Set 3 - Tour of the Cell - Bio 180

Eukaryotic cells (do/do not) have a nucleus and other membrane-bound organelles, and (do/do not) contain DNA.

Prokaryotic cells (do/do not) have a nucleus and other membrane-bound organelles, and (do/do not) contain DNA.

Eukaryotic cells DO have a nucleus and other membrane-bound organelles, and DO contain DNA.

Prokaryotic cells DO NOT have a nucleus and other membrane-bound organelles, and DO contain DNA. (ALL living cells contain DNA!)

Which of the following (if any) do not have a cell membrane surrounding their cells?

Plant cells, Animal cells, Bacterial cells

Which of the following (if any) do not have a cell wall surrounding their cells?

Plant cells, Animal cells, Bacterial cells

All have a cell membrane!

Of the three types, only animal cells do not have a cell wall!

Animal cells vs. Plant cells - which have the following?

~ lysosomes

~ central vacuole

~ chloroplasts

~ centrosome

~ cell wall

~ mitochondria

~ cell membrane

Lysosomes - only animal cells

Central vacuole - only plant cells

Chloroplasts - only plant cells

Centrosome - only animal cells

Cell wall - only plant cells

Mitochondria - BOTH animal and plant cells

Cell membrane - BOTH animal and plant cells

Which 3 organelles are surrounded by a double membrane (a double lipid bilayer) in a plant cell?

Nucleus, Mitochondrion and Chloroplast

The outer membrane of the nucleus is continuous with which organelle?

Rough Endoplasmic Reticulum (Rough ER)

Which organelles (there are actually two of them) have ribosomes attached to its membrane? What are these ribosomes doing?

Rough ER and the nucleus (the outer membrane of the nucleus, as it is continuous with the rough ER).

They are making proteins

Where is the nucleolus in a cell and what does it look like? What is being assembled in the nucleolus?

The nucleolus is a dark staining region within the nucleus. Ribosome subunits are being assembled in the nucleolus (the large and small subunit are assembled separately).

Where is a ribosome fully assembled? (i.e., large and small subunit attached together) When does this occur?

While the large and small subunits are assembled in the nucleolus, they are not fully assembled (both subunits together) until they reach the cytoplasm, and then not until they actually begin translation of a protein from mRNA.

Which organelle in a eukaryotic cell contains pores? What is allowed to travel through these pores? (is it highly regulated or not?)

The nucleus contains pores. Anything small enough to fit through the pore will travel passively down its concentration gradient, so it's not regulated by specific solute... just size.

Which of the following substances would freely enter the nucleus from the cytoplasm, if there was a sufficient concentration gradient driving the substance inward?

~ a 35 kilodalton protein

~ an amino acid

~ a Na+ ion

~ a gold particle of 200 kilodaltons

~ a trisaccharide consisting of all glucose

All of the substances listed except the 200 kilodalton gold particle would freely move into the nucleus through a nuclear pore.

Anything that is small enough to fit across the nuclear pores will equilibrate between the cytoplasm and nucleoplasm. The size constraints have changed over the years with more research (the pore does seem to allow larger molecules cross, but much more slowly), but anything less than 55-60 kilodaltons can definitely and quickly move across the nuclear membrane through the pores.

Proteins that are larger than the pore complex diffusion limits that DO enter the nucleus (like DNA polymerase), have what characteristic?

Describe its properties.

They have a Nuclear Localization Signal (or NLS) that is recognized by the pore complex, facilitating the movement of these proteins into the nucleus.

The NLS is one or two short (6-10 amino acids) that are rich in the positively charged amino acids, Arginine and Lysine.

DNA with bound proteins is called ____________________.

chromatin

What is one of the important functions that these bound proteins to DNA do after the DNA is replicated, and when the cell is initiating cell division?

The bound proteins help the DNA highly condense into structures called chromosomes.

What is the difference between chromatin and a chromosome?

