Cellular Physiology Flashcards
Common types of interactions between cells
Mechanical
Electrical
Chemical - neurotransmitters, neurohormones, endocrine, paracrine, autocrine
How might control be exerted on an intracellular function? 5
Activation or inhibition of enzymes
Regulation of gene expression
Changes in membrane permeability
Regulation of membrane receptor activity
Changes in membrane potential
What is cytoplasm
Everything outside the nucleus within the cell
Cytosol (water, proteins, electrolytes) and organelles
Components of cytoskeleton - diameters
Microtubules - 25nm
Muscle thick filaments - myosin - 15nm
Intermediate filaments - 10nm
Muscle thin filaments - actin - 5nm
What is the function of the cytoskeleton?
Cell structure
Cell movement
Cell shape changes
Contents of mitochondria with function
To produce ATP
folded inner membrane - cristae - oxidative phosphorylation enzymes
Matrix - citric acid cycle
Maternal DNA
Function of endoplasmic reticulum
Rough - protein synthesis
Smooth - steroid synthesis and detoxification
Ribosome size and makeup, location
Function
32nm
65% RNA, 35% protein
On rough er or loose in cytoplasm
Protein synthesis
Function of centrosome
Formation of mitotic spindle
Function of golgi
Name of sides
Prepare proteins for secretion by exocytosis
Cis (receives proteins from ER) and trans (produces vesicles to travel to cell membrane)
Classifications of cell junction and function, example
Anchoring junction - form cell cell adhesions and allow anchoring of cytoskeleton e.g. desmosome
Occluding junction - seals the extracellular space preventing passage of molecules - eg tight junction
Channel forming junction - allow for passage of small molecules between cells - e.g gap junction
Signal relay junctions - allow communication between cells
Function of lysosomes and peroxisomes
Lysosomes breakdown and eliminate intracellular debris or exogenous substances
Persoxisomes catalyse anabolic and catabolic reactions
Function of cilia
Composition
Function
Move substances across surface of cell
9 pairs of microtubules around a central pair (10 in total)
Molecular motor mechanism causing micro tubules to slide relative to each other
Functions of cell membrane
Regulation of passage of substances maintaining homeostasis
Establishment of concentration gradients
Generation of action potentials
Contain cell contents
Anchor cytoskeleton
Site of intercellular connect
Communication - chemical and electrical
Term for the polar nature of phospholipids with regards to water sensitivity
Amphipathic
What is the term for the glycoprotein coat attached to membrane proteins across the cell
Glycocalyx
Categories of protein in a cell membrane by position
Integral vs peripheral
Transmembrane vs monotopic
What are the cell adhesion molecules
Membrane proteins with wide range of functions including adherence to other cells or surfaces and signal transduction
What proteins are responsible for adhesion to other cells? Which to the extracellular matrix?
Cells - Cadherins
Matrix - integrins
Physiological and pathological processes involving cadherins
Morphogenesis
Metastasis
Embryogenesis
Physiological processes associated with integrins
Platelet adhesion
Leukocyte mobility
Cell matrix adhesion
Subunits of a G protein
Alpha beta and gamma
Activation and deactivation sequence of a G protein
Ligand binds to GPCR,
release of GDP from alpha subunit, GTP binds in place,
dissociation of G protein,
Alpha subunit interacts with effector
GTP broken down by intrinsic GTPase,
deactivation of G protein
Number of G protein coupled receptor transmembrane domains
7
Common GPCRs
Adrenoreceptors
Muscarinic ACH receptor
Opioid receptor
Types of G protein and downstream effect
Gs - stimulates adenylyl cyclase increasing cAMP - stimulates PKA (a protein kinase) causing target phosphorylation
Gi - inhibits adenylyl cyclase decreasing cAMP
Gq - stimulates phospholipase C cleaving PIP2 into IP3 (opens Ca channels) and DAG (stimulates protein kinase C causing target phosphorylation)
What substances can cross phospholipid bilayer
Water, lipid soluble substances, small molecules
Define diffusion
Movement of solute molecules due to random thermal motion with a net movement down concentration gradient (high to low)
Factors that influence diffusion across cell membrane
Concentration gradient
Surface area
Membrane thickness
Temperature
Lipid solubility
Molecular weight
Electrical charge of particle
Define osmosis
Net movement of water molecules due to diffusion between areas of different concentration
Can consider addition of a solute as diluting the water and reducing its concentration thus water diffuses from a high concentration (low concentration of solute) to low concentration (high concentration of solute)
What is osmolarity
Concentration of solution. 1 mole/litre = 1 osm/L
Define osmotic pressure
The pressure required to oppose the net movement of water across a semipermeable membrane between two solutions
What is the osmolarity of ECF normally?
