Unit 1 (Chapter 4, Part 4) Nucleus and Endomembrane System

Question 1

Where can you find genetic material other than within the nucleus?

Answer 1

Mitochondria and chloroplasts.

Question 2

What is a network of membranes that includes the nuclear envelope, the endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, peroxisomes, and plasma membrane?

Answer 2

Endomembrane System (Endo means inside)

Question 3

What is a double-membrane structure that encloses the cell’s nucleus?

Answer 3

Nuclear envelope

Question 4

What is a passageway for the movement of molecules and macromolecules into and out of the nucleus; formed where the inner and outer nuclear membranes make contact with each other?

Answer 4

Nuclear pores

Question 5

What is a discrete unit of genetic material composed of DNA and associated proteins?

Answer 5

Chromosomes. Eukaryotes have chromosomes in their cell nuclei and in plastids and mitochondria.

Question 6

What is the complex of DNA and proteins that makes up eukaryotic chromosomes?

Answer 6

Chromatin

Question 7

What is the nuclear matrix?

Answer 7

A filamentous network of proteins that is found inside the nucleus and lines the inner nuclear membrane. The nuclear matrix serves to organize the chromosomes.

Question 8

What is the chromosome territories?

Answer 8

A distinct area where each chromosome is located within the cell nucleus of eukaryotic cells; chromosome territories do not overlap.

Question 9

What happens to chromosome territories during cell division?

Answer 9

During cell division, the chromosomes condense and form more compact structures.

Question 10

Another important function of the nucleus is the assembly of ribosome subunits–Why?

Answer 10

These structures are involved in producing polypeptides during the process of translation.

Question 11

What is the droplet organelle in the nucleus of nondividing cells where ribosome assembly occurs?

Answer 11

Nucleolus (plural; nucleoli)

Question 12

How are ribosomes composed? (5) steps GOOD LUCK!

Answer 12

Two sub units.

These sub units contain one or more RNA molecules and several types of proteins.

The RNA molecules are made in the vicinity of the nucleus.

The proteins used in ribosomes are produced in the cytosol and then imported into the nucleus via the nuclear pores.

These proteins and RNA molecules then enter the nucleolus and are assembled into ribosomal subunits.

Finally, the subunits exit the nucleolus and move through the nuclear pores into the cytosol, where they carry out polypeptide synthesis.

Question 13

[ER Start] What is a convoluted network of membranes in a cell’s cytoplasm that forms flattened, fluid-filled tubules, or cisternae?

Answer 13

Endoplasmic reticulum (ER) (Greek for in the cytoplasm) and reticulum (Latin, for little net) refer to location and shape of this organelle under a microscope.

Question 14

What is the internal space or hollow cavity of an organelle or an organ, such as the endoplasmic reticulum, the stomach, or a blood vessel?

Answer 14

Lumen

Question 15

What is the single compartment enclosed by the ER membrane?

Answer 15

ER Lumen

Question 16

What are the two types of distinct, continuous, ER?

Answer 16

Rough and smooth.

Question 17

What is the part of the ER whose outer surface is studded with ribosomes; this region plays a key role in the initial synthesis and sorting of proteins that are destined for the ER, Golgi apparatus, lysosomes, vacuoles, plasma membrane, or outside of the cell?

Answer 17

Rough ER

Question 18

What does the endomembrane system move around?

Answer 18

Proteins packaged into membrane vesicles (small spheres enclosed by a membrane. (protein sorting)

Question 19

What are the two other important functions of the rough ER?

Answer 19

1. Insertion of certain newly made proteins into the ER membrane.
2. Attachment of carbohydrates to proteins and lipids. A process called glycosylation which produces a glycoprotein or glycolipid.

Question 20

What is the part of the ER whose outer surface is not studded with ribosomes. This region is continuous with the rough ER and functions in diverse metabolic processes such as detoxification, carbohydrate metabolism, accumulation of calcium ions (Ca2+), and synthesis and modification of lipids?

Answer 20

Smooth endoplasmic reticulum (smooth ER)

Question 21

In liver cells, what is the smooth ER’s role and how does it affect those who are alcoholics?

Answer 21

The smooth ER detoxifies many potential harmful organic molecules, including barbiturate drugs and ethanol.

The enzymes in the smooth ER convert hydrophobic toxic molecules to more hydrophilic molecules, which are easily excreted by the body.

