Unit 1, Topic 2 Exchange of nutrients and wastes Flashcards
Biochemistry, enzymes, exchange surfaces, excretory system
What are carbohydrates?
Carbohydrates are organic compounds composed of carbon, hydrogen, and oxygen, typically with a ratio of hydrogen to oxygen similar to water (2:1). They serve as a primary source of energy for the body. Structurally, carbohydrates can be classified into three main categories: monosaccharides, disaccharides and polysaccharides.
Provide examples of carbohydrates.
Monosaccharides, such as glucose and fructose, are the simplest form of carbohydrates and are the fundamental building blocks for more complex carbohydrates.
Disaccharides include sucrose and lactose. Sucrose is formed from glucose and fructose, while lactose is composed of glucose and galactose.
Starch is a polysaccharide primarily found in plants and serves as their main energy storage form.
What are proteins and how are they formed?
Proteins are complex macromolecules composed of long chains of amino acids, which contain carbon, hydrogen, oxygen and nitrogen. The formation of proteins begins with amino acids linking together via peptide bonds that form between the carboxyl group of one amino acid and the amino group of another. This bond is established through a condensation reaction, where a molecule of water is released as the bond is formed.
What are lipids?
Lipids are a diverse group of hydrophobic organic compounds that are composed primarily of carbon, hydrogen and oxygen, although they have a lower proportion of oxygen compared to carbohydrates.
Name and describe the types of lipids?
Triglycerides: Triglycerides are the main type of lipid used for energy storage, consisting of a glycerol molecule bonded to three fatty acid chains via ester bonds. These hydrophobic molecules store energy compactly and can be saturated (solid at room temperature, like animal fats) or unsaturated (liquid at room temperature, like vegetable oils).
Phospholipids: Phospholipids, key components of cell membranes, consist of a glycerol molecule linked to two fatty acids and a phosphate group. They have both hydrophilic heads and hydrophobic tails, forming bilayers that create semi-permeable membranes, allowing cell regulation and flexibility.
Steroids: Steroids, such as cholesterol, testosterone, and estrogen, are lipids with four fused carbon rings that function as hormones, regulating reproduction, metabolism, and immune responses.
What are enzymes?
Enzymes are proteins that act as biological catalysts, speeding up chemical reactions in cells without being consumed. They are essential for processes like digestion, metabolism, DNA replication, and energy production, allowing reactions to occur quickly under mild conditions of temperature and PH.
How do enzymes increase the rate of chemical reactions in cells?
The primary function of enzymes is to lower the activation energy required for a reaction to occur, thereby increasing the reaction rate. This is achieved through the active site, a specific region of the enzyme with a unique shape and chemical environment perfectly suited to bind to the enzyme’s substrate (the reactant molecule).
List factors impacting enzyme action and how?
Enzyme activity is influenced by several environmental and chemical factors, including temperature, pH, the presence of inhibitors and substrate concentration.
Temperature: Enzyme activity increases with temperature due to higher kinetic energy, up to the enzyme’s optimum temperature (~37°C for human enzymes). Above this, enzymes denature, losing function. Below this, reactions slow as molecules collide less frequently.
pH: Enzymes have an optimal pH; deviations disrupt bonds and enzyme shape, reducing function. Extreme pH changes can cause denaturation. Slight changes affect substrate binding.
Inhibitors:
Non-Competitive: Bind elsewhere on the enzyme, altering shape and reducing activity, not reversible by adding more substrate.
Competitive: Resemble the substrate and block the active site, decreasing reaction rate; reversible by increasing substrate concentration.
Substrate Concentration:
Low: Enzyme activity rises as substrate levels increase due to more active site availability.
High: At saturation, all active sites are occupied, and the reaction rate plateaus (Vmax).
Why and how is enzyme activity regulated?
Enzyme activity is regulated to maintain proper metabolic rates and homeostasis, adapting to conditions like diet, exercise, and stress.
Mechanisms include:
Activation and Inhibition: Enzymes can be activated (e.g., zymogens activated in the digestive tract) or inhibited (competitive/non-competitive inhibitors) to control pathways.
Feedback Inhibition: End products of pathways inhibit earlier steps, preventing overproduction.
Allosteric Regulation: Molecules binding at allosteric sites can enhance or inhibit enzyme activity based on cellular needs.
Environmental Control: Enzymes are regulated by optimal pH and temperature specific to their function and location.
Cofactors and Coenzymes: These assist enzyme activity and provide additional regulation through their availability.
Gene Regulation: Enzyme production is controlled genetically, with expression adjusted in response to body needs.
What are the role of enzymes in digestion?
During digestion, enzymes like amylase, protease and lipase catalyse the breakdown of complex food molecules into simpler, absorbable forms.
How do structural features of the digestive and circulatory systems facilitate efficient nutrient exchange in mammals?
The small intestine in the digestive system has villi and microvilli that increase surface area for nutrient absorption. A thin epithelial layer allows for a short diffusion distance, and a dense network of capillaries ensures rapid transport of absorbed nutrients into the bloodstream. This structure maximizes contact with digested food and enhances nutrient uptake efficiency.
What role do capillaries play in nutrient exchange within the circulatory system?
Capillaries, the smallest blood vessels, have thin walls of a single endothelial cell layer that allow rapid diffusion of nutrients, gases, and wastes between blood and tissues. Their extensive branching creates a large surface area for efficient exchange, ensuring oxygen and nutrients reach cells while removing carbon dioxide and wastes, supporting cellular function and homeostasis.
What role does the excretory system play in maintaining homeostasis?
It removes waste products and excess substances from the body, ensuring the proper balance of water, salts, and other solutes.
What are the primary organs of the excretory system?
The kidneys.
What are nephrons, and what is their function?
Nephrons are tiny structures within the kidneys that filter blood and produce urine through processes like glomerular filtration, selective reabsorption, and secretion.
