L5 - Intro To Cell Flashcards
Cell theory
1) All living organisms are composed of 1+ cells forming collaborative, functional networks
2) The cell is the basic unit of structure and organisation as well as the smallest unit that makes use of survival needs of the body to undertake all functions necessary for life
3) All cells arise only from pre-existing cells
4) The total function of all cells in the body reflect the total function of the body
Eukaryotic vs. prokaryotic cells
Membrane-bound organelles/nucleus
Eukaryotic and prokaryotic cells similarities
have plasma membrane, cytosol, DNA, RNA, protein and ribosomes
Endomembrane system
Work with plasma membrane to package, label and ship molecules
- INCLUDES; nucleus, endoplasmic reticulum, Golgi apparatus, lysosomes
- EXCLUDES: mitochondria (lots of membranes), ribosomes (don’t have a membrane)
Types of plasma membrane proteins
Integral (including transmembrane), peripheral
Functions of plasma membrane proteins
Transport, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, attachment to cytoskeleton and ECM
Cell-cell recognition
- Some glycoproteins serve as identification tags/molecular signatures of the extracellular side of the cell that are specifically recognised by other cells
- More short-lived than intercellular joining proteins
Components of nucleus
Nuclear envelope, nuclear lamina, nuclear pores, nucleolus
Nucleus function
- House/protect DNA in eukaryotic cells
- Make RNA and assemble ribosomes
- Pores regulate movement of substances (e.g protein and mRNA) in and out of nucleus
- Molecule segregation to allow temporal and spatial control of cell function
Condensing of DNA
Double helix, histones, nucleosomes, chromatin, chromatin fibres, looped domains, chromosomes
Ribosomes
- made of rRNA
- small and large subunits
- protein production
- free in cytoplasm (cytosolic/non-endomembrane proteins) or attached to RER (non-cytosolic/endomembrane proteins)
Endoplasmic reticulum
Extensive networks of tubes and tubules (cisternae) stretching out from nuclear membrane
Cisternae function
Serves the biosynthesis of new lipids and of membrane anchored or secretory proteins
Rough ER function
Production of:
- Secreted proteins (which leave cell via exocytosis)
- Membrane proteins
- Organelle proteins
Rough ER
- Continuous with nuclear enevlope
- Dotted with attached ribosomes (synthesis proteins)
- Proteins enter lumen within rough ER for folding
- Rough ER membrane surrounds protein to form transport vesicle destined for Golgi
Smooth ER
- Extends from rough ER
- Lacks ribosomes as they don’t make/synthesis proteins
Smooth ER function:
- Housing unit/storage for proteins and enzymes
- Synthesise lipids (including steroids and phospholipids)
- Storage of cell-specific proteins (as not all cells make all proteins)
Golgi apparatus structure
3-20 cisternae stacked on top of each other
Golgi function
- Modify, sort, package and transport proteins received from rough ER using enzymes in each cisternae (each cisternae contain enzymes for different functions)
- formation of:
— Secretory vesicles (proteins from exocytosis)
— Membrane vesicles (plasma membrane molecules that fuse to the membrane)
— Transport vesicles (molecules to mature lysosome)
Golgi process
1) Proteins received from rough ER via the convex cis face
2) Modifications occur within each sac (formation of glycoproteins, glycolipids, lipoproteins)
3) Proteins move from sac to sac and mature at exit cisternae (concave trans face)
Lysosomes
- Vesicles formed from Golgi membrane
- Contain powerful digestive enzymes (highly acidic inside)
— Membrane proteins pump H+ in to maintain acidic pH
— Rest of cell protected by membrane
Lysosome function
- Destroying/breaking down a variety of cellular components, pathogens and antigens
- digestion of:
— Substances that enter cell
— Cell components (e.g organelles) - autophagy
— Entire cells - autolysis - Once digested, all building blocks (amino acids, lipids etc.) are recycled
Components of mitochondria
- outer mitochondrial membrane
- inner mitochondrial membrane with folds (cristae)
- mitochondrial matrix
- inter membrane space
- small genome (37 genes) encoding mitochondrial specific products
Cytoskeleton
- structural support system of cell
- act as scaffolding across cell: fibres/filaments help maintain cell shape, size and integrity
Cytoskeleton function
Involved in/support:
- Intracellular transportation
- Cell movement
- Contractibility
- Tensile strength of cell structure
Types of cytoskeleton
Microfilaments, intermediate filaments, microtubules
Microfilaments structure
Two intertwined long chains/strands of ACTIN
Microfilaments location
Around periphery and lining of cell interior
Microfilaments function
Cell shape
Bear tension and weight by anchoring cytoskeleton to plasma membrane proteins
Promote amoebic mobility (crawling movement of cells) if required
Support microvilli
Muscle contraction
Division of animal cells
Cytoplasmic streaming in plant cells
Intermediate filaments structure
Fibrous protein (KERATIN) coiled into cables
Intermediate filament location
In cell cytoplasm
Intermediate filament function
- Bear tension and weight through cell (e.g during cell anchoring)
- Act as scaffold for cellular organelles (e.g nucleus)
- Formation of nuclear lamina
Microtubules structure
Hollow tubes formed by coiled TUBULIN (globular protein) dimers (alpha and beta)
Microtubules location
Extends from centriole into cytoplasm/nucleus
Microtubules function
- Support cell shape and size (compression resisting “girders”)
- Guide for movement of organelles
E.g vesicles from Golgi to membrane: motor proteins attach to receptors on vesicles and transport them by ‘walking’ along microtubules (and microfilaments in some cases) - Chromosome movement/organisation in cell division
- Support and movement of cilia/flagella - cell motility
Dynamic cytoskeleton structures
Microfilaments and microtubules (intermediate filaments are the most permanent of the three)
- can be assembled/disassembled as required
Cell-cell recognition glycoprotein composition
carbohydrates-oligosaccharides + protein
Cell-cell recognition glycoprotein example
major histocompatibility (MHC) proteins
