Q1 You got this!!!

Question 1

What is the difference between prokaryotes and eukaryotes?

Answer 1

Prokaryotes do not contain internal membranes while eukaryotes have internal membranes.

Question 2

Are viruses alive? Why or why not?

Answer 2

Viruses are NOT alive because they are not able to reproduce on their own. They hijack the cellular machinery in cells in order to reproduce.

Question 3

Describe how eukaryotes developed from prokaryotes (i.e. endosymbiotic theory).

Answer 3

There were two different stages in the development of prokaryotes to eukaryotes. 1. plasma membranes folded inward to create internal membranes. 2. the consumption and integration of other bacteria, like aerobic and photosynthetic bacteria.

Question 4

What allows certain molecules to pass through the plasma membrane and prevents others from diffusing?

Answer 4

Molecules are able to pass based on their size and charge. Large molecules and charged molecules are unable to diffuse across the membrane.

Question 5

What is the difference between the following types of proteins/membrane proteins: transporters and channels, sensors and receptors, enzymes, and anchors?

Answer 5

Transporters and channels are involved with the import and export of materials across the membrane, sensors and receptors play a role with cellular signals and information transmission, enzymes assist in the catalysis of reactions, anchors bind cytoskeletal structures and proteins to membranes.

Question 6

Describe the structure of an individual phospholipid, glycolipid, and cholesterol.

Answer 6

All three have a hydrophobic tail region as well as a hydrophilic head, meaning that these lipids are amphipathic. Phospholipids have a phosphate/alcohol head, glycolipids have a sugar head, and cholesterol has an alcohol head. Phospholipids and glycolipids have two fatty acid tails while cholesterol has a single tail with a steroid region as well as a fatty acid region.

Question 7

What factors influence membrane fluidity?

Answer 7

Temperature, tail properties, lipid composition

Question 8

How does the plasma membrane differ between colder and warmer temperatures

Answer 8

In colder temps, the lipids of the membrane are more unsaturated, have shorter tails, and more cholesterol. In warmer temps, the lipids are more saturated, have longer tails, and have less cholesterol.

Question 9

How does cholesterol assist in membrane fluidity in cold temperatures?

Answer 9

When there is cholesterol present in cold temperatures, the cholesterol prevents the solidification of the lipid bilayer as well as tight packing.

Question 10

What is the process by which new phospholipids are added to the ER?

Answer 10

New phospholipids are added to the cytosolic side of the ER membrane. ER scramblase then randomly rearranges lipids between the monolaters. This results in symmetric growth of the bilayer.

Question 11

How are lipids involved in addition to the golgi as well as the creation of vesicles?

Answer 11

After phospholipid membranes, created from the ER, are added to the golgi membrane, flippases move phospholipids from the golgi lumen face to the cytosolic face. This results in asymmetry between the monolayers that results in the eventual pinching off of a vesicle.

Question 12

What are two types of asymmetry in the membrane and why are they important?

Answer 12

The first type of asymmetry involves the proteins present on each face. Because there are different molecules on each face, it is important to have different proteins and lipids on each face. The second form of asymmetry is in respect to the monolayers of the golgi membrane. This asymmetry aids in the pinching off of vesicles.

Question 13

What are the functions of glycolipids and where are they located?

Answer 13

Glycolipids are located on the non-cytosolic face and play a role in cell recognition/information transmission.

Question 14

What face are inositol phospholipids on and how are they involved in cell signaling? What does this process look like?

Answer 14

Inositol phospholipids are present on the cytosolic face. When a signal is received by a protein on the non-cytosolic face, the signal is relayed on the interior of the cell. One of these interior receptors is phospholipase, so when the signal reaches this protein, an inositol phospholipid is hydrolyzed, resulting in the cleavage of IP3. IP3 is a signal that can trigger other mechanisms within the cell.

Question 15

How are lipid rafts different from other regions of the membrane? What important process is concentrated here?