They consist of the same material, DNA and bound proteins, but in chromatin, the DNA is loosely arranged (uncoiled and stringy), and a chromosome is highly condensed DNA (and proteins) that is visible under the microscope.

As the cell is getting ready to divide, the DNA must replicate. Once it does, we have two identical molecules of DNA held together at their ___________. The two identical molecules of DNA are referred to as ___________ ___________.

centromere; sister chromatids

If we look at human chromosomes, we have 23 pairs. Chromosomes 1-22 are known as our ____________.

autosomes

In humans, chromosome #23 is known as the _______ chromosome.

sex

Normally, if you are XX, you are ________, and if you are XY, you are _______.

female; male

In humans, who determines the sex of the offspring, the male parent or the female parent? Why?

Females can only contribute one of their X chromosomes to the offspring, whereas males can contribute either their X or their Y chromosome to the offspring (and it's random). Therefore, males determine the sex of the offspring; if they contribute their X chromosome, the offspring will be female (XX), and if they contribute their Y chromosome, the offspring will be male (XY).

What is a karyotype?

A karyotype is a visual representation of an individual's complete set of chromosomes that have been stained to show specific banding patterns. It's essentially a picture of all the chromosomes in a cell, arranged in pairs in order by size.

Which chromosome is the largest chromosome?

Chromosome 1 is the largest.

The autosomes are labeled by size, with chromosome 1 being the largest, and chromosome 22 being the smallest.

The X and Y chromosome are not included in the size labeling, and are collectively labeled as chromosome 23. The X is a relatively large chromosome and the Y is the smallest of all chromosomes.

Besides size and shape, what other two characteristics can be used to distinguish chromosomes (chromosome 1 vs. 2 vs. 3, etc.) in a karyotype?

The chromosomes are stained with dyes and they each present a specific banding pattern.

The centromere position can differ from one type of chromosome to the next (most centromeres are localized towards the center of a chromosome, but there are some that are towards the ends).

What is an allele?

An allele is a specific version of a gene. For example, there are different alleles for hair color, based on the actual pigment protein that is expressed in hair. In this case, there are multiple alleles for the gene coding for the hair color pigment (e.g., brown, black, red, blonde, etc.)

The number of full sets of chromosomes a cell contains is the ___________. (full set = 1-23)

ploidy #

In humans, the ploidy number can only be ____ or ____, depending on the type of cell you are looking at.

1 or 2

Your body cells are also known as your ______________ cells, and your reproductive cells are also known as your ______________ cells (they are also called gametes)

somatic; germ

If a cell has two copies of all of its chromosomes, it is considered a _____________ cell.

diploid

If a cell has only one copy of all of its chromosomes, it is considered a _____________ cell.

haploid

Our somatic cells are considered (haploid/diploid), whereas our germ cells are considered (haploid/diploid).

Our somatic cells are considered DIPLOID, whereas our germ cells are considered HAPLOID.

The number of different types of chromosomes a cell contains is defined with the letter "_______".

n

What is the "n" number for somatic (body) cells in humans? What is the "n" number for germ (reproductive) cells?

The "n" number for somatic cells is 23, and the "n" number for germ cells is also 23.

If a cell has a ploidy number of 2, and its total number of chromosomes is 56 , what is "n"?

28

If species has a body cell that has an "n" number of 32, what is the "n" number of the germ cells in this species?

The "n" number is the same in all types of cells, given a particular species. Therefore, if the "n" number of a body cell in this species is 32, then the "n" number in the germ cells of this species is also 32.

If the total number of chromosomes in the cells of a particular species is 88, and the "n" number is 22, what is the ploidy number in these cells?

The ploidy number would be 4 (the cells would be tetraploid - this is impossible in humans but can happen in plants!)

Describe the anatomy of a mitochondrion.

Mitochondria have an outer membrane (boring), and an inner membrane that is highly folded (where the action occurs).

The inner membrane contains very important ATP-synthesizing proteins.

