anat and phys lecture 3 (cellular biology part 2)

nucleus

control center for cellular function, contains genetic material (DNA)

• large cells with large amount of cytoplasm have to be multinucleate

• red blood cells are the only cell lacking a nucleus

nuclear envelope

double membrane-outer and inner

• outermembrane is continuous with the ER

• nucelar pores: points where inner and outer membrane fuse

• selectively permeable

• perinuclear cisterna: fluid between inner and outer membrane

nucleoli

• no membrane

• ribosome subunits are assembled here : has DNA that encodes for rRNA to be produced

chromatin

nucleosomes: structural units of chromotin/chromosome, DNA wrapped around histone (protein)

cell cycle

interphase and cell division

interphase

G1 phase (Gap Phase #1): cell carries out routine metabolic activities, little to no cell division activities

• G0 phase: cells that do not divide stay in G0 phase, could mean that cells are on their way to death (apoptosis), could be because their function doesn’t let them divide (neurons and cells of the heart), cells can return to G1 phase

S phase (Synthetic Phase): cell synthesizes DNA, DNA is replicated, centrioles are also replicaed

G2 phase (Gap Phase #2): cell grows larger, necessary proteins for division are produced,

cell division

mitosis: produces two daughter cells that are identical to the mother cell

meiosis: gamete production, two consecutive divisions that produce four daughter cells with half as many chromosomes as the mother cell and are genetically unique from mother cells

mitosis

prophase: chromatins in the nucleus condense to look like chromosomes (Chromosomes are already replicated and consist of two sister chromatids)

prometaphase; nuclear envelope and nucleleoli break down and spindle fibers from the centrioles bind to the kinechore (proteins on the centromere)

metaphase: chromosomes line at the metaphase plate

anaphase: spindle fibers pull the sister chromatids to opposite sides of poles (each chromatid becomes a chromosome), centromeres of chromosomes split, cytokinesis begins

telophase: nuclear envelope and nucleoli reform around each set of chromosome to create two separate nuclei, chromosomes uncoil to become chromatins, spindle fibers disassamble

cytokinesis

the division of cell cytoplasm to produce to new cells

• peripheral microfilaments pinch at the cleavage furrow to squeeze cells apart

meiosis

Meiosis 1:

• prophase I:

  • synapsis: the process where homologous chromosomes come together and form tetrads

  • crossing over: exchanging mother and father genetic material, exchanging parts of chromosomes

  • chiasmata: points where crossing over occurred

• prometaphase I: nuclear envelope and nucleoli break down, spindle fibers attach to centrosomes

• metaphase I: tetrads meet at the middle of cell

  • orientation of maternal/paternal chromosome is random

• anaphase I: spindle fibers pull homologous (maternal and paternal) chromosomes causing them to separate and break at crossing over points, centromeres are intact

• telophase I: nucelar envelope + nucleoli reform, chromosome uncoil to become chromatin, spindle fibers disasmble

Meiosis 2: same process as mitosis, but DNA is not replicated

transcription

• occurs in the nucleus

• DNA unwinds and a template strand is used for RNA polymerase to make mRNA (gene that is now transportable)

• tRNA and rRNA are also produced in the nucleus

• mRNA leaves the nucleus through nuclear pores and to the ribosomes of rough endoplasmic reticulum

translation

• occurs in cytoplasm, ribosomes in the rough ER

• ribosome associated with the endoplasmic reticulum holds and moves the mRNA systematically to allow protein to be synthesized (mRNA codes for the amino acids)

• there are unique tRNAs for specific amino acids, tRNAs find the amino acids and bring it to the next codon

• building hundreds/thousands of proteins at a time

free ribosome

to manufacture proteins that don’t have to be translated, packaged, and secreted, but proteins that can simply be translated and released into the cytoplasm

• manufacture proteins that don’t leave the cell

primary structure

the sequence of amino acids that is produced in the ribosome

after translation in ribosome of rough ER

proteins will be sent to golgi apparatus through a transport vesicle

after proteins are modified, sorts, packaged by Golgi Apparatus

proteins are transported through a secretory vesicle

nucleus

the large organelle that contains DNA that regulates protein synthesis/gene expression and therefore the chemical reactions in the cell

• chromatin: DNA wraps around histones (proteins in groups of eight) and give structure to DNA

  • nucleosomes: structural units of chromatin

• nuceloli: small dense region in the nucleus where ribosomal RNA is made (rRNA)

Glycolysis

• occurs in the cytoplasm

• is a anaerobic process/anaerobic metabolism (doesn’t require oxygen)

• produces small amount of ATP

• byproducts of glycolysis goes to mitochondria

In the mitochondria

• process in the mitochondria are called aerobic metabolism

• TCA cycle, electron transport, ATP synthesis

• harvests energy from glucose (in mitochondria) that couldn’t be harvested in glycolysis

Why is the process in mitochondria aerobic

• glucose: 6 carbon molecules bonded to each other

• the bonds between carbon molecules share electrons that carry energy

• when bonds are broken electrons need something that accepts them

• ½ oxygen + 2 hydrogen - oxygen accepts the electrons