Answer 15

Lipid rafts are more tightly packed than other regions of the membrane because they contain more cholesterol and sphingolipids. They contain many proteins involved with cell signaling as well as anchors. One type of phospholipid in this region are inositol phospholipids.

Question 16

What are two types of folding for transmembrane proteins?

Answer 16

alpha helix and beta sheets

Question 17

How are detergents similar to lipids? What a structure do they form with each other? with transmembrane proteins?

Answer 17

Detergents are similar to lipids in the sense that they are both amphipathic. They form micelles alone, and with transmembrane proteins, they can protect the hydrophobic region of the protein.

Question 18

What is the cortex? Where is it located? What are five functions of the cortex? What does the lattice structure of the cortex comprised of?

Answer 18

The cortex is the region right “beneath” the membrane, on the cytosolic face. It aids in mechanical strength, shape changes, movement, restriction of domains, adsorption

Question 19

What is the glycocalyx? What are some of its functions and what two molecules make up this layer?

Answer 19

The glycocalyx is also known as the carbohydrate layer “beneath” the membrane on the cytosolic face. The glycocalyx is important for cell protection, lubrication, and adhesion/recognition. There are two general molecules: proteoglycans (with a long sugar chain) and glycoproteins (with a short sugar chain).

Question 20

Describe the process by which the neutrophils migrate from the blood to infected tissues.

Answer 20

When there is infected tissues, the epithelial cells express a protein called lectin. Neutrophils have carbohydrates on their cell surface that are able to bind to these molecules, allowing them to roll along the endothelial cells until they reach a point of exit.

Question 21

Why does a cell have specific membrane domains constraining proteins? How does this occur?

Answer 21

Cells have different domains because they must maintain different asymmetries. This can occur by proteins binding to the cortex, extracellular matrix, surface proteins, or by acting as diffusion barriers.

Question 22

What are similarities between transporters, pumps, and channels? Differences?

Answer 22

All are involved in the movement of molecules across membranes. Transporters and pumps undergo conformational changes while channels do not. Pumps require energy in order to perform active transport while the transporters and channels are utilized for passive transport.

Question 23

Describe the difference between passive and active transport.

Answer 23

Passive transport flows down the concentration gradient and does not require energy. Active transport flows against the concentration gradient and does require energy.

Question 24

What are the different types of concentrated solutions? When a cell is placed in these solutions, how is the cell affected?

Answer 24

Hypotonic: Low concentration of solutes in solution compared to the cell. Water will flow into the cell and eventually cause lysing. Isotonic: Equal concentrations of solutes in solution compared to the cell. Water will flow both in and out of the cell. Hypertonic: High concentrations of solutes in solution compared to the cell. Water will flow out of the cell and cause cell shriveling.

Question 25

What channel protein is responsible for the transport of water in and out of the cell? How is this protein selective for water?

Answer 25

Aquaporins are the channel protein responsible for the movement of water. The channel is narrow to prevent large molecules from passing and the channel also has asparagines that prevent charged species from passing through.

Question 26

What ions are high in concentration inside and outside the cell? What ion is low in concentrations both inside and outside the cell?

Answer 26

Potassium is high in concentration inside the cell. Sodium and chlorine are high in concentration outside the cell. Calcium is almost non existent within the cell and in low concentrations outside the cell.

Question 27

Approximate the resting membrane potential of a cell. Using your understanding of ion concentrations in and out the cell, describe how these charges are balanced.

Answer 27

The membrane potential is ~70 mV. Sodium and chlorine outside the cell balance each other's charge. Potassium inside the cell is balanced by nucleic acids, proteins, and cell metabolites.

Question 28

Describe how passive transport of charged solutes is affected by the electrochemical gradient.

Answer 28

The electrochemical gradient can be split into the concentration gradient and the electrical gradient. When these flow in the same direction, there's high diffusion. When they flow in opposite directions, there's low diffusion. The concentration gradient is more influential than the electrical gradient.

Question 29

Describe the homeostasis of blood sugar levels.