There is a liquid between these two membranes called the intermembrane space.

The liquid enclosed by the inner membrane (center of the organelle) is called the matrix.

The inner membrane of the mitochondrion is highly folded, and those folds are called ____________. Why is the inner membrane of the mitochondria highly folded?

cristae

To provide as much surface area as possible. More surface area means more ATP-synthesizing proteins can be embedded, which means you can make more ATP.

Mitochondria can only make ATP when there is __________ present.

oxygen

ATP can be produced without oxygen, but it occurs without the use of mitochondria, and a cell cannot produce nearly as much ATP without oxygen as it can with oxygen (using mitochondria). Bottom line: mitochondria REQUIRE oxygen!

How many different types of chromosomes do we have in the nucleus of one of our body cells? _____ How many copies of each type of chromosome do we have in the nucleus of one of our body cells? _____

How many different types of chromosomes do we have in the mitochondria of one of our body cells? _____ How many copies of each type of chromosome do we have in the mitochondria of one of our body cells? _____

We have 23 different types of chromosomes in the nucleus of one of our body cells, and 2 copies of each type of chromosome (one was from your Mom, and one from your Dad), for a total of 46 molecules of DNA.

We have a SINGLE type of mitochondrial chromosome, but we have hundreds of copies of this SAME mitochondrial DNA in each mitochondria.

If you look at a typical human cell, how many nuclei does it contain? ______ How many mitochondria does it contain? _______

A typical human cell contains a single nucleus! But a typical human cell will contain many mitochondria (sometimes hundreds)!

Our nuclear DNA is arranged in (linear/circular) chromosomes, and our mitochondrial DNA is arranged as a (linear/circular) chromosome.

Nuclear DNA is arranged in LINEAR chromosomes (46 in body cells), and our mitochondrial DNA is arranged in a single CIRCULAR chromosome. (copied hundreds of times in each mitochondria)

Who did you get your mitochondrial DNA from?

Mitochondrial DNA is exclusively inherited from your MOM. It is maternally inherited.

What are the main differences between nuclear and mitochondrial DNA with regards to inheritance and how much variety there is between one sibling and another (same mother and father).

Nuclear DNA is inherited as a unique mixture of DNA from both parents, whereas mitochondrial DNA is inherited straight from your mother.

Two siblings with the same mother and father will inherit different mixtures of nuclear DNA from their parents (although some will be the same - roughly 50% identical), whereas two siblings will inherit the same mitochondrial DNA from their mother, which she inherited straight from her mother.

No two individuals are the same with regards to nuclear DNA (except identical twins), but all siblings from the same mother have the same mitochondrial DNA.

Which of the following would be expected to have different mitochondrial DNA? (put an ** next to those with different mitochondrial DNA)

a) Mother and son

b) Mother and son's daughter

c) Brother and sister (same mother, same father)

d) Brother and sister (same mother, different fathers)

e) Father's sister and his daughter

f) Mother's maternal uncle and her son

g) Mother's brother and her son

h) Mother's son and her sister's son

a) Mother and son

b) Mother and son's daughter **

c) Brother and sister (same mother, same father)

d) Brother and sister (same mother, different fathers)

e) Father's sister and his daughter **

f) Mother's maternal uncle and her son

g) Mother's brother and her son

h) Mother's son and her sister's son

All of the others will have the SAME mitochondrial DNA!

If you are at a crime scene and there is fresh blood at the scene, would you want to analyze the nuclear or mitochondrial DNA in the sample in an attempt to match it to a suspect? Why?

In this situation, you can use nuclear DNA.

Since the blood is fresh, it has likely not degraded, and it will be easy to find some intact nuclear DNA to amplify, even though there is less nuclear DNA than mitochondrial DNA overall. Nuclear DNA, if you can obtain it intact, is the "gold standard", because it is highly specific to a single individual. It is a unique mixture of BOTH the individual's parents.

