Biology Midterm 3 Study Guide

Adaptive Receptors/Surface Proteins

B cell receptor, T cell receptor, antibodies

Innate Cell Types

Neutrophil, dendritic cell, mast cell, phagocytic cells (or Professional Antigen Presenting Cells - APCs)

Adaptive Cell Types

T cells and B cells

Innate Receptors/Surface Proteins

Toll-like receptor, MHC I and II

Which interactions below are incorrectly paired? Select all that apply: a. B cell, B cell receptor -- T cell receptor, T cell b. Virally-infected somatic (body) cell, MHC I - B cell receptor, B cell c. Professional antigen-presenting cell, extracellular bacterial epitope on MHC II - T cell receptor, Cytotoxic T cell d. Somatic cell, MHC I -- T cell receptor, Cytotoxic T cell e. B cell, MHC II with extracellular bacterial epitope - T cell receptor, Helper T cell

a. B cell, B cell receptor -- T cell receptor, T cell b. Virally-infected somatic (body) cell, MHC I - B cell receptor, B cell c. Professional antigen-presenting cell, extracellular bacterial epitope on MHC II - T cell receptor, Cytotoxic T cell

Meristems located throughout the plant contribute to overall plant growth. In terms of these tissues, what below is TRUE? a. Cells further from the apical meristem are 'older'/resulted from an earlier division event than those closer to the meristem b. Xylem results from cell division of the cork cambium, a primary meristem. c. The vascular cambium promotes primary/vertical growth, while the apical meristems directly contribute to secondary/thickening growth d. Lateral meristem cells differentiate into branches e. A and B

a. Cells further from the apical meristem are 'older'/resulted from an earlier division event than those closer to the meristem

Which of the following statements about the movement of potassium ions through open stomata is true? a. K+ enters guard cells, water follows, and the cells become turgid. b. K+ leaves guard cells through plasmodesmata and they become less turgid. c. K+ enters guard cells and they become less turgid. d. K+ leaves guard cells and they become turgid. e. K+ reaches equilibrium in guard cells and their surroundings.

a. K+ enters guard cells, water follows, and the cells become turgid.

Symplastic loading of phloem a. Requires plasmodesmata to deliver sugar from mesophyll (photosynthetic cells) to companion cells and phloem. b. Occurs at sink tissues. c. Entails that sugar entry into the companion cell occurs by active transport. d. Is the only method by which photosynthates and hormones can enter into the phloem from source tissues. e. Ensures a positive water potential in the companion cell compared to the xylem nearby.

a. Requires plasmodesmata to deliver sugar from mesophyll (photosynthetic cells) to companion cells and phloem.

Pathogens can present/comprise more than 1 antigen to the immune system. a. True b. False

a. True

Toll-Like Receptors are pre-formed receptors involved in the recognition of conserved Pathogen Associated Molecular Patterns (PAMPs). These TLRs can be found on many eukaryotic cell types and activate a phosphorylation cascade of many kinases. These kinases eventually phosphorylate NF-kB, a transcription factor, that upregulates (increases) defense gene expression. a. True b. False

a. True

Plant cell wall, made largely out of structural carbohydrates, are dynamic in that they change over time (think how the cellulose microfibrils shift as the cells expand). If the cell walls are too rigid, expansion is inhibited; therefore, plants have enzymes that they exocytose into the apoplastic space (space beyond the plasma membrane) - remember apoplast vs. symplast distinction. One family of enzymes are the expansins. As the name implies, they promote expansion of the plant cell by acting kinda like door jams between cellulose microfibrils themselves (blocking H-bonding) as well as the cross-linking carbohydrates (like hemicellulose and pectin). Below in panel B is a western blot of expansins from various species (numbers refer to different plants - see the caption). Ignore the high molecular weight bands (this is due to the antibodies cross-reacting with another protein). Panel A is the protein gel stained by a protein dye called coomasie blue that mirrors the blot (in terms of protein loading). Given this data, what can you conclude? a. Only lane 8/pear, possesses expansins in their cell wall b. Lane 5/kiwifruit has the highest amount of expansin protein in their cell walls c. Lane 1/tomato and Lane 8/pear appear to have expansins that are larger/higher molecular weight than the other plant species d. This blot must utilize multiple different antibodies, because the expansin proteins from each of the species has significantly different epitopes/antigens and protein structure e. The protein makeup that comprise the apoplastic space/cell wall of these plants appears to be very uniform

c. Lane 1/tomato and Lane 8/pear appear to have expansins that are larger/higher molecular weight than the other plant species

