Biology: cell

CELL QUESTION 1983: L. PETERSON/AP BIOLOGY

Describe the fluid-mosaic model of a plasma membrane. Discuss the role

of the membrane in the movement of materials through by each of the

following processes.

a. Active Transport

b. Passive Transport

STANDARDS:

FLUID-MOSAIC MODEL: Max. = 9 points

__ Singer/Nicholson or "differs from" Davson/Danielli

__ Dynamic

__ Phospholipid Bilayer

__ Hydrophilic heads/hydrophobic tails and explanation

__ Polar/Nonpolar

__ Proteins - intrinsic/extrinsic

__ Permeases (active + passive)

__ Pores or apertures

__ Functional "R" Groups

__ Glycoproteins or carbohydrates (recognition)

__ Diagrams appropriately used with explanation

__ Selectivity

TRANSPORT Max = 9 points

PASSIVE TRANSPORT:

__ Definition of Diffusion

__ Osmosis

__ Size of molecule / polarity

__ Facilitated Diffusion

__ Function of pores

ACTIVE TRANSPORT:

__ Definition

__ ATP

__ ATPase

__ Na+/K+ Pump

__ Substances diffuse in-need transport out

__ Carrier molecules and specificity

CELL QUESTION 1984: L. PETERSON/AP BIOLOGY

Describe the structure of a generalized eukaryotic plant cell. Indicate the ways

in which a nonphotosynthetic prokaryotic cell would differ in structure from

this generalized eukaryotic plant cell.

STANDARDS:

STRUCTURE, as part of the eukaryotic cell: DESCRIPTION:

(1/2 point each) (1 point each)

__ Cell Wall __ Cellulose

__ Cell Membrane __ Protein/phospholipid or

phospholipid bilayer

__ Cytoplasm __ Fluid with dissolved substances

__ Vacuole __ Protein/phospholipid or water

__ Mitochondria __ Cristae, folding convolutions

__ Ribosomes __ Two Subunits

__ Golgi Bodies __ Phospholipid/protein, cisternae, vesicles

__ Chloroplasts __ Stroma, grana, thylakoids

__ Lysosomes __ Phospholipid/protein membrane

or digestive enzyme

__ Nucleus __ Double nuclear membrane or

envelope

__ Nucleolus __ RNA present, fibrillar

__ Chromosome __ Double strand, DNA and Protein

__ Plasmodesmata __ Cytoplasmic bridge

__ Peroxisomes __ Membrane Bound

__ Flagella __ 9 + 2

__ Microtubules, microfilaments __ Tubulin protein/actin protein

MAX. = 4 points MAX. = 7 points

TOTAL MAXIMUM = 10 points

II. STRUCTURE COMPARISONS/DIFFERENCES of a

simple cell and a complex cell.

(2 points each pair / structure and comparison)

__ Cell Wall __ No cellulose; murein present

__ Cell Membrane __ No cholesterol

__ Membrane-bound organelles absent __ Name one organelle

__ OR AT LEAST 2: vacuole, mitochondria, __ Absent

nucleus, E.R., lysosome, peroxisome,

chloroplast

__ AT LEAST 2: microtubules, microfilaments, __ Absent

plasmodesmata

__ Ribosomes __ Smaller, few, free floating

__ Nuclear membrane __ Absent

__ Genetic material __ Single, no protein, circular,

plasmids

__ Flagella __ No 9 + 2

BONUS: Elaboration: evolution, size, two additional structures and comparisons for

each structure = one point each

MAXIMUM = 10 points in Section II.

CELL QUESTION 1987: L. PETERSON/AP BIOLOGY

Discuss the process of cell division in animals. Include a description of

mitosis and cytokinesis, and of the other phases of the cell cyle.

Do not include meiosis.

STANDARDS:

PART I. DESCRIPTION OF MITOSIS IN ANIMAL CELLS: Max. = 7 points

General

__ division of nucleus

__ daughter cells acquire the same number and kinds of chromosomes as

in the mother cell

__ process for growth or repair or asexual reproduction

__ list phases in correct order (P,M,A.T)

Prophase (one point each / max. 2)

__ centrioles move apart

__ chromosomes condense

__ nucleolus is no longer visible

__ nuclear envelope disappears

__ asters and spindle form

Metaphase

__ sister chromatids (chromosomes) are in a line at the midpoint of the spindle

Anaphase (one point each / max. 2)

__ centromeres uncouple (split)

__ chromosomes move to opposite poles

__ microtubules involved in the push/pull movement

Telophase (one point each / max. 2)

__ reverse of prophase

__ nuclear envelope reforms

__ nucleolus reappears

__ chromosomes become diffuse

__ spindle and aster disappear

__ centrioles are replicated

Points less frequently mentioned:

__ function of centrioles

__ definition of kinetochores

__ description of polar microtubules and kinetochore microtubules

__ definition of chromatids

*In order to obtain a score of 10, there must be points in all three sections.

