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Transcript
Unit 1: The Unity and Diversity of Living Things “We are educated to be amazed by the infinite variety of life forms in nature; we are, I believe, only at the beginning of being flabbergasted by its unity.” Lewis Thomas author “The Lives of a Cell” Biology living/once- “the study of” living things What determines if something is living? There is no single definition of life. However, there is a list of characteristics by which we determine if something is living or not. In order to be considered “living”, you need to display the potential for all of the following life functions: 1. Nutrition- obtaining materials from the environment and processing them for use within the organism. a. heterotrophs- organisms that consume food ingestion- taking in food digestion- breaking down food egestion- removal of undigested or indigestible food ex) corn, fiber, throwing up What must an oak tree do to stay alive that both a fly and a human must also do? b. Autotrophs- “auto”= self, “trophic”= nutrition *Photosynthesis: chlorophyll CO2 + H2O light C6H12O6 + O2 + H2O enzymes *Chemosynthesis: Some types of bacteria carry out the process of making food by using energy from inorganic compounds like CO2 rather than from sunlight. •occurs deep in the ocean where there is no sunlight 2. Transport- the absorption and circulation of materials within an organism •a. single-celled organisms (or any cell w/in an organism… materials are diffused/absorbed directly across the cell membrane •b. multi-celled organisms-most cells aren’t in contact w/the environment so a circulatory system is needed 3. Respiration- The exchange of O2 and CO2 AND the release of energy that is stored in food molecules. •a. anaerobic- does not use oxygen, produces little energy •b. aerobic- does use oxygen, produces lots of energy, more efficient C6H12O6 + O2 (glucose) CO2 + H2O + Energy (36 ATP) 4. Excretion- the removal of wastes from cells + from an organism which were produced during life processes. •lungs remove CO2 + H2O •skin removes H2O, salts + urea •kidneys remove H2O, salts + urea •liver removes dead RBCs 5. Synthesis & Assimilationchemical reactions where large molecules are built from smaller ones The incorporation of these synthesized molecules into the organism’s body Ex) when proteins become part of a body builder’s muscles from a proteinrich diet “You are what you eat!!!” 6. Regulation- the control & coordination of all life activities in an effort to maintain homeostasis (stable internal environment) 2 systems involved: •a. nervous- electrical: brain, spinal cord, nerves •b. endocrine- chemical: hormones, glands 7. Growth- increase in size and/or number of cells • you grow in # of cells from infant teen • an ameba’s 1 cell can increase in size • requires materials that were synthesized from the nutrients ingested • includes differentiation (cell specialization) in multi-cellular organisms 8. Reproduction- creating a new organism/cell ~species survival is dependent on reproduction, individual survival is not. ~asexual & sexual •1 parent, •identical offspring, •no variety •2 parents, •offspring have a combination of parents’ traits Metabolism the total of all life processes/chemical reactions working together to sustain the organism anabolism- synthesis of complex molecules from simpler ones requires energy ex) photosynthesis, growth catabolism- the breakdown of complex molecules into simpler ones releases energy ex) digestion of carbohydrates Homeostasis The maintenance of a stable internal environment w/in an organism ex) maintaining a constant body temperature, blood sugar level End of notes for Life Function Quiz Borderline cases of living things: Seeds, flower bulbs, viruses, HIV They display only some of the life functions some of the time. At other times, they are said to be dormant (“sleeping”) More on viruses…….. •contain genetic material but lack other cell structures to carry out metabolism •the DNA/RNA is wrapped in a protein coat •they are not cells and do not fit into any kingdom •they cannot reproduce without a host cell •survive by attacking a living cell, use the cell’s machinery to reproduce which leads to death, disease …….disruption of homeostasis!! http://phschool.com/ Enter code cbp-6192 How did we discover the cell? The Cell `the basic unit of all living things Historical Background A. 1600s 1. Robert Hooke- coined the word “cell” when looking at cork w/a compound microscope (he was seeing their cell walls) 2. Anton Von Leeuenhoek- used a simple microscope (1 lens). He was the 1st to see living cells (blood, pond water organisms) B. 1800s 1. Dutrochet- (1824) stated that all living things are made of cells 2. Brown- (1831) 1st to see a nucleus 3. Schleiden (1838)- said that all plants are made of cells 4. Schwann (1839)- said that all animals are made of cells 4. Virchow (1855)- said that all cells arise from other cells These discoveries led to the development of the Cell Theory 1. All living things are made of 1 or more cells. 2. Cells are the basic unit of structure and function (can carry out life processes). 