Comparing primary and secondary cell walls... a. The primary cell wall is, in part, comprised of cellulose microfibrils, while the secondary cell wall does not contain cellulose b. The secondary cell wall is produced before the primary cell wall in woody tissues and plants. c. Microfibrils that comprise the primary cell wall are crosslinked by pectins and hemicellulose while secondary cell walls are also impregnated with lignins d. <diagram of plant cell> e. All answers are true.

c. Microfibrils that comprise the primary cell wall are crosslinked by pectins and hemicellulose while secondary cell walls are also impregnated with lignins

Considering the vascular tissue of green photosynthetic plants a. Xylem is comprised of sieve tube elements b. Phloem is comprised of dead cells called vessel elements c. Movement of phloem sap, termed bulk flow, is mainly due to differences in positive pressure potential (PsiP) between source and sink d. Xylem are kept alive by companion cells that are linked to these vascular cells by plasmodesmata e. None of the above are true

c. Movement of phloem sap, termed bulk flow, is mainly due to differences in positive pressure potential (PsiP) between source and sink

A college student taking a 24-hour bus trip to her summer internship is surrounded by people sniffling and sneezing. She cannot escape the pathogen involved, but she does not share the others' symptoms during her trip. Which of the following is not involved in her resistance to the illness? a. Mucus b. Lysozymes c. T cells d. The innate defense provided by her skin e. Phagocytosis

c. T cells

Positive pressure (Psi P) potential within a cell is most likely to result in a. a decrease in the diffusion of ions into that cell. b. an increase in the diffusion of ions out of that cell. c. a decrease in the uptake of water by that cell. d. an increase in the uptake of water by that cell. e. an increase in uptake of both water and ions by that cell.

c. a decrease in the uptake of water by that cell.

At a source, sucrose moves into the phloem in the apoplastic pathway by a. Tension within sieve tubes produced by sucrose unloading at sink cells b. osmosis c. secondary active transport into companion cells (using the proton gradient and symport of the sugar) d. strictly symplastic movement from adjacent mesophyll cells e. A and D

c. secondary active transport into companion cells (using the proton gradient and symport of the sugar)

An epithelial root hair plant cell has a turgor/pressure potential of 0.5 MPa and an solute/osmotic potential of -0.75. Therefore... a. the cell has a water potential of -1.25 MPa b. the cell has a water potential of 1.25 MPa c. the cell has a water potential of -0.25 d. Will take up water from the surrounding soil if the soil water potential is -1.0 MPa e. C and D

c. the cell has a water potential of -0.25

T cells are stimulated by the binding of antigen‒MHC complex to the T cells' receptors. The outcome of this interaction (i.e., whether it leads to formation of antibodies or to the death of the cell with the antigen‒MHC complex) depends on a. which class of MHC protein is involved. b. which type of T cell is involved. c. whether perforin is produced. d. All of the above e. None of the above

d. All of the above

The humoral and cellular immune responses (both part of the adaptive immune system) depend on communicating and interacting with each other as well as other cell types. Given these interactions, what is the most likely pathway/interaction for people infected with a bacterial infection in the submucosa of their GI tract? a. During the activation stage, professional antigen presenting cells (APCs: like B cells, macrophages, dendritic cells) will phagocytose, digest and present epitopes of the antigen on it's cell surface by MHC II. Release of cytokines by the APC will recruit and activate circulating TH cells to proliferate. b. During the effector stage, the activated TH cells will bind to the appropriate activated B cell through interaction of the MHC II molecule and the T cell receptor. The release of cytokines will signal to the B cell to differentiate into plasma and memory B cells. Resulting in the production of the appropriate antibodies to the bacterial pathogen. c. Given that the infection is proximal to the GI tract, the patient will exhibit raised levels of IgA antibodies to the bacterial pathogen d. All of the above e. B and C only.

d. All of the above

Which of the following factors has a direct impact on the orientation and expansion of plant cells a. Initial cellulose microfibril orientation b. Lignin deposition c. Turgor pressure d. All of the options influence cell growth

d. All of the options influence cell growth

Which of the following statements about MHC molecules is FALSE? a. MHC proteins are cell membrane glycoproteins. b. The major role of MHC proteins is to present antigens to T cell receptors. c. Class I MHC proteins are found on the surface of every nucleated cell. d. Class II MHC molecules are found on the surface of T cells. e. MHC proteins are used by the immune system to identify cells as "self" versus "nonself."

d. Class II MHC molecules are found on the surface of T cells.

