week 4 - cell compartmentalisation Flashcards
organisms are made up of…
many different types of cell
do all cells have similar organisation and DNA
yes
what is the longest cell
motorneurons of the sciatic nerve in humans
base of spine to toes
erythrocytes
have no nucleus
some form a syncytium: cells share the same cytoplasm
- cell cytoplasm is connected / gap junctions LIKE skeletal muscles
cells:
all connected together
cell junctions, connective tissue, ECM
some connected by synapses
why are cells typically small
need efficient enough surface to exchange material with environment
- slow diffusion rate
- need maintaining adequate concentration of reactants and enzymes
cell shape and organisation is..
not readily apparent
optical microscopy
1) Contrast enhancing techniques (phase contrast and DIC
2) Cell staining
3) Immunostaining
4) Fluorescence microscopy and fluorescent protein tagging
what we know about cells comes from…
microscopy
epithelial cells
In mammals, many epithelial cells are ciliated in order to sweep materials across the tissue surface. For instance, huge numbers of cilia (more than 107/mm2) cover the surfaces of mammalian respiratory passages (the nose, pharynx, and trachea), where they dislodge and expel particulate matter that collects in the mucus secretions of these tissues.
what does the plasma cell membrane do
demarks the cells boundary
- The boundary between the internal of the cell and the outside environment
- Phospholipid bilayer with embedded proteins
- selective permeability
plasma membrane
made up of
The bio/plasma/cell membrane is made of two layer of phospholipids and proteins (around 50% in weight).
Most of the membranes are those of intracellular vesicles
cell shape
cytoskeleton
cell wall (plants and yeast)
what does the cytoskeleton do
gives the differing structures
visualisation of cell structures:
Fluorescence labelling
Visualization techniques
Most cell are not round, Female rat egg: RED, F-Actin stained with Texas Red phalloidin; GREEN IS for a kinase known to cross link F-Actin.
The cell shape depends on the cortex on the inner side of the plasma membrane (part of the actin microfilaments cytoskeleton)
Spherical due to actin cytoskeleton
the nucleus
contains the chromosomal DNA
where are ribosomes made
nucleolus
(the most prominent structure/organelle in the nucleus)
chromosomes
are very apparent in polytene nuclei
Polytene chromosomes were first described in 1881 by Balbiani but only at start 20th centuary theyy were linked to heredity.
the first observations of chromosomes were made in somatic (body) cells, specifically in the cells of salamander larvae.
Walther Flemming, who coined the term “chromosome” and described these structures in 1882, conducted his studies on the developing cells of salamander embr
How did scientist found out the genes (Mendelian hereditary factors then) are linked to chromosomes?
Sex determination.
the nucleus is enclosed by a…
double membrane
nuclear envelope
- transport between nucleus and cytoplasm is critical
membrane enclosed compartments/organelles
- Trafficking vesicles/endomembrane system
- Endoplasmic reticulum (rough ER and smooth ER)
- Golgi apparatus
- Lysosomes/peroxisomes/vacuoles
- Eukaryotic cell evolution
how cells produce cell membrane? and lipids?
1) lipid synthesis
2) membrane expansion
3) vesicular transport
how cells produce cell membrane? and lipids?
1) lipid synthesis
o Cells synthesize lipids, such as phospholipids, the in endoplasmic reticulum (ER)
how cells produce cell membrane? and lipids?
- membrane expansion
o Cells increase lipid production when they need to expand their membranes (e.g. during cell division)
how cells produce cell membrane? and lipids?
- vesicular transport
o Newly synthesized lipids are transported to different membrane compartments via vesicles
Endocytosis and exocytosis
These processes help expand to recycle cell membranes
organelles are…
dynamic structures
proteins delivery to the right location mediated by…
amino acid leader sequences
pancreas
secretes insulin, glucagon, somatostatin, and function also as an exocrine gland by secreting digestive enzymes.
how do cells form lipid droplets in an organised manner?
The close proximity of LDs to mitochondria allows for efficient energy regulation.
LDs can release stored lipids for oxidation in mitochondria when the cell requires energy.
Lipid droplets in fat tissues primarily store excess energy and play roles in metabolism, insulation, cushioning, and hormone regulation. They are critical for overall metabolic health.
lysosomes carry out…
intracellular digestion of both external and internal bodies
Phagocytosis
lysosomes are the…
primary catabolic compartments of cells
lysosmes are repleated with…
enzymes
proteases, glycosidases, lipases
defects in lysosomal function results in…
diseases
lysosomal storage disease
lysosomes =
best example of compartmentalisation
tagging of lysosomal enzymes with mannose-6-phosphate in the Golgi apparatus
Lysosome internal enviroment is acidic to facilitate the breakdown of macromolecules.
Lysosomes: are also…
recycling centres
– If key enzyme is not working, material accumulate in it causing LSD
lysosomes pH
Low pH due to active pumping of protons by the H+-ATPase.
autophagy
cells continuously eat themselves
autophagy:
roles
plays specific roles in shaping immune system
development, fueling host innate and adaptive immune responses, and directly
controlling intracellular microbes as a cell-autonomous innate defense.
mitochondria:
what
- Membrane enclosed organelles found in possibly in all eukaryotic cells
mitochondria:
function
- Produce most of the ATP by oxidative phosphorylation
mitochondria:
distinctive feature
- Have a DNA genome
- Have a secondary inner membrane
each cell has …… mitochondira
many
mitochondria:
shapes
Spermatozoon
spiral
mitochondria:
fused together
Mitochondria are in fact fused together to for a retiulum/network, which is highly dynamic.
origin of the eukaryotic cell
Mitochondria and chloroplast evolved from ancient purple bacteria and cyanobacteria
Genes that are conserved across eukaryotes leave no doubt that all extant eukaryotic forms evolved from a last eukaryote common ancestor (LECA
Such endosymbiosis still occurring in protozoa and invertebrates
Biologist Lynn Margulis, recipient of the National Medal of Science, first wife of Carl Sagan,
—– Meeting Notes (30/09/16 10:47) —–
Genes that are conserved across eukaryotes leave no doubt that all extant eukaryotic forms evolved from a last eukaryote common ancestor (LECA
