cell structure and mitosis

• during interphase cells are in a state of growth and dna replication in prep for mitosis
• interphase is the longest phase of the cell cycle, lasting from 10-24 hours
• gap 1 (G1) - cell grows and prepares to divide by synthesizing proteins needed during S phase
• S phase - DNA replicates so that each daughter cell will have an exact copy of genetic material
• prophase - chromatin condenses into visible x shaped chromosomes, nuclear envelope breaks down, centrioles move towards opposite poles of cell, spindle fibers form between them
• metaphase - chromosomes line up along equator of cell, attached to spindle fibers at the centromere
• anaphase - sister chromatids separate and move toward opposite ends of cell pulled apart by shortening spindle fibers
• telophase - new nuclei begin forming around separated sets of chromosomes, spindle fibers disappear, cytoplasm divides
• cytokinesis - division of cytoplasm occurs through pinching or furrowing
• mitocondria have a double membrane, cristae structures, and a matrix
• chloroplasts have an outer membrane, thylakoid membranes stacked together as grana, starch granules store excess glucose made during photosynthesis
• cell fractionation and ultracentrifugation:

  • homogenise class to release organelles- must be done in isotonic, ice cold, ph buffered solutions
  • filtration- remove large debris such as large proteins
  • ultracentrifugation- spinning organelles at different speeds to remove organelles of different densities
• binary fission- circular DNA replicates , cell elongates, dna moves to opposite poles of the cell, cytoplasm pinches and new cell wall is formed
• the phospholipid bilayer has a hydrophobic tail and hydrophilic head in order to form a barrier for water soluble substances, allowing small, non-polar molecules through
• mitochondria are double membrane bound organelles that are the site of aerobic respiration, they have a highly folded inner membrane creating a cristae (for a high SA)
• ribosomes are made of RNA and proteins and are found in the cytoplasm, they can be free floating or attached to RER
• lysosomes are single membrane bound organelles that contain hydrolytic enzymes that digest and recycle materials
• peroxisomes contribute to cellular function by hydrolysing fatty acids
• viruses are acellular, they consist of nucleic acids surrounded by proteins
• in the phospholipid bilayer cholesterol maintains fluidity and also restricts the movement of other molecules.