Mitochondrial DNA, on the other hand, is the same in all members of a suspect's maternal family (siblings, mother, maternal grandmother, etc), so you cannot say conclusively that the blood at the crime scene is the suspect's. So while you'll be able to get a lot of it, it is not nearly as specific as nuclear DNA

If you are at a crime scene and there is a single hair shaft at the scene, without a root, would you want to analyze the nuclear or mitochondrial DNA in the sample in an attempt to match it to a suspect? Why?

In this situation, you would have to use mitochondrial DNA.

Hair without a root (the shaft) is completely dead material, and most or all of the DNA (nuclear and mitochondrial) is likely degraded. Therefore, it will probably not be possible to amplify nuclear DNA, because there is so little of it left intact (if any).

However, because there is so much mitochondrial DNA, the likelihood of finding at least some intact DNA will be higher. The problem with this is that the mitochondrial DNA will not be specific to a single person because it is the same in all members of an individual's maternal family (siblings, mother, maternal grandmother, etc), Therefore, you cannot say conclusively that the blood at the crime scene is the suspect's.

Provide a definition of endosymbiosis.

Endosymbiosis is a relationship between two organisms, where one of the organisms lives inside the other.

Examples of this include the bacteria found in the extra stomach of cows (allowing cows to break down cellulose) and the bacteria found in our colon (they benefit us in many ways, like making important nutrients and training our immune system).

The endosymbiotic theory states that mitochondria found in the cells of eukaryotes were originally ____________. These organisms presumably entered an early ___________ cell and remained there, eventually evolving into the mitochondria we have in our cells today.bacteria (or prokaryotes).

bacteria that entered an early eukaryotic cell and stayed there.

The bacteria was aerobic, and the original eukaryotic cell was not able to respire aerobically until it engulfed the bacteria.

When an oxygen-utilizing bacteria entered an early eukaryotic cell, why didn't it get kicked out? What benefit did it provide to the early eukaryotic cell?

The bacteria was "allowed" to stay in the early eukaryotic cell because it provided a huge benefit. Originally, the eukaryotic cell could only obtain limited amounts of ATP through fermentation, even with oxygen present, because it didn't have the enzymes and proteins to perform aerobic respiration. But the bacteria had the enzymes and proteins to utilized oxygen and make lots of ATP, so when it entered, it helped the eukaryotic cell make lots of ATP in the presence of oxygen! Thus, the eukaryotic cell could now undergo aerobic respiration!

When an oxygen-utilizing bacteria entered an early eukaryotic cell, why did it "want" to stay and not leave?

When the bacteria entered the eukaryotic cell, it no longer had to worry about looking for food (the eukaryotic cell takes up glucose and the bacteria can use it), and also it is now living in a cozy, warm, protected home. :-)

The theory explaining how an aerobic bacteria entered and lived in an early eukaryotic cell to eventually become a mitochondrion is an example of symbiosis. What type of symbiosis does this describe? ___________ (mutualism, commensalism, or parasitism)

mutualism

This is because both the eukaryotic cell benefits (can make a lot of more ATP in the presence of oxygen than it could without the bacteria), and the bacteria benefits (no food hunting, nice warm, cozy home).

The first photosynthesizing eukaryotes (algae) evolved the ability to make their own food through photosynthesis because they presumably engulfed a photosynthesizing bacteria. What type of bacteria was this? ______________

Cyanobacteria, which presumably evolved into the chloroplasts we see in algae, plants and other photosynthesizing eukaryotes today.

What are the two organelles that likely evolved via endosymbiosis, with an early eukaryotic cell engulfing a prokaryotic (bacterial) cell?

mitochondria and chloroplasts

Why do we call the mitochondria in our cells organelles, rather than living cells (bacteria)?

