Function organization of the body, internal environement and cell function

Question 1

What percentage of the body is made of fluid, and how is this distributed between compartments ?

Answer 1

~60% of the body is water
1/3 extracellular
2/3 intracellular

Question 2

Apart from H20, what are the most abundant components of intracellular fluid

Answer 2

K, Mg, PO4

Question 3

Apart from H20, what are the most abundant components of extracellular fluid

Answer 3

Na, Cl, HCO3+O2, glucose, fatty acids, amino acids and CO2

Question 4

what is interstitial fluid

Answer 4

Fluid between the cells

Question 5

Every cell is located within what distance of a capillary and why?

Answer 5

50um - to allow for diffusion of nutrients and cells

Question 6

Skin makes up what % of body weight?

Answer 6

12-15%

Question 7

Describe the role of the O2 buffering system.

Answer 7

O2 will stay bound to haemoglobin if this concentration in the tissues is sufficient. It unbinds when the [O2] is insufficient

Question 8

What drives respiration?

Answer 8

Co2 concentration

Question 9

How is blood pressure regulated?

Answer 9

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

Question 10

What is adaptive control

Answer 10

this is delayed negative feedback - where the body constantly corrects feed-forward controls.

Question 11

What are the substrates that make up the protoplasm and their concentrations?

Answer 11

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

Question 12

What is the structure of the cell wall and what does it may constituent allow from a diffusion stand point?

Answer 12

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.

Question 13

What molecules can passively diffuse across a lipid bilayer ?
give 2 examples

Answer 13

Fat soluble molecules such as O2, CO2

Question 14

What molecules CANNOT passively diffuse across a lipid bilayer ?
give 3 examples

Answer 14

Fat insoluble molecules (glucose, urea, ions)

Question 15

What are integral and peripheral cell membrane proteins? What are their roles?

Answer 15

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

Question 16

What is the glycocalyx?
what is its role ?

Answer 16

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

Question 17

What is the structure of the endoplasmic reticulum?

Answer 17

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

Question 18

What is the structure of the Golgi apparatus?

Answer 18

Similar structure ti to the smooth endoplasmic reticuluma and is closely associated with the endoplasmic reticulum

Question 19

What is the role of the golgi apparatus?

Answer 19

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.

Question 20

What are lysosomes, and what is their role?

Answer 20

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.

Question 21

what are perixomes?

Answer 21

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

Question 22

What is the structure of the nucleous?

Answer 22

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

Question 23

How do substances enter the cell?

Answer 23

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

Question 24

How many Cal/mole of does ATP have and where is the energy stored

Answer 24

12,000 cal/mol and the energy is stored in high energy phosphate bonds

Question 25

ATP is used to promote 3 major categories of cellular functions;

Answer 25

1) membrane transport (active transport)
2) mechanical transport such as muscle contractions, cilliary motion, ameboid movement
3) synthesis of compounds

Question 26

What is ameboid movement? what cells perform this?

Answer 26

Whole-cell changes shape to move compared to the surroundings. This is performed by monocytes, fibroblasts etc.

Question 27

What ions are in a high concentration outside the cell?

Answer 27

Na, Cl, HCO3, Ca

Question 28

What ions are high in concentration inside the cell?

Answer 28

K, Ca, Mg

Question 29

How do solutes move by diffusion?

Answer 29

They move down a concentration utilising kinetic energy

Question 30

What two types of diffusion are there?

Answer 30

Simple - down channel proteins
Facilitated - with carrier proteins

Question 31

What main factor governs how rapidly a solute moves across a membrane?

Answer 31

The lipid solubility of that product - e.g. O2 is highly lipid soluble

Question 32

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 ?

Answer 32

Lipid insoluble products cannot diffuse accross the membrane and require channel proteins.
Most are gated and thus have selective permeability

Question 33

How are protein channels gated?
give an example for each

Answer 33

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

Question 34

what is another name for facilitated diffusion?

Answer 34

carrier mediated diffusion

Question 35

What is the main difference between simple and facilitated diffusion?

Answer 35

Facilitated diffusion is limited bu the. rate at which the carrier protein can undergo a conformational change

Question 36

What are examples of molecules which use facilitated diffusion?

Answer 36

Glucose and amino acids

Question 37

What is the diffusion coeficient?

Answer 37

(permeability of the membrane) X (the area of the membrane)

Question 38

What is the net rate of diffusion into a cell?

Answer 38

difference between the concentration outside the cell minus inside the cell

Question 39

what is the Nernst equation ?

Answer 39

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

Question 40

what is osmosis

Answer 40

the process of net movement of water caused by a concentration difference of water

Question 41

Osmotic pressure is what?

Answer 41

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.

Question 42

what determines the pressure of a solution?
what is this called?

Answer 42

the number of molecules within, not their size. This is the osmole of a solution or the osmolarity

Question 43

what is 1 osmole?

Answer 43

It is 1 gram molecur weight of an undissociated solute

Question 44

what is the difference between the osmolarity of NaCl and glucose?

Answer 44

1g molecular weight of glucose is 1 osmole, while for NaCl it is 2 osmole as it dissassociates

Question 45

what is osmolalility and osmolarity?

Answer 45

osmoLALITY-osmoles per Kg of H2O
osmoLARITY- osmoles per litre of solution

Question 46

What is active transport?
what types are there?

Answer 46

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

Question 47

what are other names for secondary active transport receptors?

Answer 47

co-transporters and counter-transporters

Question 48

What is a membrane potential?

Answer 48

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