BIOL 2401 Cytology Lecture Notes

Cytology

Cells: the living units
Cell theory
 A cell is the structural and functional unit of life
 How well the entire organism functions depends on individual and
combined activities of all of its cells
 Structure and function are complementary
 Biochemical functions of cells are dictated by shape of cell and specific
subcellular structures
Cell diversity
 Over 200 different types of human cells
 Types differ in size, shape, and subcellular components; these differences
lead to differences in functions
Generalized cell
 All cells have some common structures and functions
 Human cells have three basic parts:
 Plasma membrane: flexible outer boundary
 Cytoplasm: intracellular fluid containing organelles
 Nucleus: DNA containing control center


The plasma membrane
Functions:
 Acts as an active barrier separating ___________intracellular fluid
(ICF)______________ from ____________extracellular fluid
(ECF)_____________
 Is the “contact” surface so it provides:
 a) cell adhesion- to either other cells or a surface
 b) cell identity markers
 c)receptors- for various chemicals
 Plays dynamic role in cellular activity by controlling what enters and what
leaves cell
 Has enzyme systems so it is the site of many chemical reactions
 Also known as the “cell membrane”
Structure:

,  Consists of ____________membrane lipids_____________ that form a
flexible ___________lipid bilayer______________
 Specialized ____________membrane proteins_____________ float
through this fluid membrane, resulting in constantly changing patterns
 Known as the “fluid mosaic model” because it is not rigid, rather it is a semi-
fluid bi-layer of phospholipids arranged and held together by their
relationship with water (polar heads on surface, non polar tails inside)
Membrane proteins:
 Allow cell communication with environment
 Make up about half the mass of plasma membrane
 Most have specialized membrane functions
 Some float freely, and some are tethered to intracellular structures
 Two types:
 Integral proteins
 peripheral proteins
 Integral proteins
 Firmly inserted into membrane
 Most are transmembrane proteins (span membrane)
 Have both hydrophobic and hydrophilic regions
 Hydrophobic areas interact with lipid tails
 Hydrophilic areas interact with water
 Function as:
 Transport proteins (channels and carriers)
 Enzymes
 Receptors
 Peripheral proteins
 Loosely attached to integral proteins
 Include filaments on intracellular surface used for plasma membrane
support
 Function as:
 Enzymes
 Motor proteins for shape change during cell division and muscle
contraction
 Cell-to-cell connections
 Part of _____________glycocalyx____________, serving as identification
markers for cell recognition
 Receptors for recognizing molecules