Cells Guide Notes PDF

Cell organelles perform many different functions: **mitochondria** key aerobic (with O2) metabolism, most ATP **nucleus** holds DNA and where RNA is made **centrioles** help in cell division **nucleolus** site of ribosome synthesis **ER** makes proteins or fats **Golgi** helps process and package mo...

Cell organelles perform many different functions: **mitochondria** key aerobic (with O2) metabolism, most ATP **nucleus** holds DNA and where RNA is made **centrioles** help in cell division **nucleolus** site of ribosome synthesis **ER** makes proteins or fats **Golgi** helps process and package molecules The cytoskeleton has three major size components, made of different protein building blocks. Two **motor** **proteins** can move materials forwards (kinesin) and backwards (dynein) along the routes of the microtubules. **Microfilaments** also help with cell division. DNA is open and being accessed for protein/gene information as chromatin in the nucleus, but gets compacted down into small containers (chromatids) that are copies so that they can be divided for mitosis/meiosis. Chromosomes can refer to both of these states. Humans have 23 pairs of different chromosomes, but 46 distinct items (23 from mother and 23 from father). When DNA is open one strand can be copied to RNA (**transcription**), which then leaves to become a template for protein synthesis (**translation**). Sometimes genes have extra sections of useless DNA in them (**introns**) which are cut out leaving **exons**. Protein synthesis needs amino acids, which are brought in by tRNA. Ribosomes read the mRNA template. AUG / methionine is the start of all proteins / genes. The three letter codons translate nucleotide codes to amino acids, which become protein structures. Cells can divide for cloning and copying (**mitosis**), or to make sperm and eggs (**meiosis**). Mitosis makes exact daughter cells with the same DNA numbers and content. Meiosis makes random products (4 cells) that are infinitely variable. Crossing over or chiasma is the exchange of parts from maternal and paternal chromosomes. Metaphase is when chromosomes are in the middle, anaphase is separation, and telophase is the start of cell division by cytokinesis. Egg and sperm are haploid, and need 23 other chromosomes from the other parent. Mistakes happen frequently in this process leading to many congenital defects and fetal fatalities. For sex chromosomes, many intersex conditions are related to extra X or Y chromosomes. Addition or loss of other chromosomes leads to Down syndrome and other fatal miscarriages.