(33-38) Cytoplasm, ER, Golgi, and Lysosomes

The — is not necessarily considered an organelle despite being bound by both a plasma membrane and internal membranes

cytoplasm

The cytoplasm is about — percent water and — percent protein

70;25

The cytoplasm found outside organelle is also called — while cytoplasm found within organelles is called —

ground cytoplasm; matrix cytoplasm

3 Important activities in ground cytoplasm

glycolysis, site where material is transported in from outside the cell, and protein synthesis

ER stands for

endoplasmic reticula

Reticula

network of membranes that extend out from a central region

The ER membrane is — with the nuclear membrane. What does this allow for?

contiguous; direct access between the two organelles

3 types of ER

rough, smooth, and transitional

The rough and smooth ER are — with each other

contiguous

How to identify rough vs smooth ER

rough has ribosomes attached while smooth does not

What does the rough ER cross-section look like? What does the smooth ER cross-section look like?

a flattened hollow sac with attached ribosomes; circular

2 basic functions of rough ER

protein synthesis and N-linked glycosylation

2 basic functions of smooth ER

lipid synthesis and detoxification

t/f the lumen between smooth and rough ER is connected

true

ribosomes are visible on the rough ER, what does this indicate?

Ribosomes are formed which means elongation is currently happening

Initiation of protein synthesis occurs where?

cytoplasm

Within the first — codons of mRNA is a — sequence which codes for — amino acids that, once synthesized, directs the ribosome to the rough ER

20;leader; hydrophobic

If there is a — sequence present, then that protein is destined for the rough ER (or mitochondria). If it does not contain this, it will complete translation where?

leader; cytoplasm

t/f the steps of protein synthesis is different between cytoplasmic ribosomes and ribosomes attached to the rough ER

false

t/f ribosomes attached to the rough ER elongate their proteins directly into the rough ER’s matrix (explain answer)

false; the protein is translated into the cytoplasm then threaded in some way through the ER’s membrane

When a protein is threaded into the rough ER, what does the leader sequence do then?

it is cut off

Where can proteins go after being translated on the rough ER

they may either go to the rougher ER’s lumen, become a transmembrane protein on the rough ER membrane, or become a peripheral protein located on either the lumenal or cytoplasmic side of the of rough ER membrane

What classes of proteins are synthesized at the rough ER vs the cytoplasm?

all of the membrane transport proteins whereas most enzymes or glycolytic enzymes are synthesized in the cytoplasm

Post translation modifications of proteins synthesized at the rough ER

removal of the leader sequence and glycosylation

N-linked Glycosylation

when custom made sugar (usually an oligosaccharide), is attached to the amino group of the aa asparagine of a protein. Occurs on a superlipid called dolichol on the surface of the rough ER.

Dolichol

transmembrane lipid on one rough ER where N-linked glycosylation takes place.

Process of N-linked glycosylation

using glycosylases, monosaccharides are attached one at a time to form a custom oligosaccharide attached to the base of the dolichol in the cytoplasm. The dolichol then flips to bring the oligosaccharide into the lumen of the rough ER. additional glycosylases cut it from the dolichol and attach it to the protein.

N-acetyl glucosamine

most abundant sugar in the world. Found in chitin. Usually the base monosaccharide in oligosaccharides

Sugars that are usually found in oligosaccharides in N-linked glycosylation

mannose, glucose and N-acetyl glucosamine

How is it determined where an oligosaccharide is attached during N-linked glycosylation?

it is attached to the asparagine in this specific aa sequence=[N-term] asparagine (asn)- X (any aa)- serine (ser) or threonine(thr) [C-term] <- pay attention to the terminus

What group of asparagine is where an oligosaccharide is attached during glycosylation? Because of this, what name is the process given?

amino group (-NH2), N-linked glycosylation

A leader sequence may be specific for what two organelles?

rougher ER or mitochondria

The lipid component of membranes are built where?

smooth ER

Where would proteins associated with the smooth ER membrane come from?

the rough ER

Phospholipids are primarily made on the — monolayer of the smooth ER bilayer. Because this would eventually result in an imbalance between monolayers, at a certain some of these phospholipids must be — to the — monolayer

cytoplasmic; flipped; lumenal

Which phospholipids of the smooth ER must be flipped? Which ones stay facing the cytoplasm?

phosphatidyl choline is flipped while phosphatidyl inositol, phosphatidyl ethanolamine and phosphatidyl serine are not

What exception to the movement of phospholipids is seen only in the smooth ER?

it is the only place where the phospholipids may flip monolayers

Some of the phospholipids formed in the smooth ER are pulled out as they are synthesized and moved where? Why? What do they use to get there?

mitochondria ; the mitochondria cannot make its own phospholipids; phospholipid transfer protein

Phospholipid transfer protein

protein which plucks phospholipids as they are synthesized in the smooth ER and transferred to the mitochondria

t/f phospholipids are the only lipids produced in the smooth ER (explain answer)

false; steroids and sterols are also produced there

Cytochrome P450

found in the smooth ER. named because it absorbs light at 450 nm. Oxidizes many types of molecules, which is useful for detoxification

Usually toxic compounds are — and need to be — in order to be detoxified

reduced; oxidized

Remember, oxidation is — of electrons and reduction is — of electrons

loss; gain

Nembutal

compound used in veterinary medicine as an anesthetic that is considered a toxicant. Animal cell will develop extensive smooth ER in response to exposure

Sarcoplasmic reticula

modified and extensive smooth ER found in muscle cells. Very important in calcium sequestration.