Answer 29

When there is high blood sugar levels, the pancreas releases insulin. This stimulates the conversion of glucose into glycogen in the liver as well as uptake of sugars in the blood by cells/tissues. This in turn lowers the blood sugar. When there is low blood sugar levels, glucagon is released by the pancreas. This stimulates the conversion of glycogen to glucose in the liver and raises blood sugar levels.

Question 30

What is the difference between symports and antiports?

Answer 30

Symports transport two particles in the same direction while antiports move two particles in opposite directions.

Question 31

How does the sodium/potassium pump function?

Answer 31

The sodium/potassium pump is a form of active transport. The process begins when 3 sodium ions bind to the protein. ATP is hydrolyzed, resulting in the protein phosphorylating and changing conformations. The sodium leaves and is replaced with 2 potassium ions. This binding results in the release of the phosphate and the pumps return to its original conformation, where potassium is then released.

Question 32

Why does calcium have a low cytosolic concentration?

Answer 32

Calcium has a low cytosolic concentration because it is most often used as a signal or trigger.

Question 33

How does calcium ATPase function?

Answer 33

When calcium binds to the protein, ATP hydrolyzes to cause a conformational change. the calcium is released on the other side of the membrane.

Question 34

What are the ratios for the following transporters: Na+/K+, Na+/Ca2+, Na+/glucose.

Answer 34

Na+/K+ ---> 3:2 Na+/Ca2+ --> 3:1 Na+/glucose --> 2:1

Question 35

Describe how glucose is brought from the intestinal lumen to the blood.

Answer 35

Glucose is first transported across the apical membrane from the intestinal lumen into the tight junction via Na+/glucose symporters. Glucose is then transported across the basolateral membrane into the blood via the GLUT2 transporter. Meanwhile, Na+/K+ pumps decrease the concentration of sodium in the tight junction in order to allow for further transport of glucose from the intestinal lumen to the blood.

Question 36

What types of pumps do plant cells use instead of sodium pumps?

Answer 36

Proton pumps and light-driven pumps

Question 37

How do ion channels regulate the flow of ions?

Answer 37

Ion channels can open, close, and inactivate in response to certain stimuli.

Question 38

Name and describe three types of stimuli that can open ion channels.

Answer 38

Voltage gated ion channels are controlled by the membrane potential. Ligand gated ion channels are controlled by the binding of molecules. Mechanical ion channels are controlled by mechanical forces.

Question 39

This is the only card on ion channels! Describe how ions result in the contraction of muscles.

Answer 39

A signal is propagated by neurons by the influx of Na+. This causes a depolarization event that opens the neighboring voltage gated ion channels to allow more Na+ to enter the axon. The voltage gated ion channels inactivates, resulting in unidirectional movement. After a short period, K+ leaves the axon to repolarize and restore the membrane potential. The conformation then changes to closed in order to allow more signals to be sent. When the signal reaches the axon terminal in the synaptic cleft, Ca2+ rushes into the terminal through voltage gated ion channels. This causes the exocytosis of acetylcholine into the synaptic cleft. Acetylcholine binds to the acetylcholine receptors and allows Na+ to travel across the sarcolemma into the postsynaptic cell until another depolarizing event occurs. An enzyme is released to degrade acetylcholine and the signal is propagated across the sarcolemma and down T tubules. Voltage gated ion channels in the T tubule open due to the depolarization and release Ca2+. This channel is tethered to a Ca2+ release channel in the sarcoplasmic reticulum to release more Ca2+. The calcium binds to troponin on actin, causing a conformational change of tropomyosin, and reveals the myosin binding sites on actin. Myosin then goes through a cycle of phosphorylation and dephosphorylation to "walk" on actin. Many of these myosin are undergoing the same process and allows for large scale muscle contractions.

Question 40

What drug can hinder the Na+/K+ pump/render the pump non-functional?

Answer 40

Ouabain is a drug that results in non-functional Na+/K+ pumps.

Question 41

What cytoskeletal filament provides tensile strength to cells? What happens to individual cells when this filament isn't present? What happens to tissues when this filament isn't present?

