Diffusion(B3)
Why do small molecules diffuse faster than large molecules?
Smaller molecules move faster because they have less mass and experience less resistance.
What is osmosis?
Osmosis is the movement of water molecules from a region of higher concentration to a region of lower concentration, through a partially permeable membrane.
What is active transport?
Active transport is the movement of molecules or ions from a lower concentration to a higher concentration using energy from ATP.
What is the main function of carbohydrates in the human body?
Carbohydrates provide a quick source of energy for the body.
What are the basic building blocks of proteins?
Amino acids are the building blocks of proteins.
How is diffusion different from osmosis?
Diffusion involves the movement of all molecules, while osmosis specifically involves the movement of water molecules across a membrane.
Why do plant cells not burst when placed in pure water, unlike animal cells?
The rigid cell wall prevents excessive expansion, providing structural support and stopping the cell from bursting under high turgor pressure.
How does active transport differ from diffusion?
Active transport moves substances against the concentration gradient (low to high) and requires energy, while diffusion moves substances down the concentration gradient (high to low) without energy.
What is the role of glycogen in humans, and where is it primarily stored?
Glycogen is a polysaccharide that stores glucose in the liver and muscles for quick energy use.
What is the difference between a peptide bond and a polypeptide chain?
A peptide bond links two amino acids together, forming a dipeptide, while a polypeptide chain is a long chain of amino acids linked by peptide bonds.
Why is diffusion a passive process?
Diffusion is passive because it does not require energy (ATP); molecules move due to their own kinetic energy.
A potato strip is placed in a solution and its mass decreases. What can you conclude about the solution’s water concentration?
The solution has a lower water concentration than the potato cells, so water leaves the cells by osmosis, causing the mass to decrease.
Why do cells that carry out active transport contain many mitochondria?
Mitochondria provide ATP, which is required for active transport to move substances against their concentration gradient.
What is the difference between a monosaccharide and a disaccharide? Give examples of each.
Monosaccharides are simple sugars like glucose, while disaccharides are made of two monosaccharides joined together, such as sucrose (glucose + fructose).
Explain the role of enzymes in metabolic reactions and how they are affected by temperature and pH.
Enzymes speed up metabolic reactions by lowering activation energy.
Temperature and pH can alter their shape, affecting their ability to bind to substrates, leading to denaturation if conditions are extreme.
What substances can diffuse through the cell membrane?
Oxygen, carbon dioxide, and small lipid-soluble molecules can pass freely through the cell membrane.
A plant cell is placed in a solution with lower water potential than its cytoplasm. Describe and explain what happens.
The cell loses water by osmosis, causing the vacuole to shrink and the cytoplasm to pull away from the cell wall (plasmolysis), as water moves out to balance the concentration gradient.
Why do root hair cells use active transport?
Root hair cells use active transport to absorb mineral ions from the soil, as the concentration of minerals in the soil is lower than in the root cells
Explain the difference between saturated and unsaturated fats. How do they affect human health?
Saturated fats have no double bonds between carbon atoms, while unsaturated fats have one or more double bonds. Unsaturated fats are generally healthier, while saturated fats can increase the risk of cardiovascular diseases.
What is the role of enzymes in digestion, and give an example of an enzyme involved in breaking down a specific nutrient.
Enzymes like amylase break down carbohydrates into simpler sugars,
protease breaks down proteins into amino acids, facilitating digestion.
Why is diffusion alone not enough to transport substances in large organisms?
Diffusion is too slow for large organisms, so transport systems (e.g., blood circulation) are needed for efficient distribution.
How does osmosis help plants absorb water from the soil?
The soil usually has a higher water potential than root hair cells, so water enters by osmosis through their partially permeable membranes.
Why is active transport important in the small intestine?
Active transport allows glucose and amino acids to be absorbed into the blood from the intestine, even when their concentration in the small intestine is lower than in the blood, ensuring the body gets enough nutrients.
Explain how the body uses carbohydrates during exercise and how glycogen plays a role in providing energy.
During exercise, the body uses glycogen stored in muscles and the liver. Glycogen is broken down into glucose, which is then used in cellular respiration to produce ATP, providing the energy needed for muscle contractions. When glycogen stores run low, the body switches to using fat as an energy source.
Explain the concept of enzyme activation energy and how enzymes lower it to speed up biochemical reactions.
Enzymes lower the activation energy required for a biochemical reaction to occur by providing an alternative reaction pathway. They achieve this by binding to the substrate and stabilizing the transition state, which reduces the energy needed for the reaction to proceed. This allows reactions to occur more quickly and at lower temperatures than they would without the enzyme.