Biology exam review - DIGESTIVE SYSTEM

Why do we need digestion?

it breaks down food into essential nutrients (like proteins, fats, carbs, vitamins, minerals) that your body absorbs for energy, growth, and cell repair, while also eliminating waste

What are the two main ways that cells use the nutrients they absorb?

Cells use the nutrients they absorb for synthesizing chemical compounds, and as sources of energy, just like how glucose is needed to make ATP.

What are the 2 types of digestion?

Chemical and mechanical

Distinguish between chemical and mechanical digestion

• Chemical digestion is when chemical reactions occur to break down the food. Some reactions use enzymes to break down the chyme, and the stomach acid uses chemicals to break down the food

• Occurs in the stomach, in the duodenum

• Mechanical digestion is the physical breaking down of food, like chewing your food into smaller pieces.

• Occurs in the mouth, in the stomach

What is an enzyme?   Would they be a part of chemical or mechanical digestion? 

An enzyme is a protein catalyst that regulates reactions that occur in living organisms. Enzymes would be a part of chemical digestion because they interact with the chemical compounds in the substrate to break it down to the molecular level.

What does it mean that enzymes are target specific?

Enzymes being a “target specific” means that it can only act on one substrate. A substrate is the molecule that the enzyme works on. For example, Maltase breaks down maltose, and sucrase breaks down sucrose.

Can you think of any pros and cons of having target specific enzymes?

• Pros: specific enzymes can work better and more optimal since they focus on building down a certain molecule rather than more. It allows them to quickly break down molecules and efficiently. Efficient breakdown = better absorption of materials.

• Cons: If a person lacks a certain enzyme, the substrate wouldn’t be able to be digested properly. If the body doesn’t produce enough enzymes, it can impair the digestion of the substrate and affect how many key nutrients are absorbed.

Describe the stages of digestion

• Ingestion is when you eat the food. You put it in your mouth and chew it, and then swallow it. It is to get food into our digestive system

• Digestion is when the food you ingest makes its way down the esophagus and into the stomach. The pieces of food form a bolus in the esophagus. The bolus goes into the stomach and get broken down into chyme by the stomach acid to get it smaller.

• Absorption is when Nutrients from food and materials pass through a membrane and go into the bloodstream.

• Elimination: Getting food out of our digestive system. The chyme that forms turns into fecal matter after all the nutrients get absorbed

What is peristalsis and why is it vital for functioning of the digestive system?

Peristalsis is a wave-like muscle contraction that helps push substances (food, bile) down organs such as the esophagus and intestines, and to churn food in the stomach. It is vital for functioning of the digestive system because it is what moves the food through each stage of the digestive process. Even if the body is upside down, peristalsis will make sure that the food makes its way through the digestive tract.

What happens to food while it is still in your mouth?

When food is still in your mouth, mechanical digestion starts. The salivary glands produce saliva to chemically digest the food. The mouth secretes water, mucus, and a starch digesting enzyme called amylase. The epiglottis closes the trachea and opens the pharynx, leading to food to the esophagus. The esophagus transports food to the stomach through peristalsis, and the lower esophageal sphincter closes to prevent food from coming up.

How is the stomach involved in both mechanical and chemical digestion?

Mechanical Digestion	The stomach churns the food to physically break it down into smaller pieces. This allows there to be more surface area to cover, breaking down the bolus into chyme easier.
Chemical Digestion (general)	The initial protein digestion starts here. The stomach produces stomach acid which breaks down the food even more so the nutrients can be closer to being broken down to a molecular level.
Chemical Digestion (specific)	The gastric juices the stomach contains are hydrochloric acid, which breaks down fiber, and enzymes and pepsin, which further break down proteins

Why is the liver considered a “processing plant”? 

Tiny processing plants in the liver called lobules filter the blood that comes from the hepatic artery and the hepatic portal vein. This fills the liver with nutrients such as carbs, fats, and vitamins that it sorts, processes, and stores. The blood also delivers the oxygen needed for the liver to function. The liver breaks down these nutrients into energy and sends the filtered blood back out.

