Chapter 7.3 & 7.4Chapter 7.3 & 7.4

7.3 7.3 All organisms and all cells must maintain All organisms and all cells must maintain homeostasishomeostasis (stable internal environment) and adjust to (stable internal environment) and adjust to their environment.their environment.

Cell membraneCell membrane = plasma membrane = plasma membrane description – a lipid bi-layer (has 2 layers) w/ description – a lipid bi-layer (has 2 layers) w/

proteins that are stuck w/in itproteins that are stuck w/in it

Is Is selectively permeableselectively permeable – allows some things in & – allows some things in & not othersnot others

FunctionsFunctions

1.1. Controls what gets into & out of the cellControls what gets into & out of the cell

2.2. Protects & supports the cellProtects & supports the cell

SolutionSolution – – mixture of 2 or more substancesmixture of 2 or more substances1. 1. solutesolute – dissolved substance – dissolved substance2. 2. solventsolvent – does the dissolving – does the dissolving3. 3. concentrationconcentration – mass of solute in a given volume – mass of solute in a given volume

-12g/31 saline (salt) solution - 2x more -12g/31 saline (salt) solution - 2x more concentratedconcentrated

-12g/61 saline solution-12g/61 saline solution4. particles move constantly & randomly4. particles move constantly & randomlyCytoplasmCytoplasm – solution of many different substances – solution of many different substances

Cell wall is found in plants, algae, fungi & Cell wall is found in plants, algae, fungi & many prokaryotesmany prokaryotes

located outside of the membranelocated outside of the membrane will allow water, Owill allow water, O22 & CO & CO22 to pass through easily to pass through easilyMain function Main function → support & protection of the cell→ support & protection of the cellMade by the cellMade by the cell

DiffusionDiffusion – movement across a cell membrane – movement across a cell membrane from an area of high concentration to low from an area of high concentration to low concentrationconcentration

FactsFacts depends on random movement depends on random movement → requires → requires NONO

energyenergy when concentration is the same throughout, when concentration is the same throughout,

equilibriumequilibrium exists exists

when when equilibriumequilibrium is reached, there is no is reached, there is no change in concentration & particles continue change in concentration & particles continue to move in both directions at the same rateto move in both directions at the same rate

OsmosisOsmosis – diffusion of water– diffusion of water

Sugar molecules are large & can NOT Sugar molecules are large & can NOT pass through the membranepass through the membrane

Water molecules are small & pass easilyWater molecules are small & pass easily

Water will flow from high concentration Water will flow from high concentration to low concentration until equilibrium to low concentration until equilibrium is reachedis reached

Types of SolutionsTypes of Solutions

IsotonicIsotonic – same strength – same strength

HypotonicHypotonic – below strength – below strength

HypertonicHypertonic – above strength – above strength

Direction of movement of water depends Direction of movement of water depends on the concentration of soluteson the concentration of solutes

For organisms to survive, it must balance intake & For organisms to survive, it must balance intake &

loss of waterloss of water Cell is filled w/ salts, sugars, proteins & other Cell is filled w/ salts, sugars, proteins & other

substances and is hypertonic to fresh water. substances and is hypertonic to fresh water. Water will move Water will move → the cell and it would burst→ the cell and it would burstOsmotic pressureOsmotic pressure – –The pressure exerted by the flow of The pressure exerted by the flow of

water through a semi permeable membrane water through a semi permeable membrane separating two solutions with different separating two solutions with different concentrations.concentrations.

TurgidityTurgidity - -The state of being swollen, especially The state of being swollen, especially due to high fluid content.due to high fluid content.

Ways to control swelling and/or bursting:Ways to control swelling and/or bursting:1.1. Plant & fungal cells – cell wallsPlant & fungal cells – cell walls2.2. Unicellular eukaryotes use Unicellular eukaryotes use contractile vacuolescontractile vacuoles – –

pumps out excess waterpumps out excess water3.3. Animal cells – remove dissolved particles from the Animal cells – remove dissolved particles from the

cytoplasmcytoplasm

Active TransportActive TransportUsed when cells need to move Used when cells need to move

substances against the concentration substances against the concentration differencedifference

Requires Requires energyenergySome processes use transport proteins Some processes use transport proteins

or “pumps” to move molecules from or “pumps” to move molecules from lowlow concentration to concentration to highhigh concentration. concentration.

EndocytosisEndocytosis – – movement is from an area of lower movement is from an area of lower concentration to higher concentration.concentration to higher concentration.

A. ProcessA. Process

1. Cell membrane forms a vesicle 1. Cell membrane forms a vesicle around particles. around particles.

vesicle = vacuolevesicle = vacuole

2. Vesicle travels to the target organelle.2. Vesicle travels to the target organelle.

3. Vesicle may fuse with the organelle & release 3. Vesicle may fuse with the organelle & release its its contents. contents.

B. Two typesB. Two types

1. 1. phagocytosisphagocytosis – cell membrane forms a vesicle – cell membrane forms a vesicle around large particles.around large particles.

example: white blood cell eating bacteriaexample: white blood cell eating bacteria

2. 2. PinocytosisPinocytosis- cell membrane forms a vesicle around - cell membrane forms a vesicle around small particles to bring into the cell.small particles to bring into the cell.

ex: moving liquid into the cell ex: moving liquid into the cell

ExocytosisExocytosis – – movement is out of the cell movement is out of the cell

A. ProcessA. Process1. Vesicle forms around small particles.1. Vesicle forms around small particles.2. Vesicle moves to the cell membrane and fuses 2. Vesicle moves to the cell membrane and fuses with it. with it.3. Vesicles releases contents outside of the cell3. Vesicles releases contents outside of the cell

B. Used to export proteins released by the ER or Golgi B. Used to export proteins released by the ER or Golgi apparatus. apparatus.

7.4 Diversity of Cellular Life7.4 Diversity of Cellular Life

Sometime the cell is the organism Sometime the cell is the organism → → UnicellularUnicellular organism – one celled organism – one celled organismorganism

They do everything other organisms doThey do everything other organisms do

Ex. Yeast, bacteriaEx. Yeast, bacteria

Multi-cellularMulti-cellular Organisms – more Organisms – more than one cell (many cells)than one cell (many cells)– Need specialized cellsNeed specialized cells– Cell specializationCell specialization – process of cells – process of cells

developing in different ways to perform developing in different ways to perform different tasksdifferent tasks

– Ex: Ex: red blood cells red blood cells – carry oxygen– carry oxygen Muscle cells – packed with cytoskeleton Muscle cells – packed with cytoskeleton

fibers to allow movementfibers to allow movement

Levels of organizationLevels of organization1.1. CellCell2.2. TissueTissue – similar cells that perform a – similar cells that perform a

particular functionparticular function4 types include:4 types include:

1.1. EpithelialEpithelial2.2. MuscleMuscle3.3. NervousNervous4.4. ConnectiveConnective

3.3. OrganOrgan – group of tissues that work – group of tissues that work together to perform a jobtogether to perform a job

Ex: stomachEx: stomach4.4. Organ systemOrgan system – a group of organs that – a group of organs that

work together to perform a specific work together to perform a specific functionfunction

Ex: digestive systemEx: digestive system