lec 3- cellular interactions in animals Flashcards
what does the cell surface consist of?
The cell surface consists of the plasma membrane and a protective layer just beyond the plasma membrane made of fibre composites
what is the fibre composite that is secreted by most animal cells called?
extracellular matrix (ECM)
what is the extranuclear matrix made of?
fibrous part consists of collagen, while the ground part consists of proteoglycans
what holds animal cells together?
Animal cells are held together by tight junctions (seals cell together), desmosomes (connect to cytoskeleton of cell), and gap junctions (communication)
what are tight junctions made of and what do they do?
Tight junctions are composed of membrane proteins in adjacent animal cells, chains of these proteins line up and bind to each other, resulting in a water tight stitch to occur
where are tight junctions found?
Tight junctions are found in epithelia and are dynamic and variable
what are desmosomes made of and what do they do?
Desmosomes are composed of proteins that link the cytoskeletons of adjacent cells and they resist pulling/shearing forces
where are desmosomes found?
Mainly found in epithelial and muscle tissue
what do gap junctions do?
help cells communicate by letting ions and small molecules to pass through channels
why are chemical signals different from action potentials?
because chemical signals last longer
what are the five categories of chemical signals?
-Autocrine signals
-Paracrine signals
-Endocrine signals
-Neural signals
-Neuroendocrine signals
what do an autocrine signals do?
Acts on the same cell that secreted them, eg. of autocrine signals is cytokines
what do a paracrine signals do?
Diffuse locally and act on target cells near the source cell, eg. of paracrine signals are insulin and glucagon
what do endocrine signals do?
Are carried to distant cells by blood or other body fluids and act upon them
what organ makes endocrine signals?
glands
what do neural signals do?
The presynaptic neuron releases neural signals (neurotransmitters) that bind to the receptor on the postsynaptic neuron resulting in a change in the membrane potential
why are neural signals fast?
Neural signalling is fast because action potentials spread rapidly and have a short distance to diffuse across the synaptic cleft
what do neuroendocrine signals do
Hormones released from neurons that are carried by blood or other body fluid to act upon another cell, eg. ADH
what are hormones?
Hormones are signalling molecules sent from a cell to another with a distance between them
how do integrators send a response to effectors?
by using horomones
what molecule does a hormone bind to and what happens to it?
it binds to a receptor molecule and it causes it to change shape and activity
what are the three types of hormones?
-Peptides and polypeptides
-Amino acid derivatives
-steroids
which hormones bind to outside receptors and inside receptors, as well as which are not soluble, mostly not soluble, and soluble?
-Peptides are not soluble so they bind to surface receptor
-Amino acids are mostly not soluble so they bind to surface receptor
-Steroids are soluble so they bind to inside receptor
can signal receptors be blocked?
yes
how are lipid-soluble hormones processed?
Lipid binds to receptor inside cell, triggers change in cell activity, the hormone-receptor complex is transported to nucleus, where it alters gene expression
where does the hormone-receptor complex bind to?
The hormone-receptor complex only binds to hormone-response element part of DNA
how are lipid-insoluble hormones processed?
Hormone binds to plasma membrane receptor, this results in signal transduction where either the signal is amplified and the extracellular signal turns into a intracellular signal with many downstream molecules causing a response, or it is diversified and a cell receives the signal causing it to change several times.
what is G-protein coupled receptors?
A type of plasma membrane receptor that works with intracellular G-proteins which trigger a second messenger after being activated by the signal receptor.
what is a second messenger?
a non protein, such as other molecule or ions
what are the three steps of G-protein coupled signalling?
- G protein is inactive (bound to GDP) and then signal arrives and binds to receptor
- Signal-receptor complex changes conformation resulting in G protein binding to GTP (activated) and splitting into two parts
- Activated G protein binds to enzyme and induces production of second messengers which triggers a response
is signal Amplification a 1:1 ratio?
No
what happens when glucose is high?
decrease in blood pH and chance for diabetes, so insulin is released to decrease it
what happens when glucose is low?
not enough fuel for brain, so glucagon is released to increase it
what does GLP-1 do?
GLP-1 increases insulin secretion and inhibits glucagon release, it also lowers appetite
what does Ozempic drug do?
binds to GLP-1 to trigger it
