Subcellular Architecture of the Eukaryotic Cell Prokaryotic Cells v Eukaryotic Cells Prokaryotic No nucleus No membrane bound organelles Unicellular Reproduces by binary fission Smaller than eukaryotes Eukaryotic Nucleus Membrane bound organelles Uni Multicellular Reproduces by mitosis and meiosis Larger than prokaryotes Both Have ribosomes Outer membrane DNA genetic material Organelles Nucleus Found in eukaryotic cells Most visible organelle seen through a microscope Surrounded by a membrane nuclear envelope Home of the nucleolus involved in first state of protein synthesis transcription Site of gene expression Houses DNA Ribosomes Protein synthesis occurs here Polypeptides that are synthesized in the rough ER are targeted by signals embedded in amino acid sequence Ribosomes receive the amino acid sequence from the nucleolus Free ribosome makes a polypeptide with a signal sequence that tells the cell it is going to be sent out into the body The signal reception particle connects to the signal sequence SRP helps move ribosome to rough ER which makes the ribosome bound The ribosome then binds to the rough ER The protein chain is released into the rough ER for transport and the ribosome unattaches back into the cytoplasm Two types free and bound one ribosome can be free or bound only depends on where it is needed at what stage it is in the protein synthesis cycle Free make proteins needed within the cell float around freely in cytoplasm Bound make proteins needed to be transported outside of the cell bound to the rough endoplasmic reticulum Found in both prokaryotic and eukaryotic cells Endoplasmic Reticulum ER Two types rough and smooth Rough ER involved in protein production and transport Smooth ER no ribosomes are present involved in steroid production and helps us detox degrades toxins from our bodies Golgi Apparatus Functions pack ship and store proteins into vacuoles Glycosylation occurs here Glycosylation carbohydrates sugar is added to the protein making it fully functional Lysosome Cytoskeleton Function break down material Contains hydrolytic enzymes that help degrade the molecules Used for structure and support of cell Consists of three components microfilaments intermediate filaments and microtubules Microfilaments important for cell movement support and phagocytosis cell eating consists of actin which is important for muscle contraction Intermediate Filaments most abundant component used for structure and support Microtubules made of tubulin protein important for transport within a cell and cell division mitotic spindle cilia and flagella consist of microtubules Mitochondria Functions ATP production and cellular respiration Two membranes smooth outer membrane and folded inner membrane Have their own DNA circular Many are found in the muscle cells Found in animals plants fungi protists not all throughout all Eukarya Similar to chloroplasts Endosymbiont Theory This theory states that mitochondria and chloroplasts came to be in eukaryotic cells because they used to be bacteria who became engulfed by larger anaerobic cells and had an endosymbiotic relationship in order to survive the Oxygen Revolution because mitochondria and chloroplasts need oxygen to produce energy Evidence both mitochondria and chloroplasts Double membrane Circular DNA similar to bacteria More than one within one cell hints at possible binary fission Size similar to bacteria Protein synthesis similar to bacteria Mitosis and Meiosis Cell Cycle Eukaryotic G1 growth phase S synthesis phase DNA is replicated G2 growth phase M Mitosis Meiosis Function of mitosis used for growth in multicellular organisms and used for reproduction for unicellular organisms Karyokinesis splitting of chromosomes nucleus Cytokinesis splitting of cytoplasm other organelles Cytokinesis and mitosis are not related one can occur without the other Mitosis creating a new cell that is genetically identical to the parent cell Cloning Equatorial division amount of DNA in parent cell amount of DNA in daughter cell 1 2N 2 2N Genetically identical daughter cell unless there is a mutation 2N diploid chromosomes come in pairs 2 copies of each type of chromosome One from mother and one from father Stages of Mitosis Prophase chromosomes condense Prometaphase fibers microtubules attach to chromosomes at the kinetochore Kinetochore protein structure that forms at the centromere Metaphase chromosomes align in the center Anaphase chromosomes are separated and moved towards opposite poles by the microtubules Telophase chromosomes decondense cytoplasm divides equally cytokinesis In mitosis meiosis the nucleus divides Microfilaments constrict forming a cleavage furrow in animal cells Cell plate forms in the middle causing the cytoplasm to split in plant cells Chromosomes are counted by the centromere not by how many arms there are Asexual vs Sexual Reproduction Asexual Typically involves one parent Involves two parents Cloning Offspring is genetically identical to parent Sexual Genetic variation occurs since offspring is a combination of both maternal and paternal genes Both Reproduce a new individual Meiosis one parent cell divides and creates four new haploid cells creates genetic variation Reductional division Ploidy level decreases 1 2N 4 1N Generates genetic variation Crossing over Prophase 1 During Prophase 1 homologous chromosomes synapse which means they move together and physically connect through that connection crossing over can occur between non sister chromatids within a homologous pair Independent assortment Metaphase 1 During Metaphase 1 the non homologous chromosomes move independently from each other to the metaphase plate this causes different combinations of genes Fertilization restores diploid number 1N 1N 2N Meiosis 1 separates homologous chromosomes Meiosis 2 similar to mitosis equational division separates sister chromatids Only organisms with even ploidy levels can undergo meiosis All ploidy levels can undergo mitosis