3. New cells arise from other cells. Exceptions to the Cell Theory ~where did the 1st cell come from? ~viruses: not made of cells, contain DNA, can only reproduce w/host cell Laser clip “Intro to Cell Study” Microscopes 1. Simple•1 lens •magnifies 3-10 times •AKA magnifying glass 2. Compound- (what we use at school) •2 lenses •magnifies 40-400 times • See diagram ocular/eyepiece body tube nosepiece objective lens arm objective lens objective lens stage clips stage coarse adjustment diaphragm light fine adjustment base 3. dissecting/stereo microscope•2 eyepieces: binocular •magnifies 6-60 times •shows external features (ex. fly, ladybug) •creates a 3-D image 4. Electron- SEM video •developed in 1930s •bounces electrons off of specimen (instead of light) •creates a 3-D image •magnifies more than 250,000 times •views specimens in a vacuum (kills live specimens) Tips for microscope use: •Start on low power •Brighter •Larger field of view •When you switch from low to high: •center your specimen, b/c you will only see a fraction of the center of the specimen when you go to high power •the field of view gets smaller and darker •only use fine adjustment on high power •objects appear upside down and backwards in the field under the becomes scope •when you move the slide to the left, the image moves to the right & vice-versa Preparing a wet mount slide: •add a drop of water to a slide •add specimen (cheek cell, onion cell, etc.) •put coverslip on at a 45o angle (removes air bubbles) Staining a specimen: •Place 1 drop of stain at the edge of the coverslip •Place a paper towel at the opposite edge so that the water from under the coverslip is absorbed and stain is drawn under coverslip paper towel stain Microscopic Measurement: Units: in a meter, there are 1000mm (millimeters) in 1 mm., there are 1000 um (micrometers/microns) Determine the approximate diameter of the cell in um. The cell takes up approx one quarter of the field 1.6 mm. (diameter of the field of view) 1.6 / 4 = .4 mm. = 400um Other laboratory equipment: Centrifuge/ultracentrifugemachine that spins specimens at high speeds which separates the materials w/in the specimen according to density heaviest materials settle to the bottom can be used to separate out cell parts (nucleus from ribosomes…) Micro-dissection Instrumentssurgical instruments that cut apart microscopic things (ex. removing a nucleus from a cell) Incubatorkeeps specimens warm (premature babies, cell samples) Chromatography “chrom” = color process in which a substance (ink, chlorophyll) is separated into its component parts/colors The rate at which the components move/separate are unique to the substance being tested By comparing the separation of the unknown substances to that of a known substance, an identification may be made. Misc Lab Tips…. Always wear goggles when using chemicals. When heating a material in a test tube: point tube away from you never put a stopper in the tube glassware: beaker test tube Graduated cylinderflasks always read volume at meniscus Science uses the metric system: grams liters meters with prefixes such as millicentikilo- Conducting an Experiment: A valid experiment must have the following elements: A question you are trying to answer or problem you want to investigate A control- the setup that remains the same through the experiment; provides a comparison A variable- the element/factor that changes in the experiment (amount of sun, water) -a valid experiment tests only ONE variable at a time independent- variable that does not depend on a factor in the experiment (ex. time, days) dependent- relies on the independent variable ex) plant growth depends on time, time does not depend on plant growth A hypothesis- possible answer to the question you are asking often posed as an “if…then…” statement An observation- what you see happening; provides data for analysis A conclusion- Sums up the findings. Scientists use the data to determine whether the hypothesis was supported or refuted Sample size- Refers to the # of organisms being tested. The larger the sample size, the more valid the results are. The Cell Smallest unit of living things 2 types of cells: Prokaryotic Lack membrane-bound organelles No nucleus 1 to 10 um. (smallest organisms) Include bacteria/Monerans cell membrane DNA Slimy coating ribosome (only organelle) Cell wall (not the same as in plants) Eukaryotic Present in all living things but bacteria Have many tiny “organs” called organelles These organelles carry out life functions Cells can be organized into more complex levels: organelle cell tissue organ organ system organism Cell size & scale animation Cells are specialized to perform different functions ex)nerve cells carry electrical messages muscle cells move body parts gland cells produce hormones Cells are most often microscopic (10- 100 um) exceptions: chicken egg- 6 cm. nerve cell- up to 1 meter! Importance of cell size: cells are small so that they can get materials in & out at rates that meet the cell’s needs (nutrients in, wastes out) Surface Area to Volume Ratio The larger the ratio, the more materials that can pass across the membrane Small cells have a bigger ratio Larger cells have smaller ratios (less efficient) Many structures outside large cells are farther from the membrane than in a small cell To calculate surface area/volume ratio: For convenience in calcualtions, consider a cell to be shaped like a cube If the length of the side is 1 cm., surface area= l x w x # sides 1 x 1 x 6 = 6 cm.2 Volume = l x w x h 1 x 1 x 1 = 1 cm3 Surface area/volume ratio = 6/1 or 6:1 If the cell was bigger…. (sides were 2 cm.) surface area= l x w x # sides 2 x 2 x 6 =24cm.2 Volume = l x w x h 2 x 2 x 2 = 8 cm3 Surface area/volume ratio = 24/8 or 3:1 Ratio is smaller than the cell w/1 cm. sides. This is b/c volume more rapidly than surface area, causing the ratio to This can cause serious problems for the cell. therefore, larger ratios (found in smaller cells) are