The Cell

Question 1

All cells share what features?

Answer 1

1. They are all bounded by a selective barrier, called the plasma membrane.
2. Inside all cells is a semifluid, jellylike substance called cytosol, in which subcellular components are suspended.
3. All cells con- tain chromosomes, which carry genes in the form of DNA.
4. And all cells have ribosomes, tiny complexes that make pro- teins according to instructions from the genes.

Question 2

What is the major difference between prokaryotic and eukaryotic cells?

Answer 2

The location of their DNA.

1. eukaryotic cell: most of the DNA is in an organelle called the nucleus, which is bounded by a double membrane
2. prokaryotic cell:the DNA is concentrated in a region that is n_ot membrane-enclosed_, called the nucleoid

Question 3

What is cytoplasm?

Answer 3

The interior of either type of cell:

1. in eukaryotic cells: this term refers only to the region be- tween the nucleus and the plasma membrane. Within the cytoplasm of a eukaryotic cell, suspended in cytosol, are a variety of organelles of specialized form and function.
2. These membrane-bounded structures are absent in prokaryotic cells

Question 4

What does the plasma membrane function
as?

Answer 4

A selective barrier that allows passage of enough oxygen, nutrients, and wastes to service the entire cell.

Question 5

What are Eukaryote cells?

Answer 5

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Question 6

The nucleus contains?

Answer 6

Most of the genes in the eukaryotic cell. (Some genes are located in mitochondria and chloroplasts.)

It is generally the most conspicuous organelle,averaging about 5 μm in diameter.

Question 7

What is the nuclear envelope?

Answer 7

Encloses the nucleus , separating its contents from the cytoplasm.

The nuclear envelope is a double membrane.

• The two membranes, each a lipid bilayer with associated proteins, are separated by a space of 20–40 nm.

The envelope is perforated by pore structures that are about 100 nm in diameter.

Question 8

What does the intricate protein structure called a pore complex do? ( in nuclear envelope)

Answer 8

Lines each pore and plays an important role in the cell by regulating the entry and exit of proteins and RNAs, as well as large complexes of macromolecules.

Question 9

nuclear lamina

Answer 9

a netlike array of protein filaments that maintains the shape of the nucleus by mechanically supporting the nuclear envelope.

Question 10

How is DNA organised?

Answer 10

discrete units called chromosomes, structures that carry the genetic info

Question 11

chromatin

Answer 11

The complex of DNA and proteins making up chromosomes

Question 12

nucleolus

Answer 12

• prominent structure within the nondividing nucleus
• appears through the electron microscope as a mass of densely stained granules and fibers adjoining part of the chromatin.

Question 13

What happens in the nucleolus?

Answer 13

1. RNA called ribosomal RNA (rRNA) is synthesized from instructions in the DNA.
2. proteins imported from the cytoplasm are assembled with rRNA into large and small subunits of ribosomes.
   
   • These subunits then exit the nucleus through the nuclear pores to the cytoplasm, where a large and a small subunit can assemble into a ribosome.

Question 14

Ribosomes

Answer 14

ARE Complexes made of ribosomal RNA and protein, whcih are the cellular components that carry out protein synthesis

(Note that ribosomes are not membrane bounded and thus are not considered organ- elles.)

Question 15

endomembrane system

Answer 15

1. includes the nuclear envelope, the endoplasmic reticulum, the Golgi ap- paratus, lysosomes, various kinds of vesicles and vacuoles, and the plasma membrane.
2. system carries out a variety of tasks in the cell; synthesis of proteins, transport of proteins into membranes and organelles or out of the cell, m_etabolism and movemen_t of lipids, and detoxifica- tion of poisons.

Question 16

endoplasmic reticulum (ER)

Answer 16

1. Extensive network of membranes
2. Consists of a network of membranous tubules and sacs called cisternae
3. Separates the internal compartment of the ER, called the ER lumen (cavity) or cisternal space, from the cytosol.
4. Smooth ER is so named because its outer surface lacks ribosomes. Rough ER is studded with ribosomes ..

Question 17

glycoproteins

Answer 17

Most secretory proteins are glycoproteins, proteins with carbohydrates covalently bonded to them.

Formed as:

As a polypeptide chain grows from a bound ribosome, the chain is threaded into the ER lumen through a pore formed by a protein complex in the
ER membrane.

The new polypeptide folds into its functional shape as it enters the ER lumen.

The carbohydrates are attached to the proteins in the ER lumen by enzymes built into the ER membrane.

Question 18

Golgi apparatus

Answer 18

consists of flattened membranous sacs—cisternae

Question 20

what is the endosymbiont theory?

Answer 20

Theory that proposes the MITOCHONDRION could have originated from an oxygen using bacterium which lived as a parasite in a eukaryotic cell

ANCESTOR CELL: ER , nuclear envelope and nucleus

NON PHOTOSYNTHETIC EUKARYOTE: mitochondrion enters

Question 21

How does the primitive eukaryotic cell engulf the prokaryotes?

Answer 21

Thropugh a process Endosymbiosis by extending pseudopdia ( temporary protusion of amoeboid cell for feeding and movement.)

Question 22

What are the similarities between the mitochondrion and the bacterium?