Homeostasis,cell structure and function Flashcards
The maintenance of a steady state in the internal environment despite changes in the external environment is called?
Homeostasis
What can be referred to the internal environment of the body
The Extracellular fluid
T/F all the organ system of the body function to achieve homeostasis
T
Name the component structure of the cell membrane
- Composed of 50% protein
- Hydrophilic(Lipophobic)Outward oriented head and the hydrophobic(Lipophilic)Inward oriented tail.
- Peripheral protein and integral protein.
The Energy needed for cells to use is produced from the reaction between?
Oxygen, carbohydrates, fats, and protein
What is the component of the fluid mosaic model of the cell membrane
- Extracellular Fluid
- Intracellular fluid
- Lipid Bi-layer
- peripheral and Integral protein
What are the properties of the cell membrane
- It’s selectively permeable.
- Lipid soluble substances dissolve in Hydrophobic bilayer, thereby crosses the cell membrane.
- Water-soluble substances cannot dissolve in the lipid bilayer, but some can cross through water-filled channels or pores and also transported by carrier molecules
What are some examples of Lipid soluble substances
CO2, O2, steroid hormones
What are some examples of water-soluble substances
Na,cl,Glucose,Water
What are the two types of membrane protein
Peripheral and integral protein
what are the functions of the cell membrane protein
Enzyme,transporter,channel,receptors, antigen
What is the function of Integral /intrinsic /transmembrane proteins:
Acts as ion channels, transport proteins. These span the entire cell membrane or are embedded in the membrane
What is the function of Peripheral or extrinsic proteins :
They are not embedded & are located on one side of the cell membrane, either intra- or extracellular side. Ex: ankyrin, which anchors the cytoskeleton of the red blood cells to an integral membrane protein, the Cl–HCO3- exchanger
What is HOMEOSTASIS
The maintenance of constant internal environment (Claude Bernard’s “milieu interieur”) despite changes in the external environment
What are the types of membrane transport
Simple diffusion Facilitated diffusion primary active transport secondary active transport osmosis
What is Simple diffusion
Movement of substance down a concentration gradient
From high to lower concentration until the concentration is even on both sides
3 factors that affect the rate of diffusion are?
Concentration gradient
•Permeability of the membrane
•Surface area
What are examples of simple diffusion
Substances that are Lipid soluble(lipophilic) such as blood gases(Co2, O2) or steroids, can diffuse directly through the lipid Bilayer
What is facilitated Difusion
Transport of a substance along its concentration gradient, facilitated by a carrier protein in the cell membrane
•A type of passive transport
•Rate of diffusion is faster due to the presence of the carrier protein (“facilitated” by the carrier protein) at lower concentrations
•Rate of diffusion reaches saturation at higher concentrations
•Follows all features of a carrier-mediated transport: saturation, specificity, competition
In simple diffusion, the rate of diffusion is directly proportional to the concentration difference true or false
True
Name 3 examples of Facilitated diffusion
- Glucose transport from the intestinal epithelial cells/renal tubules into the blood
- Transport of glucose into skeletal muscle & adipose cells by GLUT-4 transporter
- Transport of fructose in the gut all the way from the lumen into the blood
Name 1 protein that has a facilitated diffusion property
The serotonin transporter is an example of a protein with facilitated diffusion properties whose function is to clear neurotransmitter from the synaptic cleft of brain cells
Name the 3 types of carrier-mediated transport
- Facilitated diffusion
- Primary active transport
- Secondary active transport
All forms of carrier-mediated transport have 3 common features namely?
