Biology: Gas Exchange

Biology: Gas Exchange

• Gas exchange surfaces must be permeable to oxygen (O2) and carbon dioxide (CO2) as the cell membrane facilitates their passage.
• A large surface area to volume ratio maximizes diffusion efficiency.
• Thin surfaces minimize the distance for gas exchange/travel.
• A moist environment is necessary as gases need to dissolve into a liquid to diffuse across membranes.

Maintenance of Concentration Gradient

• Diffusion requires a concentration gradient, which must be maintained for it to occur.
• Equilibrium stops diffusion.
• Cell respiration maintains the concentration gradient.
• Cells continuously use O2, keeping the inside concentration lower than the outside.
• Cells produce CO2, resulting in a higher concentration inside compared to outside.
• At the tissue level, constant blood flow maintains the concentration gradient between blood and tissue.
• Low O2 in cells causes O2 in the blood (high amount) to diffuse into the cells.
• High CO2 in cells causes CO2 to filter into the blood.

Adaptation of Lungs

• The upper respiratory tract (nose, mouth, pharynx, larynx) warms and humidifies air.
• The lower respiratory tract (trachea, bronchi, bronchioles) transports air to/from the lungs.
• The lungs are a pair of spongy organs.
• Gas exchange occurs between blood and air in the lungs.

Muscles and Breathing

• Muscles contract and relax to facilitate breathing.
• Intercostal muscles, antagonistic muscles, are located between the rib bones.
• The trachea contains cartilage rings to prevent collapse and is lined with cilia (hair) that sweeps out foreign particles.
• Bronchi branch off the trachea, and bronchioles connect to alveoli.

Alveoli

• Alveoli have extremely thin walls, consisting of a single layer of pneumocytes, and are surrounded by capillaries.
• A large surface area to volume ratio is important for gas diffusion.
• Type II pneumocytes secrete surfactant, which consists of phospholipids and proteins forming a film on the alveolar surface.
• Surfactant reduces surface tension, preventing the walls from sticking together/collapsing.
• Blood flow through capillaries maintains a concentration gradient.
• As soon as diffusion finishes, blood moves on to prevent equilibrium.

Ventilation

• As the volume for a gas decreases, the pressure increases (vice versa).
• Gases move from high to low pressure.

Inspiration and Expiration

• During inspiration, the diaphragm moves down, the chest expands outward, and the chest cavity volume increases, allowing air to move in due to low pressure.
• Intercostal muscles relax.
• External intercostal muscles contract, lifting the rib cage up and out.
• During expiration, the diaphragm moves up, the chest relaxes, and the volume decreases, creating high pressure that forces air out.
• Intercostal muscles contract, pulling the rib cage in and down.
• External intercostal muscles relax.

Respiratory Measurements

• A spirogram shows the volume and frequency of breaths over time and measures lung function.
• The ventilation rate is the number of inspiration and expiration cycles per minute (12-20).
• Tidal volume is the volume of air inhaled or exhaled during a normal breathing cycle (500mL).
• Vital capacity is the maximum amount of air that can be inhaled or exhaled after a breath (3-5 Liters).
• The inspiratory reserve is the additional air that can be forcefully inhaled after a normal breath.
• The expiratory reserve is the maximum air that can be exhaled.
• A spirometer measures lung volumes through computer or water displacement.

Capillary Adaptations

• Capillaries facilitate exchange between blood and the surrounding environment.
• Branching increases the surface area between blood and surrounding tissue.
• Capillaries have a narrow lumen diameter and thin walls (flattened cells).
• The basement membrane anchors cells and regulates substance passage between blood and tissues.
• Fenestrations exist which are pores allowing molecules to pass through
• A capillary network creates a large surface area relative to volume for more efficient exchange.
• The narrow lumen forces blood to travel slowly.
• The wall is one cell thick (endothelial cells) for efficient diffusion.
• This ensures more cell membrane is available to touch the surrounding environment and are flat so they can be scrunched.
• Fenestrations allow molecules to pass through.
• Blood plasma can leak out, but cells cannot move through.
• The number or size of fenestrations depends on the location, such as in areas with high metabolic demand, needing plasma and tissue fluids to be exchanged.

