neuroscience - cell types and subcellular structures

define the notions of cell theory

• all living organisms are made up of one or more cells

• cells are the most basic unit of life

• all cells arise from divided preexisting cells

why do we need cells?

• allow perpetuation of genetic material - RNA/DNA ensures daughter cells have similar features to parent cell

• small size of cells allows for effective diffusion of nutrients, oxygen, signalling factors and metabolites

• cells enable modularity by building tissues and organs and entire organisms from smaller cells

what are the 2 cell types and examples

prokaryotes: anucleate, single celled organisms e.g bacteria (includes photosynthesising cyanobacteria) archae living in extreme environments ( halophiles in salty environments and thermoacidophiles in hot sulfur springs)

eurkaryotes: have nucleus and can be single or multi-cellular organisms incl. plants, animals, fungi (molds, yeasts, mushrooms) protozoans

state the evolution of cells

ancestral prokaryote → bacteria, anaerobic ancestral eukaryotes, archae

bacteria→ nonphotosynthetic bacteria, photsynthetic bacteria

anaerobic ancestral eukaryotes → plants, animals, fungi

archae → archae

features of plasma membrane

• bilayer of phospholipids, cholesterol and embedded transmembrane proteins

• phospholipids - amphipathetic

• cholesterol - fluidity

• embedded transmembrane protein - mediate cell communication e.g. receptors binding to ligands

• roles of plasma membrane: barrier, communication, import and export, electrical capacitor

features of cytoplasm/cytosol

aq. solution of pH 7.2 and ion composition but also contains:

• high concentration of proteins (20-30% metabolic enzymes, intracellular messengers)

• tRNAs

• free ribosomes

• inclusion bodies e.g. glycogen granules

features of cytoskeleton

network of protein fibres: actin filaments, intermediate filaments, microtubules

main roles:

• maintain shape and stability

• adaptation of shape

• cell division

• motility

• movement of particles within cells

features of nucleus

• surrounded by 2 layers of membrane making up the nuclear envelope

• contains nucleoplasm

• contains chromosomal DNA and packaging proteins (histones) and gene regulatory proteins

• site of RNA synthesis and splicing

• nucleolus: site of ribosome synthesis, signal recognition particle and can capture gene regulatory proteins (nucleolar detention)

features of endoplasmic reticulum

• network of interconnected membrane vesicles (cisternae) continous with the outer nuclear membrane

• rough ER: ribosomes found only on outside, synthesis of secreted and transmembrane proteins, associated with polyribosomes, in neurones: nissl bodies

• smooth ER: folding and processing of proteins, synthesis of lipids and steroid hormones, detoxification, release of glucose in liver, Ca2+ storage in muscle cells in sarcoplasmic reticulum)

features of golgi apparatus

• stack of flattened membrane vesicles

• modification of proteins destined for secretion and transmembrane proteins

features of mitochondria

• lumen - inside space of cell

• cristae - folds of mitochondria to increase S.A.

• double membrane: inner membrane folded into cristae (high transmembrane protein content)

• contains circular DNA (mtDNA) and ribosomes in matrix

• alternative genetic code

• mitochondrial disorders - mutations in mtDNA e.g. kearns-sayre syndrome / defects in nuclear genes that encode mitochondria proteins e.g. hereditary spastic paraplegia

• a

state mitochondria functions

• repiration/oxidative phosphorylation (ETC)

• krebs cycle

• heat production

• Ca2+ storage

• apoptosis

outline the endosymbiotic theory

mitochondria are likely yo have been derived from a symbiotic relationship between an engulfed bacteria inside an ancestral eukaryotic cell

features of lysosomes

• membrane bound organelles in animal cells

• degrade unwanted proteins, membranes and organelles that are no longer needed using lysozymes

• acidic pH: 4.5-5

• degradation of pathogens by macrophages

features of peroxiosomes

• degrade fatty acids and toxic compounds

• fatty acid oxidation produces precursors for biosynthetic pathways

• oxidation produces H2O2 which is corrosive

neutralisation via enzyme catalase: 2H2O2 → 2H2O + O2

detoxification of ethanol in the liver: C2H5OH + H2O2 → CH3CHO + 2H2O