Ex. Chronic alcohol consumption leads to greater amount of smooth ER in liver cells, which increases the rate of alcohol breakdown. This explains why people who consume alcohol regularly must ingest more alcohol to experience its effects.

Question 22

Explain glucose breakdown with the liver.

Answer 22

Glycogen, a polymer of glucose, granules sit close to smooth ER membrane.

When energy is needed, enzymes are activated to break down glycogen to glucose-6-phosphate.

The enzyme, glucose-6-phosphase, in the smooth ER removes the phosphate group and the glucose is exported out of the liver into the bloodstream.

Question 23

Why is it important for the smooth ER to accumulate calcium ions (Ca2+)?

Answer 23

When the Ca2+ (calcium ions) are pumped into the ER lumen, it is regularly released into the cytosol and is involved in vital cellular processes, including muscle contraction in animals.

Question 24

Where is the primary site for phospholipid synthesis, which is the main component of eukaryotic cell membranes?

Answer 24

The smooth ER. And the enzymes in the smooth ER edit lipids like cholesterol to produce hormones such as estrogen and testosterone.

Question 25

What is a stack of flattened, membrane-bound compartments that performs three overlapping functions: secretion, processing, and protein sorting?

Answer 25

The golgi apparatus (AKA golgi body, golgi complex, or simply golgi)

Question 26

What are the three compartments of Golgi? (3)

Answer 26

The cis Golgi (closest to the ER membrane)

The trans Golgi (closest to the plasma membrane)

The medial Golgi (found in the middle)

Question 27

What are two main processes that the Golgi apparatus performs?

Answer 27

1. Edits certain proteins and lipids like in glycosylation which began in the ER. Vesicles, containing protein or lipid, is transported from the ER to the cis Golgi.
2. Runs the processing event called Proteolysis where enzymes called proteases cut proteins into smaller polypeptides.

Question 28

Where does most of the glycosylation happen in the Golgi?

Answer 28

The medial Golgi

Question 29

What is an example of proteolysis within the Golgi complex? (Hint: diabetics)

Answer 29

The hormone insulin is first made as a large precursor molecule termed proinsulin.

In the Golgi complex, this is packaged with proteases into vesicles. The enzyme cuts the long polypeptide to create a smaller insulin polypeptide that is a functional hormone in which then it is secreted.

Question 30

What is a membrane vesicle carrying different types of materials that fuses with the cell’s plasma membrane to release the contents extracellularly?

Answer 30

This is cargo and is called secretory vesicles and thereby releasing their contents outside the cell.

Question 31

What do you call the route when proteins or carbohydrates are synthesized into the ER, travel to the Golgi, and then transported by vesicles to the plasma membrane where the vesicles then fuse with the plasma membrane, and the contents are secreted outside the cell?

Answer 31

Secretory pathway. A pathway for the movement of larger substances, such as carbohydrates and proteins, from the ER to the outside of the cell.

Question 32

When the Golgi vesicles travel to other parts of the cell, what are they called?

Answer 32

Lysosomes.

Question 33

Explain the procedure of a pulse-chase experiment. What is the pulse, and what is the chase? What was the purpose of this approach?

Answer 33

In a pulse-chase experiment, radioactive material is provided to cells in a single administration. This is referred to as the pulse. After a few minutes, a large amount of nonradioactive material is provided to the cells to “chase away” the ability to use the radioactive material. The researchers were attempting to determine the movement of proteins through the different compartments of a cell. Radioactive amino acids were used to label the proteins and enable the researchers to visualize where the proteins were at different times.

Question 34

Why were pancreatic cells used for the movement of cells (pulse-chase experiment) investigation?

Answer 34

Pancreatic cells produce large numbers of proteins that they then secrete. Thus, these cells provide researchers with an ideal system for studying protein movement through a cell.

Using electron microscopy, the researchers found that the proteins, labeled with radioactivity, were first found in the ER of the cells. Later the radioalabeled proteins moved to the Golgi and then into vesicles near the plasma membrane. The researchers concluded that proteins move through several cellular compartments before they are secreted from a cell. Also, the movement of proteins through these compartments is not random but follows a particular pathway: ER, Golgi, secretory vesicles, plasma membrane, and, finally, extracellular environment.

Question 35

What is a small organelle found in animal cells that contains enzymes that degrade molecules and macromolecules?

Answer 35

Lysosome (formed in the ER and arrive from the Golgi)

Question 36

What is a hydrolytic enzyme found in lysosomes that functions at acidic pH and uses a molecule of water to break a covalent bond?