Arteries and Veins

• Arteries carry blood away from the heart.
• Veins carry blood towards the heart.
• Arteries handle high-pressured oxygenated blood.
• They have thick walls with elastic fibers and smooth muscle.
• Arteries have a narrow lumen.
• The tunica intima (inner layer) lines the lumen with endothelium to provide a smooth surface and low resistance.
• The tunica media (middle layer) is thickest and has elastic fibers and smooth muscle for structural support and changing vessel diameter to regulate blood flow and pressure.
• The tunica externa (outer layer) connects the vessel to tissue with collagenous and elastic fibers.

Elastic Fibers

• Elastic fibers are specialized bands containing elastin, highly concentrated in arteries near the heart to allow expansion and recoil with each pulse of blood.

Muscle Contraction

• Muscle can contract and relax to adjust blood flow and pressure, responding to hormones and neural signals.
• Vasodilation is the widening of blood vessels, increasing blood flow.
• Vasoconstriction is the narrowing of blood vessels, decreasing blood flow.

Collagen

• Collagen is a fibrous protein with an amino acid sequence arranged in a helical structure, intertwined for support, protection, and elasticity, providing tensile strength.
• Collagen maintains shape and anchors arteries to tissue, providing elasticity.

Veins

• Veins are thin-walled and have a large lumen, carrying blood back to the heart.
• Consisting of the same three layers as arteries but with less smooth muscle and connective tissue.
• No need for elastic fibers to extend/recoil
• Blood flows continuously from capillaries to veins without a pulse.
• Do not adjust flow/pressure, so lack smooth muscle.
• Have irregular shapes due to reduce muscular support.
• Wide lumen allows for a large blood volume.
• Veins have valves to prevent backflow, especially in the extremities (against gravity).
• The skeletal muscle pump aids in circulating blood; when muscles contract, vein walls are squeezed, increasing vein pressure and forcing blood upwards.

Coronary Heart Disease

• Occlusion is a blockage of a blood vessel.
• Reduced or stopped blood flow to tissue causes reduced/stopped function.
• Caused by: atherosclerosis, thrombosis and embolism

Atherosclerosis

• The accumulation of plaque in an artery.
• Plaque is a substance of cholesterol, fat, calcium deposits, cellular debris, and fibrin (clotting protein).

Thrombosis

• A blood clot is made ot Platelets from RBCs, and fibrin
• Formed when a vessel is damaged, activating clotting.

Embolism

• Occurs when a thrombus breaks off, travels, and gets stuck in smaller vessels.
• Coronary arteries branch from the aorta and supply the heart with oxygenated blood.
• Coronary occlusion is the partial or complete obstruction of blood flow in a coronary artery.
• Without oxygen and glucose, heart muscle cells cannot produce ATP and stop contracting in synchrony.
• Heart spasms/stops, leading to myocardial infarction (MI).
• Coronary Heart Disease (CHD) results from reduced blood flow to the heart.
• Symptoms include chest pain, shortness of breath, and fatigue.

Risks Include

• High blood pressure
• High cholesterol
• Smoking
• Obesity
• Poor Diet
• Correlations coefficient (-1, +1)
• 0 = no relation between variables
• -1/1 = perfect predictability
• +1 = variables move in the same direction, if one increases so does the other.
• -1 = correlation is opposite direction, if one increases other decreases
• Visualized on a scatterplot
• tight to a line = strong correlation, provides a statistically significant association of two factors

Lipid Bilayer

• The lipid bilayer is not permeable to large, charged particles, but permeable to small hydrophilic polar molecules (semi-permeable).
• It’s a membrane barrier separating the inside from the outside of cells and organelles.
• Selectively permeable and surrounds cells and organelles.
• Made up of phospholipids.
• Hydrocarbon fatty acid tails are hydrophobic and form the core of the membrane.
• Low permeability to large/hydrophilic particles, ions, and polar molecules.
• Hydrophilic phosphate heads face outwards.
• Cells can accumulate nutrients in higher concentrations.
• Cells accumulate charged ions for electric potential (charge difference) across the cell membrane.

Advantages of Lipid Bilayer

• Enzymes and metabolites can be concentrated in a small space, increasing collision chance between active sites and substrates.
• Damaging substances can be isolated within a membrane.
• Conditions like pH can be maintained.
• Membrane areas can become dense with proteins.
• Focuses on specialized tasks, such as protein receptors or transport proteins (diffusion).
• Net movement of particles from areas of high to low concentrations, a passive process, requires no energy.
• Not selective; if something can diffuse, it will.
• Completely impermeable to non-polar and small hydrophilic molecules like O2, CO2, Na, and steroids, require facilitated diffusion/active transport.
• Permeable (mostly), often repelled; Requires facilitated diffusion/ active transport.
• Small, uncharged molecules such as H2O and glycerol.
• Large, uncharged molecules: glucose, fructose.
• Fully charged ions Na+, K+, Cl-, H+.