300mOsm/L
What is tonicity?
What does it depend on?
The ability of a solution to cause shrinkage or swelling of a cell placed in it.
ECF and ICF osmolarity
Cell membrane permeability to the solute particles.
Types of gated ion channels
Stretch (mechanically gated)
Chemical (ligand gated)
Electrical (voltage gated)
What sort of carriers are there for active transport (by substance exchange method)
Uniport - carries one specific substance
Symport - transports combination of substances
Antiport - exchanges one substance for another
What occurs with membrane proteins when they facilitate active transport? What is the impact of this on transport speed, what else contributes?
They undergo a conformational change - speed is in part determined by how fast they can change. Also how dense the carriers are and how saturated they are.
Features of NaKATPase
Primary active transporter
Uses ATP to phosphorylate
Antiporter exchanging 3 Na for 2 K both against concentration gradient
Define primary and secondary active transport
Primary - use of energy directly at carrier proteins
Secondary - uses an ion gradient set up by primary active transport in order to facilitate the transport of another molecule - substance binds at first carrier site, ion binds at a secondary site on the protein, allosteric modulation causes transport of substance whilst ion travels down diffusion gradient.
What are the two sorts of secondary active transport
Co transport - ion and substance carried in same direction
Counter transport - ion and substance carried in opposite directions
What is facilitated diffusion? Difference and implication to normal diffusion?
Transport of a substance down concentration gradient via a carrier.
Not a diffusion mechanism - no energy is required but transport kinetics are characteristic of carrier mediated transport
Thus carrier saturation occurs limiting rate.
What are exo and Endocytosis
Transport of substances by fusion of membrane covered vesicles with cell membrane
What surrounds the nucleus
Features
Nuclear envelope
Double membrane with nuclear pores that allow passage of specific proteins
What is the function of the nucleolus
Synthesis of ribosome subunits.
Components of a nucleotide
Base (Purine/pyramidine)
Sugar (ribose or deoxyribose)
Phosphate group
Bases in DNA
Adenine
Guanine
Cytosine
Thymine
Three types of rna
Messenger
Transport
Ribosomal
What is the main sort of rna in a cell?
Ribosomal - constitutes 2/3rds of ribosome
Number of chromosomes in human
23 pairs
What is chromatin
The clumped dna protein complex seen in the nucleus
Phases of mitosis
Prophase - separation of centrioles and formation of chromosomes from chromatin
Prometaphase - nuclear membrane and nucleolus disitigrates
Metaphase - chromosomes line up on cell equator
Anaphase - chromatids split
Telophase - chromosomes, nuclear membrane and nucleoli reform, cytokinesis begins
Which enzyme is instrumental to transcription
RNA polymerase
Which enzyme is instrumental for Translation
Aminoacyl-tRNA synthetase
How many tRNAs are bound to mRNA at any one time during translation? What are they doing?
2, once carrying the amino acid chain, an adjacent one carrying the next amino acid.
What are the regions of DNA? Which are used for protein synthesis?
Introns - cut out in post transcription processing of pre-mRNA into mRNA
Exons - used
What are transcription factors
Controlling factors that influence RNA polymerase binding to certain (one or multiple) genes. Can originate in the cell or external to it.
