Week 11 Recall Questions

Question 1

What characterizes the bacterial chromosome and ribosomes and differentiates them from eukaryotic
ones?

(Not finished)

Answer 1

Bacterial chromosomes have a single circular DNA, while eukaryotes have linear DNA (have terminal ends to them, are arranged usually in multiple linear chromosomes).

Bacterial ribosomes function in polypeptide assembly or chains of amino acids that are being put together. (Primary, secondary, tertiary, quaternary sequence as proteins), while eukaryotic ribosomes do this as well, they also make products that function in organelles of endomembrane system

Question 2

What is the function of plasmids?

How are plasmids used in biotechnology?

Answer 2

Function is to convey resistance to antibodies, provide flexibility to changes in their environment. Such as, giving them the ability to use new nutrients.
Function like a first aid box.

-smaller, about 5% the length of bacterial chromosome
In biotech they can be used to insert genes of interest from 1 cell into another cell plasmids.
- done when we clone a gene, copy it, or to get the product the gene produces (ex: insulin)

Question 3

Could eukaryotes have plasmids?

(Not finished?)

Answer 3

Yes, some occur naturally in eukaryotes

Question 4

What are the differences between eukaryotic and prokaryotic cells?

(Not finished)

Answer 4

Prokaryotic cells:
- lack membrane bound nucleus
- lack a lot of internal membrane bound specialized structures called organelles
- Nucleoid region: site of genomic DNA (chromosomes)
- 50S + 30S = 70S (sevburg sedimentation rate)
- have capsule

Eukaryotic cells:
- have membrane bound nucleus
— has double membrane (or nuclear envelope with pores)
- have many organelles
— ER
— Golgi apparatus, etc
- linear DNA
- 60S + 40S = 80S

Question 5

Where are bacterial ribosomes produced?

Where are eukaryotic ribosome produced?

Answer 5

Bacterial ribosomes are produced in the cytoplasm.

Eukaryotic ribosomes are produced in the nucleolus as SSU and LSU and moved to cytoplasm where they come together and are used for the translation of mRNA into polypeptides.

Question 6

What is produced by free ribosomes?

What is produced by bound ribosomes?

Answer 6

Free ribosomes produce:
- proteins like cytosol
- products vary by location, local proteins are produced in fluid of cytoplasm.

Bound ribosomes produce: (bound to nuclear envelope)
- products that are inserted into membranes
- products that function inside organelles of endomembrane system
- products that are secreted from the cell (exocytosis)

Question 7

What is the function of histones?

Answer 7

Function is to package DNA into structural units called nuleosomes.

Histones are the main proteins in chromatin. And chromatin’s are a combination of DNA and proteins which makes up the contents of a cell nucleus.

Because DNA wraps about histones, they also play a role in gene regulation.

Not packed into chromosomes = chromatin

Condensed into chromosomes using histones, b/c they’re positively charged proteins and therefore naturally attracted to DNA, which as an overall negative charge.

Question 8

What is the function of a nuclear pore?

Answer 8

It is a large complex of proteins that allows small molecules and ions to freely pass or diffuse, into or out of the nucleus.

Products made in the nucleus, such as ribosomal subunits are able to move out.

Question 9

What is the function of the endomembrane system and what are the main components?

Answer 9

Made up of
- nucleus (nuclear envelope)
- endoplasmic reticulum
- lysosomes
- various vesicles
- Golgi apparatus
- plasma membrane

This Internal membrane system helps the cell to produce products, such as proteins and then get them to their destination.

Function: it’s a group of membranes and cell organelles in eukaryotic cells that work together to modify, package, and transport lipids and proteins.

Question 10

What are the differences of SER and RER and what is their respective function?

