1. Cell Boundaries Notes
Biology I

2. 7-3 Cell Boundaries
All cells are surrounded by a thin, flexible barrier known as the cell membrane.
Many cells also produce a strong supporting layer around the membrane known as a cell wall.
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3. Cell Membrane: a bilipid structure that is the outermost portion of the cell
Functions include:
A boundary between the cell’s contents and the environment which regulates what enters and exits the cell.
Communicates with other cell within an organism or unicellular organisms
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4. Functions include: C) Contains proteins that identify the cell
D) It serves as an attachment site for some organelles and near-by cells.
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5. Cell Membrane Outside of cell Carbohydrate chains Proteins
Inside of cell (cytoplasm)
The cell membrane regulates what enters and leaves the cell.
Protein channel
Lipid bilayer
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6. Cell Wall- A tough, supportive and protective covering of plants (of cellulose), fungi, most bacteria and some protists.
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7. Cell Walls Cell Wall The cell wall lies outside the cell membrane.
Most cell walls are porous enough to allow water, oxygen, carbon dioxide, and certain other substances to pass through easily.
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8. Prokaryotes vs. Eukaryotes
Ex. Bacteria
Cell Wall
Present in all prokaryotes
No Nucleus
Contain Ribosomes
No membrane bound organelles
Ex. Protists, fungi, plants, animals
Cell Wall
Present in Fungi and plants ONLY
Has Nucleus
Contain Ribsomes
Membrane bound organelles
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9. Measuring Concentration
Solution: a mixture of two or more substances
The substance dissolved in the solutions are called solutes
Concentration: of the solution is the mass of the solute in a given volume of solution or mass/volume
Mass of Solute/Volume of Solvent=Concentration

10. Measuring Concentration
Solvent: the liquid into which the solute is poured and dissolved
Solute: substance that is dissolved or put into the solvent

11. Membranes Permeable=substance is able to pass through membrane
Selectively permeable=some substances can pass through membrane and others cannot

12. Diffusion In solution particles move CONSTANTLY
Diffusion: particles move from an area of HIGH concentration to an area of LOW concentration

13. Diffusion
Equilibrium: Concentration of the solute is the same throughout a system.

14. Diffusion Through Cell Boundaries
Diffusion is the process by which molecules of a substance move from areas of higher concentration to areas of lower concentration. Diffusion does not require the cell to use energy.
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15. There is a higher concentration of solute on one side of the membrane as compared to the other side of the membrane.
Diffusion is the process by which molecules of a substance move from areas of higher concentration to areas of lower concentration. Diffusion does not require the cell to use energy.
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16. Solute particles move from the side of the membrane with a higher concentration of solute to the side of the membrane with a lower concentration of solute. The solute particles will continue to diffuse across the membrane until equilibrium is reached.
Diffusion is the process by which molecules of a substance move from areas of higher concentration to areas of lower concentration. Diffusion does not require the cell to use energy.
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17. When equilibrium is reached, solute particles continue to diffuse across the membrane in both directions.
Diffusion is the process by which molecules of a substance move from areas of higher concentration to areas of lower concentration. Diffusion does not require the cell to use energy.
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19. Diffusion Diffusion depends on: Random particle movements
Diffuse across membrane WITHOUT ENERGY!!!!!
Passive Transport

20. Osmosis
Osmosis: the diffusion of water through a selectively permeable membrane

21. Osmosis
**Water tends to diffuse from a HIGH concentrated region to a LESS concentrated region.

22. membrane water sugar solution 6
There are as many water molecules on the right as there are on the left but many of them are attached to sugar molecules and are not free to move.

23. Because there are more freely moving water molecules on 7
Sugar molecules can pass through the membrane but, being surrounded by a cloud of water molecules, they move more slowly.
Because there are more freely moving water molecules on
the left, more diffuse through the pores of the membrane from
left to right than from right to left.
Molecular movement

24. Osmosis in animal cells11
Osmosis in animal cells
so water diffuses into the cell
by osmosis
There is a greater concentration of free water molecules outside the cell than inside
and the cell swells up

25. Plant cells cell wall vacuole cytoplasm and cell membrane18
Plant cells
cell wall
vacuole
cytoplasm and
cell membrane
A useful analogy is the bicycle tyre. The outer casing represents the cell wall; the inner tube represents the cytoplasm and the air inside represents the vacuole. When the tyre is pumped up, the air pressure pushes the inner tube against the outer casing. The outer casing cannot expand and so the pressure in the tube builds up until the tyre is firm
The cell absorbs water
by osmosis ....
....but the cell wall stops the
cell expanding any more

26. Osmosis in Cells When comparing two solutions:
The more concentrated solution is hypertonic
“Above Strength”
The more dilute solution is hypotonic
“Below Strength”
When the concentrations are equal it is isotonic
“Same Strength”

28. Osmosis in Living Cells
Cellulose in cell wall

30. Bell Ringer 3/28/12
What is the difference between diffusion and osmosis?
If a cell shrinks after putting it into a unknown solution….what type of solution would it be?
What does the concentration have to be for the cell to swell? (what type of solution is it?)
What are the two types of transports?