Answer 36

Acid hydrolase (Remember: Hydrolysis)

Question 37

Since lysosomes are capable of breaking down various complex materials to include carbohydrates, proteins, and lipids, what do we call this process when lysosomes digest these materials within its cell?

Answer 37

Endocytosis.

Question 38

What is autophagy?

Answer 38

This is the process of lysosomes when they break down intracellular molecules and molecules to recycle their building blocks to make new molecules.

Question 39

What allows the lysosome to have the enzymes it does?

Answer 39

The pH level of a lysosome is 4.8 (acidic) versus the pH of the entire cell at approximately 7.2.

Question 40

[End Lysosome] What are specialized compartments found in eukaryotic cells that function in storage, the regulation of cell volume, and degradation?

Answer 40

Vacuoles (plant, fungal, and certain protists)

This is latin for empty space.

Question 41

What do you call vacuoles that temporarily store materials or transport substances?

Answer 41

Storage vacuoles

Question 42

What is a central vacuole?

Answer 42

An organelle that often occupies 80% or more of the volume of a plant cell and stores a large amount of water, enzymes, and inorganic ions.

Question 43

What is important for plant structure and is accomplished by central vacuole’s exerting pressure on the cell wall preventing it to wilt? This happens when the plant becomes dehydrated.

Answer 43

Turgor Pressure.

This pressure and expansion of the cell is what is necessary for growth.

Question 44

Where might you find a contractile vacuole?

Answer 44

This small, membrane-enclosed, water filled compartment eliminates excess liquid from the cells of certain protists.

Question 45

How do contractile vacuoles work?

Answer 45

They expand as water enters the cell they reside. When reaching a certain size, they fuse with the plasma membrane expelling the contents of their interior to the exterior of the cell.

Question 46

What do you call the function of vacuoles when they contain hydrolytic enzymes that break down macromolecules in food like in food vacuoles?

Answer 46

Phagocytosis

Question 47

What is the name of a cell found in an animal’s immune system that engulfs bacterial cells into phagocytic vacuoles, and then fuse with fuse with lysosomes to destroy the contents?

Answer 47

Macrophages

Question 48

What is a relatively small organelle that is found in all eukaryotic cells and that catalyzes detoxifying reactions?

Answer 48

Peroxisomes.

There are typically hundreds of them within a cell.

Question 49

What type of bi-product does peroxisomes create when oxidizing (removal of electrons) toxic molecules?

Answer 49

Hydrogen peroxide (H2O2)

RH2 (toxin) + O2 —-> R + H2O2

Question 50

What metal within healthy living cells breaks down hydrogen peroxide into a hydroxide ion (OH-) and a hydroxide free radical (dot OH)?

Answer 50

Iron (Fe 2+)

Fe2+) + (H2O2) —-> (Fe3+) + OH- + (dot OH

Question 51

Why is the breakdown of hydrogen peroxide dangerous?

Answer 51

Because the hydroxide free radical can damage proteins, lipids, and DNA. This radical is highly reactive and it is benficial for cells to break it down differently.

Question 52

What enzyme does Peroxisomes use to break down hydrogen peroxide to make water and oxygen gas (hence the name peroxisome)?

Answer 52

Catalase

2 H2O2 ——> (reaction with Catalase) 2 H2O + O2

Question 53

What is a specialized organelle within plant seeds that contains enzymes needed to convert fats to sugars?

Answer 53

Glyoxysome. Seeds typically store fats which makes them smaller and less heavy because of this.

When a seed germinates, the enzymes become active to create energy for the seedling to grow.

Question 54

What is the most important function of cellular metabolism of the plasma membrane? Cell adhesion, membrane transport or cell signaling.

Answer 54

Of these three functions, membrane transport is probably the most important to metabolism because it determines which molecules can enter the cell and participate in metabolism and which products of metabolism are exported from the cell.

Question 55

What is membrane transport?

Answer 55

The movement of ions or molecules across a biological membrane.

Question 56

What is cell signaling?

Answer 56

A vital function of the plasma membrane in which cells sense changes in their environment and communicate with each other.

Ex. When insulin is released into the blood, this signal (or hormone) is received by receptors on cells which tell it to take up energy in the form of glucose.

Question 57

What is cell adhesion?

Answer 57

A vital function of the cell membrane that allows cells to bind to each other. Cell adhesion is critical in the formation of multicellular organisms and provides a way to convey positional information between neighboring cells.