Structure and Function of Cells

Definition and types of cells

  • A cell is a basic living structural and functional unit of the organism.
    Types of Cells: Skeletal Muscle cells, smooth muscle cells, cardiac muscle cells, nerve cells, blood cells, red blood cells, white blood cells, epithelial cells, cells of the immune system, cells of the organs.

    Anatomy of a generalized cell: structures of cells and their functions.

    Nucleus – type of organelle that contains genes and controls cellular activity.
    Cytoplasm. Contents inside cell between the membrane and nucleus.
    Plasma membrane or cell membrane. Divides the extracellular material from the material inside the cell and determines what goes in and out of the cell.
    Functions of cell membrane – gives shape to cell and protects cell contents, separates cell from external environment, provides receptor sites for hormones, antibodies and other chemicals.
  • Movement of material across the cell membrane.
    Extracellular fluid – outside the cell
    Interstitial fluid – between the cells.
    Plasma- fluid in blood vessels
    Lymph – fluid in lymphatic vessels
    Intracellular fluid – inside cell
  • Common cellular processes
    Transporting nutrients and wastes across plasma membranes.
    Breaking down glucose to produce energy for cellular work.
    Building essential proteins for growth and repair.
    Adapting to changes in the environment.
  • Passive movement of fluids:
    Diffusion – molecules move from higher concentration  to lower concentration
    Facilitated diffusion– proteins are carriers to move large molecules that are insoluble in lipids to move through cell membrane.
    Osmosis – movement of water through a membrane from an area of higher concentration to lower concentration.


Active Processes that require ATP as an energy source:
Active transport – move from low concentration to high concentration using integral proteins.

Endocytosyis: Large molecules pass through the cell membrane and the membrane surrounds the substance, encloses it and brings it into the cell.
Pinocytosis – cell drinking. Liquid encased in pinocytic vesicle and dissolved by enzymes.

Phagocytosis – cell eating. The membrane engulfs a particle and forms a sac called the phagocytic vesicle. Enzymes in the sac breakdown the particle

Metabolic Function:  Anabolic, Catabolism

Homeostasis: Mechanisms, Negative Feedback, Hormonal and neural homeostatic regulators.

  • Cytosol – acts as a 75-95% water medium to suspend the organelles, and chemical reactions of the cell.
  • Organelles are permanent structures inside cells that have specific functions. 
    Nucleus – type of organelle that contains genes and controls cellular activity
    Nucleoli – aggregations of deoxyribonucleic acid (DNA, genetic material) and ribonucleic acid (RNA) which are both involved in protein synthesis.
    Mitochondria – cell powerhouse; produces ATP. Have their own DNA and self replicate.
    Endoplasmic reticulum (ER) – double membranous winding channels (think waterways through Venice) called cisternae that create a large surface to support its functions. Functions as mechanical support, transportation, protein synthesis  and lipid synthesis (smooth).  Two types- rough has ribosomes embedded into it and smooth that does not have ribosomes. Smooth regulates CA++, metabolizes carbohydrates and breaks down toxins.
    Ribosomes – protein synthesis site; Ribosomal RNA is created DNA in nucleolus and exits through nuclear pores into the cytosol. Amino acids join to form protein chains.
    Lysosomes– enzymes that  digest unwanted substances.
    Flagella –long projection of the cell membrane used to propel the cell
    Cilia – Short projections of the cell membrane that move particles over the surface of the tissue
    Golgi apparatus –four to six membranous sacs called cisternae that are stacked together that sort, package and deliver proteins to the cell. Centrosomes
  • Normal Cell Division
    Somatic Cell Division (Mitosis) – Parent cell divides into two identical daughter cells that have the same number and kind of chromosomes that the parent cell has. The DNA which has two strands that form a double helix, untwist and then separate with one half of the genetic material. The strands then reproduce more identical material.
    Reproductive Cell Division (Meiosis)- Sex cells or gametes (ovum/egg, sperm) grow through fertilization or the fusion of two gametes.
  • Abnormal Cell Division
    Tumor or Neoplasm-
    excess tissue that forms when a cell duplicates without control.  Malignant: cancerous growth.  Benign: Non-cancerous
    Types of Cancers – often named for the type of tissue that they grow from.  Melanoma – from the melanocytes of the skin
    Adenocarcinoma- from a gland
    Growth and spread of tumors – Primary tumor – original site.  Metastasis- spread through body.  Secondary Tumor – result of metastasis.
  • Other cell terms
    Atrophy –
    Decrease in size of cells
    Dysplasia- (Dys- abnormal, plas – to grow) change in size, shape and organization of cell
    Hyperplasia (hyper=over) increase in number of cells due to overreplication
    Hypertrophy –
    increase in size of cell without an increase in replication
    Necrosis – (necro-death, osis- condition)-
    death of a group of cells
  • Diversity of cells in the body and specific cell types and their functions (e.g., fibroblasts, erythrocytes, epithelial cell, macrophage, neuron.