HESI A2 BIOLOGY STUDY
GUIDE
,HESI A2 Biology Study Guide
HESI A2 Biology Study Guide
Cellular respiration
Cellular respiration is the process inside of cells that converts nutrients (such as sugars, amino acids, and
fatty acids) into ATP (adenosine triphosphate), which is used throughout the organism for energy. Large
molecules are broken into smaller molecules, which releases both energy and waste.
Aerobic respiration occurs in the presence of Oxygen and has four main stages:
Glycolysis: Larger sugar molecule is broken down into 2 smaller sugar molecules in the cytoplasm.
Net gain of 2 ATP and 2 NADH
Formation of Acetyl CoA: Pyruvate undergoes oxidative decarboxylation to form Acetyl coenzyme
A. 1 CO2 is released as waste. Net gain of 2 NADH.
Citric acid cycle: also known as Krebs cycle. The 2 small sugar molecules produced during
glycolysis are oxidized forming new products. Gain of 2 ATP, 6 NADH, 2 FADH2.
Electron transport chain: redox reaction involving the electrons removed during glycolysis and the
Krebs cycle. Protons are pumped across the mitochondrial membrane to form a gradient, which
drives the synthesis of 34 ATP.
Anaerobic respiration is a type of cellular respiration which occurs when oxygen is not present. This process
is most commonly performed by bacteria and Achaea. These organisms use this process to obtain energy
because they live in environments with low oxygen levels. Example: Achaea called methanogens use
carbon dioxide to accept electrons. Methanogens can be found in soil and the digestive systems of animals
called ruminants, which includes cows and sheep.
Anaerobic respiration, similar to aerobic cellular respiration, uses electrons from the fuel molecules to pass
through the electron transport chain, which drives ATP synthesis. The electron transport chain moves
electrons to create a proton gradient that allows for the synthesis of ATP. Electron transport chains are
used for extracting energy. This can happen in plants, where the energy from the sunlight is used to create
glucose and oxygen through photosynthesis in the chloroplast. Eukaryotes perform this process in the
mitochondria.
Fermentation is another type of cellular respiration which occurs in the absence of Oxygen. Organisms
capable of fermentation include prokaryotes, yeast, and multicellular organisms such as humans.
Feature Aerobic Respiration Anaerobic Respiration
Oxygen requirement Yes, always No, never
Waste products Carbon dioxide and water Carbon dioxide and ethanol
Very efficient Less efficient
Efficiency in releasing energy
(most of the energy is released (some energy locked in ethanol
from glucose
from glucose) is not released)
Yes, but less than that for
Some energy released as heat Yes
aerobic respiration
2|Page
© 2017 All Rights Reserved. www.ReadyForTheHESI.org
,HESI A2 Biology Study Guide
Antibiotics
Antibiotics are a kind of medicine used to treat bacterial infections. Not all bacteria are bad or unhealthy.
Humans and other animals actually have a healthy ecosystem of bacteria, called normal flora. These are
the good kind of bacteria.
Pathogenic bacteria are the type which can cause infection. Some bacteria will cause infection no matter
where they are, but others are safe in some areas of the body, but become infectious when they wander to
a new location in the body. An example of this is if the bacteria in the gut, or intestines, were to try and live
in the bladder or another organ. This is what happens in case of a urinary tract infection. The body’s immune
system must try to fight and destroy the invading bacteria.
Antibiotics are chemicals that enter and stick to
certain parts of the bacterial cell. The parts where
the antibiotics can attach can be the
proteins/sugars in the bacterial cell wall or the
important enzymes that make new bacterial DNA
or proteins. This act of blocking these parts
interferes with the bacteria’s ability to survive and
multiply. If the correct antibiotic is used, the
bacteria will stop growing or die.
Without antibiotics, bacteria can grow and
multiply, especially if the immune system cannot
battle the bacteria. If enough antibiotic is present,
the bacterial cell is crippled and stops growing,
known as bacteriostatic, or it simply dies, known
as the bactericidal effect. Antibiotics do not affect
viruses, fungi or parasites as they bind only to
bacterial cell targets.
Some bacteria have the ability to become antibiotic resistant. This happens when bacteria have
overexposure to antibiotics. The bacteria no longer are affected by the antibiotic because it undergoes
mutations.