Answer 10

Both a part of endoplasmic reticulum (ER)

Smooth ER (SER):
- no ribosomes attached
- function in phospholipid production
- function in detoxification of drugs and poisons.
- cisternae

Rough ER (RER):
- covered with bound ribosomes
- function in protein synthesis
- structure is maze like, structure is called cisternae = flattened membranous sacs

Question 11

What is the function of the Golgi complex?

Answer 11

Receives proteins from the ER (by vesicles) and further processes/modified them and then sorted for transport to their eventual destinations: lysosomes, the plasma membrane, or secretion

Structurally and functionally different than ER, not maze like, but separate individual pockets or cisternae folded membranes. (Not physically attached to these sacs)

Analogy: shipping and receiving centre.

Has CIS and Trans face

Vesicles are small membrane bound sacs
— function to transport cell products like proteins between parts of the endomembrane system. In cytoskeleton transport molecules using parts of cytoskeleton and motor proteins.

Question 12

How do the cis- and trans-side of the Golgi-complex differ?

Answer 12

Proteins enter the Golgi on the side facing the ER (cis side)

Proteins exit on the opposite side of the stack, facing the plasma membrane of the cell (trans side)

Both are essentially responsible for the task of sorting proteins and lipids that are received at the cis face or released at the trans face by the organelle

Question 13

What are the final destinations of some of the vesicles produced by the Golgi -complex?

Answer 13

• Lysosomes
• the plasma membrane
• or secretion

Question 14

What is the function of lysosomes?

How do they maintain and acidic pH and how is this beneficial?

Answer 14

Lysosomes are membrane bound with hydrolytic enzymes (digestive enzymes)

In order to keep enzymes active, lysosomes use active transport to pump H+ inside the lysosome.
— have very high acidic pH, that’s required for digestive enzymes to be active.

The cytoplasm has a more basic pH, so the acidity projects the cell.
— so say some lysosomes rupture, it won’t digest the cell itself b/c the enzymes inside vesicles are neutralized by the basic pH of cytoplasm.

Also function with autophagy

Question 15

What is authophagy and why is it beneficial?

Answer 15

Means self eating.

Refers to cells recycling worn-out or damaged cell organelles.

• fuses a lysosome to organelle to auto phagocytose it (eat it)
• digestion is a hydrolysis process

Question 16

What are the functions of vacuoles?

What is a key function of vacuoles in plant cells?

Answer 16

Large membrane bound structures, sac-like

Serve functions in food storage, contractile functions in protists.

Many functions in plants such as, energy storage in seeds, store toxins, pigments, and water.
— plants rely on the water crew takes between their central vacuole and their cell wall to give them form (tonicity)

Question 17

What is the Theory of Endosymbiosis?

What is the main statement?

(Not finished and needs to be revised)

Answer 17

Postulated events that’ve driven evolution of eukarya and their cell organelles, specifically mitochondria and chloroplasts.

Eukaryotic cell organelles evolved from free-living prokaryotes

• the mitochondria are thought to originate from an aerobic prokaryote that lived as an Endosymbiont within an anaerobic prokaryotic
• the chloroplasts are thought to originate from a photosynthetic prokaryotic that lived as an endosymbiont within a aerobic cell that already had mitochondria

Question 18

What is the sequence of main events according to the Endosymbiotic Theory (Fig 21.17)

(Needs to be revised)

Answer 18

1. Ancestral prokaryote (likely domain archaea) that was anaerobic respiring, engulfed an aerobic bacteria (also prokaryote)

• mutually beneficial: bacteria protected by larger cell. And bacteria provided to larger host cell aerobic metabolism = ability to deal with O2 and produce a lot more ATP

2. (Only in some cell populations) photosynthetic bacteria (ancestors of cyanobacteria) were engulfed by host cell —> formation of chloroplasts

Question 19

What are lines of evidence suggesting the mitochondria and chloroplasts have bacterial characteristics and are related to bacterial groups?

Be specific, give at least 4 pieces of evidence.