Proteins in Membrane

• Integral proteins extend across the bilayer, with hydrophobic amino acids interacting with the tail of phospholipids.
• Peripheral proteins are hydrophilic, anchored on the surface, and interact with integral proteins and phospholipids.

Functional Aspects

• Transport (active/passive)
• Recognition (between proteins)
• Receptors: binding hormones and transmitters (intracellular reaction).
• Enzymatic activity: catalyze reactions.
• Adhesion/Anchorage (peripheral).

Sensory Receptors

• Sensory receptors trigger a stimulus, like sensory neurons, open or close ion channels and send a message from receptor cells to the nervous system (for detection). examples: Temp, touch, sound and baroreceptors.

Water Movement

• Water movement, high to low concentration.
• Osmosis is a type of diffusion that involves the random movement of water molecules.
• Passive process (no energy required).
• Semi-permeable membrane.
• High to low water concentration.
• Depends on the difference in concentrations (less to more concentrated/low water).
• Selectively permeable due to being small and not having a full charge (though polar).
• Cell actively pumps solutes in and out to maintain a gradient.

Channel Proteins

• A type of transport protein that forms a continuous pathway, allowing specific hydrophilic solutes to cross without making contact with the hydrophobic bilayer.
• Creates pores in the membrane bilayer when open
• Facilitated diffusion for specific solutes can occur.
• Passive, no ATP needed.
• Moves with concentration gradient high-low.
• Highly selective and can be "gated" (open/close based on signal response) allowing for a selectively permeable membrane.
• Voltage Gated channel, open/close based on fluctuations in electrical energy potential of the membrane.
• Responsible for functions triggered by electricity (muscle cell contraction, neuro signaling).
• Ligand-Gated channel, only allows passage when a chemical messenger (ligand) is bound.

Protein Pumps

• Protein Pumps highly selective.
• Involved in active Transport with the use of ATP.
• AGAINST the concentration Gradient (Low/high).
• A particle enters, embedded into plasma membrane.
• ATP changes Proteins shape (chemically stable-less stable).
• When changing shape, moves + released to otherside.
• Pump protein coverts back to general shape without the need for additional energy.
• Proton pumps for Photosynthesis/cellular respiration, intestines absorb glucose, etc.

Glycoproteins/lipids

• Form when carbohydrates are linked to either proteins/lipids
• Consists of 3-10 sugar units linked together.
• Found on the extracellular surface of the plasma membrane.

Cell Recognition

• Glycoprotein of one cell can be recognized by receptors on the other.
• Allows for the immune system to identify cells as own vs. foreign such as bacteria.
• Blood cells have their own distinguished glycoprotein on the membrane surface (ABO).
• Wrong blood Transfusion results in severe consequences.

Cell Adhesion

• Can form a layer on membrane outside called glycocalyx = physical barrier.
• Can fuse with adjacent glycocalyx to adhere, tissue does not fall apart.
• In veins: lines wall of endothelial cells preventing direct contact with fluids such as blood.

Fluid Mosaic Model

• Dynamic flexible membrane made up of different components (1970s).
• Fluid: components can move laterally.
• Mosaic: lipids, proteins, carbohydrates that combine to form a mosaic pattern.
• asymmetry one side is different from the other.

Cell Theory

• A) All living things are composed of cells.
• B) Basic unit of life that can be used to makedeductions.
• C) comes from preexisting cells.

Cell Types

• Cells can be either Prokaryotic or Eukaryotic.
• Has some components that remain the same.

Cytoplasm

• Contains cytosol, liquid part of the cytoplasm.
• Gel-like fluid made up of water-dissolved fluids/solutes like salts, fatty acids, sugar, proteins, enzymes, etc.
• Needed to carry out metabolic processes.

Plasma Membrane

• Acts as a barrier (bilayer of phospholipids) separating the interior from the exterior.

