lecture 5

• cytology is the study of the structure and function of the cell
• cytology focuses on cell shape, internal structure and organization, and organelle number, location, relative size, and productivity
• cytology is examined through microscopes
• the brightfield microscope works by staining acidic molecules and examining them under light
• the florescent microscope works by dyeing the nuclei based on their composition
• the electron microscope provides a much closer image; only typically a couple cells at a time
• the basic animal cell is found nowhere in the body; all cells contain the same parts, but cells take different forms and functions depending on location in the body
• in reality, all cells contain the same components, BUT: are specialized to meet tissue needs and function, are organized according to function, and are similar and different at the same time
• the phospholipid (plasma) membrane envelopes the cell
• phospholipid heads are hydrophilic
• fatty acid tails are hydrophobic
• the phospholipid membrane forms a bilayer, with the heads facing outward and then tails pointing inward
• the phospholipid membrane is important for keeping stuff in and out (solutes and substrates)
• it is important that the phospholipid membrane is flexible to prevent rupturing (especially in muscles and vessels)
• the phospholipid membrane contains: transporters, receptors, and cholesterol
• the phospholipid membrane makes a concentration gradient of ions and can facilitate diffusion of these ions across the membrane
• the nucleus of he cell contains 95% of the cellular DNA; the other 5% is located in the mitochondria
• the nucleus contains the genetic material of the cell; all cell nuclear DNA is the same within an organism, it is packaged differently to create different functions
• nuclear structure/packaging/patterns is associated with what genes are turned on/off and are expressed or not
• heterochromatin indicates dense packaging, meaning those genes are wrapped tightly and are therefore turned off
• euchromatin indicates loose packaging, meaning those genes are unwound and the genes are turned on
• DNA--> transcription --> RNA --> translation --> protein
• transcription: RNA pass through nuclear pore to cytosol or RER
• translation: RNA translated to AA by ribosome
• the mitochondria is the powerhouse of the cell because it makes energy in the form of ATP
• the relative number of mitochondria is an indicator of cellular activity and metabolic rate
• myocytes have higher mitochondria levels than fibroblasts because they are more active and have a higher need
• mitochondria generate ATP via oxidative phosphorylation through the Krebs cycle
• the mitochondria concentration is associated with the number of times a cow is milked in one day and the overall milk synthesis levels
• endoplasmic reticulum can have ribosomes associated with the membrane or not
• endoplasmic reticulum is the membrane inside of the cell that interfaces with the nucleus
• the endoplasmic reticulum is the key site of protein synthesis and has enzymes to activate proteins
• milk lipid droplet assembly, specifically triglycerides, occurs in the ER or SER
• the golgi apparatus was discovered by Camillo Golgi using the light microscope; he indicated that organelle size is also related to cell activity
• the golgi apparatus is a series of cell membranes that interact and communicate with the ER
• the function of the golgi apparatus is to package proteins and milk components for secretion; they can modify protein (post translation), drops packages on a conveyor belt
• the golgi apparatus is the site of lactose synthesis; packaged into membrane vesicle for exocytosis
• the trans side of the golgi body is located further away from the nucleus
• the cis side of the golgi body is located closer to the nucleus
• the cytoskeleton is the skeleton/matrix of the cell that helps organize delivery