Over millions of years, the bacteria within the eukaryotic cells streamlined their DNA (so they could replicate faster), and some of the DNA required to make a mitochondrion was transferred to the cell's nucleus. That means some of the proteins synthesized by this bacteria, were now encoded by the nuclear genome. When that happened, the bacteria was unable to live or replicate on its own, as a free-living cell, and no longer met all the criteria for "life". So we now call it an organelle, rather than a living bacterial cell.

What is the evidence that mitochondria and chloroplasts evolved from bacteria?

1) Bacteria, mitochondria and chloroplasts are the same size and shape

2) Bacteria, mitochondria and chloroplasts are all surrounded by a double membrane (a double lipid bilayer)

3) Bacteria, mitochondria and chloroplasts all have the important proteins and enzymes required for unique their function in the same membrane (e.g. bacteria and mitochondria have their ATP-producing proteins in their inner membrane)

4) Bacteria, mitochondria and chloroplasts all have a single circular genome. This is different from the nuclear genome which is arranged in multiple (different) linear chromosomes.

Chloroplasts, like the nucleus and mitochondria, have a double membrane. However, in addition to this they have an additional internal group of membranes called the _________ membranes that are arranged in stacks. A stack of these membranes is called a __________.

thylakoid; granum

The liquid inside the chloroplast is called the ________________.

stroma

The liquid within the thylakoid membranes is called the ____________________.

thylakoid space

The thylakoid membrane found in chloroplasts is equivalent to the _____________________ found in mitochondria.

inner mitochondrial membrane

The stroma found in chloroplasts is equivalent to the _____________________ found in mitochondria.

matrix

The thylakoid space found in chloroplasts is equivalent to the _____________________ found in mitochondria.

intermembrane space

What are embedded in the thylakoid membranes that absorb light energy from the sun?

light-absorbing pigments

Which organelles in an animal cell have DNA? What about a plant cell?

The nucleus and mitochondria have DNA in an animal cell. The nucleus, mitochondria and chloroplasts have DNA in a plant cell.

How can you tell the difference between the smooth and rough endoplasmic reticulum (ER) just by looking at it under an electron microscope?

The rough ER has black dots all over it (these are ribosomes) but the smooth ER lacks ribosomes.

What are ribosomes doing in the cell?

They are making proteins.

Which organelle makes the majority of our lipids?

Smooth ER

Nearly all of the cholesterol that your body makes is made in which organelle of the cells of which organ?

Cholesterol is made in the smooth ER of the liver.

Drugs, including alcohol, and other toxins are detoxified in which specific organelle? And which organ in the body is the primary site of this detoxification?

Detoxification of drugs and toxins occurs primarily in the smooth ER of the liver.

What is the role of the smooth ER in muscle cells?

The smooth ER stores calcium ions that will be released when a muscle gets a signal to contract.

What is the role of the smooth ER in our reproductive organs, the ovaries and testes?

The smooth ER synthesizes reproductive steroid hormones such as estrogen and testosterone. They are synthesized from cholesterol made in the liver that has been transported to these reproductive organs.

Why do we need a specialized pathway within the cell (the secretory pathway) to transport newly synthesized proteins out of the cell (e.g. insulin)?

Proteins are large and polar, and they cannot freely cross the plasma membrane. Therefore, to get them out of the cell, you have to package them into membrane vesicles that will fuse with the plasma membrane and dump the proteins out of the cell (secrete them). This is different than nonpolar substances which can freely diffuse out of the cell.

The copying of a gene into a single strand of mRNA is called ____________. The decoding of an mRNA sequence into an amino acid sequence (a protein) is called ____________.

transcription; translation

Where in the cell does transcription take place in a eukaryotic cell? ________ Where does the mRNA go after it is transcribed? __________ Where in the cell does translation begin? ____________

Transcription takes place in the nucleus. The mRNA then leaves the nucleus through a nuclear pore and enters the cytoplasm. Translation of all cytoplasmic and secretory proteins begins in the cytoplasm.

