Chapter 15 - Intracellular Compartments Flashcards
How do cells carry out multiple reactions concurrently that are mutually incompatible?
Require isolated environments for incompatible reactions. Recall, membranes are good selectively permeable barriers in providing these environments.
Eukaryotic cells are able to compartmentalize cellular functions within what?
Organelles
What do organelles do?
1) Enhance local concentration of reactants and enzymes - allowing chemicals to be concentrated and chemical reactions to proceed more efficiently.
2) Provide isolated environments.
3) Enable specialized but mutually incompatible processes to occur simultaneously without interfering with each other.
Each organelle contains a unique set of ___ and ___ molecules and carry out ___ functions.
large, small, specialized
Cytosol
Contains many metabolic pathways, protein synthesis, and the cytoskeleton.
Nucleus
Contains main genome; DNA and RNA synthesis.
Endoplasmic Reticulum (ER)
Synthesis of most lipids; synthesis of proteins for distribution to many organelles and to the plasma membrane.
Lysosomes
Intracellular degradation
Endosomes
Sorting of endocytosed material.
Mitochondria
ATP synthesis by oxidative phosphorylation.
Chloroplasts (in plant cells)
ATP synthesis and carbon fixation by photosynthesis.
Peroxisomes
Oxidation of toxic molecules.
Which organelle houses and protects genetic information?
Nucleus.
(T/F) The nucleus contains main genome and is the site of DNA and RNA synthesis.
True.
Does the nucleus have a double membrane?
Yes, in the form of a nuclear envelope.
In a nucleus, the ___ membrane is continuous with the ___.
outer, ER membrane.
The nucleus ___ with the ___ via nuclear pores embedded in the envelope.
communicates, cytosol.
How many kinds of endoplasmic reticular exist?
Two, rough and smooth ER.
Rough ER
Characterized by ribosomes attached to the cytosolic side (outer surface) of the membrane and usually forms large flattened sheets.
Smooth ER
ER without ribosomes attached and generally forms tubular structures.
Ribosomes
a minute particle consisting of RNA and associated proteins, found in large numbers in the cytoplasm of living cells. They bind messenger RNA and transfer RNA to synthesize polypeptides and proteins.
Microsomes
Broken fragments of ER that spontaneously form sealed vesicles upon homogenization of cells/tissues.
The rough ER is involved in the ___ and ___ of proteins.
Biosynthesis, processing
What is the rough ER responsible for?
Synthesizing both membrane-bound and soluble proteins.
The rough ER is the site for the initial steps of ___.
protein glycosylation.
Protein Glycosylation
Site of addition of preassembled carbohydrate trees to lumenal and transmembrane proteins.
(T/F) The rough ER is the site of folding of polypeptides?
True
The rough ER is the site for the assembling of which type of proteins?
Multimeric proteins.
What is the importance of the smooth ER?
It plays a central role in:
1) Biosynthesis
2) Lipids
3) Detoxification
4) Calcium Storage
The smooth ERis the ___ source of ___ lipids (e.g. phospholipids and cholesterol).
Primary, membrane.
For the smooth ER, lipid biosynthesis occurs only to the ___ (cytosolic face) of the ER.
outer monolayer
What is the membrane flow and the endomembrane system?
A flow that travels from the endoplasmic reticulum, to the golgi complex, to the endosomes, to the lysosomes, and finally the peroxisomes.
The Golgi Complex consists of what type of sacs? What are they called?
A stack of flattened, membrane-enclosed sacs called cisternae.
What is the use of the Golgi complex?
The sorting and packaging center of proteins destined for endomembrane compartments and for secretion.
Further processing of protein ___ - finishing the job started at ER
glycosylation
Lysosome
An organelle containing digestive enzymes capable of degrading all the major classes of biological macromolecules.
What type of membrane do lysosomes have?
Single membrane
What type of environment does the lysosome have?
Acidic enviornment
What maintains the acidic environment of the lysosome?
ATP-H+ pump
What are the enzymes lysosomes use?
Nucleases, proteases, glycosidases, lipases, phosphatases, sulfatases, and phospholipids.
Where do lysosomes develop?
From endosomes
The lysosome is the ___ center of the cell: controlled intracellular __ of both ___ materials and ___ out organelles.
Recycling, digestion, extracellular, worn.
What happens if a lysosome leaks out?
A chain reaction of destruction occurs which causes digestion of the whole cell.
The lysosome is analogous to a what?
Atomic bomb, made with fail safes to prevent accidental explosion while being made.
What are additional fail safes for lysosomes?
1) Must be taken to pH 2 before they become active at pH 7.
2) Synthesized in Zymogen form
Lysosome membrane proteins facing the lumen are highly what?
Glycosylated.
The Mitochondria is referred to as what?
The cell’s power plant.
How many membranes encase the mitochondria?
2, outer membrane, and innter membrane (called the Cristae).
Do mitochondria have a matrix?
Yes
Are mitochondria part of the endomembrane system?
No
(T/F) The mitochondria generates the majority of the energy a cell uses to carry out its functions.
True
The chloroplast is referred to as what?
The site of photosynthesis.
How many membranes encase the chloroplast?
2, outter and innter membrane.
Stroma
Fluid inside the inner membrane of the chloroplast.
What are the stacks inside the third membrane called?
Thylakoids
What are a stack of thylakoid sacs?
Granum
___ is the fluid inside the thylakoid.
Lumen
What are similarities between mitochondria and chloroplasts?
Inner and outer membranes, DNA, and ribosomes.
What are differences between mitochondria and chloroplasts?
Mitochondria has a matrix which is comparable to the stroma in chloroplasts. Chloroplasts have thylakoid membranes while mitochondrion do not.
How did Eukaryotic cells originate?
Maybe in two ways:
1) The endomembrane system and cell nucleus may have originated from the inward folds of plasma membrane of prokaryotes.
2) Mitochondria and chloroplast may have evolved from bacteria that were ingulfed by pre-eukaryotic cells, also known as the endosymbiotic origin.
Nuclear membranes and ER have evolved via ___ of the plasmid membrane.
Invagination.
What is supporting evidences to the theory that nuclear membranes and ER may have evolved via invagination of the plasmid membrane.
1) In bacteria, the DNA molecule is typically attached to the plasma membrane.
2) The nuclear envelope has a double membrane.
3) the outer membrane of the nuclear envelope is connected to the ER membrane.
4) The space between the inner and outer nuclear membrane is continuous with the ER lumen.
5) The interiors of endomembrane systems are treated by the cell as extracellular.
What is supporting evidence to the theory of Aerobic bacteria or photosynthetic bacteria engulfed by larger pre-eukaryotic cells initially lived in symbiosis and later became organelles.
1) They have their own genomes - used to be independent organisms.
2) Genes in their genomes are homologous to those of bacteria.
3) These organelles have double membrane surrounding them.
4) They are not interconnected with the endomembrane system and do not participate in the vesicular traffic of the endomembrane system.
5) Endocytosis is still happening.
What are living examples of endosymbiosis?
The discovery of a single-celled eukaryote, Hatena, that ingests a green alga, Nephroselmis.
The green alga lost most of its structures and acts as a chloroplast.
How do you identify a specific organelle or its fragment vesicles?
By assaying their unique enzymes - we call them Marker Enzymes.
How do you identify an unknown protein and study the function of this protein after identification?
By identifying its localization in a specific organelle.
