Cells

Cells

1. Plasma Membrane

   • Makes up the cells outer membrane, a selective barrier, that regulates material in and out of the cell, also plays a key role in communication among cells. Made up of 3 types of lipid molecules
     • Phospholipid: makes up 75% of the membrane
     • Cholesterol: makes up 20 of the membrane.
     • Glycolipids: makes up 5% of the membrane

2. Nucleus

   • Large organelle that houses the cells DNA, directs cellular activities, produces ribosomes in nucleoli, controls cellular structure.

3. Cytoplasm

   • all the cellular contents between plasma membrane and the nucleus, two components:
     • Cytosol
       • the fluid portion or ICF, makes up 55% of the cell, has water, dissolved particles, glucose, amino acids, fatty acids, lipids, proteins etc.
         • Cytoskeleton: network of protein filaments that extend through the cytosol
           • Microfilaments: made up of actin and myosin, help generate movement, and mechanical support for the cell, muscle contraction, cell division
           • Intermediate Filaments: help with stabilizing position of organelles such as the nucleus, and help cells attach to one another/give cells their shape
           • Microtubules: help determine cell shape, also function in movement of organelles of secretory vesicles and of chromosomes during cell division such as cilia and flagella.
     • Organelles
       • have characteristic shape and perform specific functions
         • Ribosomes: sites of protein synthesis, located in the mitochondria, also have high content of ribonucleic acid (ribosomal rRNA)
         • Endoplasmic Reticulum: network of membranes that form sacs or tubules, two kinds:
           • Smooth ER: has no ribosomes, synthesizes fatty acids, steroids and detoxes the body from drugs and other harmful substances
           • Rough ER: has lost of ribosomes, synthesizes glycoproteins and phospholipids.
         • Mitochondria: the powerhouse of the cell, generates ATP through cellular respiration, also participates in Apoptosis, the orderly, genetically programmed death of a cell.
         • Microvilli: increase surface area of the cell membrane to speed up exchange of substances for absorption
         • Lysosomes: digest substances that enter a cell via endocytosis, transport final products into cytosol, two types of digestion
           • Autophagy: is the digestion of worn out organelles
           • Autolysis: is the digestion of the entire cell