The Cell: An Overview Ch. 5; 5.3-5.5

Eukaryotes: The Nucleus Nucleus is membrane bound nuclear envelope (2x layer) How do things move through the envelope? Just like the plasma membrane, proteins (nucleoporins) channels allow entrance (nuclear pore complexes) How do they know what goes in? Short AA sequence (nuclear localization signal) acts like a zip code for the nucleus

Eukaryotes: The Nucleus What do you find inside the nucleus? nucleoplasm cytoplasm in nucleus Chromatin DNA/Protein complex Chromosomes condensed DNA Nucleolus mixture of gene regions and RNA complexes

Eukaryotes: Ribosomes Why do we have free floating and membrane bound ribosomes? Different products for different environments 1) Free ribosomes produce proteins to be used in the cytosol 2) Attached ribosomes produce proteins to be embedded in membranes or secreted Both have complex organelle path after completion

Eukaryotes: Endoplasmic Reticulum Smooth ER makes lipids and digestive enzymes for drugs and toxins Rough ER makes secreted proteins and digestive enzymes What cells in the body would have the largest smooth and rough ER? Liver cells (smooth) Digestive tract (rough)

Eukaryotes: Golgi Complex Rows of flatten sacs (cisternae) receive vesicles from areas of the cell (at cis face), modify the contents, and send them to their next location (at trans face) Most proteins are embedded or secreted (exocytosis) Some molecules drawn into the cell (endocytosis) and destroyed by fusion with lysosomes

Eukaryotes: Lysosomes Digestive sacs in animals cells (over 300) that act like recycling centers Acidic (pH ~5) Why is it important they only work in a high pH? Lowers risk of activity outside of lysosome; wont work in basic cytosol Enzymes made in rough ER and then vesicle formed from Golgi complex Roles: Autophagy digest useless organelles Phagocytosis digest bacteria pulled into the cell

Eukaryotes: Mitochondria Site of cellular respiration Double layered membrane with reactions between the cristae and the matrix What about mitochondria suggest that they used to be independent organisms? The have their own DNA and ribosomes

Eukaryotes: Microbodies Large vesicles that do various tasks: Phospholipid synthesis Breakdown fats and proteins to make ATP Breakdown toxins Peroxisomes vesicles of catalase What do they do? Breakdown hydrogen peroxide

Eukaryotes: Cytoskeleton Reinforce cell shape and allow movement around the cell Like your organs, a cells organelles must be held in place 3 groups: Microtubules Intermediate Filaments Microfilaments

Eukaryotes: Microtubules Long, wide tubes (25nm) made of α and β tubulin Charge ends, with more activity on the + end Why do they need charged ends? Can use ionic forces to hold them in place in the cell Network radiates from the cell center (centrosome) and have two perpendicular barrels (centrioles) Hold organelles in place and are tracks for vesicle movement Motor proteins (kinesins and dyneins)

Eukaryotes: Microtubules Main part of flagella and cilia 9 + 2 complex  9 double tube units around 2 single tube units Wave and oar-like movements push cell through mediums Flagella are found in all 3 domains, but their genes are different. What does this tell us about flagella evolution? It was independent even though they have the same structure and function

Eukaryotes: Intermediate Filaments Medium sized (8-12nm) fibers that connect microtubules/ microfilaments together; adds stability Not found in single-cell organisms Tissue specific have different proteins depending on the what part of the organism they are in

Eukaryotes: Microfilaments Thin fibers (5-7nm) of actin units Charged ends with more growth on the + end Main part of muscle tissue Myosin (motor protein) moves back and forth along microfibers causing contractions Cytoplasmic streaming movement of the cytoplasm Cause amoeboid movement Divided cytoplasm during division

Eukaryotes: Chloroplasts Plastid Amyloplasts starch forming cells (potato) Chromoplasts red and yellow pigments give color to fruits and autumn leaves Double membrane around the stroma (inner area) which is filled with a 3rd membrane that makes the thylakoids/grana Thylakoids have chlorophyll pigments that absorb light energy How are chloroplast and mitochondria similar? Both have their own DNA and ribosomes

Eukaryotes: Central Vacuole Functions are giant lysosome for the cell; also a storage unit Stores pigments that give flowers their color Tonoplast channels that allow transportation of materials Turgor pressure pushes against weight of cell well What happens with plants are low on water? The wilt; sag because turgor pressure drops

Eukaryotes: Cell Wall Extracellular Structure Primary soft/flexible layer expands as cell grows Secondary harder cellulose fibers used to strengthen wall lignin complex alcohol structure stronger than concrete (by weight) Polysaccharide layer (middle lamella) acts like glue to hold plant cells together Pectin used in syrup and jams How do cells communicate through these think walls? Channels (plasmodesmata) allow instant communication between plant cells

There is too much vocabulary! Homework Read Ch. 6 Vocabulary for Ch. 6 “Test Your Knowledge” Multiple choice questions on p. 114 and “Interpret the Data” on p. 115 There is too much vocabulary!