t/f it is hard to move molecules between the smooth and rough ER (explain answer)

false; contiguous membrane

There is a — across the ER membrane which helps to guide molecules from the cytoplasm into the ER

electronic potential

The golgi looks like a series of — stacked on one another connected by — to more of these stacks

flattened sacks; tubules

t/f the golgi has a low SA/V ration

false, it is extremely high

The golgi apparatus is composed of multiple — all stacked on another and connected to each other by —

golgi stacks; tubules

The golgi is — with respect to the ER and — with respect to the plasma membrane

convex; concave

Draw a golgi with respect to the ER and label the cis and trans face

The cis face of the golgi is also called — while the trans face is also called —

forming face; maturing face

The cis face looks more like the — membrane because it is (thinner or thicker) at — nm in thickness while the trans face looks more like the — membrane as it is (thinner or thicker) at — nm in thickness

ER; thinner; 3-4; plasma; thicker; 4-5

What face of the golgi is fenestrate and what does this mean? Why does it appear this way?

cis face; rough appearance (like a mud puddle hit by rain drops); Used to describe the cis face of the golgi as it accepts vesicles from the transitional ER.

Transitional ER

looks like smooth ER but has no enzymatic activity for lipid production or detoxification. The function is producing vesicles which travel to the cis surface of the golgi.

Primary means of trafficking material between ER and golgi

vesicles

Vesicles come off of the transitional ER in a — like process which enter the the golgi in a — like process

exocytosis; endocytosis

— of vesicles hit the golgi at one time which give the — face a — appearance

thousands; cis; fenestrate

The — face of the golgi accepts vesicles while the — face exports vesicles

cis; trans

The trans face of the golgi has what main function

exporting vesicles either into the cell or to the cell membrane

Functions of the golgi apparatus

O-linked glycosylation, Pro-processing, secretion, membrane recycling, and lysosome production

Glycosylation in the golgi is – -linked. What does this mean?

O-linked; serine or threonine contained hydroxyl (-OH) groups which the sugar is attached to instead of the amino group on asparagine

What monosaccharides are involved in the oligosaccharides of O-linked glycosylation

in addition to mannose, glucose and N-acetyl glucosamine there is also Fucose, sialic acid, or galactose

How do the monosaccharides involved in O-linked glycosylation get into the golgi?

it is guided by UDP (uracil diphosphate) or GDP (Guanine diphosphate) as they connect to the sugar and move through into the golgi via an antiport transport system which moves in the the sugar-GDP/DP and moves out a matching GDP or UDP

Pro-processing in the golgi

When the Golgi apparatus performs post-translational modifications on proteins transported from the rough ER

Examples of proteins that require pro-processing in the golgi

proinsulin or proglucagon

Benefit of pro-processing

allows for storages of pro-proteins to be made which can be released into the golgi for pro-processing when they are needed. This is faster than making them from scratch.

A lot of proteins that are made in a — form within the rough ER and require — within the — to become functional/active

naive; pro-processing; Golgi apparatus

Secrete vs excrete

excrete means the cell is ridding waste or other “bad” molecules while secretion involves purposeful release of bioactive compounds which affect other cells in the body

When the golgi of a pancreas cell sends vesicles filled with insulin to be released out of the cell at the cell membrane, what function/s is it performing?

secretion and membrane recycling

Zone of exclusion

area around the golgi where no other organelles are associated. The only thing going in and out of this zone are vesicles

Lysosomes are involved in both — and — digestion

intracellular and extracellular

— will digest any nutrient vesicle brought in via — or —

lysosomes; phagocytosis or pinocytosis

t/f lysosomes will digest parts of the cell that aren't needed anymore

true

Lysosomes contain — enzymes. There are about — different types of this enzyme in the lysosome

hydrolytic; 50

t/f hydrolytic enzymes had a leader sequence when they were produced (explain)

true; they must have been produced in the rough ER since they are inside lysosomes which are made in the Golgi apparatus

The only cells that don't have lysosomes are —

bacteria

Lysosomes are very (stable or unstable). Why must this be the case?

stable; if the hydrolytic enzymes are released inside the cells, it will kill the cell

Lysosomes have a membrane lined with — to make it resistant to what?

sugars; its hydrolytic enzymes

Most lysosomes function only at a — ph. Why? How is this ph achieved?

low (5); the hydrolytic enzymes are ph-sensitive. This acidic ph is achieved with a pump that brings in protons (H+) which activates the enzymes

Lysosomes are Polymorphic. What does this mean?

they may take on many odd shapes

Primary lysosome

brand new lysosome, fresh from the trans side of the golgi. Contains one type of hydrolytic enzyme

There may be up to — different types of primary lysosome

50

Secondary lysosome

occurs when a primary lysosome binds to another primary lysosome, secondary lysosome or an endocytotic vesicle.

3 types of secondary lysosome

digestive vacuole, autophagic vacuole, Residual vacuole

Digestive vacuole

secondary lysosome formed from one or multiple primary lysosomes and a nutrient containing endocytotic vesicle which digests the materials. The small organic molecules that result from this digestion are then released from this lysosome.

Autophagic vacuole

secondary lysosome; “self-eating”; primary lysosomes that bind to organelles to digest their materials. More common in cells that are losing mass.

Residual vacuole

secondary lysosome. Contains indigestible materials. May be stored on the cell membrane surface on the cytoplasmic side or exocytosed out of the cell. Used in some cells of animals to copy the color of a consumed organism.

Acrosome

specialized lysosome found on the head of a sperm cell which is used to digest the jelly coat of an egg and allow fertilization to occur

Lysosome dysfunction may be associated with diseases such as what?

arthritis, gout, or tay sachs