BASIC TISSUES - PARTS OF CELLS

Nucleus

Membrane bound structure that contains hereditary information and controls cell's growth ( cell division) and reproduction

Genes without these chromosomes represent nuclear genome

DNA is in complex with proteins

Regulates gene expression

Consists of nuclear envelope, nucleoplasm, chromatin and nucleolus

Chromatin

Made of DNA and histone proteins

Heterochromatin - condensed "inactive" DNA

Euchromatin - active DNA, relatively extended form and condenses to form chromosomes during cell division

Nuclear envelope

Nuclear pores where 2 membranes fuse

Surrounds nucleus

Double layered membrane

Outer membrane continues with rough ER

Nucleolus

Nucleoli formed around specific genetic loci called nucleolar organizing regions (NORs)

Manufactures and assembles ribosomes = protein producing structures

Well developed in cells active in protein synthesis

Consists largely of RNA and protein

Nuclearmatrix

Network of fibres found inside the nucleus

Contains nuclear proteins, RNA, DNA and phospholipid

Cytoplasm

Material between cell and nuclear membrane

Provides structural framework and individual components for genetic info expressed in nucleus to be translated to cell function

Organelles and cytosol (highly organized in which protein fibres (cytoskeleton) are arranged in complex latticework surrounding the organelle) surround

Site where most cellular activities occur

Cytoskeleton

Highly organized "living gel"

Provides binding sites for protein and enzymes

3 distinct stuctures

Microfilament (thinnest)

Made up of action protein

Is attached to plasma membrane and defines surface morphology of cell

Exhibits polarity and promotes motility

Microtubules (thickest)

Made up of protein tubulin (hollow tubes)

Major role in movement of chromosomes during mitosis

Bound to other cytoskeletal elements and organelles

Intermediate filaments

More stable

Provides cells with mechanical strength

Vacuoles

Membrane bound sac

Functions

Storing water, food, enzymes, waste etc

Digestion

Waste removal

Mitochondria

Double membrane

Smoother outer and folded inner (cristae) for increase surface area

Produce energy

Involved in cell signalling, differentiation and growth

Exclusive maternal inheritance (animals)

Mutations leads to "mitochondrial diseases" often neurological

Ribosomes

Complexes of RNA and protein

Directly involved in protein synthesis

Transcription takes place in cell nucleus

mRNA leaves nucleus and travels to cells ribosomes where translation occurs

Consists of 2 subunits (composed of RNA and protein): small (30S) and larger (50S)

Stationary type: embedded in rough ER

Mobile type: injects proteins directly into cytoplasm

Endoplasmic reticulum

Network of tubules, vesicles and sacs that are interconnected

Smooth ER

Not associated with ribosomes

Involved in storage, action and transport of key enzymes and lipids

Structure allows increased surface area for action or storage of key enzymes and products of these enzymes

Rough ER

Fused to nuclear membrane

Has ribosomes constantly binding and releasing

Functions

Manufacture lysosomal enzymes, secreted proteins, protein glycosylation and folding

Golgi apparatus

Consists of flattened, curved saccules

Modifies proteins and lipids made in ER

Steps

  1. Receives vesicles from ER on cis
  1. Modifies them and repackages in vesicles

Releases from trans

Lysosomes

Contains hydrolytic enzymes

Used to destroy invading matter and unwanted cellular material

Can function to help repair damage to plasma membrane as membrane patch

Derived from Golgi network = primary lysosomes

Primary lysosomes + substance to be digested = secondary lysosome

Numerous in disease fighting cells

Cell/ Plasma Membrane

Interface between inside cell machinery and outside fluid

Selectively permeable lipid bilayer

Made up of primarily protein and lipids (phospholipid bilayer) hydrophobic tail and hydrophilic head

Flagella

Functions

Structural support

Transport of molecules across membrane

Enzymatic control of chemical reactions

Receptors for hormones and other regulatory molecules that arrive at cell surface

Cell adhesion

Whiplike strcuture

Propels sperm

Structures associated

Cilia

Tiny hairlike structures on surface of cells

Primary purpose - move fluid, mucous or cells

Respiratory system - defense (move mucous)

Female reproductive system - move egg

Microvilli

Tiny finger like projections of cell membrane

Areas where rapid diffusion ocuurs

Increased surface area

Found in kidney - reabsorption of molecules that are filtered out