Function organization of the body, internal environement and cell function Flashcards
What percentage of the body is made of fluid, and how is this distributed between compartments ?
~60% of the body is water
1/3 extracellular
2/3 intracellular
Apart from H20, what are the most abundant components of intracellular fluid
K, Mg, PO4
Apart from H20, what are the most abundant components of extracellular fluid
Na, Cl, HCO3+O2, glucose, fatty acids, amino acids and CO2
what is interstitial fluid
Fluid between the cells
Every cell is located within what distance of a capillary and why?
50um - to allow for diffusion of nutrients and cells
Skin makes up what % of body weight?
12-15%
Describe the role of the O2 buffering system.
O2 will stay bound to haemoglobin if this concentration in the tissues is sufficient. It unbinds when the [O2] is insufficient
What drives respiration?
Co2 concentration
How is blood pressure regulated?
Baroreceptors in the aortic arch and carotid bifurcation contain nerve endings which respond to arterial wall stretch. When stretched ( high atrial pressure) the message the vasomotor center of the medulla which decreases SNS tone, causing vasodilation, reduced HR and Decreased CO. Opposite is occurs when BP is low
What is adaptive control
this is delayed negative feedback - where the body constantly corrects feed-forward controls.
What are the substrates that make up the protoplasm and their concentrations?
1) Water - makes up 70-85% of the cell, esp cytosol
2) electrolytes
3) proteins - 10/20% of cell mass
- structural - filamentous proteins
- functional - enzymes
4 Lipids- soluble in fat solvets
- phospholipids + cholestrorle; 2% of cell mass and form membranes
- Triglycerides; stored fat (95% of cell fat reserve
5) carbohydrates
- glycoproteins i.e. structural
- dissolved glucose
- glycogen
What is the structure of the cell wall and what does it may constituent allow from a diffusion stand point?
Lipid bilayer, with phosphorous head facing the outside and inside of the cell. Between the phosphorous heads there are lipid tails. Within the wall there are also dissolved proteins for transport and signaling and cholesterol units. Colesterole control permeability to water.
What molecules can passively diffuse across a lipid bilayer ?
give 2 examples
Fat soluble molecules such as O2, CO2
What molecules CANNOT passively diffuse across a lipid bilayer ?
give 3 examples
Fat insoluble molecules (glucose, urea, ions)
What are integral and peripheral cell membrane proteins? What are their roles?
Integral; transverse the whole lipid bilayer - channels, pores, carrier proteins or receptors
Peripheral; attached to only one surface - act as enzymes or signal transduction molecules
What is the glycocalyx?
what is its role ?
This is made of carbohydrates (glycoproteins or glycolipids) that are positioned on the outside of the cell
- Have a negative electrical charge
- attach to other cells
- act as receptors
- important immune regulator
What is the structure of the endoplasmic reticulum?
flattened vescicular network made of lipid bilayer with a large surface area which is important for cell signaling and metabolic function. Comes in two forms;
- RER; contains ribosomes -> released into the cytosol during protein synthesis
- SER; synthesis of phospholipids and cholesterol. Also contains enzymes which hydrolyze glycogen and detoxify substances
What is the structure of the Golgi apparatus?
Similar structure ti to the smooth endoplasmic reticuluma and is closely associated with the endoplasmic reticulum
What is the role of the golgi apparatus?
vescicles from the endoplasmic reticulum fuse with the golgi so that the contents can be used for intracellular functions. Also produce hyaluronic acid and chondrotin sulfate
1) major component of proteoglycans and ground substance
2) principle component of organic matrix, cardtilage and bone.
What are lysosomes, and what is their role?
Break-off parts of the Golgi form vesicles which perform intracellular digestion. These contain granules of hydrolytic enzymes which are used for digesting waste/bacteria/damaged cells.
what are perixomes?
Similar to lysosomes but differ in 2 ways;
1) formed by self-replication or budding of the SER, not by the Golgi
2) Contain oxidases (not hydrolases) = oxidize unwanted substances by combining H2->H2O2
What is the structure of the nucleous?