more efficient in the transport of materials across cell membranes End quiz info (no scientists on quiz) Cell Organelles subcellular structures suspended in cytoplasm (the watery material inside the cell where chemical reactions occur) carry out life functions 1. Cell (plasma) membrane- surrounds the cell is selectively permeable (regulates the passage of materials into and out of the cell) and therefore maintains homeostasis (tries to) 3 components: a. cholesterol (soft, waxy substance) b. double lipid layer: Video clip: membrane hydrophillic (H2O loving head) hydrophobic (H2O fearing tail) c. proteins- float in lipid layer ~transport- helps move substances across membrane ~receptor- acquire info from extracellular area & relays it into cell via cytoplasm - posseses special shape that fits particular molecules; helps regulation - disruption of homeostasis…..HIV fools receptors w/its shape!! ~markers- often have branching carbohydrates - like “name tags” on cells that identify them as your cell & not someone else’s Fluid Mosaic Model cell membrane described as such by J.S. Singer (1972) due to the fluid movement of the differently shaped (“mosaic”) molecules of the membrane *Life function: Transport, Regulation, Excretion endocytosis: cell membrane forms a pocket to take in materials pinocytosis- materials are small molecules/ liquids phagocytosis- materials are large solids (ex. when a WBC engulfs a virus 2. nucleus- control center for the cell (brain) membrane contains pores to allow exchange of materials btwn. nucleus & cytoplasm contains: nucleolus- (directs ribosome production) chromatin-(DNA in thread-like form) chromosomes- (DNA in rod-like, coiled form) *Life function: regulation, reproduction, metabolism, etc 3. nucleolus inside nucleus produce ribosomes & ribosomal RNA *Life function: synthesis 4. ribosomes synthesize proteins may be free in cytoplasm or lining E.R. *Life function: synthesis 5. Endoplasmic Reticulum- (“ER”) a network of fluid filled channels connected to the nuclear membrane transport proteins w/in cell smooth ER- not lined w/ ribosomes also responsible for lipid synthesis & detoxification rough ER- lined w/ribosomes also responsible for protein synthesis small regions of ER bud off to produce vesicles (pouches) containing the newly synthesized proteins (then transported to golgi for packaging *Life function: transport, synthesis 6. Golgi body/complex stack of membranes/enclosed sacs receives vesicles from ER, packages & ships them to cell membrane for release (exocytosis) secretory vesicles that are produced in the golgi also release their contents by exocytosis *Life function: none 7. lysosomes- “stomach” of the cell small sacs that contain hydrolytic (digestive) enzymes carry out intracellular digestion fuse w/vacuoles to break down ingested materials can break down cell’s own materials & release endproducts into cytoplasm for reuse has an acidic pH (5) as opposed to the cytoplasm (7) *Life function: nutrition 8. vacuole membrane enclosed sacs formed after endocytosis (transporting material into a cell via a vesicle) ~food: contain food & fuse w/lysosome ~ contractile: in freshwater protists, pumps out excess water plant vacuoles are much larger than animal *Life function: nutrition, excretion, homeostasis 9. mitochondria- (powerhouse) site of cellular respiration; releases energy, ATP Inner membrane (cristae) is highly folded. This increases surface area for chemical reactions to occur; very efficient *Life function: respiration Test your skills w/this activity: “Name that organelle” 10. centrioles found only in animal cells function in cell division *Life function: reproduction, synthesis 11. plastids- found in photosynthetic eukaryotes a. chloroplasts- contain chlorophyll • site of photosynthesis • contains its own DNA • membranes arranged in stacks called grana • the protein-containing material that fills the rest of the chloroplast is called stroma b. leucoplasts- colorless, stores starch c. chromoplasts- contain pigments that give color to fruits, flowers & leaves. *Life function: synthesis, nutrition 12. Cell wall non-living surrounds & supports plant cells composed of cellulose (complex carbohydrate) 13. cytoskelton- structures that provide support & shape for the cell microtubules~hollow rods made of a protein called tubulin ~make up centrioles, cilia & flagella ~give structures their shape ~also found in cytoplasm microfilaments~long, solid thread-like strands ~made of a protein called actin ~thought to have the ability to contract; responsible for: cyclosis- movement of cytoplasm in cell muscle contraction intermediate fibers~size is “intermediate” btwn. microtubules & filaments ~provide structure for the cell ~thought to form a basketlike structure to hold Protein Activity inside Cells: nucleolus makes ribosomes E.R. ribosomes make proteins E.R. proteins taken to proteins E.R. membrane packaged & released in golgi to body so they can be used body synthesis & assimilition *reminder……… A cell can be part of a multicellular organisn (dog, tree) OR A cell can be an entire organism (ameba, paramecium) HOW?! • the organelles present in a single celled organism act like the systems (resp., excretory, etc) in a multicellular organism • these organisms perform all of the life functions needed to stay alive *reminder……… plant cells Large vacuoles Chloroplasts No centrioles Cell membrane & cell wall “cyto” = prefix meaning cell Laser clip: cell *review life funct animal cells Small vacuoles No chloroplasts Centrioles Cell membrane only