cell processes middle school science. moving materials in cells cells need energy 24/7 they cannot...
Post on 29-Dec-2015
218 Views
Preview:
TRANSCRIPT
Moving materials in cellsMoving materials in cells
Cells need energy 24/7Cells need energy 24/7 They cannot make their own, but can They cannot make their own, but can
change energy from one form to anotherchange energy from one form to another Cells obtain energy from their Cells obtain energy from their
environment and convert it to a usable environment and convert it to a usable formform
Complex processComplex process
Moving materials in cellsMoving materials in cells
MetabolismMetabolism The sum of all activities within a cellThe sum of all activities within a cell Cannot just happenCannot just happen Need raw materialsNeed raw materials Need to eliminate wasteNeed to eliminate waste All material needs to enter and exit through All material needs to enter and exit through
the cell membranethe cell membrane
Moving materials in cellsMoving materials in cells
Materials enter and leave a cell by one of Materials enter and leave a cell by one of three methods:three methods: DiffusionDiffusion OsmosisOsmosis Active transportActive transport
DiffusionDiffusion
Cell membranes in living things need to Cell membranes in living things need to allow materials to pass throughallow materials to pass through Selectively-permeable membraneSelectively-permeable membrane Substances pass through the poresSubstances pass through the pores
Driving force behind the movement of Driving force behind the movement of many substances into or out of the cell is many substances into or out of the cell is diffusiondiffusion
DiffusionDiffusion
The process by which molecules of a The process by which molecules of a substance move from areas of higher substance move from areas of higher concentration of that substance to areas of concentration of that substance to areas of lower concentration of that substancelower concentration of that substance
DiffusionDiffusion
What causes diffusion to occur?What causes diffusion to occur? Mainly small moleculesMainly small molecules Driving force behind movementDriving force behind movement
All molecules are in motionAll molecules are in motion Solids – molecules move slowlySolids – molecules move slowly Liquids – move more quicklyLiquids – move more quickly Gases – move quicklyGases – move quickly
Molecules collide with each other, pushing away Molecules collide with each other, pushing away from one anotherfrom one another
DiffusionDiffusion
What causes diffusion to occur?What causes diffusion to occur? Driving force behind movementDriving force behind movement
Collisions will continue as molecules spread out evenlyCollisions will continue as molecules spread out evenly
DiffusionDiffusion
Why don’t the organelles and cytoplasm Why don’t the organelles and cytoplasm pass through the cell membrane?pass through the cell membrane? Cell membrane is selectively permeableCell membrane is selectively permeable
Permits only certain substances to diffusePermits only certain substances to diffuse Oxygen, water, and food molecules are permitted to Oxygen, water, and food molecules are permitted to
diffuse into the celldiffuse into the cell Carbon dioxide and other waste materials are Carbon dioxide and other waste materials are
permitted to diffuse out of the cellpermitted to diffuse out of the cell
OsmosisOsmosis
A special kind of diffusionA special kind of diffusion The diffusion of water across a selectively The diffusion of water across a selectively
permeable membrane = osmosispermeable membrane = osmosis
Water is the most important substance Water is the most important substance that passes through a cell membranethat passes through a cell membrane About 80% of the cell is waterAbout 80% of the cell is water
Diffusion and OsmosisDiffusion and Osmosis
Diffusion and osmosis are types of passive Diffusion and osmosis are types of passive transporttransport They do not require energy to be able to happen – They do not require energy to be able to happen –
they just happenthey just happen
Active TransportActive Transport
What if the cell needs materials that What if the cell needs materials that cannot diffuse through the membrane?cannot diffuse through the membrane? Active transport “carries” the materials into Active transport “carries” the materials into
or out of the cellor out of the cell Cells have several forms of active transportCells have several forms of active transport Transport proteins can “pick up” molecules Transport proteins can “pick up” molecules
and carry them into or out of the celland carry them into or out of the cell Requires energyRequires energy
Ex: calcium, potassium, and sodiumEx: calcium, potassium, and sodium
Active TransportActive Transport
What if the cell needs materials that What if the cell needs materials that cannot diffuse through the membrane?cannot diffuse through the membrane? Transport by engulfingTransport by engulfing
Another method of active transportAnother method of active transport Cell membrane surrounds, or engulfs, a particleCell membrane surrounds, or engulfs, a particle Once surrounded, the cell membrane wraps Once surrounded, the cell membrane wraps
around the particle and forms a vacuole within around the particle and forms a vacuole within the cellthe cell
Requires energyRequires energy
Cell Growth and DivisionCell Growth and Division
Limits on Cell GrowthLimits on Cell Growth Why don’t cells get bigger and bigger?Why don’t cells get bigger and bigger?