Outer membrane is continuous with the ER which are penetrated by pores with complex protein molecules. Contains the chromatin which form the chromosomes needed for mitosis. Within the structure, there is a nucleous which is not covered by a membrane but is an accumulation of rRNA/proteins (eg ribosomes) where protein synthesis occurs
How do substances enter the cell?
1) Passive diffusion
2) Active diffusion
-> Pinocytosis - ingestion of small globs of extracellular fluid with dissolved materials. Require ATP and Ca and once internalised the blobs are transported by clathrin fibrillar proteins and actin myosin contractile units
-> phagocytosis - ingestion of large particles (bacteria, cells, dead tissue) and is similar to pinocytosis but this is usually done by macrophages and WBC’s
How many Cal/mole of does ATP have and where is the energy stored
12,000 cal/mol and the energy is stored in high energy phosphate bonds
ATP is used to promote 3 major categories of cellular functions;
1) membrane transport (active transport)
2) mechanical transport such as muscle contractions, cilliary motion, ameboid movement
3) synthesis of compounds
What is ameboid movement? what cells perform this?
Whole-cell changes shape to move compared to the surroundings. This is performed by monocytes, fibroblasts etc.
What ions are in a high concentration outside the cell?
Na, Cl, HCO3, Ca
What ions are high in concentration inside the cell?
K, Ca, Mg
How do solutes move by diffusion?
They move down a concentration utilising kinetic energy
What two types of diffusion are there?
Simple - down channel proteins
Facilitated - with carrier proteins
What main factor governs how rapidly a solute moves across a membrane?
The lipid solubility of that product - e.g. O2 is highly lipid soluble
Why have channel proteins when products can simply diffuse through the membrane?
Are channel proteins that are involved in simple diffusion specific or specific, and why ?
Lipid insoluble products cannot diffuse accross the membrane and require channel proteins.
Most are gated and thus have selective permeability
How are protein channels gated?
give an example for each
Voltage - gates open in accordance to an electrical potential across the membrane - e.g. when inside the cell becomes more positive Na channels open
Chemical - involves opening of channels after a molecule binds t the protein channel. E.g. acetylcholine binding to acetycholinergic channel
what is another name for facilitated diffusion?
carrier mediated diffusion
What is the main difference between simple and facilitated diffusion?
Facilitated diffusion is limited bu the. rate at which the carrier protein can undergo a conformational change
What are examples of molecules which use facilitated diffusion?
Glucose and amino acids
What is the diffusion coeficient?
(permeability of the membrane) X (the area of the membrane)
What is the net rate of diffusion into a cell?
difference between the concentration outside the cell minus inside the cell
what is the Nernst equation ?
when a charge is applied across a membrane, molecules will move towards the opposite charge irrespective of their concentration gradient. At normal body temperature, the electrical difference that will balance a given concentration difference can be determined by the Nernst equation
what is osmosis
the process of net movement of water caused by a concentration difference of water
Osmotic pressure is what?
The amount of pressure needed to exactly stop or oppose the diffusion of water across a water gradient.
As water moves across a membrane, pressure builds up on the other side, eventually opposing the gradient.
what determines the pressure of a solution?
what is this called?
the number of molecules within, not their size. This is the osmole of a solution or the osmolarity
what is 1 osmole?
It is 1 gram molecur weight of an undissociated solute
what is the difference between the osmolarity of NaCl and glucose?
1g molecular weight of glucose is 1 osmole, while for NaCl it is 2 osmole as it dissassociates
what is osmolalility and osmolarity?
osmoLALITY-osmoles per Kg of H2O
osmoLARITY- osmoles per litre of solution
What is active transport?
what types are there?
this is the movement of molecules against a concentration gradient (Na, K, Ca)
Divided into 2 types;
- Primary active transport - uses ATP
- Secondary active transport - utilises energy by establishing a gradient with primary active transport
what are other names for secondary active transport receptors?
co-transporters and counter-transporters
What is a membrane potential?
It is the concentration difference of ions across a semipermeable membrane which causes the creation of a membrane potential - e.g. accumulation of Na on the inside of the cell will prevent further accumulation of positive charges within the cell due to the electrical gradient