3|Page
© 2017 All Rights Reserved. www.ReadyForTheHESI.org
, HESI A2 Biology Study Guide
Cells and tissues
The basic building block of the body is the cell. Cells can perform a wide variety of functions, depending on
the specialized type of cell that it is. Every type of cell plays a vital role in growth, development, and
maintenance of the body.
Cells from all organisms, ranging from humans to plants to bacteria, share certain characteristics. There
are two categories that cells fall into: prokaryotic and eukaryotic. Prokaryotic cells are single-celled
organisms from the domains Bacteria and Archaea. “Pro-” means before and “kary-” means nucleus, hence
prokaryotic cells lack a nucleus and other membrane-bound organelles. Eukaryotes are made of two or
more cells. “Eu-” means true, which means that eukaryotic cells have a nucleus. All types of cells share
four key components: plasma membrane, cytoplasm, DNA and ribosomes.
Prokaryotic cells have DNA, but it is not housed in a
nucleus. The majority of the DNA in prokaryotic cells is
found in a central region of the cell called the nucleoid.
Bacteria are a specific type of prokaryotic cell. Most
bacteria are surrounded by a rigid cell wall, which
provides an extra layer of protection, helps the cell
maintain its shape and prevent dehydration. Many
bacteria have an outermost capsule that is sticky and
helps the cell attach to its surroundings. Some bacteria
also have a flagellum. It is a whip-like structure that acts
like a motor to help the bacteria to move. Fimbriae are
hair-like structures that are used to attach to other
surfaces or host cells. Sometimes bacteria have pili,
which allows the cell to transfer DNA to other bacteria or
helps with locomotion (movement).
Eukaryotic cells are significantly more complex
compared to prokaryotic cells. They contain a variety of
different compartments that have specialized
functions, and are separated by layers of
membrane. This organization allows each
compartment to maintain its respective conditions
and do what it needs to carry out its job. These
compartments are called organelles. Unlike
prokaryotic cells, eukaryotic cells have a nucleus,
membrane-bound organelles, and multiple linear
chromosomes. Eukaryotic cells have an array of
organelles that are important for energy balance,
metabolism, and gene expression.
4|Page
© 2017 All Rights Reserved. www.ReadyForTheHESI.org
GUIDE
,HESI A2 Biology Study Guide
HESI A2 Biology Study Guide
Cellular respiration
Cellular respiration is the process inside of cells that converts nutrients (such as sugars, amino acids, and
fatty acids) into ATP (adenosine triphosphate), which is used throughout the organism for energy. Large
molecules are broken into smaller molecules, which releases both energy and waste.
Aerobic respiration occurs in the presence of Oxygen and has four main stages:
Glycolysis: Larger sugar molecule is broken down into 2 smaller sugar molecules in the cytoplasm.
Net gain of 2 ATP and 2 NADH
Formation of Acetyl CoA: Pyruvate undergoes oxidative decarboxylation to form Acetyl coenzyme
A. 1 CO2 is released as waste. Net gain of 2 NADH.
Citric acid cycle: also known as Krebs cycle. The 2 small sugar molecules produced during
glycolysis are oxidized forming new products. Gain of 2 ATP, 6 NADH, 2 FADH2.
Electron transport chain: redox reaction involving the electrons removed during glycolysis and the
Krebs cycle. Protons are pumped across the mitochondrial membrane to form a gradient, which
drives the synthesis of 34 ATP.
Anaerobic respiration is a type of cellular respiration which occurs when oxygen is not present. This process
is most commonly performed by bacteria and Achaea. These organisms use this process to obtain energy
because they live in environments with low oxygen levels. Example: Achaea called methanogens use
carbon dioxide to accept electrons. Methanogens can be found in soil and the digestive systems of animals
called ruminants, which includes cows and sheep.
Anaerobic respiration, similar to aerobic cellular respiration, uses electrons from the fuel molecules to pass
through the electron transport chain, which drives ATP synthesis. The electron transport chain moves
electrons to create a proton gradient that allows for the synthesis of ATP. Electron transport chains are
used for extracting energy. This can happen in plants, where the energy from the sunlight is used to create
glucose and oxygen through photosynthesis in the chloroplast. Eukaryotes perform this process in the
mitochondria.
Fermentation is another type of cellular respiration which occurs in the absence of Oxygen. Organisms
capable of fermentation include prokaryotes, yeast, and multicellular organisms such as humans.
