cell structure and function chapter 7. recognize anything?
TRANSCRIPT
PLANT AND ANIMAL CELLS
onion cell slide
Elodea cell slide
human cheek cell slide
*If your slides look nothing like these, you need to let me know!
7-1 LIFE IS CELLULAR
• What is a cell?
• The smallest unit of living things
• One of the 8 characteristics of living things
• If they are so small, how did we ever find them?
• The invention of the microscope!
THE DISCOVERY OF THE CELL
• “out of sight, out of mind”
• 2 inventors of the microscope
• Robert Hooke
• Looked at cork (plant) cells
• First to use the term “cell”
• Anton van Leeuwenhoek
• We know him!
• Saw organisms in pond water
CELL THEORY
• What is a theory?
• Schleiden- claimed all plants made of cells
• Schwann- claimed all animals made of cells
• Virchow- claimed new cells only come from existing cells
• The Cell Theory states:
• 1. all living things are composed of cells
• 2. cells are the basic unit of structure and function in living things
• 3. new cells are produced from existing cells
EXPLORING THE CELL
• The advancement of microscopes
• New technologies:
• Fluorescent labels- track certain parts
• 3D- structural detail
• HD videos- show movement
• Light microscopes still a challenge- why?
• Light rays can be diffracted
• So, what else can we use?
ELECTRON MICROSCOPY
• Beams of electrons- show more detail
• What are the 2 types?
• Transmission EM
• Shows internal structures
• Specimen must be very thin
• Scanning EM
• Shows 3D surface images
• Must be in a vacuum- preserved and dehydrated
SCANNING PROBE MICROSCOPES
• 1990s
• View the surface with very fine probes
• No need for a vacuum
• Can view single atoms
WIDE VARIETY OF CELLS
• Cells come in all sizes- from 0.2nm to amoeba
• 2 characteristics of ALL cells:
• 1. Surrounded by a barrier (membrane)
• 2. Contain DNA (at some point)
• So if all cells have these, then how do we classify them…?
• By the presence/absence of a nucleus!
PROKARYOTES & EUKARYOTESProkaryotes Eukaryotes
No nucleus Has a nucleus
Smaller, simple Larger, complex
Still has genetic material Genetic material in nucleus
Follows 8 characteristics Follows 8 characteristics
Internal structures/membranes
Specialized
Can be single or multi-celled
Ex: bacteria Ex: humans
7-2 EUKARYOTIC CELL STRUCTURE
• Eukaryotic cells = very complex
• Drive processes of all living things
• Remember the 8 characteristics?
• Contain many common organelles
• “Little organs”
THE CELL AS A “FACTORY”
• Each organelle has a specific function/role
• 2 main parts:
• Cytoplasm- part of the cell outside the nucleus
• Nucleus- control center
• “the boss”
THE NUCLEUS
• Job: control center of the cell
• Contains all DNA
• Instructions for proteins, etc. to be made by cell
• Structure:
• Double membrane
• Nuclear pores- allows material in/out
• Chromatin- DNA + protein
• Condenses to form chromosomes
• Nucleolus- where ribosome production begins
RIBOSOMES
• Job: make proteins!
• Gets all “orders” from the nucleus
• Consists of RNA and protein
• Free or bound
ENDOPLASMIC RETICULUM (ER)
• Job: conveyor belt for protein synthesis
• For proteins going out of the cells
• Rough ER: ribosomes attached
• Smooth ER: no ribosomes
• Enzymes here
• Produce membrane lipids
• Detox drugs (liver)
GOLGI APPARATUS
• Job: modify, sort and package proteins
• Sent to be stored or secreted
• Like a UPS store- final touches and ship!
LYSOSOMES
• Job: digestion of carbs, proteins and lipids for cell use
• Enzyme filled “clean-up crew”
• Get rid of “junk”
• Old organelles
VACUOLES
• Job: storage
• Water, salt, proteins, carbs, etc.
• Plants- large vacuoles- pressure gives support
• Animals- maintain water balance
• Maintaining a balance? What’s that called?
• Homeostasis!
