Cells & Membranes - WCS · Cells & Membranes How do the structures of cells and biological...

Cells & MembranesHow do the structures of cells and biological membranes enable

the functions that are required to sustain life?

Essential Understandings2.A.3 Organisms must exchange matter with the environment to grow, reproduce and maintain

organization.2.B.1 Cell membranes are selectively permeable due to their structure.2.B.2 Growth and dynamic homeostasis are maintained by the constant movement of molecules

across membranes.2.B.3 Eukaryotic cells maintain internal membranes that partition the cell into specialized

regions.4.A.2 The structure and function of subcellular components, and their interactions, provide

essential cellular processes.4.B.2 Cooperative interactions within organisms promote efficiency in the use of energy and

matter.

Major Connections:1.B.1b Organisms share many conserved core processes and features that evolved and are

widely distributed among organisms today: Structural evidence supports the relatedness of all eukaryotes.

3.D.1 Cell communication processes share common features that reflect a shared evolutionary history.

3.D.2 Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling.

Textbook ReferencesChapter 4 and 5

LaboratoriesDiffusion & Osmosis Lab Investigation 4

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*Remember to mark the key terms required to understand a statement or question*

2.A.3 Organisms must exchange matter with the environment to grow, reproduce and maintain organization.

b. What factors affect the ability of the cell to obtain necessary resources or eliminate waste products?

b.1. For each of the following structures, explain how it functions to meet the need to exchange materials and energy with their environment:

• Root hairs• Cells of the alveoli• Cells of the villi• Microvilli

b.2. Surface area-to-volume ratios affect biological systems.

• How do surface area-to-volume (SA/V) ratios change as the size and shape of cells and organisms change? To answer this, calculate the SA and V of a cube 1 mm on a side. Then do the same for cubes that are 2 mm and 4 mm on a side and compare their SA/V ratios.

• In general, how does surface area change as linear dimensions increase twofold?

• In general, how does volume change as linear dimensions increase twofold?

• In general, how do SA/V ratios change as linear dimensions increase twofold?

• Assume a bacterium is 10 µm in linear dimension. Fill in the chart.

a. If modeled as a cube, what would its SA, V, and SA/V ratio be?

b. If modeled as a sphere, what would its SA, V, and SA/V ratio be?

c. What are the SA and V values and the SA/V ratios for a cube-shaped eukaryotic cell that is 100 µm in linear dimension?

a. 10-!m bacterium as a cube

b. 10-!m bacterium as a sphere

c. 100-!m eukaryote cube-shaped

SA

V

SA/V ratio

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• Is it possible to change the SA/V ratio of an organism or cell by changing its shape? To prove this to yourself and to help you determine the changes in SA/V ratios that occur, use modeling clay or dough to make a cube that is 1 inch on a side. The cube will obviously have a constant mass or volume.

• Assume that every cell requires a minimum of 1 unit of oxygen per um3 per second to stay alive. Fill in the chart below.

a. How much oxygen must cross each µm2 of surface area per second in the 10-µm bacterium versus the 100-µm eukaryote to keep each alive?

b. What effects might this difference have on metabolic rates in these organisms?

10-!m bacterium 100-!m eukaryote

a. Oxygen/!m2 of SA/second

b. Possible effect(s) on metabolic rate

2.B.1 Cell membranes are selectively permeable due to their structure.

a. Cell membranes separate the internal environment of the cell from the external environment.

b. Describe the fluid-mosaic model of a plasma membrane and its overall properties.

b.1. Review fluid mosaic membrane structure by labeling (and coloring) the diagram below. Start with the cytoplasm and extracellular fluid. In the membrane, color phospholipids gray, embedded protein molecules purple, carbohydrates, glycoprotein and glycolipid molecules green, and cholesterol molecules yellow. Also show the functions of certain proteins by labeling them enzyme, receptor protein, and transport protein.

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Exercise 8

Review fluid mosaic membrane structure by coloring and labeling this diagram. Label the items in boldface type: Start with the cytoplasm and extracellular fluid. In the membrane, color phospholipids gray, protein molecules purple, carbohydrate LD. tags on glycoprotein and glycolipid molecules green, and cholesterol molecules yellow. Also show the functions of certain proteins by labeling them enzyme, receptor protein, and transport protein.

