Fundamental Units of Life – CELLS!

Living Compartments Organisms can exist as a single cells - amebas Cells vary in size and shape; each is basically a fluid filled bag in which various structures are housed Ok.. Why do have this fluid filled bag? Why is it’s composition similar to sea water? Internal structures are called organelles (little organs in latin)

Living Compartments Intracellular = “inside of the cell” Extracellular = “outside of the cell” Organelles are small membrane bound structures that have specific functions within the cell Prokaryotic = DO NOT have a membrane-bound nucleus or organelles Eukaryotic = Have a membrane bound nucleus and membrane-bound organelles

Living Compartments

Prokaryotic vs. Eukaryotic

Plant Cells vs. Animal Cells Cell Wall Vacuole

Cell Structure Cell Wall PLANT CELLS ONLY!! Composed of complex carbohydrate-cellulose Humans are unable to digest cellulose because the appropriate enzymes to breakdown the beta acetal linkages it has are lacking. FIBER! Support, rigidity, and protection Surrounds plasma membrane PLANT CELLS ONLY!!

Cell Structure Plasma membrane (cell skin?) Double lipid bilayer (2 layers) Composed of protein and phospholipids The membrane regulates the exchange of substances (nutrients/waste/signaling molecules) between the cell and its surrounding BOTH animal and plant cells have a plasma membrane.

Cell Structure Cytoplasm (cell blood?) BOTH plant and animal cells liquid substance inside the plasma membrane and outside the nucleus Where biochemical reactions occur and organelles are suspended BOTH plant and animal cells

Cell Structure Flagella / Cilia (cell feet/arms?) Aid in locomotion BOTH Plant and Animal cells can have these. Flagella Cilia

Cell Structure - Organelles Nucleus (cell brain?) Contains genetic instructions (DNA) Controls cellular activities BOTH plant and animal cells

Cell Structure - Organelles Mitochondria (cell engine?) Release of energy from sugars in the form of ATP through cellular respiration BOTH plant and animal cells

Cell Structure - Organelles Chloroplasts Acquire energy through light (absorb photons!) and convert into chemical energy by photosynthesis Contain green photosynthetic pigments - chlorophyll. PLANT Cells ONLY!!!

Cell Structure - Organelles Ribosomes Protein synthesis BOTH Plant and Animal Cells

Cell Structure - Organelles Endoplasmic reticulum (cell circulatory system?) Transport of proteins and synthesis of lipids BOTH Plant and Animal cells

Cell Structure - Organelles Golgi Bodies (cell post office) Modification, packaging and shipping of proteins, lipids and carbohydrates BOTH Plant and Animal cells

Cell Structure - Organelles Central vacuoles (plant cell stomach?) Storage of water, wastes, and nutrients Influences cell size and shape – TURGOR PRESSURE PLANT cells ONLY!!!

Cell Structure - Organelles Lysosomes – (cell digestive tract?) Contain enzymes for intracellular digestion of bacteria, cellular debris, and worn out cell parts Animal Cells ONLY!!! Centrioles (cell bones?) Organize part of the cytoskeleton (protein filaments) in animal cells Animal Cells ONLY!!!

Things to do Today Observing Unicellular organisms Paramecium Euglena Volvox Amoeba (from video) Observing cells of multicellular organisms Animal Plant Steps of the scientific method

Observing Unicellular organisms Most bacteria and protists are usually unicellular organisms All protists are eukaryotic; depending on their means of acquiring energy, they might have different organelles Protists are particularly abundant in aquatic habitats Preparation of a wet mount

Preparation of a Wet Mount Put 1 small drop of sample from dropper onto the glass slide Slowly lower the cover slip onto the drop of sample at an angle to avoid air bubbles between the slide and the cover slip Find sample with the 10X and move onto the 40X (4x won’t give you any image) Some organisms move rapidly; if it’s not moving or if you are using the 4x you probably aren’t looking at the right thing After viewing each sample wash the slide with water at the sink and dry it with KIMWIPES If you broke a cover slip or a slide, place the pieces in the red “sharps” box

Unicellular organisms

Observing the Cells of Multicellular Organisms Multicellularity allows specialization of cells and division of labor Example: Spermatocytes (“sperm”) are extremely specialized cells that transport chromosomes from a male’s reproductive system to an egg in a female’s reproductive system. Plant cells produce their own food and thus are more stiff, green and stuck in one place Animal cells are more mobile and are able to seek out and consume plants and other animals

Preparation of a Wet Mount Pluck single leaf from the Elodea, place the leaf on the slide and put 1 drop of water on the leaf Place a cover slip on the leaf slowly to avoid air bubbles Make sure the leaf is spread flat against the slide as you add the cover slip Locate the: cell wall, central vacuole, and chloroplasts

Preparation of a Wet Mount Obtain human epithelial cells from inside of your mouth with a toothpick Put a drop of methylene blue on a glass slide and dip the end of the toothpick with the sample into the drop and stir Place the cover slip onto the slide and observe Make sure you see the: Plasma membrane, cytoplasm and nucleus

Elodea vs. Epithelial Cells

The Study of Life Scientific method: biologists used to study life in systematic way Observation  Question  Hypotheses Predictions Experiment  Collect/Analyze data  Conclusions  Report findings Hypothesis can be written in several forms Null (no effect) statement/ hypothesis Alternative hypothesis

The Study of Life Predictions: often written as “If…, then…” statements e.g. If I show up late to class, then my teacher will kill me.

The Study of Life Elements to consider in the design of experiments Independent or experimental variables Factors deliberately manipulated that will result in a measurable effect (water) Dependent or measured variables Dependent variables DEPEND upon the INDEPENDENT variable Factors that are measurable (plant height) e.g. My grade is dependent upon how much I study? Grade = dependent variable Time Studying = independent variable

The Study of Life Elements to consider in the design of experiments Confounding variables Standardized variables Factors that could influence the outcome of the exp. but are not of primary interest to the investigator. These are kept the same across all treatments.

The Study of Life Elements to consider in the design of experiments. Experimental treatments Independent (experimental) variable is manipulated. Control treatments Independent (experimental) is eliminated or set to standard

Test your understanding Read the paragraph and identify the variables and different groups. Exercise 3: Investigating what lives in pond water. (pg. 18-20)