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MindMap Gallery Physiology - basic functions of cells
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Physiology - basic functions of cells
About physiology - a mind map of the basic functions of cells, including the material transport function of the cell membrane, cell signal transduction, muscle cell contraction, cell electrical activity, etc.
Edited at 2024-02-14 11:53:52
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Physiology - basic functions of cells
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- Outline
basic functions of cells
Material transport function of cell membrane
chemical composition of cell membrane
Lipids
Phospholipids>70%, cholesterol<30%, glycolipids<10%; Content in phospholipids: phosphatidylcholine (outer layer of membrane) > phosphatidylserine > phosphatidylethanolamine > phosphatidylinositol (the lowest, can be used as a donor for intracellular second messenger inositol triphosphate IP3 and diacylglycerol DG)
protein
Surface membrane proteins: 20%~30%, mainly attached to the inner surface of the cell membrane; Integral membrane proteins: 70% to 80%, whose peptide chains pass through the membrane lipid bilayer once or repeatedly; generally speaking, proteins related to substance transmembrane transport and receptor functions are integral membrane proteins, such as carriers , channels, ion pumps, G protein-coupled receptors
carbohydrate
Mainly some oligosaccharide and polysaccharide chains, combined with membrane proteins or membrane lipids in the form of covalent bonds to form glycoproteins or glycolipids
Transport of substances across membranes
simple diffusion
The diffusion of substances across the membrane from the high-concentration side of the plasma membrane to the low-concentration side through the interstitial space between lipid molecules. Oxygen, carbon dioxide, ethanol, urea, glycerin and other fat-soluble substances; Determining factors: concentration difference on both sides of the membrane, membrane permeability to the substance
facilitated diffusion
It refers to the transmembrane transport of non-lipid-soluble small molecule substances or charged ions with the help of transmembrane proteins along the concentration gradient and potential gradient.
Facilitated diffusion through channels: also called ion channels, without the ability to decompose ATP
There are also water channels
Ion selectivity
Gating properties
Voltage-gated channels: regulated by membrane potential
Chemically gated channels: regulated by certain chemicals inside or outside the membrane, and have both channel and receptor functions
Mechanically gated channels: regulated by mechanical stimulation, the plasma membrane senses stretch stimulation, causing the channels in it to open.
Ungated channels: always open, such as potassium leak channels on nerve fibers
Facilitated diffusion via carrier
The transport of water-soluble small molecules across membranes along a concentration gradient mediated by carrier proteins; Glucose, amino acids, etc.
structure specificity
saturation phenomenon
competitive inhibition
active transport
Certain substances are transported across membranes against concentration gradients and potential gradients with the help of membrane proteins and energy provided by cell metabolism. According to whether membrane proteins directly consume energy, they are divided into primary active transport and secondary active transport.
primary active transport
The process by which cells directly use the energy generated by metabolism to transport substances against concentration gradients or potential gradients; The membrane protein or carrier that mediates this process is called an ion pump, which is essentially an ATPase.
Sodium-potassium pump: It is composed of two subunits a (catalytic subunit, which requires the participation of sodium ions inside the membrane and potassium ions outside the membrane to have ATPase activity) and b. Each time a molecule of ATP is decomposed, 3 sodium ions move out of the cell and 2 potassium ions move into the cell
Calcium pump: also called Ca2-ATPase. The calcium pump on the plasma membrane is called plasma membrane calcium ATPase (PMCA). The calcium pumps on the sarcoplasmic reticulum and endoplasmic reticulum are called sarcoplasmic reticulum and endoplasmic reticulum calcium ATPase ( SERCA); PMCA can transport 1 calcium ion from the cytoplasm to the outside of the cell for every molecule of ATP broken down; SERCA can transport 2 calcium ions from the cytoplasm to the endoplasmic reticulum for every molecule of ATP broken down.
