Cell Structure and Function AP Biology

Activities of Life Most everything you think of a whole organism needing to do, must be done on the cellular level… Reproduction Growth and development Energy utilization Response to environment Homeostasis AP Biology

Cell Characteristics What do all cell types have? Plasma membrane Cytosol Chromosomes Ribosomes What organelles are found only in animal cells? Lysosomes Centrosomes What organelles are found only in plant cells? Cell wall Vacuole Plasmodesmata Chloroplast AP Biology

Types of Cells Prokaryote Eukaryote DNA in nucleoid region No nuclear membrane separating DNA from rest of cell No organelles made of membranes Eukaryote Chromosomes in nucleus Chromosomes enclosed in nuclear membrane Membrane bound organelles present (compartmentalization) AP Biology

Limits to cell size Lower limit Upper limit Smallest bacteria, mycoplasm 0.1 to 1.0 microns Upper limit Eukaryotic cells 10-100 microns Micron = micrometer = 1/1,000,000 meter Diameter of human hair = 20 microns AP Biology

Surface area increases while total volume remains constant Fig. 6-8 Surface area increases while total volume remains constant 5 1 1 Total surface area [Sum of the surface areas (height  width) of all boxes sides  number of boxes] 6 150 750 Total volume [height  width  length  number of boxes] 1 125 125 Surface-to-volume (S-to-V) ratio [surface area ÷ volume] 6 1.2 6

What limits cell size? Surface area to volume ratio As cell gets bigger volume increases faster than surface area Smaller objects have greater surface area to volume ratios AP Biology

Limits to cell size Metabolic requirements set upper limit large cells, cannot move material in and out of cell fast enough to support life What process is this? aa O2 O2 CHO CHO CHO aa NH3 NH3 O2 CHO aa aa O2 NH3 aa O2 What’s the solution? AP Biology

How to get bigger? Become multi cellular (cell divides) AP Biology

Cell membrane Exchange organelle Functions as a selective barrier Allows passage of oxygen, nutrients and wastes AP Biology

Organelles and Internal Membranes In eukaryotic cells, internal membranes: Partition cell into compartments Create different local environments Compartmentalize functions Different structures for specific functions Unique combination of lipids and proteins AP Biology

Endomembrane System Play key role in synthesis (& hydrolysis) of macromolecules in cell Organelles Endoplasmic reticulum Golgi apparatus Lysosomes (animals only) Vacuoles (plants only) Vesicles Pay attention to How structure relates to function Cell type in which you would typically find structures What happens if organelle is not functioning correctly AP Biology

Fig. 6-16-1 Nucleus Rough ER Smooth ER Plasma membrane

Nucleus Rough ER Smooth ER cis Golgi Plasma membrane trans Golgi Fig. 6-16-2 Nucleus Rough ER Smooth ER cis Golgi Plasma membrane trans Golgi

Nucleus Rough ER Smooth ER cis Golgi Plasma membrane trans Golgi Fig. 6-16-3 Nucleus Rough ER Smooth ER cis Golgi Plasma membrane trans Golgi

Peroxisomes Other digestive enzyme sacs Found in plant and animal cells Break down fatty acids into sugars Easier to transport and use sugar as energy source Detoxifies cell Alcohol and other poisons Produces hydrogen peroxide (H2O2) Waste product Harmful to cell Must be broken down to H2O AP Biology

Apoptosis Programmed Cell death Occurs when digestive enzymes from lysosomes or peroxisomes are released into cell Critical role in programmed destruction of cells in multicellular organisms Some cells have to die in an organized fashion, especially during development Cancer over rides this to enable tumor growth AP Biology

Theory of Endosymbiosis mitochondrion internal membrane system aerobic bacterium Ancestral eukaryotic cell Eukaryotic cell with mitochondrion Paramecium & symbiont Chlorella photosynthetic bacterium chloroplast AP Biology Eukaryotic cell with chloroplasts

Cell Specializations What would be the function of a cell with the following properties? Large number of mitochondria Large amount of RER, SER and Golgi Absence of mitochondria, RER, SER, Golgi Absence of nucleus Presence of Chloroplast Large, flattened cell Elongated cell with many extensions Flagella, nucleus and mitochondria Large number of ribosomes AP Biology