Exercise 9

Review diffusion and the function of cell membranes by matching each of the phrases on the right with the appropriate mechanisms from the list on the left. Two questions require more than one answer.

A. Diffusion

B. Active transport

C. Osmosis

D. Phagocytosis

E. Passive transport

F. Facilitated diffusion

G. Pinocytosis

H. Receptor-mediated endocytosis

I. Exocytosis

1. ___ Diffusion across a biological membrane

2. ___ Moves solutes against concentration gradient

3. ___ Any spread of molecules from area of higher concentra-

tion to area of lower concentration

4. ___ Diffusion with help of transport protein

5. ___ Three types of endocytosis

6. ___ Engulfing of fluid in membrane vesicles

7. ___ Diffusion of water across selectively permeable mem-

brane, from hypotonic to hypertonic solution

8. ___ Transport molecules need ATP to function

9. ___ Enables cell to engulf bulk quantities of specific large

molecules

10. ___ How oxygen and carbon dioxide enter and leave cells

11. ___ Two types of passive transport

12. ___ Engulfing of particle in membrane vesicle

13. ___ Fusion of membrane-bound vesicle with membrane, and

dumping of contents outside cell

14. ___ How a cell might capture a bacterium

• Now, draw from memory a labeled diagram of the fluid mosaic membrane!

b.2. Diagram an individual phospholipid molecule.

• What properties do the phospholipids give the membrane?

b.3. Which properties of the embedded proteins are similar to that of the phospholipids?

b.4. For each of the following types of molecules, explain whether or not it can freely pass through the membrane:

• small nonpolar molecules• large polar molecules• ions• water

• For the types of molecules that do not pass freely through the membrane, how do they move across? Include specific examples.

c. Some cells have cell walls. What are the two major functions of cell walls?

c.1. What types of cells have a cell wall? What kind of molecules are unique to each type.

2.B.2 Growth and dynamic homeostasis are maintained by the constant movement of molecules across membranes.

a./b./c. For each of the types of transport listed below:

• Describe the transport process and explain how the organization of cell membranes functions in the movement of specific molecules across membranes; and,

Explain the significance of each type of transport to a specific cell (you may use different cell types as examples.)

passive transportactive transport endocytosisexocytosisosmosis (include hypotonic, hypertonic, and isotonic)facilitated diffusionglucose transport

Na+/K+ transport

• Add to your diagram of the fluid mosaic membrane. Show the types of transport across the membrane.

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Review diffusion and the function of cell membranes by matching each of the phrases on the right with the appropriate mechanisms from the list on the left. Two questions require more than one answer.

A. Diffusion B. Active transport C. Osmosis D. Phagocytosis E. Passive transport F. Facilitated diffusion G. Pinocytosis H. Receptor-mediated endocytosis I. Exocytosis

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1. ___ Diffusion across a biological membrane 2. ___ Moves solutes against concentration gradient 3. ___ Any spread of molecules from area of higher

concentration to area of lower concentration4. ___ Diffusion with help of transport protein 5. ___ Three types of endocytosis6. ___ Engulfing of fluid in membrane vesicles7. ___ Diffusion of water across selectively permeable

membrane, from hypotonic to hypertonic solution 8. ___ Transport molecules need ATP to function9. ___ Enables cell to engulf bulk quantities of specific large

molecules10. ___ How oxygen and carbon dioxide enter and leave cells 11. ___ Two types of passive transport12. ___ Engulfing of particle in membrane vesicle13. ___ Fusion of membrane-bound vesicle with membrane,

and dumping of contents outside cell

Experiment Analysis

Graph 1: Percent Change in Mass of Dialysis Tubing in Sucrose Solutions of Different Molarities

Answer the following questions, based on Graph 1 above. These results were obtained by the following method: Dialysis tubing was soaked for about 24 hours. One end of each tube was tied off with clamps. Each tube was filled with a different solution (distilled water, 0.2 M glucose, 0.4 M glucose, 0.6 M glucose, 0.8 glucose, and 1.0 M glucose) using a funnel and tying off the end again leaving empty space, but no air. Each bag was weighed separately on the electronic balance and the mass recorded. The bags were immersed in separate cups filled with distilled water for about 30 minutes. The bags were removed and gently blotted dry with paper towel, reweighed and the mass recorded for each.

