Nonnuclear submarines use batteries for power when submerged. (a) Find the magnetic field 50.0 cm from a straight wire carrying 1200 A from the batteries to the drive mechanism of a submarine. (b) What is the field if the wires to and from the drive mechanism are side by side? (c) Discuss the effects this could have for a compass on the submarine that is not shielded.
Unit 7 - Cell Structure & Organelles The Nucleus • Nucleus - carries and shields the DNAinformation of a eukaryotic cell and provides a special environment for DNAreplication processes, 1-10 um in size. • DNAtranscribes RNA • RNAare then exported from the nucleus out into the cytoplasm, translation occurs there. • Nuclear envelope - encloses the nucleus, separates the cytoplasm from the nucleoplasm. • Double membrane, each consisting of a lipid bilayer with appropriate proteins (e.g histidine). • The envelope has pores. • Transport in and out of the pores are selective. • Each pore = 100nm across • The endoplasmic reticulum is connected to the membrane (NOTE: do not mistake the connection for a “gate” into the nucleus, the ER is not directly related to transport in and out of the nucleus). • Nucleolus - a structure within a nucleus that synthesizes rRNAas and the rRNAassembles of proteins imported from the cytoplasm. • They then exit the nuclear pore onto their next step. Transport in/out of the Nucleus • Transport in and out of the nucleus is a selective process. • mRNAexit the nucleus and is translated in the cytoplasm. • DNA/RNApolymerases and other nuclear proteins enter the nucleus while other cytoplasmic material and organelle proteins are kept out. • Nuclear Targeting signal - a signal specifically designed to specify cellular destination. • Sequence contains 4-8 amino acids. • Often K, R, and P. Why is secretion important • Cells need s