Answer 41

The intermediate filament provides tensile strength to the cell. Individual cells will rupture and tissues will tear apart without the presence of intermediate filaments. Desmosomes normally connect intermediate filaments, but there isn't enough strength to prevent them from pulling apart.

Question 42

How are intermediate filaments structured from monomers to polymers? What is unique about the structure of this filament when compared to microtubules and actin?

Answer 42

Intermediate filaments are oriented in a rope-like structure. Intermediate filaments are non polar. The ends are unstructured, so they are able to interact with other cytoskeletal structures.

Question 43

What is the role of plectin in relation to filaments?

Answer 43

Plectin is able to crosslink filaments. For example, actin can be bound to intermediate filaments and the connection between intermediate filaments and desmosomes are strengthened.

Question 44

What important organelle do intermediate filaments form a net-like network around? What is this called?

Answer 44

Intermediate filaments form the nuclear lamina around the nucleus.

Question 45

How does phosphorylation of intermediate filaments play a role in mitosis? What enzymes are involved?

Answer 45

When intermediate filaments in the nuclear lamina are phosphorylated by kinases, the heads are moved apart from each other. This weakens the structure to free chromosomes for mitosis. Lamins are dephosphorylated by phosphatase to form a stronger nuclear lamina.

Question 46

How are microtubules grown? Where do they start and what end are monomers added?

Answer 46

Microtubules are grown on the nucleation site of centrosomes. Alpha and beta tubulin adds to the tube-like structure onto the + end (which has nothing to do with charge).

Question 47

What does dynamic instability mean for microtubules? Describe this in the context of microtubule growth.

Answer 47

Dynamic instability is the rapid polymerization and depolymerization of microtubules. The process is driven by ATP hydrolysis. There is a GTP cap on the ends of the microtubules that assist with growth because it has stronger bonds and are more tightly packed. When hydrolysis of GTP dimers to GDP is faster than the addition of GTP dimers, then the GTP cap is eventually lost and the filament peels away.

Question 48

How are microtubules stabilized?

Answer 48

Microtubules are grown in many different directions in an exploratory manner, and occasionally, the filament will become stabilized by a capping protein that prevents depolymerization.

Question 49

How are centrosomes beneficial to microtubules growth?

Answer 49

Centrosomes are useful for a nucleation site. The initial growth of microtubules is highly unfavorable, with growth after being much more rapid, so it is useful to have an additional structure aid in the beginning stage.

Question 50

What are three functions that microtubules carry out/are a part of?

Answer 50

Microtubules act as transport tracks within the cell because they are polar, they are used as mitotic spindles, they provide the main structure for cilia and flagella.

Question 51

What do drugs that inhibit the polymerization of microtubules have in common? Talk about the three examples.

Answer 51

All three of this drugs prevent/hinder polymerization of microtubules by targeting microtubules. Colchicine binds to free floating monomers to prevent growth. Taxol and vinblastine bind to the tubulin to prevent monomers from binding to the filament. These structures can be used as a cancer treatment because they can prevent microtubules from pulling chromosomes to proliferate as well as triggering cell death.

Question 52

How does the polarity of microtubules influence cell asymmetry?

Answer 52

Microtubules have two types of transport proteins, kinesins and dyneins. Kinesins move towards the + end while dyneins move towards the - end. They both carry different cargo towards different sections of the cell to maintain symmetry.

Question 53

Describe the process by which kinesin, dyneins, and myosins travel across filaments.

Answer 53

The globular heads have ADP bound to them. One head binds to the filament and ADP is released, followed by ATP binding. This causes the other head to be thrown forward. ATP is hydrolyzed and the head is dephosphorylated to release the head while the other head binds to the filament.

Question 54

What proteins are present on the nuclear membrane to hold structures close to it.

Answer 54

SUN and CASH proteins are connected within the nuclear membrane to hold structures like centrosomes, intermediate filaments, and actin close to it. SUN proteins stick out the nucleus face while KASH proteins stick out the cytosolic face.

