ends termed...

Telomeres

What does the nucleolus consist of?

The nucleolus consists of loops of DNA, RNA polymerases, rRNA, and the protein components of the ribosome.

Proteins synthesized on the rough ER will end up where?

1. Secreted into the extracellular environment. 2. As integral plasma membrane proteins. 3. In the membrane or interior of the ER, Golgi apparatus, or lysosomes.

How many different human chromosomes are there?

23

Molecules that are smaller than..., Including small proteins, can freely diffuse from the cytoplasm into the nucleus through the nuclear pores.

60 kilodaltons

The different system of transcription and translation possessed by the mitochondria includes what?

A unique genetic code and unique RNA polymerases, DNA replication machinery, ribosomes, and aminoacyl-tRNA synthetases.

What happens to ATP produced within the mitochondria?

ATP produced within mitochondria is transported out into the cytoplasm to drive a great variety of cellular processes.

Chromosomes have a... Near the middle to ensure that newly replicated chromosomes are sorted properly during cell division. How many copies to each daughter cell in meiosis and mitosis?

Centromere; One copy to each daughter cell in both mitosis and meiosis

The inner membrane of the mitochondria is folded into the matrix in projections called...

Cristae

Since humans and most adult animals are ...., They have two copies of each chromosome, except for which chromosomes?

Diploid; except for the sex chromosomes

Why is the rough ER called rough?

Due to the large number of ribosomes, bound to its surface.

Name the sites of protein synthesis in the eukaryotic cell.

Either on ribosomes free in the cytoplasm, or on ribosomes bound to the surface of the rough ER.

The... Is a large system of folded membrane accounting for over half of the membrane of some cells.

Endoplasmic reticulum (ER)

Some regions of a chromosome termed ...., Are more loosely packed (although still packaged into chromatin) and allow jeans to be activated.

Euchromatin

Describe the basic structure and shape of DNA in eukaryotes and prokaryotes.

Eukaryotic genome are organized into linear molecules of double-stranded DNA, while the genome of prokaryotes is a single circular DNA molecule.

True or false. Polar substances can freely diffuse across the inner membrane of the mitochondria.

False the inner membrane is impermeable to the free diffusion of polar substances, like protons.

True or false. RNA freely diffuses into the cytoplasm via nuclear pores..

False, it appears likely that RNA is transported out of the nucleus by a specific transport system, rather than freely diffusing into the cytoplasm.

True or false. Fungi, plants, and protists are covered on the MCAT.

False. Animal cells are covered on the MCAT. Fungi, plants, and protists are not covered.

True or false. Transcription of mRNA and tRNA occurs in the nucleolus.

False. It is the site of transcription of rRNA by RNA pol I. Transcription of mRNA and tRNA is performed by other polymerases in other areas of the nucleus.

True or false. The system of transcription and translation used by mitochondria is the same as that for nuclear genes.

False. Mitochondria use a different system of transcription and translation than nuclear genes do.

True or false. The ribosome is fully assembled while still in the nucleolus. Explain.

False. The ribosome is partially assembled while still in the nucleolus. The protein components of the ribosome are not produced in the nucleolus; they are transported into the nucleus from the cytoplasm (remember that all translation takes place in the cytoplasm). After partial assembly, the ribosome is exported from the nucleus, remaining inactive until assembly is completed in the cytoplasm. This may serve to prevent translation of hnRNA.

True or false. Within each chromosome lies the genome in its entirety.

False. Within each chromosome is a portion of the many thousands of genes in the genome as a whole.

Some regions of a chromosome are folded into densely, packed, chromatin, termed..., within which genes tend to be inaccessible and turned off.

Heterochromatin

The... Is the surface of the nuclear envelope, facing the nuclear interior, and the... Faces the cytoplasm.

Inner nuclear membrane; outer nuclear membrane

The space between the inner and outer mitochondrial membranes is called the ...

Intermembrane space

What is encoded by the genome of the mitochondria?

It encodes rRNA, tRNA, and several proteins, including some components of the electron transport chain and parts of the ATP synthase complex, although most mitochondrial proteins are encoded by nuclear genes.

Because many unique mitochondrial polypeptides are encoded by the cellular genome and not the mitochondrial genome what has been suggested?

It has been suggested that the genes coding for these proteins may have been transferred to the nuclear genome over time.

Jeans can be mapped genetically, and physically to the chromosome. They reside on into a specific location on that chromosome, a(n) ...

Locus

The term for the interior of the endoplasmic reticulum is the ....

Lumen

What type of inheritance do mitochondria exhibit? Explain what this means.

Maternal inheritance. This means that mitochondria are inherited only from the mother, since the cytoplasm of the egg becomes the cytoplasm of the zygote.

Maternal inheritance, depart from the rules of..., Which state that traits are inherited from both parents.

Mendelian genetics

How does the genome of the mitochondria compared to the cellular genome and what is its structure?

Mitochondria possess their own genome, which is far smaller than the cellular genome, and consist of a single circular DNA molecule.

Most organelles are bounded by what? What purpose does this structure serve?

Most organelles are bounded by their own lipid bilayer membrane. The membrane acts like a plastic bag to seal off the contents of the organelle from the rest of the cytoplasm and control what enters and exits.