(Needs to be revised)

Answer 19

1. Both replicated by binary fission. Replicate inside eukaryotic cells, fairly independent of the main cell (euk) that uses mitosis or chromosome sorting.
2. Presence if double membrane. Both double or triple.
   — Inner membrane has same structure and protein composition as living bacteria.
   - host cell membrane and inner membrane (originally from prokaryote)
   - enzymes and enzyme systems for metabolism are similar too and located in inner membrane
3. Presences of their own DNA.
   - a single circular chromosome without histone proteins.
   - able to sequence this and look at relationships, which show they most closely match with prokaryotic organisms.
4. Contain their own ribosomes. Similar to prokaryotes but not cytoplasmic eukaryote ribosomes.
   - genes often referred to what we call 16S rRNA = ribosomes inside mitochondria and chloroplasts are most similar to prokaryotic ribosomes (bacteria)
   - 16S rRNA are for ribosomal RNA genes that form small subunit (these most related to bacteria)
   — ribosomes have own DNA = contain protein coding, non-coding genes, similar to prokaryotes. Have own transcription and translation machinery.

Question 20

How did eukaryotes solve the increased need for energy due to their increased complexity?

Answer 20

They took advantage of aerobic prokaryotes that use O2 and therefore are able to produce more ATP through cellular respiration.

Question 21

What is the main function of mitochondria?

Is the “powerhouse of the cell” a good description?

Answer 21

Function: they transfer energy in cells, the energy from nutrients and make ATP for the cell (cellular respiration)

Question 22

How many membranes do mitochondria have?

What are the names of the different compartmental spaces (between/inside the membranes)?

Answer 22

Bean like structure with double membrane (origin in prokaryotic ancestors)

• has outer, inner membrane, intermembrane space, matrix

Intermembrane space where mitochondria pumps protons

Question 23

What is the main function of chloroplasts?

Is the “powerhouse of the cell” a good description?

Answer 23

General function: site of light rxns for photosynthesis

Essentially a cell organelle that has a 3 membrane structure.
- outer, inner, thylakoid membrane

Thylakoid membrane where light rxns of photosynthesis take place, they sit in a gelatinous fluid of the chloroplast of the stroma (the fluid).

Inside thylakoids there’s a space called thylakoid lumen, this is where protons are pumped.

Question 24

What are the general functions of the cytoskeleton?

Answer 24

• It spatially organizes the contents of the cell
  — like aiding in the correct positioning of organelles
• generates coordinated forces that enable the cell to move and change shape.
• supports plasma membrane
• gives cell overall shape
• provides tracks for the transport of vesicles

Question 25

What are more specific functions of the cytoskeleton in a) animal cells and b) plant cells?

Answer 25

Animal cells:

Microfilaments
- assembled in cell cortex or endoplasm, outer cytoplasm helping to support cell shape or modify membrane behaviour (important b/c lack cell wall)

Plant cells:

Microfilaments
- cytoplasmic streaming
— refers to how cells create flow in their cytoplasm to distribute nutrients within a plant cell. Works by actin filaments connecting with motor proteins and dragging organelles along MFs.

Question 26

What are the 3 major structural elements of the cytoskeleton?

Answer 26

Microfilaments

Intermediate filaments

Microtubules

Question 27

What are the functions and what is the composition (building block, monomer) of microtubules?

Answer 27

Function:
- primarily cell shape, build cell shapes especially odd/asymmetrical shapes. Ex: neurons that have dendrites and axons.

• used to build cilia and flagella to form a supportive functional structure. (9+2 arrangement)
• form mitotic spindle, which helps sort the chromosomes in cells and also push cells apart. (A part of the polar MT organizing centre)
• used to move organelles around, act as a highway for motor proteins such as kinesin to move things such as vesicles

Composition:
Long, slender, hollow and unbranched tube like structures made of globular proteins called tubulin.

Tubulin exists as a dimer (2 units) that are assembled and disassembled rapidly as overall MT structures. = monomer

Alpha and beta tubulin = building blocks

Question 28

How do microtubules and kinesins work together?