Why is the liver considered a “storehouse”?

When the body has leftover nutrients that it doesn’t immediately need, the liver stores them until the body needs those nutrients in the future.

Why is the liver considered a “manufacturing hub”?

Sometimes our blood contains products that are toxic and useless, so the liver either converts it to a product that can’t hurt the body, or isolates it and sends it to the kidneys and intestine to be excreted. The liver also makes stuff such as various blood plasma proteins that transport fatty acids and help form blood clots, cholesterol that helps the body create hormones, vitamin D and substances that help with digestion, and bile.

What is bile?

The liver uses hepatocytes to convert toxic waste products into a bitter greenish liquid called bile. This liquid is funneled into a small container below the liver called the gall bladder, before being put into the intestine to help break down fats, destroy microbes, and neutralize extra stomach acid. It also helps carry extra toxins from the liver out of the body

How do the presence of multiple enzymes, length and twisting shape, and amount of villi of the small intestine lead to more absorption of nutrients?

Feature of Small Intestine	How it increases absorption
Presence of multiple enzymes	The multiple enzymes break down complex food molecules in the chyme into their smallest and most absorbable units. This allows almost all of the nutrients in the chyme to be absorbed into the body since they’re all small enough to be absorbed
Length and twisting shape	The length of the small intestine and the twisting shape lets the chyme stay in the intestine for longer, allowing for more time to fully absorb all the nutrients in the chyme.
Amount of villi	The large amount of villi on the walls of the small intestine increase the surface area of the intestine’s internal area, which allows for more contact with the chyme to better absorb and efficiently absorb the most nutrients possible.

Why are the terms ingestion, absorption, digestion, and egestion important when learning about the digestion system?

they define the four fundamental stages of transforming food into energy

Function of the teeth:

• Part of mechanical digestion and ingestion

• Invisors - bite food to get it into our mouth (fromt 4 teeth)

• Molars - grind food down

• Bicuspids - Canines, tear meat.

Function of the toungue

• Part of ingestion and moves food towards teeth, aiding in mechanical digestion

• Moves food into esophagus

• Helps us eat the right food

Function of salivary glands

• Part of ingestion and chemical digestion

Produces saliva which:

• makes food softer and slippery

• Makes food easy to swallow and start digestion

• Salivary amylase breaks down amylose (carb)

Function of uvula

• Ingestion

• Hanging ball at the back of your throat that stops food from going up your nose

Function of Epiglottis

• Ingestion

• A flap of skin that closes the trachea so that food doesn’t go in your lungs

Function of esophagus

• Ingestion

• Performs peristalsis

• Connects the oral cavity to stomach

• Doesn’t have a very good mucus lining which can lead to heart burn

Function of cardiac sphincter

• Ingestion because it opens to let the bolus into the stomach

• Digestion because it stays closed so the stomach acid doesn’t go back up

• A ring of muscle that squeezes and closes and relaxes and opens. It connects the esophagus to the stomach

Function of the stomach

1. Mechanical Digestion: has 3 layers of muscle to churn the food

2. Chemical digestion: produces hydrochloric acid and releases an enzyme called pepsin

3. Produces mucus for protecting itself and the lining from stomach acid.

Function of pyloric sphincter

• Digestion - Controls the release of chyme from the stomach into the duodenum and makes sure the chyme is only releaseed when it is properly digested from the stomach. It stays closed so that the chyme can stay in the stomach longer

• Absorption - regulates the rate of how fast chyme enters the duodenum, preventing the small intestine from being overwhelmed.