Feature Aerobic Respiration Anaerobic Respiration
Oxygen requirement Yes, always No, never
Waste products Carbon dioxide and water Carbon dioxide and ethanol
Very efficient Less efficient
Efficiency in releasing energy
(most of the energy is released (some energy locked in ethanol
from glucose
from glucose) is not released)
Yes, but less than that for
Some energy released as heat Yes
aerobic respiration
2|Page
© 2017 All Rights Reserved. www.ReadyForTheHESI.org
,HESI A2 Biology Study Guide
Antibiotics
Antibiotics are a kind of medicine used to treat bacterial infections. Not all bacteria are bad or unhealthy.
Humans and other animals actually have a healthy ecosystem of bacteria, called normal flora. These are
the good kind of bacteria.
Pathogenic bacteria are the type which can cause infection. Some bacteria will cause infection no matter
where they are, but others are safe in some areas of the body, but become infectious when they wander to
a new location in the body. An example of this is if the bacteria in the gut, or intestines, were to try and live
in the bladder or another organ. This is what happens in case of a urinary tract infection. The body’s immune
system must try to fight and destroy the invading bacteria.
Antibiotics are chemicals that enter and stick to
certain parts of the bacterial cell. The parts where
the antibiotics can attach can be the
proteins/sugars in the bacterial cell wall or the
important enzymes that make new bacterial DNA
or proteins. This act of blocking these parts
interferes with the bacteria’s ability to survive and
multiply. If the correct antibiotic is used, the
bacteria will stop growing or die.
Without antibiotics, bacteria can grow and
multiply, especially if the immune system cannot
battle the bacteria. If enough antibiotic is present,
the bacterial cell is crippled and stops growing,
known as bacteriostatic, or it simply dies, known
as the bactericidal effect. Antibiotics do not affect
viruses, fungi or parasites as they bind only to
bacterial cell targets.
Some bacteria have the ability to become antibiotic resistant. This happens when bacteria have
overexposure to antibiotics. The bacteria no longer are affected by the antibiotic because it undergoes
mutations.
3|Page
© 2017 All Rights Reserved. www.ReadyForTheHESI.org
, HESI A2 Biology Study Guide
Cells and tissues
The basic building block of the body is the cell. Cells can perform a wide variety of functions, depending on
the specialized type of cell that it is. Every type of cell plays a vital role in growth, development, and
maintenance of the body.
Cells from all organisms, ranging from humans to plants to bacteria, share certain characteristics. There
are two categories that cells fall into: prokaryotic and eukaryotic. Prokaryotic cells are single-celled
organisms from the domains Bacteria and Archaea. “Pro-” means before and “kary-” means nucleus, hence
prokaryotic cells lack a nucleus and other membrane-bound organelles. Eukaryotes are made of two or
more cells. “Eu-” means true, which means that eukaryotic cells have a nucleus. All types of cells share
four key components: plasma membrane, cytoplasm, DNA and ribosomes.
Prokaryotic cells have DNA, but it is not housed in a
nucleus. The majority of the DNA in prokaryotic cells is
found in a central region of the cell called the nucleoid.
Bacteria are a specific type of prokaryotic cell. Most
bacteria are surrounded by a rigid cell wall, which
provides an extra layer of protection, helps the cell
maintain its shape and prevent dehydration. Many
bacteria have an outermost capsule that is sticky and
helps the cell attach to its surroundings. Some bacteria
also have a flagellum. It is a whip-like structure that acts
like a motor to help the bacteria to move. Fimbriae are
hair-like structures that are used to attach to other
surfaces or host cells. Sometimes bacteria have pili,
which allows the cell to transfer DNA to other bacteria or
helps with locomotion (movement).
Eukaryotic cells are significantly more complex
compared to prokaryotic cells. They contain a variety of
different compartments that have specialized
functions, and are separated by layers of
membrane. This organization allows each
compartment to maintain its respective conditions
and do what it needs to carry out its job. These
compartments are called organelles. Unlike
prokaryotic cells, eukaryotic cells have a nucleus,
membrane-bound organelles, and multiple linear
chromosomes. Eukaryotic cells have an array of
organelles that are important for energy balance,
metabolism, and gene expression.
4|Page
© 2017 All Rights Reserved. www.ReadyForTheHESI.org
