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Chapter 4 Key Terms
Aerobic
Glycolysis
Codon
Intracellular Digestion
Cellular Respiration
Photosynthesis
Stroma
Anaerobic
Krebs Cycle
Translation
Extracellular Digestion
Fermentation
Chemosynthesis
Calvin Cycle
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Biology Chapter 4
CELLULAR PROCESSES
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Cellular Energy

Cells require a constant supply of energy in order for them to
perform all of their processes

A cell dies when it stops using energy

2 basic groups when referring to how organisms obtain energy
 Autotrophs
(primary producers)
 Organisms
 Heterotrophs
 Organisms
that make their own food (plants, algae…)
(consumers)
that depend on other organisms for their energy
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Cellular Energy

Autotrophs use photosynthesis to make and store food

Both autotrophs and heterotrophs use cellular respiration to
release energy from storage

The energy in the cell needs to be converted to smaller usable
units

ATP
 Adenosine
 Used
triphosphate
by cell to perform different functions
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Cellular Energy

Structure of ATP
 Ribose
sugar
 Adenine
3

phosphate groups
ATP stores energy between the 3 phosphate groups
 When
 More
ATP is broken down, energy is released
than 1 ATP molecule is needed for most processes
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Cellular Energy

When ATP is broken down, it becomes ADP and releases
energy
 ATP
 ADP + P + Energy
 Exothermic

reaction
ADP can be reused to form ATP when another phosphate is
bonded with ADP
 ADP
+ P + Energy  ATP
 Endothermic

reaction
ATP is a temporary, unstable energy storage
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Cellular Energy
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Photosynthesis

The process of absorbing light energy and converting it into
usable chemical energy
 Performed

by autotrophs (green plants and algae)
These autotrophs provide the energy needed for all life
 Consumers

consume the food produced by producers
Also important because this process produces oxygen
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Photosynthesis

Chlorophyll
 Green
pigment that is the primary catalyst of photosynthesis
 Chlorophyll
a and Chlorophyll b are found in the membranes of
the grana of chloroplasts

The sun gives off all wavelengths of light

Objects absorb certain wavelengths and reflect others
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Photosynthesis

Process
 Takes

place in the grana (thylakoids or stroma)
2 phases:
 Light-Dependent
Phase
 Light-Independent
Phase
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Photosynthesis

Light-Dependent Phase
 This
phase occurs in the thylakoid membrane
 Chlorophyll
a absorbs light energy which energizes electrons
from the chlorophyll a molecule
 Electrons
pass through a series of proteins called the electron
transport chain
 As
electrons pass through the chain, some energy is used to
make ATP and NADPH
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Photosynthesis

Light-Dependent Phase
 Photolysis:
process of splitting a water molecule into H+ ions,
electrons, and O2
 Electrons
replace those lost by the chlorophyll a molecule
 H+
ions remain in thylakoids
 O2
is either released into the atmosphere or used by the cell
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Photosynthesis

Light-Independent Phase
 AKA
Calvin Cycle
 Takes
place in the stroma of the chloroplast
 Does
not need light; however, does need the products from the
light-dependent phase (ATP, NADPH) and CO2
 CO2
binds with RuBP and produces a 3-carbon sugar called PGAL
 Some
PGAL molecules are used to make RuBP so Calvin Cycle
can continue, while others are used to make glucose
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Photosynthesis
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Photosynthesis

Conditions for photosynthesis
 The
 Cell
right amount of light is needed
must have sufficient CO2
 Correct
temperatures are needed
 Sufficient
water supply
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Cellular Respiration

Breaking down of food into usable cellular energy – ATP
 Glucose
 Lipids
 Monosaccharides
 Proteins

Two types of cellular respiration
 Aerobic:
Requires O2
 Anaerobic:
Does not require O2
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Cellular Respiration

Glycolysis
 Breakdown
of glucose into pyruvic acid, hydrogen ions, and e Takes place in the cytoplasm
 Products are used in mitochondria to continue cellular respiration
Step 1: Two ATP molecules provide activation energy to start
 Step 2: PGAL molecules release e- and H+ ions to electron
carrier molecule
 Step 3: Total of 4 ATP molecules made from ADP and
phosphates made in steps 1 and 2

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Aerobic Respiration

Krebs Cycle (AKA Citric Acid Cycle)
 Pyruvic
acid diffuses into mitochondria and reacts with enzymes
to remove carbon which produces acetyl CoA, H+, e-, CO2, ATP
 Carrier

molecules carry high-energy e- needed for next phase
Electron Transport Chain
 This
chain is formed by molecules in the cristae of the
mitochondria
 Electrons
 On
are used in reactions to generate large amounts of ATP
average, 1 glucose molecule generates 32 ATP molecules
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Anaerobic Respiration

Bacteria and fungi carry out anaerobic respiration only

Fermentation: breakdown of food without oxygen

Alcoholic Fermentation
 Pyruvic

Lactic Acid Fermentation
 Pyruvic

acid is changed to ethyl alcohol and ATP
acid is changed into lactic acid and ATP
Fermentation only yields the energy provided by glycolysis

2 ATP molecules
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Metabolism

The sum of all its life processes
 Photosynthesis
 Respiration
 Movement
 Growth
Important because it can help us determine what is causing
certain diseases/problems in the cells
 Cells are controlled by proteins and are made of structural
proteins

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Protein Synthesis

Controls all other metabolic pathways

The process of the cell making proteins based on the
information found in DNA

The sequence of bases determines the order in which amino
acids are arranged to form specific proteins

This sequence is formed in triplets of bases called codons

These codons are “read” to form a chain of amino acids
(polypeptide chain) which makes the protein
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Review

DNA replication
 DNA
strand is copied to make 2 new DNA strands
 Each
new DNA strand contains ½ of old strand and ½ of new
strand

Differences between DNA and RNA
 RNA
contains ribose: DNA contains deoxyribose
 RNA
contains Uracil: DNA contains Thymine
 RNA
is single strand: DNA is double strand
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Types of RNA

Messenger RNA (mRNA)
 Copies

DNA code and takes it out of nucleus to ribosome
Transfer RNA (tRNA)
 “reads”
mRNA sequence and lines up amino acids
 Contains

the anticodons which will be lined up with the codons
Ribosomal RNA (rRNA)
 Combines
with proteins to form a ribosome
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Protein Synthesis

Transcription
 Copying
nucleus

of the DNA code to make mRNA which will leave the
Translation
 Ribosomes
“read” the codons and attach appropriate tRNA
molecules to the codons
 tRNA
molecules line amino acids in correct order
 Proteins
are made
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