proton pump
Hydrogen-potassium pump: Mainly distributed on the apical membrane of gastric gland parietal cells and renal collecting duct intercalary cells, it secretes hydrogen ions and absorbs potassium ions, secretes hydrogen ions into gastric juice or urine against the concentration gradient, and participates in the formation of gastric acid and renal excretion. acid function
Hydrogen pump: Distributed in the membranes of various organelles, transporting hydrogen ions from the cytosol to lysosomes, endosomes, Golgi complex, endoplasmic reticulum, and synaptic vesicles
secondary active transport
It does not come directly from the decomposition of ATP, but uses the sodium ion or hydrogen ion concentration gradient established by the primary active transport mechanism to cause other substances to cross the membrane against the concentration gradient and potential gradient while sodium ions or hydrogen ions diffuse along the concentration gradient. transport
Symmetric transport: The transported molecules or ions all move in the same direction; such as glucose reabsorption in the small intestinal mucosal epithelium (2 sodium ions and 1 glucose in the same direction) and reabsorption in the proximal renal tubule epithelium (1 Sodium ions and 1 glucose move in the same direction) through the sodium-glucose symporter
Antitransport: The transported molecules or ions move in the opposite direction; Sodium ion-calcium ion exchanger, sodium ion-hydrogen ion exchanger
Membrane vesicle transport: macromolecules and particulate matter entering and exiting cells do not directly pass through the cell membrane, but are surrounded by the membrane to form vesicles. The transport is completed through a series of processes such as membrane wrapping, membrane fusion, and membrane separation.
Enter the cell
Phagocytosis: the transported substance enters the cell in solid form
Swallowing: The transported substance enters the cell in liquid form
Coming out of the cell
Continuous exocytosis: When the cell is quiet, the secretory vesicles spontaneously fuse with the cell membrane and the macromolecular substances in the vesicles are continuously discharged from the cell.
Regulated exocytosis: When cells are induced by certain chemical signals (such as hormones) or electrical signals (such as action potentials), a large number of secretory vesicles stored in certain parts of the cell fuse with the cell membrane and expel the vesicle contents out of the cell. the process of
cell signal transduction
The process by which biological information (excitation or inhibition) is converted and transmitted between cells or within cells and produces biological effects, usually refers to transmembrane signal transduction, that is, biologically active substances (hormones, neurotransmitters, cytokines, etc.) pass through receptors The process of activating or inhibiting cellular functions through the action of ion channels. Signaling molecules: Chemical substances involved in completing intercellular signal communication or intracellular signal transduction. Messenger molecules: small molecules specialized in carrying biological information. Signal transduction pathway: a chain of signal molecules that completes the conversion and transmission of biological information between cells or within cells
Ion channel mediated
Chemically gated channels have the functions of both receptors and ion channels, also known as ion channel receptors, eg nicotinic acetylcholine receptors, ionotropic glutamate receptors Voltage-gated channels and mechanical-gated channels have "ion-promoting" signal transduction functions similar to chemical-gated channels. They can also be classified as ion channel-type receptors, but only accept electrical signals or mechanical signals.
G protein coupled receptor mediated
G protein-coupled receptor: refers to a type of receptor that, after being activated by a ligand, acts on the G protein coupled to it, and then triggers a series of cascade reactions dominated by signaling proteins to complete transmembrane signal transduction. The signaling molecules involved in this type of transduction include a variety of signaling proteins (G protein-coupled receptors, G proteins, G protein effectors, protein kinases) and second messengers
G protein coupled receptor
There are many types and widely distributed, and it is a 7-transmembrane receptor; after being activated by a ligand, the G protein-coupled receptor binds and activates the G protein by changing the molecular conformation.
G protein
The abbreviation of guanylate-binding protein is a trimeric G protein that exists on the inner side of the cell membrane and is composed of three subunits: a, b, and g; The a subunit is the main functional unit, having both the ability to bind GTP or GDP and GTPase activity; the b and g subunits form a functional complex; G protein binds to GDP to form a G protein trimer-GDP complex, which is in the inactive state, and binds to GTP to form the activated state (the activated G protein dissociates into two parts, a-GTP and bg complex, each activating downstream effectors, transduce signals into cells
G protein effector
G protein effectors, targets directly acted on by G proteins, include effector enzymes, membrane ion channels, and membrane transport proteins; Effector enzymes include adenylyl cyclase AC, phospholipase C (PLC), phospholipase A2 (PLA2), and phosphodiesterase PDE. Their function: catalyze the generation (or decomposition) of second messengers.