If only two sections are written the maximum is 9.

PART II. CYTOKINESIS:

__ division of cytoplasm

__ formation of a cleavage furrow

__ occurrence of cytokinesis in the cell cycle

Points less frequently mentioned:

__ function of cytokinesis

__ dense belt of actin and myosin microfilaments

__ purse-string mechanism

__ furrow occurs at location of equatorial plane

__ cytochalasin blocks activity of microfilaments (stops cytokinesis)

PART III. OTHER PHASES OF THE CELL CYCLE (INTERPHASE):

General

__ list G1, S, and G2 in correct order

__ G1, S, and G2 are part of interphase

__ chromosomes appear as a mass of chromatin material

__ synthesis of cell organelles or cell doubles in size

__ restriction (decision) point or point of no return

__ synthesis or replication of DNA or DNA replication occurs during interphase

__ synthesis of microtubular assembly, or prepare for mitosis

Points less frequently mentioned:

__ description of nucleosomes

__ times in each phase

__ growth factors

__ some cells do not go beyond G1

__ after cell passes "S", mitosis will usually continue

__ colchicine prevents the formation of microtubules

CELL QUESTION 1992: L. PETERSON/AP BIOLOGY

A laboratory assistant prepared solutions of 0.8 M, 0.6 M, 0.4 M, and 0.2 M sucrose,

but forgot to label them. After realizing the error, the assistant randomly labeled the

flasks containing these four unknown solutions as flask A, flask B, flask C, and flask D.

Design an experiment, based on the principles of diffusion and osmosis, that the

assistant could use to determine which of the flasks contains each of the four unknown

solutions.

Include in your answer

(a) a description of how you would set up and perform the experiment;

(b) the results you would expect from your experiment;

and

(Be sure to clearly state the principles addressed in your discussion.)

STANDARDS:

A. EXPERIMENTAL SET-UP (1 point each)

___ 1. Experiment based on concentration gradient

___ 2. Experiment based on semipermeable membrane

(dialysis tubing, thistle tubes, plant or animal cells)

___ *3. Experimental set-up (design) adequate to produce measurable results

___ *4. (2 max) Experimental variables are eliminated

(mass, volume, time, temperature, tissue type, etc.)

___ *5. Experimental set-up is exemplary

(must include semipermeable membrane)

B. RESULTS ( 1 point each)

___ *1. Describes a measurable change

___ *2. Correctly correlates the observed changes with molarities of unknowns

C. APPLICATION OF PRINCIPLES TO RESULTS (1 point each)

___ *1. Correctly applies principles of diffusion and osmosis in the interpretation of

results

(a correct analysis)

___ 2. Demonstrates an understanding of the concept of water potential

(hydrostatic/turgor pressure) in analysis of results

D. PRINCIPLES (1 point each)

___ 1. Demonstrates an understanding, or gives a correct definition of diffusion

___ 2. Demonstrates an understanding, or gives a correct definition of osmosis

** (must include both water and semipermeable membrane)

___ 3. Demonstrates an understanding, or gives a correct definition of selective

permeability

___ 4. Describes how solute size and/or molar concentration (hypertonic/hypotonic) affect the process of diffusion through a membrane

_______________________

Max possible = 14

* No points if the lab will not work.

**Osmosis: the diffusion of water through a selectively (semi)permeable membrane in

the following directions:

-from higher water potential toward lower water potential

-from hypotonic (hypoosmotic) solution toward hypertonic (hyperosmotic) solution

-from higher water concentration toward lower water concentration

-from lower solute concentration toward higher solute concentration

-from region of lower osmotic pressure toward regions of higher osmotic pressure

-from region of higher osmotic potential toward region of lower osmotic potential

CELL QUESTION 1993: L. PETERSON/AP BIOLOGY

Membranes are important structural features of cells.

(a) Describe how membrane structure is related to the transport

of materials across a membrane.

(b) Describe the role of membranes in the synthesis of ATP in either

respiration or photosynthesis.

Membranes serve diverse functions in eukaryotic and prokaryotic cells. One

important role is to regulate the movement of materials into and out of cells.

The phospholipid bilayer structure (fluid mosaic model) with specific membrane

proteins accounts for the selective permeability of the membrane and passive

and active transport mechanisms. In addition, membranes in prokaryotes and in

the mitochondria and chloroplasts of eukaryotes facilitate the synthesis of ATP

through chemiosmosis.