Has to do with the transportation of materials into Has to do with the transportation of materials into and out of the celland out of the cell
If a cell were to get too large, its membrane If a cell were to get too large, its membrane would not be able to handle the flow of materials would not be able to handle the flow of materials passing through itpassing through it
The amount of raw materials needed by a large cell The amount of raw materials needed by a large cell couldn’t enter fast enoughcouldn’t enter fast enough
The wastes produced couldn’t leave fast enoughThe wastes produced couldn’t leave fast enough
Cell DivisionCell Division
In order for an organism to grow, the total In order for an organism to grow, the total number of cells must increasenumber of cells must increase Cell divisionCell division
One cell divides into two new daughter cellsOne cell divides into two new daughter cells Occurs in a series of stages, or phasesOccurs in a series of stages, or phases
The process of cell division = mitosisThe process of cell division = mitosis
MitosisMitosis
Phase 1: Chromosomes are copiedPhase 1: Chromosomes are copied InterphaseInterphase
Cell is performing life functions, not dividingCell is performing life functions, not dividing Chromosomes appear as threadlike coils called Chromosomes appear as threadlike coils called
chromatinchromatin In animal cells, the two centrioles can be seen In animal cells, the two centrioles can be seen
outside the nucleusoutside the nucleus Most plant cells do not have centriolesMost plant cells do not have centrioles
MitosisMitosis
Phase 1Phase 1 Near the end, the process of cell division Near the end, the process of cell division
beginsbegins The chromosomes are duplicatedThe chromosomes are duplicated
Doubling the normal chromosome number in the Doubling the normal chromosome number in the cellcell
Each chromosome and its sister chromosome Each chromosome and its sister chromosome (copy) are attached at an area called the (copy) are attached at an area called the centromerecentromere
At this time the sister chromosomes are called At this time the sister chromosomes are called chromatidschromatids
MitosisMitosis
Phase 2: Mitosis beginsPhase 2: Mitosis begins ProphaseProphase
Mitosis beginsMitosis begins Mitosis = the process by which the nucleus of a cell Mitosis = the process by which the nucleus of a cell
divides into two nuclei and the formation of two new divides into two nuclei and the formation of two new daughter cells beginsdaughter cells begins
Threadlike chromatin shorten and form rodlike Threadlike chromatin shorten and form rodlike chromosomeschromosomes
Centrioles begin to move to opposite ends of cellCentrioles begin to move to opposite ends of cell Meshlike spindle develops, forming a bridge Meshlike spindle develops, forming a bridge
between opposite ends of the cellbetween opposite ends of the cell
MitosisMitosis
Phase 3: Chromosomes attach to the Phase 3: Chromosomes attach to the spindlespindle MetaphaseMetaphase
The chromosomes begin to attach to the spindleThe chromosomes begin to attach to the spindle Chromosomes are attached to the spindle by the Chromosomes are attached to the spindle by the
centromere, which still connects each chromatid centromere, which still connects each chromatid to its identical sister chromatidto its identical sister chromatid
MitosisMitosis
Phase 4: Chromosomes begin to Phase 4: Chromosomes begin to separateseparate AnaphaseAnaphase
The centromere splitsThe centromere splits The sister chromatids separate from each otherThe sister chromatids separate from each other Chromatids move to opposite ends of cell along Chromatids move to opposite ends of cell along
the spindlethe spindle The chromatids are again called chromosomes at The chromatids are again called chromosomes at
this pointthis point
MitosisMitosis
Phase 5: Two new nuclei formPhase 5: Two new nuclei form TelophaseTelophase
The chromosomes begin to uncoil and lose their The chromosomes begin to uncoil and lose their rodlike appearancerodlike appearance
A nuclear membrane forms around the chromatin A nuclear membrane forms around the chromatin at each end of the cellat each end of the cell
In each nucleus, a nucleolus reappearsIn each nucleus, a nucleolus reappears At this point, mitosis is complete but the cell still At this point, mitosis is complete but the cell still
has one phase to go throughhas one phase to go through
MitosisMitosis
Phase 6: Two daughter cells formPhase 6: Two daughter cells form CytokinesisCytokinesis
Final phase of cell divisionFinal phase of cell division Involves the division of the cytoplasmInvolves the division of the cytoplasm The membrane surrounding the cell begins to The membrane surrounding the cell begins to
move inward until the cytoplasm is pinched in twomove inward until the cytoplasm is pinched in two Each part contains a nucleus with identical Each part contains a nucleus with identical
chromosomeschromosomes The cell membrane (or cell wall) complete the The cell membrane (or cell wall) complete the
divisiondivision
top related