a) Chemical specificity / stereospecificity
b) Competition
c) Saturation
The transporter for glucose in the renal proximal tubule is specific for D-glucose, true or false
True
What is Saturabilty of carrier-mediated Transport
Carrier proteins have a limited number of binding sites for the solute
•At low solute concentrations, many binding sites are available & the rate of transport increases rapidly with increasing concentrations
•At high solute concentrations, the rate of transport reaches a plateau, as all the binding sites are saturated (occupied)
What is Transport Maximum
(Tm) represented by the plateau phase in the graph
•Transport Maximum (Tm) is defined as the maximum rate at which the substance can be reabsorbed
What is Primary Active transport and characteristics
Transport of solutes against the concentration gradient
•An active process requiring the use of energy (ATP)
•Energy is used directly to pump solutes
•Carrier protein has ATPase activity
•Follows all features of a carrier-mediated transport: saturation, specificity, competition
Give examples of primary active transport
- Sodium-potassium ATPase (Na+-K+ pump)
- Calcium ATPase (Ca2+ pump)
- Hydrogen-potassium ATPase (H+-K+ pump)
what are the characteristics of the Na-K pump(ATPases)
- Maintains the gradients of Na+ and K+ between intracellular and extracellular compartments
- Electrogenic pump; 3 for 2 exchange of Na+ for K+
What is the mechanism of action of digitalis
Digitalis is a cardiac glycoside derived from foxglove and is used in heart failure patients. It inhibits the Na+-K+ ATPase in cardiac myocytes which indirectly raises intracellular Ca++ and thereby promotes cardiac contractility.
what are the characteristics of Ca2+ ATPasee3(also primary active transport)
Ca2+ ATPase (Ca2+ pump) present in cell membrane, sarcoplasmic & endoplasmic reticulum transports Calcium against an electrochemical gradient
What are the characteristics of H+-K+ ATPase (Proton pump)
H+-K+ ATPase (Proton pump) in gastric parietal cells transports H+ into lumen of the stomach against its electrochemical gradient. Acidifies gastric contents.
The H+-K+ ATPase is inhibited by proton pump inhibitors (omeprazole). Omeprazole blocks the primary active transport, reducing gastric acid secretion. True/False
True
What are the characteristics of secondary active transport
Type of transport in which transport of a solute is coupled with sodium transport and is transported against its gradient
•It is an active, carrier-mediated process
•Sodium moves down its gradient but provides energy for moving the solutes uphill
•Energy is used indirectly; not directly by the carrier
•The driving force for the carrier is the sodium concentration gradient, created by primary active transport
•If there is no sodium gradient, transport stops
•Inhibiting Na+-K+ pump stops this transport
•The carrier may transport one or more solutes
e.g>Glucose Transport in Gut.
Glucose movement into the cell stops if the Na+-K+ pump is blocked.
Sodium-Glucose cotransport (SGLT)
e.g>Calcium transport out of heart muscle: Sodium-calcium exchange
Uniport
Transport of a single substance
Symport
Transport of more than one substance in the same direction(also called cotransport)
Antiport
Transport of more than one solute in opposite directions across the cell membrane (also called countertransport or exchange)
Examples of symporter
i)Na+ -glucose cotransport in the small intestine using carrier SGLT-1
•ii) Na+-amino acids cotransport
Examples of Antiport
Na+ - Ca2+ exchange and Na+ - H+exchange
What is Osmosis and the properties
- Movement of water across the cell membrane OR selectively permeable membrane due to the difference in concentration of solutes
- Water moves from a region of higher water concentration to a region of lower water concentration
- The water concentration of a solution is determined by the concentration of solute.
- Concentration difference of solutes creates an osmotic pressure that makes water to move
- Water continues to move until the concentration of solutes become equal on both sides32
State the differences between osmosis and diffusion
- Osmosis is NOT the diffusion of water
- Osmosis occurs because of a pressure difference
- Diffusion occurs because of a concentration difference
What are examples of osmosis
Movement of water from the intestinal lumen into the blood when solutes move in the same direction;
•Movement of water from tubular fluid of the kidney into the blood when solutes move in the same direction
What is physiology
The study of the function the body at the molecular, cellular, organ system and organismal levels
Is energy required for simple diffusion?
No
Is energy required for facilitated diffusion?
No
Can Ions get through the cell Membrane?
No; small non-charged particles get through the cell Membrane.
Is Antiport and symport a form of primary or secondary active transport?
Secondary
