BMA lecture 2
1. Fructose 2. Glucose 3. water will move into the cell 4. Cell will swell (Lyse)
An artificial cell with an aqueous solution enclosed in a selectively permeable membrane has just been immersed in a beaker containing a different solution. The membrane is permeable to water and to the simple sugars glucose and fructose, but is completely impermeable to the disaccharide sucrose. If the cell contains: • 0.03M sucrose • 0.02M glucose and the surrounding fluid contains: • 0.01M sucrose • 0.01M glucose • 0.01M fructose 1. Which solute(s) will exhibit net diffusion into the cell? 2. Which solute(s) will exhibit net diffusion out of the cell? 3. In which direction will there be osmotic movement of water? 4. Will the cell crenate or swell?
Monosaccharides -simple sugars or monomers -glucose, fructose
What are monosaccharides
mitochondria produce energy in the form of ATP, active muscle cells require much energy
Why do muscle cells have large numbers of mitochondria?
not embedded within the lipid bilayer, are attached loosely to integral proteins or float free
what are peripheral proteins
a buffer is a molecule that can bind or release H+ ions to counter changes in pH Albumin
what is a buffer and give an example
higher concentration of solutes than present in the cell (a strong saline solution) cells lose water by osmosis and shrink or crenate
what is hypertonic
Houses DNA → instructions for protein synthesis Nucleolus → site of mRNA synthesis within nucleus
Nucleus
The resting membrane potential = the voltage (potential energy) that exists across the plasma membrane resulting from separating oppositely charge ions by the plasma membrane
Objective 3:Define the resting membrane potential and explain how it is generated and maintained
1. ↓ in fibroblasts = ↓in collagen & elastin fibres ↓ in subcutaneous fat 2. ↓in collagen = ↓ strength and resilience ↓ stem cell activity = cell loss > cell replacement = skin thins 3. ↓ sebaceous & sweat gland activity
When changes occur in the structural features of the skin layers, the appearance and properties of skin alters. Explain the following properties of old skin: 1. wrinkled skin 2. skin easily damaged 3. dry, itchy skin
Collagen is part of the connective tissue found in the dermis (papillary and reticular layers) Collagen makes the skin strong and resilient to jabs and scraps. It also helps keeps the skin hydrated as it binds water.
Where can collagen be found in the skin and what is its function?
fat cells function as long term storage and make little protein, ribosome's are involved in protein formation and are not required by fat cells
Why do adipose (fat) cells have small numbers of ribosomes?
the golgi apparatus secretes cell products such as hormones, endocrine cells produce and secrete hormones
Why do endocrine cells have prominent Golgi apparatus?
synthesise and secrete plasma proteins
Why do liver cells contain abundant ribosomes and rough endoplasmic reticulum?
lysosomes contain powerful enzymes which digest engulfed material
Why do phagocytic cells contain abundant lysosomes?
skeletal muscle cells function via contractile proteins, microfilaments are contractile, e.g. actin
Why do skeletal muscle cells have high numbers of microfilaments?
polar head= hydrophilic on the outside nonpolar tail= hydrophobic on the inside (contain fatty acids) fatty acids do not like water
describe the phospholipids
they are: -controlled, open or closed, by chemical or electrical signals
explain gated channels
they are channel-mediated facilitated diffusion and leakage channels are: -always open -allows ions or water to move according to concentration gradients
explain leakage channels and what are they
the ability of a solution to change the shape or tone of cells by altering the cell's internal water volume
explain tonicity
they pass through by facilitated diffusion : voltage gated channels
how does Sodium ions pass through the lipid membrane
water is the only substance that can cross freely and also uses protein channels called aquaporins (like a drinking straw)
how does water (lipid insoluble) passes the membrane freely, how?
Maintained by the active transport of ions using the carrier protein called the Na+/K+ ATPase pump.
how is the membrane potential maintained?