Larger proteins cannot pass freely through nuclear pars and are excluded from the nuclear interior unless they contain a sequence of basic amino acids called a(n) ... Explain how this works.

Nuclear localization sequence; proteins with a nuclear localization sequence are translated on cytoplasmic ribosomes, and then imported into the nucleus by specific transport mechanisms.

If nuclei are treated with DNase and with detergent, and insoluble mesh of protein, known as the... Or..., Is left behind.

Nuclear matrix or nuclear scaffold

The nuclear envelope is punctuated with large... The allow the passage of material into and out of the nucleus.

Nuclear pores

The... Is a region within the nucleus, which functions as a ribosome factory.

Nucleolus

One of the primary features of eukaryotic cells distinguishing them from prokaryotic cells is the..., Which contains the genome, surrounded by the... That separates the contents of the nucleus into a distinct compartment, isolated from other organelles, and from the cytoplasm.

Nucleus; nuclear envelope

A(n) .... Is a small structure within a cell that carries out specific cellular functions.

Organelle

The rough ER is the site of proteins synthesis for what proteins?

Proteins targeted to enter the secretory pathway.

Name the one group of organisms in Domain Eukarya for whom the kingdom classifications are under debate.

Protists

What are the two types of endoplasmic reticulum?

Rough ER and Smooth ER

What is the expression of eukaryotic genes regulated by?

Specific promoter, and enhancer elements of that gene but also it can be affected by the position of the gene on the chromosome.

Describe the general DNA sequencing of telomeres and what the basic job of telomeres is. What element helps with this job?

Telomeres have large numbers of repeats of a specific DNA sequence, and, with the help of a special DNA polymerase termed telomerase, maintain the end of the linear chromosomes during DNA replication.

In order to explain the fact that mitochondria possess a second system of inheritance, investigators have postulated what? This is known as the... Theory of mitochondrial evolution.

That mitochondria originated as independent unicellular organisms living within larger cells. This is known as the endosymbiotic theory of mitochondrial evolution (endo = within; symbiotic = living together). In fact, if you compare a mitochondrion to a Gram - negative bacterium, you'll note that they look pretty similar. Pay attention to where the enzymes of electron transport are located and the genome shape. Remember that bacterial electron transport depends on a proton gradient across the cell membrane. In a gram - negative bacterium, this membrane would correspond to the mitochondrial inner membrane.

What part of the mitochondria is the location of the electron transport chain and ATP synthase?

The inner membrane

What is the site of the proton gradient used to drive ATP synthesis by ATP synthase?

The inner membrane of the mitochondria

The interior of the mitochondria is termed, the what?

The matrix

What part of the mitochondria contains pyruvate dehydrogenase and the enzymes of the Krebs cycle?

The matrix

The matrix of the mitochondria is bounded by what two structures?

The matrix is bounded by the inner and outer mitochondrial membranes.

The membrane of the endoplasmic reticulum is joined with what membrane in places? What does this mean?

The membrane of the Eos reticulum is joined with the outer nuclear membrane in places, meaning that the space within the nuclear membranes is continuous with the interior of the ER (the ER lumen).

Explain how the endoplasmic reticulum in the nuclear envelope relate to another with respect to structure.

The membrane of the endoplasmic reticulum is at points, continuous with the outer nuclear membrane of the nuclear envelope, making the interior of the ER (the lumen of the ER) contiguous with the space between the two nuclear membranes.

What is the site of oxidative phosphorylation in a eukaryotic cell?

The mitochondria

What part of the mitochondria is smooth and contains large pores that allow free passage of small molecules?

The outer membrane

What is the role of the nuclear matrix? How does this relate to the role of the cytoskeleton in the cytoplasm?

The role of the nuclear matrix is to support and provide overall structure. The matrix may also play a role in regulating gene expression. The DNA in chromosomes is attached to the matrix at specific sites, and these (in some cases) appear to be involved in regulating gene expression, or in limiting the effects of promoters and enhancers to discrete chromosomal regions, known as domains. The role of the nuclear matrix may be in part analogous to the role of the cytoskeleton in the cytoplasm.

The rough ER plays a key rule doing what?

The rough ER plays a key role directing protein traffic to different parts of the cell.

What is the function of the smooth ER?

The smooth ER is not actively involved in protein processing, but can contain enzymes involved in steroid hormone biosynthesis (gonads) or in the degradation of environmental toxins (liver).

Proteins translated on free cytoplasmic ribosomes are headed where?

They are headed toward peroxisomes, mitochondria, the nucleus, or will remain in the cytoplasm.

True or false. All true living organisms are either prokaryotes or eukaryotes..

True

True or false. Mitochondria possess their own genome.

True

True or false. The sperm contributes only genomic [nuclear] DNA.

True.

True or false. In prokaryotes, the genome lacks a nuclear envelope to form a separate compartment and thus remains accessible to the cytoplasm.

True. In prokaryotes, the genome may be localized in the cell, but without a nuclear envelope to form a separate compartment, the genome remains accessible to the cytoplasm.

Where do replication, transcription, and translation occur in prokaryotes?

cytoplasm. In prokaryotes, replication, transcription, translation, and everything else happens in the same compartment, the cytoplasm.

The nucleolus is the site of transcription of ... by ...

rRNA by RNA pol I