• Explain the relationship between the change in mass and the molarity of sucrose within the dialysis bags.

• Predict what would happen to the mass of each bag in this experiment if all the bags were placed in a 0.4 M sucrose solution instead of distilled water. Explain your response.

• Why would you calculate the percent change in mass rather than simply using the change in mass?

• A dialysis bag is filled with distilled water and then placed in a sucrose solution. The bag’s initial mass is 20g, and its final mass is 18g. Calculate the percent change of mass.

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Graph 2: Percent Change in Mass of Potato Cores at Different Molarities of Sucrose

Answer the following two questions, based on Graph 2 above.

• Determine the osmotic molar concentration (Molarity) of the potato core. *Indicate this point on the graph.

Molar concentration of sucrose = _________M

• What is the osmotic potential (water potential) of the sucrose solution at 22oC? The solute potential of this sucrose solution can be calculated using the following formula: !s = -iCRT

Where, i = ionization constant (for sucrose this is 1 because sucrose does not ionize in water) C = osmotic molar concentration R = pressure constant (handbook value: R = 0.0831 liter • bars/mole • K) T = temperature in K (take an average of recorded temperatures)

• If a potato is allowed to dehydrate by sitting in the open air, would the water potential of the potato cells decrease or increase? Why?

• If a plant cell has a lower water potential than its surrounding environment, and if pressure is equal to zero, is the cell hypertonic or hypotonic to its environment? Will the cell gain water or lose water? Explain your response.

• What effect does adding solute have on the solute potential component of that solution? Why?

• Explain what would happen to a red blood cell placed in distilled water in terms of concentration of water molecules and water potential.

• Relate water potential to the transport of water in plants - in terms of transpiration.

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2.B.3 Eukaryotic cells maintain internal membranes that partition the cell into specialized regions.

a. Identify the two main functions that internal membranes serve to help facilitate cellular processes.

b. Explain how each of the following membranes and membrane-bound organelles in eukaryotic cells localize (compartmentalize) intracellular metabolic processes and specific enzymatic reactions.

• endoplasmic reticulum• mitochondria• chloroplasts• lysosomes• vacuoles• Golgi• nuclear envelope

• Sketch and label the endomembrane system on this diagram. Include rough ER, smooth ER, ribosomes, Golgi apparatus, lysosome, and transport vesicles. (1) Trace the path of a protein from its site of manufacture to the outside of the cell with a red arrow. (2) Trace the path of a protein incorporated into a lysosome in blue. (3) Trace the path of a protein incorporated into the plasma membrane in green. (4) Trace the path of a lipid secreted from the cell in yellow.

Exercise 4

Sketch and label the endomembrane system on this diagram. Include rough ER, smooth ER, ribosomes, Golgi apparatus, lysosome, and transport vesicles. (1) Trace the path of a protein from its site of manufacture to the outside of the cell with a red arrow. (2) Trace the path of a protein incorporated into a lysosome in blue. (3) Trace the path of a protein incorporated into the plasma membrane in green. (4) Trace the path of a lipid secreted from the cell in yellow.

Exercise 5

Both mitochondria and chloroplasts are energy converters, but their functions are quite different. Compare them by filling in the chart below.

C h lo ro p l a s t

Mi t o c h o n d ri o n

Found in the following organisms ...

Carries out process of ...

Converts energy of ...

Into chemical energy in ...

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Review the nucleus and the various structures that make up the endomembrane system by matching each phrase on the left with a structure from the list on the right. Answers can be used more than once.