Question 55

How do cilia and flagella move?

Answer 55

Cilia and flagella have microtubules in the structure. As a result of dyneins moving towards the - end of microtubules, movement is generated.

Question 56

How is actin similar in functionality to microtubules and intermediate filaments?

Answer 56

Actin is similar to microtubules and filaments in the sense that all of them provide support to the cell. They also all have the capability to assemble and disassemble (but dynamic instability is reminiscent of microtubules). Like microtubules, actin is polar and can act as transport tracks.

Question 57

What functions are unique to actin when compared to other filaments?

Answer 57

Actin is involved with cell motility, phagocytosis, and muscle contraction.

Question 58

What's the process of phagocytosis in dendritic cells? What process do these cells take to reach the lymph node?

Answer 58

Bacteria release a signal that influences the cortical actin of the cell. This causes the cell to chase after the bacteria by crawling. The cell then consumes the bacteria via endocytosis. The phagosome is transported to the lysosome for digestion via motor proteins on microtubules. The dendritic cell expresses the receptors of the bacteria in order to inform lymphosomes to produce antigens that will target these bacteria. Cells crawl and roll in the blood until it reaches the lymph node.

Question 59

Describe actin growth and structure.

Answer 59

Actin has both a + and - end, where actin monomers can add to either side. Typically, the + end polymerizes while the - end depolymerizes. This is because the + side adds ATP bound actin, which has stronger bonds than the ADP bound actin on the - end. Hydrolysis of the ATP bound actin to ADP weakens the bonds of the actin and results in depolymerization.

Question 60

What are four drugs that affect actin polymerization and how do they function?

Answer 60

Cytochalasin binds to the + end of the actin in order to prevent polymerization. Latrunculin binds to the free floating monomers to prevent polymerization. Phalloidin stabilizes the actin against depolymerization. Jasplakinolide promotes the polymerization of actin.

Question 61

Describe two proteins that bind to actin. What are their effects?

Answer 61

Thymosin binds to actin to prevent polymerization. Formins/ARPs (actin-related proteins) promote actin polymerization.

Question 62

What are the major steps in cell crawling?

Answer 62

Cells begin by receiving a signal to determine the direction they will crawl. Actin is polymerized by formins and ARPs in oder to extend the lamellipodium. When this extends, integrins stick to the surface creating tension in the cell. Myosin motor proteins near the rear of the cell move along actin filaments to move the cell forward.

Question 63

How do capping proteins and formins/ARPs (actin-related proteins) work together to extend the lamellipodium?

Answer 63

Capping proteins stop the polymerization of actin. Formins and ARPs act as nucleation sites that induce growth outwards.

Question 64

How do integrins anchor the lamellipodium for cell contraction?

Answer 64

Integrins are connect the cortical actin with the extracellular matrix.

Question 65

What determines the direction a cell travels? What signals and proteins are involved?

Answer 65

Cells receive extracellular signals to determine the growth of actin and thus cell movement. These signals are received by monomeric GTPases that can rearrange the actin by going from the active GTP-bound state to the inactive GDP-bound state. When Rho GTPase is activated, actin is bundled into stress fibers. Activated Rac GTPase causes lamellipodia formation. Activated Cdc42 GTPase causes filopodia growth.

Question 66

Where is actin concentrated?

Answer 66

Actin is concentrated in the cell cortex and interacts with the spectrin lattice.

Question 67

What is the difference between myosin-1 and myosin-2?

Answer 67

Myosin-1 only has 1 globular head while myosin-2 has 2 globular heads. Myosin-1 is involved in vesicle movements towards the + end as well as cell shape changes. Myosin-2 is involved in muscle contraction.

Question 68

What are three types of cytoplasmic intermediate filaments? What types of cells are these located in?

Answer 68

Keratin filaments are located in epithelial cells. Vimentin filaments are located in connective tissue, muscle, and glial cells. Neurofilaments are located neurons.

Question 69

What are the functional differences between the primary and secondary cell wall?