Give specific examples

(Needs revising)

Answer 28

Kinesin is a motor protein, has globular head that anchor to the MT (cytoskeleton highway) and carries cargo.

• walks across MT
• also moves Mitochondria
• uses ATP to swing heads in order to walk
  —> ATP hydrolysis

transports vesicles and organelles in the direction of microtubule plus ends, which extend toward the cell periphery. (Unidirectional)

Question 29

How do microtubules and dyneins work together?

Give specific examples

Answer 29

Cytoplasmic dynein is responsible for transporting intracellular cargos in interphase cells and mediating spindle assembly and chromosome positioning during cell division.

• move toward the minus end of microtubules. (Unidirectional)

Question 30

What are the functions and what is the composition (building block, monomer) of microfilaments?

Answer 30

Functions:
Cell shape-
- MF’s allow cell to create tension and change their shape
— often found near surface of plasma membrane or in form of actin filaments
— use from microvilli (small finger-like projections) = important in intestinal cells to create extra surface area to trap food particles
- muscular contraction
— motor protein myosin
- cytoplasmic streaming
- cell mobility
- cell division

Composition:
- polymer if intertwined strands of actin.
- monomer = actin
- association with myosin protein

Question 31

How do microfilaments and myosins work together?

Give specific examples

Answer 31

Myosin motors move on actin filaments.

• convert the energy from ATP into force and movement on Microfilaments

cell mobility
— via pseudopodia, use an assembly of actin MF in outer cortex to form a gel-like network, which is in a solution mesh. Cell then thins and another are of cytoplasm forms a more fluid like component. Gel-like area squeezes and forms a pseudopod, and this enables cells to move. Can form multiple (ex: amoeba)
— analogy; squeezing a water ballon in hand and one area extends outward

cell division
— use myosin as motor protein, use MF to draw cell into 2 (form a cleavage furrow). This contracts and pinches cell apart to form daughter cells.

Muscular contraction
— motor protein myosin as a hook like structure, attaching and detaching using ATP to MF complex. Allowing muscle cells to contract.

Question 32

What are the functions and what is the composition (building block, monomer) of intermediate filaments?

Answer 32

Functions:
- cell shape (tension) (maintain it)
- help anchor nucleus and other cell organelles
- form nuclear lamina = support nucleus on the inside of the nuclear envelope.

Composition:
- are fibrous proteins supercooled into cables.
— fibrous subunit is keratins coiled together
- monomer = keratin
- form relatively permanent structures (shapes). Made from a variety of proteins.
— permanent shapes, if cell wants to provide more tension or fibrous like structures, they’ll contain some proteins like keratin.
- between microfilaments and microtubules

Question 33

What organisms are intermediate filaments found in?

Answer 33

found only in some metazoan species, including vertebrates, nematodes, and molluscs.

Question 34

What is the structure or cilia and flagella?

What is the difference between cilia and flagella?

(Needs revising)

Answer 34

Both built from microtubules (eukaryote)
Both filaments have 9+2 arrangement. 9 pairs are doublets, 2 are MT in the Center.

Prokaryote ones have different protein and move flagella differently.
— spin like propellers.
Analogy: uncooked spaghetti for flagella

Eukaryotic flagella are whip like in motion.
Analogy: move like cooked spaghetti

Eukaryotic cilia move in an “oar” like motion.

Question 35

How do cilia and flagella bend?

Describe the structure (cross section), the process and how this leads to motion (forward movement)

(Needs revising)

Answer 35

Doublets are connected by dynein proteins (exist between adjacent MT’s), which attach and detach from adjacent MT’s with ATP (energy input).

MT bend vs slide past 1 another as the radial spoke proteins anchor then to ensure they don’t slide.

Bending results from dynein attaching and detaching and contracting as a motor protein on the MT’s.