DNA

• Stores and transmits genetic information.
• Used to code for specific genetic codes/proteinsynthesis to control cell growth, division and enviornmental response. (ex: hemoglobin is coded in RBCs)
• Prokaryotic: freely in cytoplasm vs. in nudeus tightly packed

Ribosomes

• Catalyzes polypeptide synthesis (chain of amino acids).
• Building proteins by linking amino acids in the correct order based on mRNA instruction.
• Reads 3 bases atatime (A,T,C,G) = codon
• Each codon matches to a certain + RNA carrying the correct amino acid.
• Prokaryotes= smaller (70s)
• Eukaryotes bigger (80s) ribosomes.

Homeostasis

• Homeostasis: Internal environment kept to a certain Range despite external changes.
• Metabolism: Sum of all chemical reactions in a cell.
• Anabolic: small molecules jointo make largerones
• Catabolic: release energy, large molecules are broken down into smaller ones
• Exertion: metabolic waste is eliminated.

Prokaryotic cells

• Bacteria tarchaea (single cell)
• no nucleus + membrane bound organelles.
• has a capsule that keeps cell from dehydrating, adheres to surfaces
• Ribosomes (70s)
• builds proteins from mRNA codons.
• translation is used during replicated
• Pili is used to enables cells to attatch to surfaces, acquirel transport ONA.
• Cell wall wittstand tugorvacuole Parvicles that shapes expands.
• Gel like flud dissolves with solute molecules (site of metabolic reactions). cell wall, withstands more pressure.

Eukaryotic cells

• Plants (boxy), animal, fungi.. Nucleus with : -Nucleolus the nuclealus (production of ribosomes Lo rRNA (ribosomal) is transcribed from DNA-binds with proteins forming Ribosome subunits. double membrane with Pores

Ribosome

-80s, build Proteins, either

• Free enzymes floating in cytoplasm, synthesize proteins
• Bound to the rough ER that synthesizes/builds proteins to be secreted or embedded, and integral proteins in the cellmembrane

Rough Endoplasmic Reticulum

• Flattened membrane socs, synthesizer transport polypeptides
• Once they are synthesized, they are released into ER
• Surrounds Nucleus

Smooth Endoplasmic Rericulum

• Flattened membraneous Sacs.
• Lacks ribosomes, not involved in protein synthesis used is a synthesis of phospholipias + cholesterol,
• Modofies/sorts packages proteins into vesicles and other components.

Lysomes

• Small/ spherical organelles.
• Contain Enzymes which digest the large Molecules, recycle cell components that are old or damaged
• Immune defense for the body as well, digest all pathogens.

Mitochondria

• Glucose + oz carbon dioxide + water.
• Produce ATP by cellular Respiration via double membrane
• Chlaraplasts light+h₂O glucose+02.
• Adapted for Photosynthesis, makes light absorbingpigments and Chlorophyll

Vacuoles

• occupies 30%-90% of cell volume and stores water, waste, and nutrients
• Maintains tugor pressure and keeps plants upright.

Cuterskeleton

• Bath prokaryotic- + eukaryotic maintains shape and organizes enables cell to move tdivide threads that are made of DNA and histone and Protens/
• Microtubules intracellular transport, seperates chromosomes during mitosis.
• Centrioles organize microtubuer during celldivision, anchor point for microrucurest celia and flagella.

More On Cell Type

• Animal cells multicellular, no cell wall
• Fungus cell wall can be a uniceluar ( Yeast) or multi (mushroom), secretes enzymes into environment
• Plant cell, multicellular and does autorophs

Comparrisions

• Plastid located in a doulbe membrane which makes its own food
• Cell wall protects, against mechanical and osmotic stress
• Located vacuoles store and remove waste products and other chemicals
• No centriles structure seperates structures/pirileapparato but only in mass/terms, not in condir or flowers

Cell Comparison

• Prokaryotics can be smaller (bacteria), no nucleus/membrane bound organelles , but DNA is single.
• Eukaryotes complex, multiple, linear DNA, etc.
• compartimentilisation Both have Double membranes 6) Mitochondria -7Nucleus Organelles,adapted to prefe(M and have both cells types (a) cell Wall Enzyes and cytoplasm

Fertilization

• multi-step process in which a spermand cell fuse and cells divide resulting in:
• cells speciation for increased efficiency, can developped into specific shape and increase sizes.
• differentition of development
• Postitioning, allows embryo/ direct cell fata concentration
• • Controls differentiation to orchestrale tissue, organ formation