Answer 69

The primary cell wall is present in earlier stages of life and are less rigid to allow for the growth and expansion of the cell. The secondary cell wall is later produced and is much more rigid because the cell is no longer growing.

Question 70

What is present in plant cells that provides tensile strength and resists compression? How are these organizes in the cell wall?

Answer 70

Plant cell walls contain cellulose that creates a grid like structure of interwoven rods. In the primary wall, pectin and hemicellulose provide looser support for the wall. Throughout the wall, polysaccharides and proteins provide additional support.

Question 71

Describe how cellulose is produced.

Answer 71

Along the plasma membrane, microtubules are bound and act as tracks for organized growth. Cellulose synthase complexes add to preexisting walls in the extracellular space.

Question 72

What are three types of macromolecules that make up the extracellular matrix? Name the molecules that make up each category.

Answer 72

Structural proteins: collagen, elastin, fibrillin Specialization proteins: laminin, fibronectin Proteoglycans: hyaluronan

Question 73

Name the four main functions of the extracellular matrix.

Answer 73

Mechanical support of organs and tissues, regulation of cellular behavior, support and anchorage for cells, exchange of molecules between cells

Question 74

What is the main provider of tensile strength in animal cells? How do connective tissues demonstrate different characteristics?

Answer 74

Collagen is the main source of tensile strength. Based on the type and amount of collagen, as well as other interwoven molecules, the characteristics of the tissues change.

Question 75

How does collagen change with age?

Answer 75

Older tissues will have less collagen and will therefore experience things such as wrinkles.

Question 76

What is the difference between fibroblasts and osteoblasts?

Answer 76

Fibroblasts are located in skin, tendons, etc. While osteoblasts are only present in bones.

Question 77

Describe the process of collagen synthesis.

Answer 77

Collage synthesis begins in the ER and is then transported to the golgi for exocytosis. When the collagen leaves the cell, fibroblasts/osteoblasts organize the collagen into cable-like structures.

Question 78

How is cell choking by collagen avoided?

Answer 78

Collagen is unraveled, loose ends, so that if it is released into the cytoplasm, they can unwind. Once the collagen leaves the cell, peptidases cleave the ends to stabilize the structure.

Question 79

What is responsible for the breakdown of collagen? Why does this need to be broken down?

Answer 79

Matrix proteases break down collagen and other extracellular proteins for tissue growth/repair.

Question 80

What function does integrin aid in? How does it interact with collagen and fibronectin to achieve this?

Answer 80

Integrin plays a role in cell crawling. When it is activated, integrin grabs hold of collagen, through the intermediate fibronectin, for anchorage.

Question 81

What are GAGs? What structure are they apart of and what about the chain results in its core function?

Answer 81

GAGs are glycosaminoglycans. They bind to core proteins to form proteoglycans. The polysaccharide chain is hydrophillic and draws water towards it.

Question 82

How does hyaluronan affect cancer?

Answer 82

Hyaluronan, when in high concentrations, draws large amounts of water into the matrix, compressing the blood vessels. This hinders the ability of immune cells and anti-cancer treatments from traveling to eliminate cancer cells.

Question 83

What are some functions of the epithelial sheet?

Answer 83

The epithelial sheet acts as a protectant, it secretes specific hormones, receives signals, and accepts/releases molecules.

Question 84

Describe the basal lamina.

Answer 84

The basal lamina is composed of IV collagen as well as laminin. Integrins on the bottom of the cell bind to laminin and connect with the basal lamina.

Question 85

What role do claudins hold for cell junctions?

Answer 85

Claudins create the tight junctions.

Question 86

What are the different types of junctions?

Answer 86

Trisha Ate Doritos, Guac, and Hot dogs!!! Tight junctions (claudins), adherens (cadherins with actin), desmosomes (cadherins with IFs), gap junctions (open and close with connexons), and hemidesmosomes (IFs to basal lamina).

Question 87

What do plant cells have in order to allow for the diffusion of molecules across the cell wall?

Answer 87

Plasmodesmata