The term, secretion, means "to release a useful substance from the cell". A protein that is released from the cell is called a _________ protein.

secretory

What is the main difference between ribosomes synthesizing proteins in the cytoplasm and ribosomes synthesizing proteins on the rough ER?

There is no difference between them, physically. The only difference is the type of protein they are synthesizing. If a ribosome happens to bind to an mRNA that codes for a cytoplasmic protein, then it will be a cytoplasmic ribosome. And if a ribosome is translating a protein destined to leave the cell, it will be go to the rough ER and finish translation there.

How does a ribosome that is translating a protein "know" that it has to go to the rough ER to complete translation?

There is an amino acid sequence at the beginning of proteins that are destined for secretion that "tell" the ribosome to go to the rough ER.

The signal that indicates that a protein is a secretory protein (called a signal peptide) has what characteristics?

Signal peptides are short amino acid sequences (at least 15 amino acids) that are generally found at, or very close to, the beginning of a protein sequence (the N-terminus).

These sequences must have a stretch of (about 6-12) consecutive nonpolar amino acids. (hydrophobic side chains).

Why is is important to have a string of hydrophobic amino acids in a signal peptide?

The string of hydrophobic amino acids allows for the targeting and initial insertion, or translocation, of the protein into, or through, the rough ER membrane.

If a signal peptide is revealed as the ribosome synthesizes a protein, what binds the signal peptide?

SRP (Signal Recognition Particle)

As soon as SRP binds the signal peptide and the ribosome, what happens to protein synthesis?

Protein synthesis stops when SRP binds to the signal peptide and the ribosome.

This gives the entire complex enough time to get over to the rough ER membrane and bind to the SRP receptor on the membrane.

As SRP binds to its receptor (SRP receptor) and the ribosome binds a ribosome receptor on the rough ER membrane, what happens next?

SRP detaches from the complex, while the ribosome remains bound to the ribosome receptor in the rough ER. The removal of SRP from the complex allows protein synthesis to begin again.

Once translation resumes (with the ribosome bound to the rough ER membrane), where does the synthesized protein go?

As protein synthesis resumes, the protein is threaded through the rough ER membrane into the lumen of the rough ER (liquid inside the rough ER).

What happens to most signal peptides as the protein is threaded through the rough ER membrane?

Most signal peptides are removed by an enzyme (signal peptidase)

What other modifications to a secretory protein (besides signal peptide removal) often happens in the rough ER?

Disulfide bonds may be formed if there are two cysteines close together

Sugars are added to certain amino acids on the protein (glycosylation)

What type of environment in the rough ER lumen allows for disulfide bonds to form in proteins synthesized there?

The rough ER is an oxidizing environment... oxidizing enough to form disulfide bonds between nearby cysteines in proteins

How might disulfide bonds and glycosylation benefit a protein that is going to be secreted from a cell?

These modifications may protect a protein. Disulfide bonds provide stability (it is harder to unfold proteins with disulfide bonds because they are resistant to denaturants), and sugars may cover the protein, masking its access from proteases that may otherwise degrade the protein.

Of the following locations in a cell, which two locations would you expect to see a lot of chaperone proteins? Why?

~ smooth ER

~ cytoplasm

~ nucleus

~ Golgi

~ rough ER

~ plasma membrane

~ lysosome

You would expect to see a lot of chaperone proteins in regions where there is protein synthesis. This would be both the cytoplasm and the rough ER.

Note: I didn't put mitochondria on the list, but you have a lot of chaperones there too, as there are a number of mitochondrial proteins synthesized in the mitochondria. You also see some chaperones in the nucleus, but not a lot.

After a secretory protein is modified in the rough ER and folds, it is put into a ___________ to be sent to its next destination, which is the ____________.

vesicle; Golgi apparatus

What two roles does the Golgi apparatus have with respect to the secretory proteins it receives?

1) The Golgi further modifies the protein with sugars and other "tags" that help determine where it will end up.

