Cellular physiology Flashcards
why do organelles have membranes
to keep things contained eg. especially those things that might be damaging to the cell such as free radicals
membranous organelles examples
○ Nucleus, mitochondria, lysosomes, peroxisomes, endoplasmic reticulum, and Golgi apparatus, vesicles
non-membranous organelles examples
○ Ribosomes, centrioles, flagella
largest organelle is
nucleus (5 micrometer diameter)
example of nuclear cell
red blood cell
example of multinucleate cell
skeletal muscle cell
chromatin composed of
DNA and protein (that hold it together)
ribosome biogenesis occurs at
nucleoli
nucleoli are
protein/DNA/RNA masses
nuclear envelope made of
double phospholipid bilayer
nuclear envelope has
○ Perforated by nuclear pores formed by rings of proteins
§ Regulate molecular traffic through envelope
ribosomes are
- Protein-making machines
○ Very small molecular machines
ribosomes are found
○ Found free in the cytoplasm’s, or on membranes (RER, nuclear envelope) or in other organelles (nucleus, mitochondria)
ribosomes do
○ They read coded genetic messages (messenger RNA) and assemble amino acids into proteins specified by the code (called translation)
endoplasmic reticulum
- System of channels (cisternae: flat sacks) enclosed by a membrane
○ Continuous with outer membrane of nuclear envelope
name of channels of the endoplasmic reticulum
cisternae
smooth ER
no ribosomes
□ Synthesises fats and lipids
□ Synthesised steroid hormones
□ Detoxifies alcohol and other drugs
□ Calcium storage (esp. in muscle = sarcoplasmic reticulum)
rough ER
is covered with ribosomes
□ Produces phospholipids and proteins of the plasma membrane
□ Synthesises proteins that are packaged in other organelles or secreted from the cell
□ Ribosomes make proteins
space between the two nuclear membranes
fluid filled gap called the intermambrane space
outer membrane of the nucleus becomes
endoplasmic reticulum
nuclear pores
create a gap between the nuclear envelope to allow things to get in and out
Golgi apparatus
- System of cisternae; synthesizes carbohydrates and puts finishing touches on proteins (post-translational mod)
function of the Golgi apparatus
○ Receives newly synthesized proteins from rough ER (cis)
○ Adds carbohydrates/sulphates to come (glycosylation/sulfation)
○ Packages them into membrane bound vesicles (trans)
○ Sorts and targets proteins to their correct destinations
§ Some -> lysosomes
§ Some -> plasma membrane
§ Some -> secretes
post translational protein modifications by the golgi apparatus
glycosylation - adding sugars
sulfonation - adding sulphates
something leaving a cell
exocytosis
something entering the cell
endocytosis
types of endocytosis
big things - phagocytosis
small things - pinocytosis
the cytoskeleton
- Network of protein filaments and cylinders
○ Grow and shrink to determine cell shape, structure, organizes cell contents, move materials within cell and contribute to cell movement (yes, many cells are mobile)
3 constituents of cytoskeleton
microfilaments, interveniate filaments, microtubules
Microfilaments
6nm actin
§ Cell shape and movement
Intermediate filaments
8-10nm
§ Provide mechanical strength
Microtubules
tubulin
§ Intracellular transport
§ Position of organelles
§ Cell shape and division
motor proteins
attaches vesicle onto a microtubule and moves it along the microtubule
lysosomes
○ Membrane bound package of enzymes
○ Digestion of proteins, nucleic acids, complex carbohydrates, phospholipids, and other substances
peroxisomes
○ Use hydrogen peroxide (H2O2 -> H2O and O2)
○ Neutralise free radicals, detoxify alcohol, other drugs, and a variety of blood borne toxin
○ Break down fatty acids into acetyl groups for mitochondrial use in ATP synthesis
difference between lysosomes and peroxisomes
lysosomes use enzymes, whereas peroxisomes use oxidation via (H2O2 -> H2O and O2)
peroxisomes are less selective
proteosomes and autophagosomes
- Clear old/damaged proteins and organelles to provide the cell with building blocks for renewal
- Non-membrane bound
proteosomes
digest proteins
○ Contain enzymes that break down targeted tagges (with ubiquitin) proteins into short peptides and amino acids
Autophagosomes
digest organelles
○ They form, then engulf cellular contents, such as damaged proteins and organelles
○ Fuses with the lysosome, where the contents are degraded into smaller constituents
main differences between proteosomes and autophagosomes
proteosomes digest proteins and autophagosomes digest organelles
autophagosomes fuse with
lysosomes
membrane of the mitochondria
double membrane
inner membrane of the mitochondria
has folds called cristae
spaces between the cristae are called
matrix
matrix of the mitochondria contains
ribosomes, enxymes used for ATP synthesis, small circular DNA molecule mtDNA
how is ATP generated
- burn feuls in the mitochondria forcing protons into the inter membrane space
- protons fall back into the centre and are driven through ATP synthase which mechanically adds a phosphate group onto ADP
enzyme responsible for making ATP
ATP synthase
ATP synthase works by
having protons driven through it
3 types of junctions between cells
tight, desmosomes, gap
tight junctions
(occluding)
○ Cell adhesion proteins (claudins) attached to plasma membranes
○ Seals gap between cells (prevent leakage in or out)
desmosomes
○ Adheaerans junction
○ Cadherins attach to the cytoskeleton
○ Super strong - holds cells together
gap junctions
(connexons)
○ Pores connecting cytoplasms
○ Allows direct communication between cells (shared cytoplasm)