31. 2 Types of Transport 1. Passive Transport
No energy required to pass through membrane
Ex. Water, ions
Facilitated Diffusion: movement of molecules across cell membrane through protein channels

32. Glucose molecules
Protein channel

33. 2 Types of Transport 2. Active Transport
Requires energy to transport molecules against a concentration gradient
Energy in the form of ATP

34. Molecule to be carried
Active Transport

36. Active Transport Endocytosis and Exocytosis
Large molecules and even solid clumps of material may undergo active transport by means of the cell membrane.
Endocytosis is the movement of substances into a cell by being surrounded/engulfed by the cell’s membrane.
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37. Active Transport Two examples of endocytosis are: phagocytosis
pinocytosis
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38. Active Transport
In phagocytosis, extensions of cytoplasm surround a particle and package it within a food vacuole. The cell then engulfs it.
Phagocytosis requires a considerable amount of energy.
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40. Active Transport
In pinocytosis, tiny pockets form along the cell membrane, fill with liquid, and pinch off to form vacuoles within the cell.
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41. Active Transport Exocytosis
The movement of large molecules or quantities of fluids/dissolved substances out of the cell

42. Learning Goals: What is cell specialization?
Why do cells need specific roles?
What are the four levels of organization in multicellular organisms?

43. The Diversity of Cellular Life
Photo Credit: ©CNSI/Science Photo Library/Photo Researchers, Inc.
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44. The differences among living things arise from the ways in which cells are specialized to perform certain tasks and the ways in which cells associate with one another to form multicellular organisms.

45. Unicellular Organisms
Unicellular organisms are made up of only one cell.
Unicellular organisms dominate life on Earth.

46. Multicellular Organisms
Organisms that are made up of many cells are called multicellular.
There is a great variety among multicellular organisms.

47. Multicellular Organisms
What is cell specialization?

48. Multicellular Organisms
Cells throughout an organism can develop in different ways to perform different tasks.
This process is called cell specialization.

50. Multicellular Organisms
Red blood cells transport oxygen.
Photo Credit: ©Dr. Dennis Kunkle/Phototake
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51. Multicellular Organisms
Cells in the pancreas produce proteins.
Photo Credit: ©Don Fawcett/Photo Researchers, Inc.
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52. Multicellular Organisms
Muscle cells allow movement.
Photo Credit: ©Manford Kage/Peter Arnold, Inc.
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53. Multicellular Organisms
Specialized Plant Cells
Plants exchange carbon dioxide, oxygen, water vapor, and other gases through tiny openings called stomata on the undersides of leaves.
Highly specialized cells, known as guard cells, regulate this exchange.

54. Multicellular Organisms
Stomata enclosed by guard cells.
Photo Credit: ©Ron Boardman/Getty Images, Inc-Stone
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55. Levels of Organization
What are the four levels of organization in multicellular organisms?

56. Levels of Organization
The levels of organization in a multicellular organism are:
individual cells
tissues
organs
organ systems

57. Levels of Organization
Muscle cell
Smooth muscle tissue
Stomach
Digestive system
The levels of organization in a multicellular organism are individual cells, tissues, organs, and organ systems. In this example, muscle cells make up smooth muscle tissue, which, along with other tissues, makes up the stomach, an organ. The stomach, in turn, is part of an organ system, the digestive system.
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58. In multicellular organisms, cells are the first level of organization.
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59. Levels of Organization
Tissues
Similar cells are grouped into units called tissues.
A tissue is a group of similar cells that perform a particular function.

60. Levels of Organization
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61. Levels of Organization
Most animals have four main types of tissue:
muscle
epithelial
nervous
connective
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62. Levels of Organization
Organs 
Organs are groups of tissues that work together to perform a specific function.

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64. Levels of Organization
Organ Systems  
In most cases, an organ completes a series of specialized tasks.
A group of organs that work together to perform a specific function is called an organ system.
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