2) The Golgi sorts the protein to its final destination (sort of like how a post office worker sorts the mail).

What are the three sets of Golgi stacks, and in which order does a secretory protein travel through them? Which is closest to the rough ER?

The three stacks, in order of travel, are the cis, medial and trans Golgi stacks. The first ones that are encountered, the cis stacks, are closest to the rough ER.

If a protein is destined to reside in the rough ER (like a chaperone in the ER), what would be the chronological order in which it would travel through the secretory pathway? What would direct it to its final destination? Begin with the rough ER.

Rough ER --> vesicle --> Golgi --> vesicle --> back to the rough ER

A "tag" present on the protein (it's an amino acid sequence in this case) will allow for it to be brought back to the rough ER.

The process by which vesicles fuse with the plasma membrane and release their contents to the outside of the cell is called _____________.

exocytosis

Let's pretend we are studying a protein which has to leave the cell and enter the bloodstream.

What is the pathway this protein would take to get out of the cell and into the bloodstream? Assume you are starting from the moment it is being synthesized on a ribosome in the cytoplasm and has revealed its "tag" to enter the secretory pathway.

The pathway this protein would take to get out of the cell would be as follows:

Note: it would begin its synthesis on a ribosome in the cytoplasm and then the ribosome would move to the rough ER. Then...

rough ER --> vesicles --> Golgi --> vesicles --> plasma membrane --> out (exocytosis)

If a protein gets to the trans Golgi network and is directed further along the secretory pathway, but is NOT destined for exocytosis, where is it likely to end up?

It will likely end up in the lysosome.

After the trans Golgi, proteins are either destined to be secreted via secretory vesicles (exocytosis), or they'll end up in the lysosome.

The lysosome functions as the cell's main __________ organelle, and the pH of the lysosome is significantly (higher/lower) _________ than the rest of the cell.

digestive; lower

Why is it important that the lysosomal enzymes only work at the low pH found in the lysosome and not at the higher pH found in the rest of the cell?

If they functioned at the pH of the rest of the cell, they would digest anything they encountered on their way to the lysosome, even things that weren't supposed to be digested!

This is because it isn't until secretory proteins get to the Golgi that they are sorted into specific vesicles. A lysosomal enzyme would first leave the rough ER in a vesicle along with any other secretory proteins that were made in the ER, even ones that are destined for secretion. If it were active, it would digest these proteins!

Let's pretend we are studying a digestive enzyme whose role is to digest other molecules that are damaged. Where would you expect to find this digestive enzyme (which organelle)? ___________

What is the pathway this digestive enzyme would take to get to this organelle? Assume you are starting from the moment it is being synthesized on a ribosome in the cytoplasm and has revealed its "tag" to enter the secretory pathway.

You would find this enzyme living in the lysosome.

The pathway it would take to get to the lysosome would be as follows:

Note: it would begin its synthesis on a ribosome in the cytoplasm and then the ribosome would move to the rough ER. Then...

rough ER --> vesicles --> Golgi --> vesicles --> lysosome

What does the term, autophagy, literally mean? What happens during autophagy?

It means "self-eating" (eating oneself).

During autophagy, old or damaged organelles are sent to the lysosome for digestion and recycling of their parts.

When the cell takes up molecules from the outside environment via a vesicle, the process is called ____________, and the molecules are usually sent directly to the ____________.

endocytosis; lysosome

List the three types of endocytosis. Which of the three types is most specific for the molecules that enter the vesicle used in the process?

1) phagocytosis

2) pinocytosis

3) receptor-mediated endocytosis

Receptor-mediated endocytosis is the most specific because it uses a receptor to bind to a specific molecule that will enter the vesicle. Those molecules are then concentrated in high levels in the vesicle and sent to the lysosome.

Phagocytosis is also known as cell _________.

eating

In phagocytosis, the cell takes up large molecules that it may want to "eat", or which are foreign to it, and sends those molecules to the lysosome for digestion.