Digestion and Homeostasis Flashcards
what is exchange?
animals exchange materials with the environment through digestion, respiration, circulation, and excretion
when does exchange occur?
as substances (molecules) dissolved in an aqueous solution move across plasma membrane of a cell
how does amoeba exchange?
entire surface area in contact with environment so exchange is easy
how do simple animals exchange?
can have efficient direct exchange with environment if they have:
- thin, flat shape
- very few cell layers
- live in moist environment
how can complex animals exchange?
have specialized exchange surfaces
- composed of living cells
- thin (layer of epithelial tissue: composed of specialized cells that line our internal and external body surfaces)
- large surface area through folds and branches
- moist (interstitial fluid surrounds cells)
- external or internal
- connected to circulatory system (blood vessels)
why do we eat?
- food supplies building blocks for biological molecules
- essential nutrients
- chemical energy (electrons) to make ATP
what are the 4 stages of food processing?
ingestion
digestion
absorption
elimination
how do filter feeders eat?
pass water through specialized filtering organs and strain suspended particles and digestible matter from water (ex: whale)
how do fluid feeders eat?
obtain nutrients from fluids of other organisms (ex: mosquito)
how do substrate feeders eat?
live on or in food surface (ex: beetles)
how do bulk feeders eat?
obtain nutrients from large pieces of food
what is chemical digestion?
chemical breakdown by hydrolytic enzymes
polysaccharides -> monosaccharides, polypeptides -> amino acids, triglycerides -> glycerol + fatty acids, nucleic acids -> nucleotides
what is mechanical digestion?
physical breakdown of food molecules (chewing) creates more SA for chemical digestion in stomach
what is intracellular digestion?
food vacuoles
food particle engulphed by cell and food vacuole fuses with lysosome and digestion occurs inside cell (ex: in sponges)
what is extracellular digestion?
in most animals
digestion of food in compartments
- one type: gastrovascular cavity: compartment with one opening, food comes in and waste exists. cells secrete hydrolytic enzymes and engulph food particles and complete digestion intracellularly
- another type: alimentary canal: digestive tube with 2 openings in more complex animals, one way
how does food move through our body
mouth -> esophagus -> stomach -> small intestine -> large intestine -> rectume -> waste out anus
bunny eat food
a) mechanical digestion
b) chemical digestion (enzymatic hydrolysis)
c) nutrient molecules enter body
d) undigested material out anus tehe
Identify adaptive variation in vertebrate tooth shape
Incisors:
Shape: Flat, sharp-edged teeth.
Function: Used for cutting and shearing food.
Adaptation: Found in herbivores (e.g., rodents) for cutting plant material and in carnivores (e.g., carnivorous mammals) for biting into flesh.
Canines:
Shape: Pointed, conical teeth.
Function: Used for tearing food, especially in carnivores.
Adaptation: Prominent in carnivores like dogs and cats for hunting and killing prey. Herbivores may have smaller or absent canines.
Premolars and Molars:
Shape: Flat, broad surfaces with ridges.
Function: Used for grinding and crushing food.
Adaptation:
Herbivores (e.g., cows, horses) have large, flat molars for grinding plant material.
Carnivores (e.g., lions) have sharp-edged molars for cutting meat.
Omnivores (e.g., humans) have a mix of sharp and flat teeth for both cutting and grinding.
Carnivore Teeth:
Adaptation: Specialized for shearing and tearing. Sharp incisors and large, pointed canines are prominent. Premolars and molars have a cutting function.
Herbivore Teeth:
Adaptation: Flattened molars and premolars for grinding plant material. They may also have sharp incisors for cutting plants but lack sharp canines.
Omnivore Teeth:
Adaptation: A combination of sharp and flat teeth (incisors, canines, and molars) to handle both plant and animal matter.
Explain why the cells that secrete the components of gastric juice are able to survive
Mucous Layer:
Mucous cells secrete a thick, alkaline mucus that coats the stomach lining. This mucus acts as a barrier, protecting the stomach lining from the corrosive effects of the gastric acid and enzymes.
Bicarbonate Secretion:
The epithelial cells of the stomach lining secrete bicarbonate ions (HCO₃⁻) into the mucus, which helps neutralize the acidity near the stomach lining, maintaining a pH close to neutral on the surface of the stomach.
Tight Junctions:
The epithelial cells of the stomach lining are tightly bound together by tight junctions, which prevent gastric juice from leaking between cells and damaging the underlying tissues.
Regeneration:
The stomach lining has a high rate of cell turnover, with epithelial cells being replaced every 3 to 5 days. This rapid regeneration ensures that any damaged or dead cells are quickly replaced, preventing long-term damage to the stomach lining.
Prostaglandins:
Prostaglandins play a role in maintaining the protective mechanisms of the stomach lining, including increasing mucus and bicarbonate secretion and promoting blood flow to the stomach lining.
Explain why the stomach does not digest itself
mucus layer, rapid cell turnover, inactive enzymes (The digestive enzymes in the stomach, such as pepsin, are secreted in an inactive form known as pepsinogen. They only become active when they encounter the acidic environment of the stomach. This prevents them from digesting the stomach lining before they are activated.)
Explain what digestive processes take place in the small intestine
In the small intestine, the main digestive processes are:
Chemical digestion:
Pancreatic enzymes break down carbs, fats, and proteins.
Bile from the liver emulsifies fats.
Brush border enzymes break down sugars.
Mechanical digestion:
Peristalsis moves food.
Segmentation mixes food with digestive enzymes.
Absorption:
Nutrients like sugars, amino acids, and fats are absorbed through the villi into the bloodstream or lymph.
Structure of the Small Intestine & Importance in Absorption
The small intestine has villi and microvilli that increase surface area for nutrient absorption. The epithelial cells of the villi absorb nutrients into the bloodstream or lymphatic system.
Absorption of Fats vs Other Food Molecules
Fats are absorbed through the lymphatic system as chylomicrons after being emulsified by bile and broken down by lipase.
Carbs and proteins are absorbed into the bloodstream through the villi after being broken down by enzymes like amylase and proteases.
Role of the Large Intestine
The large intestine absorbs water, salts, and some vitamins, and forms feces for elimination. It also houses bacteria that help digest remaining food and produce vitamins like K
Importance of Tight Junctions
Tight junctions between epithelial cells in the digestive tract prevent leakage of digestive enzymes and harmful substances. When compromised, it can lead to conditions like leaky gut, where harmful particles leak into the bloodstream.
Digestive System of Plant-Eaters vs Meat-Eaters:
Plant-eaters (herbivores) have longer intestines with larger cecum for digesting cellulose.
Meat-eaters (carnivores) have shorter intestines, as animal proteins are easier to digest.
Digestive Adaptations of Pythons:
Pythons have specialized digestive enzymes to break down large prey and can expand their stomachs to accommodate large meals. They also have a slower metabolism and an energy-efficient digestive system.
Chemical Digestion of Macromolecules
Carbs: Broken down by amylase (mouth, pancreas).
Proteins: Broken down by pepsin (stomach) and trypsin (pancreas).
Fats: Broken down by lipase (pancreas).
Enzymes are produced in the mouth, pancreas, and stomach.
Insulin and Glucagon in Blood Sugar Regulation:
Insulin lowers blood sugar by facilitating glucose uptake into cells.
Glucagon raises blood sugar by stimulating the liver to release stored glucose.
Leptin’s Role in Appetite Suppression:
Leptin is produced by fat cells and signals the brain to reduce appetite when fat stores are sufficient. Lack of leptin (as in obesity) can cause increased appetite, while higher leptin levels correlate with smaller fat cells.