Other than transcription factors how else can protein synthesis rate be controlled
At the translation stage
Controlling mRNA breakdown
Classifications of first chemical messengers between cells
Neurotransmitters
Neuromuscular transmitters
Endocrine agents
Paracrine agents
Autocrine agents
Definition of ligand affinity
Strength of binding with receptor
Definition of ligand competition
Ability of different ligands to bind with same receptor
Definition of ligand agonist
Ability of ligand to trigger cell response
Definition of ligand antagonist
Ability of ligand to bind to receptor without triggering a response
Definition of ligand half life
Time take for ligand to be metabolised to half its concentration
Consequence of ligand lipid solubility
Lipid insoluble ligands active cell surface receptors
Lipid soluble ligands active intracellular or intranuclear receptors
Definition of receptor specificity
Selectivity of a receptor to a single ligand
Definition of receptor saturation
Percentage of receptors already occupied by ligand
Definition of receptor down regulation and up regulation
Decrease / increase in number of receptors available for given ligand
Definition of receptor sensitivity
What controls it
Responsiveness of a get full to given ligand - dependant on concentration of receptors
Definition of receptor supersenstitivity
Increased sensitivity of cell due to receptor upregulation
What are the two processes that allow ligand binding to receptor with conformational change? Brief desription
Allosteric modulation - separate modulator binds away from binding site resulting in conformational change allowing ligand binding
Covalent modulation - phosphorylation of receptor with conformational change allowing ligand binding.
Group of proteins responsible for phosphorylation
Kinases
What ways might a receptor result in signal transduction into the cell?
Opening or closing of integral ion channel
Activation of intracellular protein kinase
Activation of G proteins mediating further action
How can lipid soluble ligands exert their intracellular effect
Complex formation with cytosol receptor which moves to nucleolus and promotes gene expression
Ligand moves directly into nucleus and forms complex with nuclear receptor and promotes gene expression,
What is the effect of the second messenger system within a cell on signals strength
Acts as a cascade amplyfing the signal
What is the effect of caffeine and theophylline on the second messenger system?
Inhibit phosphodiesterases reducing breakdown of cAMP and cGMP augmenting the second messenger cascade.
What is the approx gradient of extracellular to intracellular calcium concentration? Implication?
10^4
Rapidly enters cell when given chance
Where is calcium stored intracellular
ER
How are calcium levels reduced in the cell
C H ATPase
NaCa Antiporter
Reuptake into ER
Examples of intracellular proteins that calcium can bind to
Other functions when released
Calmodulin
Troponin
Calbindin
Synaptic function
Protein synthesis
What occurs downstream after binding of calcium to calmodulin
Acts as a protein kinase
Effect of IP3 production from G proteins
Release of calcium from ER
Mediator that is activated by Gq receptors causing cleavage of PIP2 to IP3 and DAG
Phosphlipase C
Effect of DAG
Activation of protein kinase C
Definition of aging
Physiological process involving general changes in body systems (usually decline) distinct from the pathological changes of disease
Three theories of aging
Wear and tear - natural deterioration as a result of continuous functioning
Adaptive evolution - genetically programmed termination of life in interests of evolutionary selection
Non-adaptive evolution - evolved as optimum balance between limited energy sources available and demands of normal function and repair
Cellular mechanisms associated with ageing
Accumulation of cells with random mutations
Crosslinking of collagens and proteins by glycosylation
Accumulation of oxidant radicles and lipofuscin granules
Genetic clock determining number of cell reduplications
Pleiotropic genes with good effects in early life and bad in later life
Cardiac output and renal blood flow of a 70 year old vs young adult
64 and 60%
Muscle mass of a 70 year old vs young adult
74%
Cardiovascular changes in aging
Lower cardiac output and reserve
Decreased heart rate
Decreased stroke volume
Decreased LV compliance
Respiratory effects of aging
Decreased pao2, lung elasticity, compliance, vital capacity
Increased residual volume
Gi changes with age
Decreased smell and taste
Decreased coordination and swallowing
Decreased gastric and pancreatic secretions
Decreased large bowel motility
Endocrine effects with aging
Increased norad and vasopressin
Decreased RAAS, carbohydrate tolerance, oestrogen and testosterone
Renal changes with ageing
Decreased kidney mass, ability to concentrate urine, renal response to vasopressin
Increased prostate mass
CNS changes with ageing
Decreased brain mass, ACh activity, cerebral blood flow, short term memory
Increased reaction time
Immunological change with ageing
Decreased cellular and humoral immunity
Musculoskeletal changes with ageing
Decreased bone and muscle mass