Second messenger: Refers to the intracellular messenger molecules produced after extracellular messenger molecules (first messengers) such as hormones, neurotransmitters, and cytokines act on membrane receptors. They usually refer to effector enzymes activated by G proteins that are then broken down into cells. Small molecules produced by substrates; can further activate protein kinases Cyclic adenosine monophosphate cAMP, inositol trisphosphate IP3, diacylglycerol DG, cyclic guanosine monophosphate cGMP, calcium ion, arachidonic acid AA
protein kinase
A type of enzyme that transfers the phosphate group on the ATP molecule to the substrate protein to produce protein phosphorylation; If the substrate protein is also a protein kinase, it can trigger a waterfall-like sequential phosphorylation, called a phosphorylation cascade reaction; Phosphorylation caused by protein kinases can be terminated by dephosphorylation of the substrate by protein phosphatase present in the cell eg: cAMP-dependent protein kinase (protein kinase A, PKA), Ca2-dependent protein kinase (protein kinase C, PKC)
Enzyme-linked receptor mediated
Refers to a membrane receptor that itself has enzymatic activity or is combined with an enzyme; Structural features: Each receptor molecule has only a single transmembrane segment, the extracellular domain contains a site that can bind ligands, and the intracellular domain has enzymatic activity or a site that can bind to an enzyme.
Tyrosine kinase receptor TKR
The intracellular domain has tyrosine kinase activity, including epidermal growth factor, platelet-derived growth factor, fibroblast growth factor, hepatocyte growth factor, and insulin; Binds to ligand - tyrosine kinase is activated - phosphorylates the tyrosine residues of downstream proteins (if it is a structural protein or functional protein - directly changes cellular function; if it is a signaling protein - triggers downstream signal transduction processes)
Tyrosine kinase binding receptor TKAR
It has no enzymatic activity. After activation, it binds to the tyrosine kinase in the cytoplasm and activates it, thereby phosphorylating the tyrosine residues of downstream signaling proteins. The ligands that activate this type of receptor are various growth factors, such as erythropoietin, interferon, interleukin, growth hormone, prolactin, and leptin
Guanylyl cyclase receptor GC
It is a single transmembrane α-helical molecule with a ligand-binding domain at the extracellular N terminus and a GC active domain at the intracellular C terminus; Atrial natriuretic peptide ANP/brain natriuretic peptide BNP - guanylyl cyclase receptor - generates GTP to generate cGMP - cGMP activates cGMP-dependent protein kinase PKG - PKG acts as a substrate for serine/threonine protein kinase Phosphorylation of substances to achieve signal transduction; The receptor on which NO acts is a soluble GC free in the cytoplasm, which also produces biological effects through the cGMP-PKG pathway after activation.
serine/threonine kinase receptor
The intracellular domain of this type of receptor has serine/threonine kinase activity. After activation, it phosphorylates the serine/threonine residues of the Smad protein and translocates into the nucleus to regulate the expression of specific protein genes.
recruitment receptor mediated
A single transmembrane receptor. The intracellular domain has no enzymatic activity. However, once the extracellular domain binds to a ligand, its intracellular domain can recruit kinases or adapter proteins in the cytoplasm to activate downstream signals that do not involve classical second messengers. transduction pathways; Mainly regulates the functions of hematopoietic cells and immune cells
nuclear receptor mediated
Intracellular receptors are collectively called nuclear receptors
muscle cell contraction
skeletal muscle neuro-muscle junction
Structure
It is a specialized structure between motor nerve endings and the skeletal muscle cells they innervate. It is composed of pre-joint membrane, post-joint membrane and joint gap. prejunctional membrane: part of the terminal membrane of a motor nerve axon Post-joint membrane: The skeletal muscle cell membrane opposite to the pre-joint membrane, also called the end plate membrane, is a shallow groove that is depressed inward. The end plate membrane at the bottom of the groove is sunk inward to form many wrinkles.
excitement transfer process
The AP transmitted from the motor nerve fiber to the axon terminal triggers the outflow of calcium ion-dependent synaptic vesicles from the prejunction membrane and releases Ach into the junction gap. Ach activates the nitrogen molecule type Ach receptor cation channel on the terminal plate membrane. produce changes in membrane potential
excitation-contraction coupling
concept
The intermediary mechanism that links the electrical excitation process of AP produced by striated muscle cells with the mechanical contraction of myofilament sliding.
The basic steps
1. Action potential conduction of T-tubule membrane: The action potential on the sarcolemma is transmitted along the T-tubule membrane to the inside of the cell, and activates L-type calcium channels in the T-tubule membrane and sarcolemma.