Function of the liver

• Digestion: Produces bile and sends it through the duodenum. The bile goes down the hepatic duct to the common bile duct into the duodenum

Function of gallbladder

• Digestion: stores extra bile in case needed. Sends bile through the cystic duct to the common bile duct into the duodenum

Function of pancreas

• Digestion: Produces enzymes like trypsin and pancreatic amylase along with pancreatic juices that release bicarbonate for protecting the duodenum from stomach acid by neutralizing it

• Sends it through pancreatic duct to the common bile duct and then to the duodenum

Function of small intestine

• Digestion: Completes the digestion or carbs, fats, and proteins. Bile from the liver and gallbladder and enzymes from the pancreas go into the duodenum and mix with the chyme to break it down to a molecular level. The long and twisty structure also let the food sit in the small intestine longer, allowing it to have enough time to break down

• Absorption: structures called villi in the small intestine line the surface to increase absorption surface area

Parts of the small intestine

• Duodenum: first part of the small intestine, enzymes and bile from the common bile duct enters it and neutralizes stomach acid and further digests it to its best ability

• Jejunum: the middle section, food is still digesting, and the jejunum absorbs the most nutrients from the food with villi

• Ileum: final section, absorbs essential nutrients and the rest of the fats, proteins, and carbs. It passes undigested material to the large intestine.

Why is the small intestine so good at its job?

It’s really long and twisty which keeps food in our body longer for better absorption, and also so the chyme can be digested to its smallest form

Function of the Ileocecal sphincter

• Digestion: stays closed so chyme can stay in small intestine for longer

• Absorption: stays closed which allows more time for nutrient absorption

• Egestion: Allows undigested matter to enter the large intestine

In between small intestine and large intestine

Function of large intestine

• Absorption: Reabsorbs water

• Egestion: The cecum (first part) Forms the shape of fecal matter

Has a really good environment to house good bacteria that can make vitamin b and vitamin k for us. The good bacteria also takes up space so no bad bacteria can grow.

Function of Anal sphincter

• Egestion: releases fecal matter

Describe how proteins get digested

• In the stomach: The polypeptides get broken down by the pepsin in the stomach to produce peptides.

• The peptides get broken down in the duodenum by trypsin from the pancreas to produce dipeptides

• The Dipeptides get broken down into amino acids in the small intestine by Erepsin from the walls of the small intestine

Describe how fats/lipids get digested

• In the stomach they are triglycerides.

• In the duodenum, bile from the liver breaks them down. Lipase from the pancreas then breaks the triglycerides into Glycerol + fatty acids in the small intestine

Describe how carbs like starch get digested

• In the mouth: Salivary amylase from the salivary glands break down starch to Amylose.

• In the duodenum: Pancreatic Amylase from the pancreas breaks down amylose to maltose

• In the small intestine: Maltase from the lining of the small intestine breaks down maltose into 2 glucose molecules

Describe how carbs like milk get digested

• In the duodenum: Pancreatic amylase breaks down milk into lactose

• In the small intestine: lactase from the small intestine breaks down lactose into 1 glucose and 1 galactose molecule

Describe how carbs like apples get digested

• In the duodenum: Pancreatic amylase from the pancreas breaks down the apple into sucrose

• In the small intestine: Sucrase from the small intestine breaks down sucrose into glucose and fructose

What stages do all carbs go through when being digested?

1. They are polysaccharides

2. They become disaccharides

3. They become monosaccharides

What are 2 examples of digestive disorders?

• Acid reflux: stomach acid flows back into the esophagus causing heartburn

• Ulcers: When the stomach acid erodes the stomach lining causing pain and indigestion

Why does our body need carbs?

They are the body's primary and preferred source of quick energy, broken down into glucose to fuel the brain, muscles, and cells.

Why does our body need protein

Proteins are used for repair in cells because they are the building blocks that build up the cells. The code for the proteins that build up everything in the cell is stored in the DNA. Whenever the cell undergoes damage, the proteins get used to fix whatever is wrong structurally.

They also provide amino acids

Why does our body need vitamins

Vitamins are needed for cells to stay healthy and to protect against damage. Vitamins maintain the immune system by supporting it and providing nutrients to keep the cells healthy.