1. ___ Lipids manufactured here2. ___ Small structure that makes protein 3. ___ Contains chromatin4. ___ Sac of enzymes that digest things5. ___ Carries secretions for export from cell 6. ___ Breaks down drugs and toxins in liver 7. ___ Makes cell membranes8. ___ Cell control center9. ___ Numerous ribosomes give it its name10. ___ "Ships" products to plasma membrane, outside, or to other organelles 11. ___ May store water, needed chemicals, wastes,

pigments in plant cell 12. ___ Buds off from Golgi apparatus13. ___ Defective in Pompe's disease and Tay-Sachs disease 14. ___ Proteins made here for secretion from cell15. ___ Pumps out excess water from some cells 16. ___ Nonmembranous organelle17. ___ Takes in transport vesicles from ER and modifies their contents 18. ___ Digests food, wastes, foreign substances19. ___ Surrounded by double layer of membrane with pores20. ___ How proteins, other substances get from ER to Golgi apparatus

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A. Nucleus

B. Transport vesicle

C. Central vacuole

D. Smooth ER

E. Lysosome

F. Golgi apparatus

G. Rough ER

H. Contractile vacuole

I. Ribosome

c. Examine cell diagrams and then compare the structures of the cells of prokaryotes, plants and animals by checking off their characteristics below.

Characteristic Prokaryote Cell Plant Cell Animal Cell

Prokaryotic structure

Eukaryotic structure

Relatively large size

Relatively small size

Extensive internal memb.Plasma membrane

Cell wall

Cytoplasm

Ribosomes

Nucleus

Rough ERSmooth ERGolgi apparatus

Lysosome

Peroxisome

Mitochondrion

Chloroplast

Central vacuole

Cytoskeleton

Cilia/Flagellum (9+2)

Flagellum

Centriole

Linear chromosomes

Circular chromosome

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4.A.2: The structure and function of subcellular components, and their interactions, provide essential cellular processes.

Explain how the following organelles work together to perform living functions:

1. Nucleus and ribosomes

2. Endoplasmic reticulum and ribosomes

3. Golgi bodies and lysosomes

4. Nucleus and endoplasmic reticulum

5. Endoplasmic reticulum and Golgi bodies and vesicles

6. Endoplasmic reticulum and Golgi bodies and cell membrane

4.B.2: Cooperative interactions within organisms promote efficiency in the use of energy and matter.

a. Explain how organisms, at the cellular level, have areas or compartments that perform a subset of functions related to energy and matter, and how these parts contribute to the whole.

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How do the following topics connect to what you are learning in this unit?

1.B.1b Organisms share many conserved core processes and features that evolved and are widely distributed among organisms today: Structural evidence supports the relatedness of all eukaryotes.

3.D.1 Cell communication processes share common features that reflect a shared evolutionary history.

3.D.2 Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling.

Enrichment

1. Explain how technology can be used to better understand living processes at the cellular level.

2. Compare the components of the cytoskeleton by indicating with a checkmark which of the following are characteristics of microfilaments or microtubules.

Microfilaments Microtubules

Hollow tubesSolid rodsMade of tubulinMade of actinHelp cell change cell shape Act in muscle cell contraction Move chromosomesAct as tracks for organellesGive cell rigidity, shapeIn ciliaIn flagellaIn centrioles

3. Match each cell surface characteristic or structure on the left with a phrase on the right.

A. Tight junction B. Plasmodesma C. Anchoring junction D. Cell wallE. Communicating junction F. Extracellular matrix

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Exercise 6

Compare the components of the cytoskeleton by indicating with a checkmark which of the following are characteristics of microfilaments or microtubules.

Micro f i l a m e nts Mic ro tu b u l e s Hollow tubes

Solid rods

Made of tubulin

Made of actin

Help cell change shape

Act in muscle cell contraction

Move chromosomes

Act as tracks for organelles

Give cell rigidity, shape

In cilia

In flagella

In centrioles

Exercise 7

Match each of the cell surface characteristics or structures on the left with a phrase on the right. A. Tight junction B. Plasmodesma C. Anchoring junction D. Cell wall E. Communicating junction F. Extracellular matrix

1. ___ Channel between animal cells 2. ___ Made of cellulose 3. ___ Link animal cells in leakproof sheet 4. ___ Channel between plant cells 5. ___ Connects animal cells, leaving space between them 6. ___ Sticky layer holds animal cells together

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