2. Calcium ion release in the JSR: Depolarization of the sarcolemma causes skeletal muscle to trigger a calcium release mechanism through conformational changes. In the myocardium, calcium induces a calcium release mechanism, causing calcium ions in the JSR to be released into the cytoplasm.
3. Calcium ions trigger myofilament sliding: The increase in cytoplasmic calcium ion concentration prompts calcium ions to bind to Tnc and trigger muscle contraction.
4. Calcium ions are taken back up by JSR: In skeletal muscle, almost all the calcium ions in the cytoplasm are taken back into the SR through the calcium pump in the activated LSR membrane. Most of the calcium ions in the myocardial cytoplasm are taken up by the calcium pump in the LSR membrane Recycled, a small part is discharged to the outside of the cell by the sodium ion-calcium ion exchanger and calcium pump in the sarcolemma
myofilament gliding
cell electrical activity
Cells are accompanied by electrical phenomena when they carry out life activities, which is called cellular bioelectricity; It is generated by the flow of some charged ions across the membrane and manifests itself as a certain transmembrane potential, referred to as membrane potential.
Resting potential RP
concept
The potential difference between the inner negative and outer positive that exists on both sides of the cell membrane in the resting state
production mechanism
Basic Cause: Transport of charged ions across membranes; In a quiet state, the permeability of the cell membrane to various ions is highest with potassium ions, and the resting potential is closer to the equilibrium potential of potassium ions (because the cell membrane still has a certain permeability to sodium ions at rest, the actual measurement is slightly less than equilibrium potential of potassium ions)
action potential AP
concept
After cells receive effective stimulation based on the resting potential, they generate a rapid membrane potential fluctuation that can propagate to a distance.
composition
Go to extremes
Repolar phase
Peak potential
back potential
After depolarization potential ADP
after hyperpolarization potential AHP
Features
The “all or nothing” phenomenon
propagation without attenuation
Pulse delivery
production mechanism
Two factors: 1. Electro-chemical driving force 2. Permeability of the cell membrane to ions; The generation of action potential is the result of changes in the resting potential.
Tetrodotoxin (TTX) blocks sodium channels; tetraethylamine (TEA) blocks potassium channels
AP trigger
Threshold intensity: The minimum stimulus that can cause cells to generate action potentials. Stimuli equivalent to the threshold intensity are called threshold stimuli; stimuli greater than or less than the threshold intensity are called suprathreshold stimuli and subthreshold stimuli respectively. Threshold potential: The critical value of membrane potential that can trigger action potential is called threshold potential; The intensity of the threshold stimulus is just enough to depolarize the resting potential of the cell to the threshold potential level.
Propagation of AP
Spread on the same cell
Propagates in the form of local current; conducts in a jumping manner on myelinated nerve fibers
spread between cells
Some tissues, such as the brain's inner core, cardiac muscle, and certain types of smooth muscle, have gap junctions between cells; There are electrical and chemical synapses between nerve cells
Periodic changes in excitability after cell excitation
absolute refractory period
relative refractory period
supernormal period
low normal period
electrotonic potential
concept
The membrane potential whose spatial distribution and temporal changes are determined by the passive electrical properties of the membrane is called point tension potential.
Spread scope
Described by a space constant, it refers to the spatial distance spread when the membrane potential decays to 37% of its maximum value, represented by l; Increasing the membrane resistance or reducing the axial resistance can increase l
Generation speed
The time constant is used to describe the time change characteristics of the electrotonic potential, which refers to the time required for the membrane potential to rise to 63% of the maximum value during charging or drop to 37% of the initial value during discharge, represented by t; Reducing membrane capacitance shortens the time it takes for the electrotonic potential to reach a stable value.
polarity
Injecting a positive charge into a cell exhibits a depolarizing electrotonic potential; injecting a negative charge into a cell exhibits a hyperpolarizing electrotonic potential.
feature
graded potential
attenuating conduction
Potentials can be fused
local potential
concept
After the cell is stimulated, the change in membrane potential that is formed by the active characteristics of the membrane, that is, the opening of some ion channels, and cannot propagate to long distances is called local potential.
feature
graded potential
attenuating conduction
no refractory period
Reactions can be superimposed, time summation, space summation