When sucrose is added to phloem cells at a source via the apoplastic pathway of loading a. water follows by osmosis and the hydrostatic pressure pushes the sucrose toward a sink b. water follows primarily by mass/bulk flow through abundant plasmodesmatal connections to adjacent mesophyll cells c. most of the sugar is loaded directly into the sieve tube elements, bypassing the companion cell d. active transport of sucrose molecules from a leaf's apoplast to its phloem requires cotransport with protons e. A and D

e. A and D

The western blot below detects a sucrose channel protein called LeSUT (tomato sucrose transporter) found in the plasma membrane of companion cells. Assuming equal loading of total protein in all lanes. a. The sucrose transporter is approximately 55 kilodaltons in size b. The sucrose transporter is in lowest amount in the dark, suggesting this protein's accumulation depends on light levels c. The same primary antibody is used to detect the transporter in every lane d. It is likely that this plant likely uses apoplastic loading of photosynthate/sugars into the companion cell e. All of the above are true

e. All of the above are true

Below is an experiment to see how the plant cell wall (remember, this is made up of cellulose microfibrils, cross-linking polysaccharides, and some proteins - like expansins!) is synthesized/organized. The authors treat plant cells with oryzalin, a microtubule disrupting agent that inhibits microtubule polymerization, and assess the impact on cellulose and xylan (two polysaccharides in the plant cell wall). The mock means the plants have been sprayed with the same fluid that oryzalin is dissolved in, and acts as a control. You can conclude (select all that apply)... a. Mock-treated plant cells appear to have ring-like microtubule structures that run the circumference of the plant cell plasma membrane b. cellulose microfibrils and xylan molecules seem to overlap, and maybe interact with each other c. The primary antibody used to detect xylan is the same antibody used to detect cellulose d. Treatment of oryzalin, disrupting microtubules, also seems to impair proper orientation/organization of cellulose and xylan e. Cellulose and xylan deposition do not appear to depend on proper polymerization of microtubules

answer choices a-e; all apply

Which immune protein(s) below is/are correctly described? Select all that apply: a. Antibodies: bind to specific epitopes, or molecular patterns, present on antigens. Antibodies comprise the B cell receptor. Secreted antibodies produced by plasma cells enable opsonization and agglutination b. Major histocompatibility complex (MHC): MHC II is present on professional antigen presenting cells (APCs) and present antigens to the T cell receptor (TCR) of T helper cells. MHC I is present on most nucleated cells and can present self-antigens as well as internal pathogen antigens to the T cell receptor. c. T cell receptor (TCR): membrane receptors on T cells that enable these lymphocytes to bind to epitopes presented by MHC molecules. Involved in the activation of T cells. d. Complement: innate immune system protein. Cascade of activation that enables the binding to invading microorganisms and promotes opsonization (phagocytosis) by phagocytic cells. e. Cytokines: small signaling proteins produced by various cell types. Involved in the activation and proliferation of B and T lymphocytes

answer choices a-e; all apply

In comparing the B and T cell receptors, which of the following statements is FALSE? a. B and T cell receptors can recognize the same antigens. This would be required for the humoral immune responses to respond to pathogenic challenge. b. B and T cell receptors directly interact with each other when bound to the appropriate antigenic epitope. c. B and T cell receptors comprise conserved and variable regions and are bound to the lymphocyte cell surface d. The T cell receptor binds to MHC class I or II molecules depending on the type of T cell. The B cell receptor binds to a specific epitope presented by the antigen e. All of the above are true

b. B and T cell receptors directly interact with each other when bound to the appropriate antigenic epitope.

