Cell Boundaries Notes Biology I

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. Copyright Pearson Prentice Hall

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 Copyright Pearson Prentice Hall

Functions include: C) Contains proteins that identify the cell D) It serves as an attachment site for some organelles and near-by cells. Copyright Pearson Prentice Hall

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 Copyright Pearson Prentice Hall

Cell Wall- A tough, supportive and protective covering of plants (of cellulose), fungi, most bacteria and some protists. Copyright Pearson Prentice Hall

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. Copyright Pearson Prentice Hall

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 Copyright Pearson Prentice Hall

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

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

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

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

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

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. Copyright Pearson Prentice Hall

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. Copyright Pearson Prentice Hall

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. Copyright Pearson Prentice Hall

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. Copyright Pearson Prentice Hall

Diffusion Diffusion depends on: Random particle movements Diffuse across membrane WITHOUT ENERGY!!!!! Passive Transport

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

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

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.

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

Osmosis in animal cells 11 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

Plant cells cell wall vacuole cytoplasm and cell membrane 18 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

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”

Osmosis in Living Cells Cellulose in cell wall

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?

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

Glucose molecules Protein channel

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

Molecule to be carried Active Transport

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. Copyright Pearson Prentice Hall

Active Transport Two examples of endocytosis are: phagocytosis pinocytosis Copyright Pearson Prentice Hall

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. Copyright Pearson Prentice Hall

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Active Transport In pinocytosis, tiny pockets form along the cell membrane, fill with liquid, and pinch off to form vacuoles within the cell. Copyright Pearson Prentice Hall

Active Transport Exocytosis The movement of large molecules or quantities of fluids/dissolved substances out of the cell

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

The Diversity of Cellular Life Photo Credit: ©CNSI/Science Photo Library/Photo Researchers, Inc. Copyright Pearson Prentice Hall

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.

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

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

Multicellular Organisms What is cell specialization?

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

Multicellular Organisms Red blood cells transport oxygen. Photo Credit: ©Dr. Dennis Kunkle/Phototake Copyright Pearson Prentice Hall

Multicellular Organisms Cells in the pancreas produce proteins. Photo Credit: ©Don Fawcett/Photo Researchers, Inc. Copyright Pearson Prentice Hall

Multicellular Organisms Muscle cells allow movement. Photo Credit: ©Manford Kage/Peter Arnold, Inc. Copyright Pearson Prentice Hall

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.

Multicellular Organisms Stomata enclosed by guard cells. Photo Credit: ©Ron Boardman/Getty Images, Inc-Stone Copyright Pearson Prentice Hall

Levels of Organization What are the four levels of organization in multicellular organisms?

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

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. Copyright Pearson Prentice Hall

In multicellular organisms, cells are the first level of organization. Copyright Pearson Prentice Hall

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.

Levels of Organization Copyright Pearson Prentice Hall

Levels of Organization Most animals have four main types of tissue: muscle epithelial nervous connective Copyright Pearson Prentice Hall

Levels of Organization Organs  Organs are groups of tissues that work together to perform a specific function.

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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. Copyright Pearson Prentice Hall

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