Slide 13-2 Internal structure of a cell3-2 Internal structure of a cellSlide 43-2 Internal structure of a cell3-2 Internal structure of a cellSlide 73-2 Internal structure of a cellSlide 93-2 Internal structure of a cell3-2 Internal structure of a cell3-2 Internal structure of a cellSlide 13Slide 143-2 Internal structure of a cell3-2 Internal structure of a cellSlide 173-2 Internal structure of a cellSlide 193-3 Genes, cells, and behaviorSlide 213-3 Genes, cells, and behavior3-3 Genes, cells, and behavior3-3 Genes, cells, and behavior3-3 Genes, cells, and behaviorSlide 26Slide 273-3 Genes, cells, and behavior3-3 Genes, cells, and behaviorSlide 303-3 Genes, cells, and behavior3-3 Genes, cells, and behavior3-3 Genes, cells, and behaviorChapter 3 ReviewChapter 3b:What Are the Functional Units of theNervous System?3-2 Internal structure of a cell•Ions–Charged atoms–Positive charge if an electron is lost (Na+)–Negative charge if an electron is gained (Cl-)•Ions critical to cell function–Sodium (Na+)–Potassium(K+)–Calcium(Ca2+)–chloride(Cl-)3-2 Internal structure of a cell•How do neurons store, process, send, and receive so much information?–Most characteristics and functions of a cell are determined by the proteins it creates•The neuron–Similar to other cells; organelles3-2 Internal structure of a cell•Cell Membrane: Barrier and gate keeper–Separates intracellular fluid from extracellular fluid–Double-layered structure–Regulates the movement of substances in and out of the cell•Too much water would make it burst, too little would make it shrivel•Controls ion concentrations3-2 Internal structure of a cell•Cell Membrane: Barrier and gate keeper–Phospholipids•Create a bilayer•Hydrophilic heads and hydrophobic tails–Tails point toward each other •Water molecules cannot pass through the tails•Ions cannot pass through the heads–Only a few small molecules can pass through•Oxygen, carbon dioxide, glucosehttps://www.youtube.com/watch?v=LKN5sq5dtW43-2 Internal structure of a cell•Nucleus: Site of gene transcription–Chromosomes•holds an organism’s entire DNA sequence–DNA (deoxyribonucleic acid)•Double-stranded molecule•Each strand has a variable sequence of nucleotide bases•Adenine, thymine, guanine, cytosine (A, T, G, C)–Adenine-thymine, guanine-cytosine•Sequence of bases determines the order in which amino acids are added to form a protein–Genes•Segments of DNA that encode the synthesis of particular proteins3-2 Internal structure of a cell•Transcription–A gene segment of DNA uncoils, exposing a sequence of nucleotide bases–Attracts free-floating nucleotides–Nucleotides become attached, forming a complementary strand of mRNA (messenger ribonucleic acid) •Uracil instead of thymine–mRNA leaves nucleus and comes in contact with ribosomes in the endoplasmic reticulum3-2 Internal structure of a cell•Endoplasmic reticulum (ER): Site of RNA translation–ER consists of membranous sheets folded to form numerous channels–ER may be studded with ribosomes–Ribosomes act as catalysts in the building of proteins•mRNA genetic code is “read” in the ribosome3-2 Internal structure of a cell•Translation–Sequences of nucleotide bases of the mRNA are used to create specific sequences of amino acids•Transfer RNA assists in translation–Each group of 3 nucleotides encodes one particular amino acid•Codon: a sequence of three nucleotide bases–Example: the codon “UGG” (uracil, guanine, guanine) encodes the amino acid tryptophan–Peptide bond links amino acids•Polypeptide chainshttps://www.youtube.com/watch?v=5MfSYnItYvghttps://www.youtube.com/watch?v=5bLEDd-PSTQ3-2 Internal structure of a cell•Proteins: The cell’s product–Polypeptide chain and proteins are related, but not the same•Ribbon vs. bow analogy–A protein is a folded-up polypeptide chain–A single neuron may use as many as 10,000 proteins–Cells can make far more proteins than genes•Proteins can be folded, cut, and combined to form other proteins3-2 Internal structure of a cell•Golgi Bodies and Microtubules–Protein packaging and shipping–Proteins are wrapped in membranes and send somewhere in the cell•Vesicles (membranes containing proteins) can be carried or “walked” down microtubules to reach distal areas of the cell•Microtubules are structural proteins–Proteins that remain in the cell are unloaded into the intracellular fluid–Proteins can be exported by a process called exocytosis•Vesicular membrane fuses with the cell3-2 Internal structure of a cell•Crossing the cell membrane–Some proteins are embedded in the cell membrane to allow molecules to cross•Channels, gates, pumps–Receptors•Proteins where molecules can bind•Can cause protein to change shape3-3 Genes, cells, and behavior•Medelian genetics and the genetic code–23 pairs of chromosomes •Half from mother, half from father•22 autosomes, 1 sex chromosomes•Numbered based on size–Allele•One form of a gene (we have two)–Homozygous•Same (same allele)–Heterozygous•Different (different allele)–Wild type•Gene sequence that commonly occurs in nature–Mutation•Less frequently occurring sequence3-3 Genes, cells, and behavior•Dominant and recessive alleles–If both alleles are homozygous•Express the same protein–If heterozygous, might express physical or behavioral trait of:•The allele from the mother•The allele from the father•Both–Dominant•Allele that is routinely expressed–Recessive•Routinely unexpressed3-3 Genes, cells, and behavior•Genetic mutations–The mechanism for reproducing genes and passing them on to offspring is fallible–Errors can arise in nucleotide sequences –Genes have an average of 1200 bases•So many potential errors could arise–BRCA1•Breast cancer gene on chromosome 17•Over 1000 mutations have been found–More than 1000 ways to inherit a predisposition to breast cancer–Mutations can he beneficial or harmful•Sickle-cell anemia–Protect against malaria, but poor at carrying oxygen3-3 Genes, cells, and behavior•Allele disorders that affect the brain–Tay-Sachs Disease•Mutation of the HexA gene on chromosome 15–recessive•HexA: protein that acts as an enzyme to break down a class of lipids in the brain (but fails to do so)•Causes seizures, blindness, and degenerating motor and mental abilities–Child dies within a few years3-3 Genes, cells, and