Understanding Diffusion

Diffusion

• It is the net movement of particles from an area of high concentration to low concentration
• It occurs down a concentration gradient as a result of random movement
• The energy source is the kinetic energy of molecules or ions in random motion
• Some substances move in and out of cells by diffusion via the cell membrane
• Examples of substances include oxygen, carbon dioxide, and glucose
• Diffusion is critical in living organisms
• Gas exchange happens, with oxygen moving in and carbon dioxide moving out
• Nutrient absorption happens, with digested food diffusing into the bloodstream
• Waste removal happens, with urea diffusing into the blood for excretion

Factors Affecting Diffusion

• Surface Area: Larger surface area means faster diffusion, such as alveoli in the lungs
• Temperature: Higher temperature means faster diffusion because molecules move faster
• Concentration Gradient: Steeper gradient means faster diffusion
• Distance: Shorter distance means faster diffusion, such as in thin capillary walls

Osmosis

• It's the net movement of water molecules from high to low water potential
• This happens from a dilute solution to a concentrated solution
• It occurs through a partially permeable membrane

Key points of Osmosis

• Water dissolves substances during digestion
• Examples include enzymes breaking food down, excretion, and transport in blood plasma
• Water moves into and out of cells through the cell membrane
• In turgid cells, water enters, cells swell, and turgor pressure increases, supporting the plant
• In flaccid cells, water exits, cells shrink, and the plant wilts
• Plasmolysis is when extreme water loss causes the cell membrane to pull away from the cell wall

Importance of Osmosis

• Helps keep cell structure in plants
• It regulates water balance in organisms

Active Transport

• This is the movement of particles from low to high concentration
• It occurs against a concentration gradient
• It requires energy from respiration

Key points

• Active transport requires energy unlike diffusion and osmosis
• It uses protein carriers in the cell membrane to transport molecules or ions
• Ion uptake in plant roots involves root hair cells absorbing minerals like nitrate ions from soil
• Absorption in the intestines actively transports glucose into the blood after digestion

Chemical Elements in Biological Molecules

• Carbohydrates contain Carbon, Hydrogen, and Oxygen
• Lipids contain Carbon, Hydrogen, and Oxygen
• Proteins contain Carbon, Hydrogen, Oxygen, Nitrogen, and sometimes Sulfur

Large Molecules and Their Building Blocks

• Carbohydrates such as starch, glycogen, and cellulose are made from glucose molecules
• Proteins are made from amino acids
• Fats and oils are made from fatty acids and glycerol

Food Tests

• Iodine Test for Starch: Add iodine solution to the sample; a blue-black color indicates a positive result
• Benedict's Test for Reducing Sugars: Add Benedict's solution, heat in a water bath; a brick-red precipitate indicates a positive result
• Biuret Test for Proteins: Add Biuret reagent to the sample; a purple color indicates a positive result
• Ethanol Emulsion Test for Fats and Oils: Mix sample with ethanol, then add water; a white emulsion indicates a positive result
• DCPIP Test for Vitamin C: Add DCPIP solution drop by drop to the sample; decolorization of DCPIP indicates a positive result

Structure of DNA

• DNA has a double helix structure, where two strands coil together
• Each strand contains the bases Adenine, Thymine, Cytosine, and Guanine
• Base pairing: A pairs with T, and C pairs with G
• The bases are held together by bonds

Definition of a Catalyst and an Enzyme

• Catalyst: A substance that speeds up the rate of a chemical reaction without being changed
• Enzymes: Proteins that are biological catalysts involved in all metabolic reactions

Importance of Enzymes in Living Organisms

• Enzymes accelerate reactions that sustain life
• Without enzymes, reactions would be too slow for survival

Enzyme Action

• Enzymes have an active site with a specific shape
• The substrate fits into the enzyme's active site like a lock and key
• The enzyme-substrate complex forms, and products are released

Enzyme Specificity and Action

• The enzyme's active site is complementary to its substrate
• Only specific substrates fit the active site, ensuring enzyme specificity

Effects of Temperature and pH on Enzyme Activity

• Optimum temperature is when enzymes work best
• Denaturation: Enzymes lose their shape and stop functioning at high temperatures
• pH Changes: Enzymes function best at a specific pH; extreme pH levels can denature them

Effect of Temperature on Enzyme Activity

• Increased temperature increases kinetic energy and collisions
• Excessively high temperatures can cause the enzyme to denature, losing its shape

Effect of pH on Enzyme Activity

• Variations in pH alter the enzymes
• Extreme pH values lead to denaturation, halting enzyme function

Effect of Substrate Concentration on Enzyme Activity

• The reaction rapidly increases and becomes constant because the enzymes are occupied
• Increasing the substrate concentration has no effect on the reaction