Cell Structure and Function

Goals1. Identify the main function of the

membrane2. Describe what happens during diffusion3. Explain the processes of osmosis,

facilitated diffusion, and active transport

7.3 Movement across the cell membrane

The Cell MembraneFunctions

• Regulates what enters and leaves the cell

• Protection• Support

The Cell MembraneStructure

• Bilipid layer flexible strong• Protein molecules • Carbohydrates attached to the proteins

The Cell MembraneStructure

Outsideof cell

Insideof cell(cytoplasm)

Cellmembrane

Proteins

Proteinchannel

Lipid bilayer

Carbohydratechains

Chunk and chew

Osmosis• Diffusion movement from area of high

concentration to area of low concentration

• Selective permeability Some substances cannot cross biological

membranes• Osmosis is the diffusion of water

through a selectively permeable membrane

Diffusion•Molecules tend to move from an area of high concentration to an area of lower concentration•Equilibrium has been reached when the concentration is the same throughout the solution•Diffusion causes many substances to move across a cell membrane but does not require the cell to expend energy.

QuickTime™ and aSorenson Video decompressorare needed to see this picture.

How Osmosis Works

Cellmembrane

Higher Concentrationof Water

Lower Concentrationof Water

Water molecules

Sugar molecules

Hypertonic - Above Strength

Hypotonic - Below Strength

How Osmosis Works

Cellmembrane

Higher Concentrationof Water

Lower Concentrationof Water

Water molecules

Sugar molecules

Hypertonic - Above Strength

Hypotonic - Below Strength

How Osmosis Works

Cellmembrane

Higher Concentrationof Water

Lower Concentrationof Water

Water molecules

Sugar molecules

Hypertonic - Above Strength

Hypotonic - Below Strength

How Osmosis Works

Cellmembrane

Higher Concentrationof Water

Lower Concentrationof Water

Water molecules

Sugar molecules

Hypertonic - Above Strength

Hypotonic - Below Strength

Red blood cells burst when placed in distilled water. Make a labeled diagram to illustrate why. Use the terms osmosis, diffusion and concentration gradient.

Osmotic Pressure•Can cause problems when water moves into hypertonic cell spaces•Bursting the cell like a balloon•Most cells are bathed in isotonic fluids like blood•Some cells actively pump out water that is forced in by osmosis

Biology Warm Up: Organelle ReviewMake a sketch of a plant cell. Label two features that

identify it as a plant cell and not an animal cell.Without using your notes, draw and label1. the organelle responsible for absorbing light energy and

using it to convert carbon dioxide and water to high-energy sugars (photosynthesis).

2. the organelle that is responsible for converting sugars into high energy molecules. This is the powerhouse of the cell.

3. the organelle that stores the genetic information that controls cell activities. Include the name of the molecule that carries that genetic information.

4. the organelle responsible for assembling strings amino acids into proteins.

Observing Cell Parts and ProcessesWe’ll be doing this lab on Thursday.Please write a completeProcedure with materials and diagrams.We will be doing both parts of the lab.You must have this lab procedure written up and

ready to go in order to start the lab next class.

Facilitated Diffusion•Protein Channel•Though fast and specific, still diffusion•Requires higher concentration on one side of the membrane than on the other•Requires no energy

HighConcentration

Low

Concentration

CellMembrane

Glucosemolecules

Proteinchannel

Active Transport•Movement against the concentration difference•Requires input of energy

Molecule tobe carried Low

Concentration

CellMembrane

HighConcentration

Moleculebeing carriedLow

Concentration

CellMembrane

HighConcentrationEnergy Energy

QuickTime™ and aSorenson Video decompressorare needed to see this picture.

Active Transport•Movement against the concentration difference•Requires input of energy•Endocytosis Taking materials in through infoldings or pockets that break loose from the membrane and form a vacuole•Phagocytosis Engulfing large particles by endocytosis•Exocytosis Vacuole fuses with cell membrane to expel contents

WarmUp Osmosis/Diffusion1. Mr. Schafer adds a drop of red food coloring to a large beaker of

water. What do you expect to happen to the drop over time. Explain in terms of relative concentration of food coloring in different parts of the beaker. What word describes this phenomenon?

2. This week, you will be placing your egg into a cup of syrup. What do you think will happen? Explain in terms of relative concentration of water inside and outside of the egg. What word describes this phenomenon?

3. You will then place your egg into a cup of pure water. What do you expect to happen? Explain in terms of relative concentration of water inside and outside of the egg.

4. What quality of the membrane surrounding the egg makes possible the phenomenon described in questions 2 and 3?

5. Why do red blood cells burst when placed in water?

Diversity of Cellular Life

•Describe Cell Specialization•Identify The organization levels in multicellular organisms

Unicellular Organisms

•Cells of multicellular organism do not live on their own•Cells are specialized to perform certain functions

Multicellular Organisms

•Both prokaryotes and eukaryotes•everywhere•Some unicellular organisms are colonial

Levels of Organization

1. Cells Specialized cells such as nerve cells, muscle cells depend on other specialized cells to provide their needs (food, oxygen)

Levels of Organization

1. Cells Specialized cells such as nerve cells, muscle cells depend on other specialized cells to provide their needs (food, oxygen)

2. TissuesA group of similar cells that perform a particular funciton

Levels of Organization

1. Cells 2. Tissues

A group of similar cells that perform a particular funciton•muscle•epithelial (skin inside and out)•nervous•connective (bone, blood, cartilidge, lymph)

Levels of Organization

1. Cells 2. Tissues

•muscle•epithelial (skin inside and out)•nervous•connective (bone, blood, cartilage, lymph)

3. Organ - several tissues working together Each muscle is more than just muscle tissue

Levels of Organization

1. Cells 2. Tissues3. Organ - several tissues working together Each muscle is more than just muscle tissue4. Organ systems Organs that work together to perform a

specific function

Levels of Organization

1. Cells 2. Tissues3. Organ4. Organ system Organs that work together to perform a

specific function

Levels of Organization4. Organ system Organs that work together to perform a

specific function• Muscular• Skeletal• Circulatory• NervousWe will go through all 11 systems in unit 10

Levels of Organization

1. Cells 2. Tissues3. Organ 4. Organ system

Muscle cellSmooth muscle tissue Stomach Digestive system