Tuguegarao Archdiocesan Schools System
LYCEUM OF TUAO
Centro 02, Tuao, Cagayan, 3528
Email address: lyceumoftuao1965@yahoo.com.ph
GENERAL BIOLOGY 1
Cellular Respiration
Learning Outcomes
a. Differentiate aerobic from anaerobic respiration; and
b. Explain the major features and sequence the chemical events of cellular respiration.
Learning Content
CELLULAR RESPIRATION
Recalls how cells produce energy from food molecules inside the body. This process can be compared to using
the energy from the food. In a global scale, this can be observed in an organism feeding on another. There are
two pathways by which energy is harvested from food, with or without oxygen. The muscle cells are so special
that they can switch pathways in obtaining energy, depending on the availability of oxygen. Imagine yourself
climbing the first few floors of a building; your lungs and blood circulation help deliver oxygen to your muscles
so that aerobic pathways occurs. After climbing several more flights of stairs, your lungs, heart, and blood
vessels cannot supply muscle cells with enough oxygen. For this reason, the body switches to anaerobic
respiration.
In the previous lesson, it was discussed that plants make their own food through the process of photosynthesis.
At the end of the process, glucose with a chemical formula of C6H12O6, is produced. Glucose is the primarily
source of energy in humans.
Glucose is a high-energy molecule that needs to be broken down through the process of cellular respiration.
Cellular respiration is a process that involves the oxidation and reduction of molecules to produce energy
in the form of adenosine triphosphate (ATP).
Oxidation is the process of losing an electrons while reduction is the process of gaining electrons. Cellular
respiration uses oxygen molecules and releases carbon dioxide as one of its by-products.
The overall equation of cellular respiration is shown above. The glucose molecule is oxidized and becomes carbon dioxide
while oxygen molecules are reduced and become water molecules .
This is the reason why humans and animals need to breathe in oxygen and expel carbon dioxide. It is the
opposite of photosynthesis which requires carbon dioxide to start the process and releases oxygen as its by-
product. Cellular respiration can happen in two conditions- with or without oxygen. Aerobic respiration is the
process of producing energy that uses oxygen while anaerobic respiration is the process that does not use
oxygen.
Tuguegarao Archdiocesan Schools System
LYCEUM OF TUAO
Centro 02, Tuao, Cagayan, 3528
Email address: lyceumoftuao1965@yahoo.com.ph
How does aerobic respiration differ from anaerobic respiration?
AEROBIC RESPIRATION
Aerobic respiration is the process of breaking down organic nutrients from food, such as glucose, to produce
energy involving oxygen molecules. Organisms that are exposed to an environment where oxygen is present do
aerobic respiration to produce energy. Aerobic respiration involves four stages-namely glycolysis, Krebs cycle,
electron transport chain and chemiosmosis. In the first part of aerobic respiration which is glycolysis,
oxygen is not used. However, in the latter part of the process, oxygen is already used as an electron acceptor
which results in the formation of water molecules.
Processes in cellular respiration
ANAEROBIC RESPIRATION
How do organisms that can survive in the absence of oxygen harvest energy through alternative pathways?
Alternatively, anaerobic pathway is followed at some point to supply immediate energy source. Cells in the
body cannot store large amounts of oxygen for cellular respiration. The amount of oxygen from inhaling in air is
just enough for the cells normal activities. However, in certain high-impact activities, such as running, the body
cannot bring in enough oxygen in cells even if you breathe faster. How can cells function properly without
oxygen to keep cellular respiration going? The process involves glycolysis and fermentation, which allow
glycolysis to continue in the absence of oxygen.
Anaerobic respiration is the process of producing energy without involving oxygen. Glucose can be broken
down to produce energy without using oxygen. This happens in the muscle cells of humans and other
prokaryotic organisms like methanogens, which uses carbon dioxide as the final electron acceptor instead
of oxygen. The process of anaerobic respiration is just the same as aerobic respiration. However, the final
electron acceptors can be nitrate, sulfur, carbon dioxide instead of oxygen.
The Role of Mitochondria in Cellular Respiration
The mitochondria is the major sites of energy production. Energy is produced through the process of cellular
respiration and it plays a vital role in this. The structures of mitochondria help it to efficiently function during
cellular respiration. Mitochondria has an outer membrane, an inner membrane that folds into cristae,
intermembrane space, and a matrix.
The structure of mitochondria helps in the production of ATP during cellular respiration.
The outer membrane and the inner membrane of the cell create an intermembrane space. The
intermembrane space is responsible for holding the protons that are pumped out of the matrix. The
mitochondrial matrix is where ATP synthesis and Krebs cycle happen. Furthermore the inner membrane of
the mitochondria contains the proteins involved in the electron transport chain as well as the ATP
synthase. Cristae, on the other hand, are folds of the inner membrane which increase the surface area for
ATP production.
Tuguegarao Archdiocesan Schools System
LYCEUM OF TUAO
Centro 02, Tuao, Cagayan, 3528
Email address: lyceumoftuao1965@yahoo.com.ph
REACTANTS AND PRODUCTS OF CELLULAR RESPIRATION
In cellular respiration, the reactants are the glucose and oxygen molecules while water, carbon dioxide and
ATP molecules are the products. In the general formula of cellular respiration, glucose (C6H12O6) is oxidized
forming carbon dioxide while oxygen (O2) is reduced forming water (H2O).
The general equation of cellular respiration
Carbon dioxide is the by-product of cellular respiration is expelled from the body through the lungs in
exchange with oxygen that is obtained from the environment.
Key Points
Cellular respiration is a catabolic pathway that uses glucose molecules to produce energy in the form
of ATP (adenosine triphosphate).
Kinds of cellular respiration:
o Aerobic respiration is the process of producing energy involving oxygen.
o Anaerobic respiration is the process of producing energy without the presence of oxygen.
Glycolysis, Krebs cycle, electron transport chain and chemiosmosis are the four stages of cellular
respiration.
Krebs cycle and electron transport chain happen in the mitochondria of the cell.
Mitochondria has four main parts:
o Outer membrane
o Inner membrane
o Intermembrane space
o Matrix
Glucose and oxygen are the reactants while carbon dioxide and water are the products of cellular
respiration.
Learning Activity
A. Identify the term described in each item.
1. It is the process of producing energy without the presence of oxygen.
2. It is one of the by-products of cellular respiration that is expelled through the lungs.
3. It is a by-product of cellular respiration that is formed when oxygen reacts with hydrogen.
4. It is the space between the outer and inner membranes of mitochondria.
5. It is the last stage of cellular respiration.
6. It is where the Krebs cycle happens.
7. It is the form of energy that body cells needs.
8. It is the process of producing energy with the presence of oxygen.
9. It is the process of losing electrons.
10. What is the chemical formula of glucose.
