Digestion Basics
What is Digestion?
The process of breaking food into smaller molecules that the body can use.
Why must starch be broken down before cells can use it?
Starch is too large to pass through the cell membrane
What must happen before starch can enter a cell?
It must be broken down into simple sugar through digestion.
What is diffusion?
The movement of molecules from an area of high concentration to low concentration.
What tiny blood vessels allow nutrients to move into the blood from the small intestines?
Capillaries
What type of digestion happens when you chew food?
Mechanical Digestion
Explain how molecule size affects whether nutrients enter a cell. Use correct terminology.
Only small molecules can cross the cell membrane, so large molecules must be completely digested first.
What is the function of the cell membrane?
It controls what enters and leaves the cell.
Why does diffusion help cells get nutrients?
It allows nutrients to move into cells where they are needed.
A student claims that the circulatory system alone is enough to provide cells with nutrients. Do you agree or disagree? Explain.
Disagree. The digestive system is needed to break food into nutrients before the circulatory system can transport them.
What type of digestion uses enzymes to break food down?
Chemical Digestion
Two nutrients are present in the small intestine: one is a small molecule and one is a large molecule. Predict which one will enter the blood first and explain your reasoning.
The small molecule will enter the blood first because large molecules must be digested into smaller molecules before they can be absorbed.
Explain why a cell membrane is necessary even after digestion has already broken food into small molecules.
The membrane controls what enters and leaves the cell, protecting it and maintaining balance even when molecules are small enough to enter.
After exercise, muscle cells need more glucose. Predict how diffusion helps meet this need.
Glucose will move from the blood (higher concentration) into muscle cells (lower concentration) through diffusion.
Explain how digestion, diffusion, and the circulatory system work together to maintain cell energy.
Digestion breaks food into small molecules, the circulatory system transports them, and diffusion moves them into cells for energy use.
Why is digestion important for cells?
Because cells can only absorb small molecules, not large food particles.
If digestion stopped halfway through the digestive system, how would molecules size affect nutrient absorption?
Molecules would remain too large, so they would not pass through membranes or enter the blood, limiting nutrients reaching cells.
The cell membrane is a _______________, meaning there are _____ layers of the cell membrane that molecules must be able to pass through.
Bilayer - 2
Predict what would happen to diffusion if glucose concentration was the same inside and outside a cell.
There would be no movement of glucose because diffusion requires a concentration difference.
What would happen if the small intestine stopped absorbing nutrients but digestion still occurred?
Nutrients would not enter the blood, so cells would not receive energy despite digestion happening.
What would happen if enzymes did not work during digestion?
Food would not be broken into small molecules, so nutrients could not enter cells.
A student eats a meal high in starch but low in simple sugars. Predict what must happen to the starch before cells can use it and explain why.
The starch must be broken down through digestion into smaller molecules like glucosee because large molecules cannot pass through the cell membrane.
If a molecule is small but not needed by the cell, predict what the membrane might do.
The membrane may prevent it from entering to protect the cell and maintain proper homeostasis
Explain why diffusion does not require energy and why that is helpful for cells.
Diffusion occurs naturally due to concentration differences, saving energy from other cell processes.
Why must the digestive and circulatory systems work together for cells to get energy?
The digestive system breaks food into small nutrients, and the circulatory system transports and absorbs those nutrients in to the cell.