PART A. (6 Maximum)

Membrane Structure (3 Internal Maximum)

__ Phospholipid structure - hydrophilic, hydrophobic, amphipathic

__ Phospholipid bilayer / fluid mosaic description

__ Proteins embedded in the membrane

__ Sterols embedded in the membrane

__ Well-labeled diagram may replace one of the above

Membrane Transport (3 Internal Maximum)

__ Use of the term "selectively permeable" or a good definition of

selective permeability or an explanation of the role of phospholipids

or proteins including nuclear pore proteins in determining selective

permeability

__ Description of the effect of size, charge, polarity, lipid solubility on

membrane permeability

Mechanisms + description related to structure:

__ Passive transport: diffusion / osmosis + reference to membrane gradient

__ Ion channel: transport as a mechanism for a change in permeability

__ Facilitated diffusion: description (symport, antiport, uniport)

__ Active transport: description

__ Exocytosis, endocytosis, phagocytosis, pinocytosis: description

(1 pt additional) A good example of one of the above mechanisms

PART B. Role of the Membrane in the Production of ATP in Photosynthesis or Respiration (6 Maximum)

Chemiosmosis:

__ Involved molecules are embedded in the membrane

__ Electron carriers are sequentially organized

__ The energy comes from the flow of electrons

__ H+ / Proton / pH gradient established

__ Movement through the membrane generates ATP

__ A specific protein makes ATP

RESPIRATION or PHOTOSYNTHESIS

__ Site is the mitochondrion __ Site is the chloroplast

__ Inner mitochondrial membrane __ Thylakoid / grana membranes

(cristae) are involved in eukaryotes are involved in eukaryotes

__ Folded membrane present __ Folded membrane present

__ Cell membrane is involved in __ Thylakoid / grana membranes

prokaryotes involved in prokaryotes

__ Correct direction of H+ flow __ Correct direction of H+ flow

CELL QUESTION 1994: L. PETERSON/AP BIOLOGY

Discuss how cellular structures, including the plasma membrane, specialized endoplasmic reticulum, cytoskeletal elements, and mitochondria, function together in the contraction of skeletal muscle cells.

To earn credit a student needed to demonstrate an understanding of basic cell anatomy and physiology as they relate specifically to the structure and function to muscle contraction. Standards were established to follow the cellular activities pertinent to muscle contraction from the neuromuscular junction, through contraction, and returning to the non-contractive state. Points were also awarded if the student included information from the neuromuscular junction, demonstrated an exceptional understanding of chronological information from the neuromuscular junction, demonstrated an exceptional understanding of chronological or spatial relationships, or included an elaboration of special features specific to the process of muscle contraction.

(2 pts) Neuromuscular junction

Action potential of neuron –> neurotransmitter

Concept of neurotransmitter

(1 pt) Idea of a sarcomere as a functional unit

(1 pt) Actin and Myosin in a sarcomere – (well labeled diagram w/text)

(2 pts) Plasma membrane / sarcolemma (no point for name alone)

Receptor sites for neurotransmitters

Change in permeability / Na+ K+

Action potential distributed / depolarization

T-tubules (continuous with specialized E.R.)

(2 pts) Specialized E.R. – Sarcoplasmic reticulum (no point for name alone)

T-tubule (only if not given above)

Ca++ release / Calcium is involved with muscle contraction

Change in permeability – release of Ca++

Ca++ recaptured into S.R. – contraction ends / active transport

(5 pts) Cytoskeletal Elements

Actin and myosin (linked to muscle function)

microfilaments / myofibrils / myofibrils

Actin – thin fiber (protein structure)

Troponin (Ca++ interaction exposes active sites)

Tropomyosin (is therefore unblocked)

Myosin – thick fiber (protein structure)

'clubs' – bridges – paddles for interaction with actin / ATP binding site

ATPase site / hydrolysis of ATP

Sliding Filament Concept

Z line as a protein which separates sarcomeres (needs strong linkage)

ATP functions to release mysoin heads from actin sites

(2 pts) Mitochondria

ATP production – cellular respiration

Number of mitochondria is higher in muscle cells due to...

Proximity within muscle fiber

Chemiosmosis – elegant elaboration of ATP production

(2 pts) Other – Rarely Mentioned:

Fast twitch / slow twitch (1 pt)

Elaboration (1 pt)

(FT) – glycogen and anaerobic

(ST) – oxidation of glycogen via TCA and thus aerobic

All or nothing response

Switches to anaerobic respiration after oxygen consumed / Myoglobin

Muscles can only contract

Rigor mortis

(showing that ATP functions in release rather than contractive phase)

Muscle cell is a muscle fiber or muscle cell is multinucleate

Glycogen storage (mitochondria functions)

Creatine phosphate - PO4 replacement

(1 pt) Synoptic synchronization - exceptional chronology or spatial relationships

Biology

Tuesday, July 12, 2011

cell

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