• Ex: paramecium- contractile vacuole
SUPPLYING THE CELL WITH ENERGY!
• metabolism at the cell level
• Living things get their energy from…
• Food (animals)
• The sun (plants)
MITOCHONDRIA
• Job: powerhouse of the cell
• Chemical energy from food -> compounds the cell can use
• Double membrane (inner is folded up)
• Inherited from mother
CHLOROPLASTS
• Job: “solar powered” plants (photosynthesis)
• Energy from sun -> energy the cell can use
• Double membrane (internal folds up- chlorophyll)
ORGANELLE DNA
• Mitochondria and chloroplasts have their own DNA
• Lynn Margulis- endosymbiotic theory
• Mitochondria and chloroplasts are descendants of prokaryotes
• Symbiotic relationship with eukaryotic cell
CYTOSKELETON
• Job: structure and transport
• Protein filaments- maintain shape
• Microfilaments
• Threadlike actin- tough/flexible
• Microtubules
• Hollow tubulin- cell shape and division
• Mitotic spindle
• Centrioles
• Cell projections (cilia and flagella)- movement
7-3 CELL BOUNDARIES
• 1 of the 2 characteristics all cells have
• What is the other one?
• Separates the cell from the rest of its environment
• Cell membrane: regulates what goes in/out
• Cell wall: strong supporting layer
CELL MEMBRANE
• Thin, strong
• Job: regulates what goes in/out
• Protection/support
• Lipid bilayer
• “fluid mosaic”
• Proteins within
• Carb chain for identification
• Protein channels
CELL WALL
• Found in plants, bacteria, prokaryotes, etc.
• NOT in animals
• Outermost layer- outside membrane
• Job: support/protection
• cellulose
MOVEMENT ACROSS MEMBRANES
• Membranes regulate movement of liquid + dissolved molecules from one side to another
• Permeable= when a membrane allows a substance to cross it
• Impermeable= when a membrane does not allow a substance
• Cell membranes are selectively permeable
• Let some things in and not others
CONCENTRATION
• Particles in a solution are always moving
• Concentration: how much solute there is in a solution
DIFFUSION
• Movement of particles from high concentration to low concentration
• When equal on both sides: equilibrium is reached
• Based on random particle movement- no energy needed!
• Even at equilibrium, particles still move
• Going in = going out
OSMOSIS
• Diffusion of water through a selectively permeable membrane
• isotonic solution: at equilibrium
• hypertonic: greater concentration of solute
• hypotonic: less concentration of solute
OSMOTIC PRESSURE
• Pressure on the hypertonic end of a selectively permeable membrane
• hypertonic solution- water out (cell shrinks)
• hypotonic solution- water in (cell expands)
• isotonic solution- stays same
• bodily fluids are isotonic!
• Cell walls prevent shrink/expanding
FACILITATED DIFFUSION
• some molecules travel easily thru membrane
• Use protein channels
• Protein “facilitates” (helps) diffusion
• Still moving from hi to lo concentration- no energy needed!
ACTIVE TRANSPORT
• For SMALL molecules…
• Movement against concentration gradient
• Requires energy (lots)!
• Use protein “pump”
• Changes shape and pumps molecules across
ACTIVE TRANSPORT
• For LARGE molecules…
• Movements of the cell membrane
• Folds/extensions of membrane
• Break off to form vacuole around molecule
• Endocytosis- bring molecules IN the cell
• Exocytosis – get molecules OUT of the cell
2 TYPES OF ENDOCYTOSIS
• 1. phagocytosis: “cell eating”
• Membrane and cytoplasm extend and engulf particle
• 2. pinocytosis: take up liquid in tiny pockets of membrane
Both processes move things INTO the cell!
7-4 THE DIVERSITY OF CELLULAR LIFE
• Cells have many similarities
• What are some?
• They can also be very different
• Specialization!
CELL SPECIALIZATION
• Cell specialization: cells develop in different ways to perform different tasks (structure -> function!)
• Specialized animal cells
• RBC- O2 binding proteins
• Muscle cells- overdeveloped cytoskeleton
• Specialized plant cells
• Guard cells- open/close stomata