Anatomy 

The Cell is basic structural and functional unit of the body • can perform all basic life functions

Principal Parts of the Cell:

  1. Cell Membrane / Plasma Membrane / Plasmalemma • Composed of:
    a) phospholipid bilayer
    • phosphate head group (hydrophilic)
    • FA tails (hydrophobic)
    • separates ICF + ECF:
    i) Intracellular fluid (ICF) = inside cell
    ii) Extracellular fluid (ECF) = outside cell
    b) cholesterol
    • scattered throughout membrane
    • adds stability to the cell membrane
    c) Membrane Proteins
    • 2 types:
    i) integral proteins
    • within the membrane ∴ have a hydrophobic region
    • some extend across entire membrane =
    transmembrane
    ii) peripheral proteins
    • attached to extracellular or intracellular region of integral proteins i.e. on the periphery of the cell membrane

• Functions of Membrane Proteins:
i) enzymes
ii) transporters
iii) channels
iv) receptors
v) anchors
vi) identity markers (for immune system)
d) membrane carbohydrates
• only on outer surface
• bound to proteins (glycoproteins) or lipids (glycolipids)
• Functions:
• cell recognition e.g. egg and sperm
• anchor cells together
e) microvilli
• small projections of cell membrane to increase surface area
• best seen on cells of the small intestine and kidney
Fluid mosaic model of the cell membrane:
• fluid – membrane constituents can move around (phospholipids and some proteins)
• mosaic – proteins dot surface like tiles in a mosaic
2) Cytoplasm
• AREA between the inside of the cell membrane and the outside of the nucleus
• 2 divisions:

• a) cytosol = gel-like intracellular fluid
• contains water and a suspension of carbohydrates,
b) Organelles
3) Non-membranous organelles a) Ribosomes
proteins, and lipids
• may contain inclusions e.g. melanin (pigment), glycogen (stored glucose)
• structures that perform a specific function and are essential for life
i) non-membranous
• in direct contact with cytosol
ii) membranous
• surrounded by membrane that isolates them from the cytosol
• sites for protein synthesis
• contain ribosomal RNA (rRNA) + proteins
• May be:
b) Centrosome
i) free in cytosol - make proteins destined for cytosol, mitochondria, nucleus
ii) attached to endoplasmic reticulum (ER) - make proteins destined for all other sites
• dense area of cytoplasm, usually contains 2 centrioles (function uncertain - some cells lack them)
• organizes microtubules of cytoskeleton & spindle apparatus (for cell division) c) Cytoskeleton
• ALL types support cell shape and are formed from proteins

• important in cell movement, cell division, movement/anchoring of organelles + proteins (e.g. receptors, enzymes)
• 3 types:
i) Microfilaments
made of actin • Functions:
• muscle contraction (with myosin)
• maintenance of cell shape and projections (e.g. microvilli) • cytokinesis
ii) intermediate filaments
• composition is tissue specific e.g. keratin • Function:
• support the cytoplasm (scaffolding for the cell) iii) microtubules
• hollow tubes made of tubulin
• Function:
• form:
• 1) centrioles
• 2) spindle apparatus
• 3) cilia (short)
• 4) flagella (long)
• structural
• move or secure organelles in place

  1. Membranous organelles
    a) mitochondria
    • site of ATP synthesis
    • contains own DNA, RNA, + proteins
    • have a double membrane
    b) Endoplasmic Reticulum (ER)
    • membranous network throughout cytoplasm 2 types:
    i. Rough ER (RER)
    • ribosomes attached - synthesis of secretory, lysosomal and membrane proteins
    ii. Smooth ER (SER)
    • lacks attached ribosomes
    • continuous with RER
    • synthesizes lipids + steroid hormones
    c) Golgi Apparatus/Complex
    • stacks of membrane discs
    • modifies (e.g. trims or adds CHO groups), sorts, packages, and delivers proteins/lipids to cell membrane, lysosomes, or for secretion (cellular post office)
    d) lysosomes
    • filled with digestive enzymes
    • digest bacteria, viruses, worn-out organelles (clean up function)
  2. Nucleus
    • largest membranous organelle
    • cell control centre
    • cells may have 1 or more nuclei
    • Parts:
    a) nuclear envelope
    → double membrane with nuclear pores
    → connected to ER
    b) nucleolus
    → non-membranous
    → dense (less light gets through) region of DNA, RNA, + proteins where ribosomes
    are made and assembled
    c) chromosomes/chromatids
    → made of DNA + histone proteins
    → can be:
    i) dispersed = Chromatin
    DNA uncoiled + not individually visible
    in this form MOST of the time (when cell is not dividing) ii) condensed + chromosomes individually visible
    → found in dividing cells (during mitosis/meiosis)