Movement of mineral ions in the soil into a root's vascular tissue (xylem) takes place by apoplastic transport past the Casparian strip of the endodermis a. True b. False

b. False

Stomata, comprised of pairs of guard cells, open in response to... a. ABA (hormone) b. Low CO2 c. Low light d. Decreased water within the plant e. Decreased pressure potential in the guard cells

b. Low CO2

Which of the following processes contributes the most to generating the negative water potential in a leaf? a. The pressure placed on the leaf by the cuticle (the waxy film that protects the epidermal tissues of a leaf) b. The evaporation of water from mesophyll cells c. The movement of water into the leaf by root pressure d. The increased K+ pumped out of guard cells e. The movement of water from the veins into the leaf

b. The evaporation of water from mesophyll cells

Plants and plant cells are unique as there are defined age gradients at each level that can be observed! In terms of the plant cell wall, what below is FALSE? a. the primary cell wall is older and located outside of the plant secondary wall b. is the site of a major plant compartment of the plant body, the symplast c. largely consists of a meshwork of hydrophilic cellulose, hemicellulose and pectin in a well-hydrated (water-rich) environment d. Have a lower pH than the cytoplasm e. None of the above are false

b. is the site of a major plant compartment of the plant body, the symplast

Which statement regarding the primary cell walls of plants is false? a. They contain pectins. b. They contain hemicellulose. c. The primary cell walls of two adjacent cells are separated by the middle lamella. d. They contain high concentrations of hydrophobic lignins.

d. They contain high concentrations of hydrophobic lignins.

A plant cell placed in distilled water will a. expand until the solute potential reaches that of the distilled water. b. become more turgid until the solute potential reaches that of the distilled water c. become less turgid until the solute potential reaches that of the distilled water d. become more turgid until the pressure potential of the cell reaches its solute potential e. become less turgid until the pressure potential of the cell reaches the outside water potential

d. become more turgid until the pressure potential of the cell reaches its solute potential

Consider the diagram below to answer the following question. The Transpiration Tension Cohesion mechanism explains how water is moved through the plant from the roots to the leaf tissue. What below is incorrect in regards to this mechanism? It is important to know how water potential is driving all of this process. a. The leaves, through the process of transpiration, lose water that surrounds the mesophyll cells in the apoplastic space to outside of the leaf. This reduction of water surrounding each cell (in the cell wall) increases the negative pressure potential (Psi P) creating negative tension. (see lecture slides and data tables). b. The negative tension created by the mesophyll cells is greater than that of the xylem, the water-conducting vascular tissue. This explains how leaves stay hydrated (and replaces the water lost due to transpiration). c. The removal of water from the xylem 'veins' in turn establishes tension on the entire column of water contained in the xylem (through the veins, through the shoot, to the root). d. Due to the polar nature of water, which allows for hydrogen bonding between these molecules (resulting in cohesion), the water column is maintained (no breakage). Thus, as leaves transpire they create negative tension that draws water into them. This negative potential in turn draws water up the xylem to replace the respired water. e. All of the above are true and explain the mechanism.

e. All of the above are true and explain the mechanism.

What molecule/cell is not involved in the generation of the inflammatory response in response to a bacteria-covered splinter puncturing the skin? a. Mast cells b. Prostaglandins (which we didn't really talk about) and cytokines c. Neutrophils d. Complement proteins e. All of the above contribute to generating the inflammatory response

e. All of the above contribute to generating the inflammatory response

The transpiration stream... a. Is bidirectional from roots to shoots or shoots to roots. b. Cannot be slowed by altering the size of cellulose beads in the pits connecting xylem vessels/tracheids c. Is responsible for the transport of photosynthetically produced sugars d. Carries water and mineral ions from source to sink. e. Movement of the fluid relies on negative water potential and negative pressure potential.

e. Movement of the fluid relies on negative water potential and negative pressure potential.

What below does NOT influence plant growth and development? a. Plant cell expansion, perpendicular to cellulose microfibril deposition, is due to positive 'turgor' pressure within the plant cell b. Production of woody secondary cell walls that halt cell expansion c. The coordinated activity and effects of multiple plant hormones d. Rapid cell division and differentiation into dermal, ground, or vascular tissues e. The availability of carbon in the soil used in the production of macromolecules like carbohydrates or protein

e. The availability of carbon in the soil used in the production of macromolecules like carbohydrates or protein