Cell Membrane
advertisement
Ch 1 - The Cell & Cell Processes The Cell P All cells have < Cell membrane - phospholipid bilayer surrounding cell parts < Cytoplasm - everything between cell membrane + nucleus P Most cells have < Nucleus - “brain” of the cell < Contains DNA (instructions) P Prokaryotes < Have no nucleus in cell(s) < Ex. Bacteria, red blood cells P Eukaryotes < Have well organized nucleus in cell(s) < Ex. Most plant and animal cells Nucleus Site of DNA replication + transcription P Nuclear membrane < Membrane surrounding nucleus, has pores < Controls what can enter or leave nucleus P Nucleoplasm < Jelly-like material inside nucleus < Helps give nucleus shape, support P Nucleolus (or nucleoli) < Dense body rich in rRNA + subunits < Involved in ribosome production P Chromosomes (chromatin form) < Each = protein core with DNA wrapped around it < Contains instructions for cells; genes code for proteins ~ traits Cell Membrane “Selectively permeable phospholipid bilayer” P Selectively permeable < Controls what can enter and leave cell P Phospholipid bilayer < < < < < < Phospholipids are special fats Hydrophobic tails, hydrophilic heads Arrange so protect hydrophobic parts Tails go inside, heads twd water Several proteins embedded in it Cholesterol also embedded ~ rigidity P “Fluid Mosaic” Hydrophilic Head Hydrophobic Tails Membrane Proteins embedded in phospholipid bilayer P Signature molecules (glycoproteins) < have sugar part that sticks out for identification/recognition of cell P Gatekeepers < Allow only certain materials to enter or leave cell P Receptor sites < Hormones bind to receptor and initiate cell response P Enzymes < Proteins that act as catalysts for reactions (speed up) P Transport proteins (move substances across membrane) < Active transport - against [ ] gradient; requires ATP < Passive transport - down [ ] gradient; no ATP needed Cytoplasm P Contains: < Water, nutrients, wastes < Building blocks of materials needed by cell < Organelles P Organelles < “small organs” that work together to keep cell alive < Each type has a special function < Note: some differences between plant and animal cells Organelles P Mitochondria (mitochondrion, s) < < < < < “powerhouse of the cell”, oval shaped Double membrane, smooth outer Folded inner membrane Folds (cristae) allow for more SA Site of cellular respiration (food þ energy) P Ribosomes < “protein factory”, site of protein synthesis < Reads message (mRNA) from nucleus and puts amino acids in proper order < Some free in cytoplasm, some stuck on ER Organelles P Endoplasmic reticulum < < < < Double membrane channel Transports materials through cytoplasm Smooth: no ribosomes attached (~ fats) Rough: ribosomes attached (~ proteins) P Golgi Body (Golgi Apparatus) < “processing & packaging factory” < Processes and packages into vesicles < Contents sent to membrane or out of cell P Lysosomes < < < < “suicide sacs”, small round bodies containing enzymes fuse with “old cell parts” to break them down and recycle parts fuse with foreign particles to destroy them (ex. in WBCs) fuse with food vacuoles to help break down nutrients Organelles Cytoskeleton Parts P Microfilaments < Pipelike structures made of proteins (actin, myosin) < Imp for structure + mvmt, changes in cell shape < Ex. Muscle contraction, ameboid mvmt P Microtubules < < < < Hollow cylinders made of spherical protein, tubulin Transport materials through cytoplasm Part of cytoskeleton, helps give cell shape Involved in movement of cell (cilia or flagella) – Cilia - tiny hairlike structures that aid movement (oars) – Flagella - longer whiplike structures that propel cell forward Organelles P Vacuoles < Storage spaces within cell for food, water, or wastes < Animals have a few small ones < Plants have very large central one for water P Centrosome < “Microtubule organizing center” < Contains centrioles in animal cells < Involved in spindle formation during cell division Centrioles P Centrioles < < < < Chromosome Only in animal cells Composed of microtubules Involved in spindle formation during cell division Work with spindle to pull chromosomes apart during division Special Plant Cell Features P Cell Wall < Outside layer provides support, protection, shape < Composed of cellulose (provides roughage for us) P Plastids < < < < < Associated with production and storage of food