Generated by difference in sodium (Na+) and potassium (K+) ion concentrations between the extracellular fluid (ECF) and the intracellular fluid (ICF)
how is the resting membrane potential generated?
hypertonic: crenate-20% sucrose or 6% saline isotonic: no change-10% sucrose or 0.9% saline hypotonic: lyse (burst)-distilled water
hypertonic isotonic hypotonic
1. primary active transport 2. secondary active transport
name 2 types of active transport
by hydrolysis of ATP, (hydrolysis causes the release of ATP) sodium atp-ase pump (an enzyme) -In the body, K+ concentration is 10X higher inside the cell than outside. - The concentration of NA+ is lower inside the cell than outside -These concentration differences are essential for excitable cells like muscle & nerve cells to function normally Hydrolysis of ATP results in the phosphorylation of the transport protein, this cause the pump to change shape and expelling NA+ to the outside K+ diffuses out of the cell down the concentration gradient via leakage channels
primary active transport
they pass using a carrier or channel protein (sugar, amino acids)
substances that cannot pass through the lipid bilayer, how do they pass
Disaccharides -dimers (i.e. 2 joined monomers) -sucrose, lactose
what are disaccharides
proteins embedded within the lipid bilayer. The transmembrane proteins act as channels or carriers for the transport of substances that cannot pass through the lipid portion of the membrane
what are integral proteins
Polysaccharides -polymer - many monomers joined to form long, branching chains -storage products -glycogen - glucose polymer produced by animals - starch - glucose polymer produced by plant
what are polysacchardides
Functions of carbohydrates: -provide energy for all cellular func3ons - building materials - represent 1-2 % of cell mass - cell membrane receptors - part of our gene3c material (nucleic acids) Dietary sources: - mono- and disaccharides - fruits, sugar cane, honey, milk - polysaccharides - vegetables and grains
what are the functions of carbohydrates
requires a carrier protein that combine specifically and reversibly with transport substances solutes are moved "uphill" against a concentration gradient cells must spend energy
what is active transport
also called facilitated diffusion down its concentration gradient water soluble ( lipid insoluble) glucose, sugars, amino acids and ions
what is assisted diffusion
substances that bind to a protein -Glucose -moves down its concentration gradient carriers change shape to envelop the molecule, then release the transported substance, shielding it from the nonpolar regions
what is carrier-mediated facilitated diffusion
-includes leakage channels and gated channels -moves through water filled protein channels like Na+ & K+ -selective due to pore size & the charges of the amino acids line the channel
what is channel mediated facilitated diffusion
more dilute than cells, the cells take on water until they become bloated or burst or LYSE
what is hypotonic
same tonicity (0,9% saline or 5% glucose) the cells retain their normal shape
what is isotonic
the diffusion of a solvent (water) through a selective permeable membrane. Occurs when: -water concentration differs on both sides of a membrane (as solute concentration increases, water concentration decrease) -down its concentration gradient
what is osmosis and when does it occu
unassisted diffusion of lipid soluble or very small particles down its concentration gradient nonpolar & lipid solble diffuse directly through the lipid bilayer oxygen, carbon dioxide, fat soluble vitamins, alcohol diffusion continues until equilibrium is reached
what is simple diffusion
-it is a thin and flexible boundary between the ICF and ECF -it is selectively permeable controlling barrier and determines if and how substances move in and out of the cell it is also known as a Fluid mosaic model, it is composed of a lipid bilayer, and proteins float in the lipid bilayer and this forms a constant changing mosaic pattern
what is the structure of the cell membrane
1. Inflammation • Severed blood vessels bleed • inflammatory chemicals released • local blood vessels become more permeable → macrophages, fluid and clotting proteins seep into the injured area • clotting occurs, surface dries and forms a scab 2. Proliferation • Blood clot is replaced by granulation tissue (capillaries and fibroblasts) • Capillaries → restore blood supply • Fibroblasts → produce collagen fibres that bridge the gap • Macrophages phagocytise cell debris 3. Maturation / remodelling • Fibrosed area matures and contracts → forms scar tissue • Epithelial stem cells divide to replace epithelium • Scab falls off
Briefly describe the steps involved in tissue repair.
Urea leaves the cell, enters the interstitial fluid (ISF) and then the blood by diffusion down a concentration gradient. Its removal by the kidneys maintains that gradient. If the kidneys failed urea would accumulate in the blood. As a result, the rate of diffusion from the ISF into the blood would slow because the gradient is diminished and thus urea would accumulate in the ISF. Diffusion from the cell to the ISF would slow and urea would accumulate within the cells. As urea is toxic to the cell, its accumulation would impair cell function and eventually lead to cell death.
Urea is a toxic product continually produced inside cells as a result of normal metabolism. It diffuses from the inside of cells into the interstitial fluid and then into the blood, and is finally eliminated from the body by the action of the kidneys. What would happen to the intracellular and extracellular concentration of urea if the kidneys stopped functioning?
