1 Homestasis And Cell Membrane

Question 1

1. Homeostasis

Answer 1

Maintenance of nearly constant conditions in the internal environment and norm/constant ed fluid. Disease can be considered a state of homeostatic imbalance. All organs and tissues help.
Liver - reg carb metabolism, metabolise toxic
Kidney - reg salt, BP, pH
Hypothalmus + ANS, Endocrine
Open reg = input+output x connect
Closed=output info returned to same system
+ve feedback - ^>^ - amplify and can lead to instability e.g. oxytocin and hemorrhage
-ve feedback - ^>decrease, Gain = correction/error (effectiveness) e.g. barorecptors, HPA axis
Functional Systems - operate w/i organs to control fct of indiv organ (circ, respiratory, GI, liver, MSk, kidney, repro, immune, nervous)
Control sys - maintain homeostasis genetic sys, operate throughout body to control organ interaction e.g. resp/nervous [+ve/-Ve feedback]

Question 2

2. Cell membrane

Answer 2

1. Phospholipids - hydrophilic glycerol backbone head,
   and two fatty acid tails, which are hydrophobic (water-insoluble). Tails face each other and form a bilayer.
2. Lipid-soluble substances cross cell membranes
3. Water-soluble substances cannot but may cross through water-filled channels, or pores, or may be transported
   by carriers.

Integral proteins - anchored+embedded in membrane via hydrophobic interactions, may span the cell membrane. Inc: ion channels, transport proteins, receptors, and GPCR
Peripheral proteins - not imbedded + not covalently bound to membrane components, loosely attached to the cell membrane by electrostatic interactions.

Protein fct - enzymes, transport, identify, adhesion, cytoskeleton attachment

cells linked by jct - supported by matrix,
Epithelial - lines, minimal matrix >BM, polarized
Basolat memb - glu, gala, fruc via Glut2 > reabsorped via capillary wall
Luminal membrane - glu+gala by NA/Glu SGLT1, fructose=GLUT5(facilitated)

Question 3

2+3. Cell membrane transport

Answer 3

Carrier protein (conform A), channel protein (free movement of water and ions)

Passive - diffusion (perm, conc A, distance, SA, temp),e.g. Co2 facillitated diffusion (via carrier protein - more stereospecific + rapid e.g. Glu in adipose tissue),
osmosis (selectively permeable to hypotonic)

ECM:cytoplasm comp - Na (150mM:15mM =60mV), K (150:5mM =-90mv), cl (110:7mM i. 15:1 = -70mV)

Passive: Na+ = leak channel into cell 9sm no) > ^+ve > less K out

Active: Na/K pump 2Na out and 2K in against gradient (ATP phosphorylates membrane protein as bind Na and dephosphorylates as bind K)
Ca2+-ATPase - Ca2+ against an electrochemical gradient SR+ER = SERCA.
H+,K+-ATPase (or proton pump) in gastric parietal cells transports H+ into the lumen ofthe stomach against its electrochemical gradient.

Secondary active transport: Coupled - Na/K coupled w/ Na/Glu (cotransporter as Na moves back in bring in Glu)

Endocytosis - active via membrane
Phagocytosis - cell eating
Pinocytosis - cell drink
Exocytosis - active excretion