Usually contain pigments Cells reflect the color of the pigment they contain Chromoplasts - store pigments; yellow, orange, blue, red Amyloplasts - store starch; no pigment so colorless P Chloroplasts (another plastid) < site of photosynthesis; contain chlorophyll (green pigment) < Chlorophyll traps energy from sun for photosynthesis < Grana = stacks of membranes that increase SA to trap light Animal Cells vs Plant Cells Animal Cells Plant Cells 1. No cell wall 1. Have a cell wall 2. Few, v small vacuoles 2. Large central vacuole 3. Centrosome with centrioles 3. No centrosome or centrioles 4. No plastids 4. Have plastids (ex. Chloroplast) 5. No crystals 5. Have crystals (raphides, druse) 6. Store carbs as glycogen 6. Store carbs as starch 7. Can change their shape 7. Have fixed, rectangular shape Animal Cell Pinocytotic vesicle Lysosome Golgi vesicle Mitochondrion Golgi Body / Apparatus Nucleolus Rough Endoplasmic Reticulum Smooth Endoplasmic Reticulum Centrosome Vacuole Cell Membrane Nucleoplasm Nuclear Membrane Centriole Microtubule Cytoplasm Ribosome Nucleus Plant Cell Golgi vesicle Ribosome Smooth Endoplasmic Reticulum Nuclear Membrane Nucleolus Nucleus Nucleoplasm Rough Endoplasmic Reticulum Cell Wall Cell Membrane Golgi Body / Apparatus Chloroplast Granum (grana, pl) Raphide Crystal Central Vacuole Amyloplast Druse Crystal Mitochondrion Cytoplasm Cell Processes P Passive Transport < Diffusion < Osmosis < Solutions: hypotonic, hypertonic, isotonic P Active Transport < Transport proteins < Endocytosis (Phagocytosis, Pinocytosis) < Exocytosis Passive Transport Diffusion P Description < Mvmt of substance from hi [ ] / pressure to low [ ] / pressure P Example < O 2 diffuses fr blood (8 [ ] ) to tissues (lo [ ] ), CO 2 opposite Passive Transport Theory Behind Diffusion P Brownian motion < Mculs move about randomly and collide < Collisions force molecules to spread apart (to fill an area) P Factors that affect rate of diffusion < Temperature - 8 temp, 8 speed of mculs, 8 collisions, 8 rate < Concentration - 8 [ ] , 8 # particles colliding, 8 collisions, 8 rate < Pressure - 8 pressure, 8 bunched tog, 8 collisions, 8 rate Passive Transport P Facilitated Diffusion < Specialized carrier proteins aid and speed up mvmt of certain mculs across membrane < Ex. Glucose diffusion across membranes Diffusion through Channel Facilitated by Carrier Protein Passive Transport Osmosis P Description < Mvmt of water mculs fr area of hi [ ] to low [ ] < Note: mvmt of WATER molecules not solute particles < Misconception: easy to confuse with diffusion (mvmt of solute) water mcul solute mcul Osmosis = mvmt of fr hi to low [ ] Passive Transport Osmosis P Solution Descriptors < Hypertonic solution - has more solute than the one being referred to < Hypotonic solution - has less solute than the one being referred to < Isotonic solution - has the same amount of solute Which Way Will H 2O Move? Solute particle Cell Container of solution Osmosis H2 O moves in, cell swells (In plant cells, causes turgor pressure) (In animal cells, may burst = cytolysis) Cell in hypotonic solution Osmosis Cell in hypertonic solution H2 O moves out, cell shrinks (plasmolysis) Active Transport “Capture and Release” P Theory < In some cases, transport proteins capture or bind solute mculs with proper shape and move them across the cell membrane Active Transport Pumps P Theory < Some transport proteins actively pump substrates across membrane < Ex. Sodium-potassium pumps in nerve cells use energy to pump Na+ and K+ to proper sides of nerve cell membrane for nerve to fire < 3 Na+ out for every 2 K+ in Active Transport Endocytosis PGeneral Definition < Process by which materials too large to fit through pores or channels in membrane are moved from outside to inside cell PPinocytosis < Cell membrane pinches inward forming vesicle < Brings in liquid material (sm particles) PPhagocytosis < Cell membrane extends around large object < Forms vesicle as brings material in < Ex. Amoeba feeding < Ex. WBC capturing bacteria Active Transport Exocytosis P General Definition < Process by which large materials within the cell are transported to the outside of the cell < Materials are carried inside vesicle to cell membrane < Vesicle fuses with membrane and releases contents < Ex. Removal of wastes, secretion of proteins, neurotransmitter release
