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Summary Experimental Cell Biology I
- Instelling
- Vrije Universiteit Amsterdam (VU)
Experimental Cell Biology I
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ECBI Monday, 5 September 2022The Basics
BASIC FEATURES OF THE CELL
Cells are known as an membrane-closed unit of life. This means their form of life is
encapsulated in a membrane. Cells contain a metabolis, allowing them to grow and divide.
Cells response to environmental signals via internal and external communication.
Cells contain DNA, which is their genetic material. They also contain proteins, which are the
workhorses of the cell. The metabolites are molecules produced and altered by the cell.
Interplay between DNA, proteins, and metabolites is very important for the survival of the
cell
Prokaryotic cell and eukaryotic cell
A prokaryotic cell is usually small and single-celled. They have no membrane enclosed
compartments and are biochemically flexible. The human cell is an eukaryotic cell. These
are typically larger and are many multi-cellular. They also have membrane enclosed
compartment. Basically, the prokaryotic and eukaryotic cell are the opposite of each other
COMPARTMENTS OF THE EUKARYOTIC CELL
Nucleus
The nucleus is important for both DNA and RNA synthesis via transcription. All the DNA and
RNA synthesised is also located in the nucleus. The nucleus is surrounded by a
phospholipid membrane. Nuclear pores allow particle exchange/transport.
Besides the nucleus is also a nucleolus, which is responsible for the synthesis of ribosomes
and RNA. It is involved in protein quality control
Endoplasmatic Reticulum
The ER is responsible for protein modification and transport and sorting. It is closely
connected to protein synthesis. Membrane proteins are inserted in the ER, making it the
first station for secreted proteins. The ER is also able to initiate mitochondrial fission, which
is the splitting of one mitochondrium into two mitochondria.
Golgi apparatus
The Golgi apparatus is a membrane system which is important in protein modification, in
particular glycosylation. It is also important for sorting and transport. Transport to, from,
and within the Golgi is mediated by transport vesicles. The vesicles enters the Golgi on the
cis-side and leaves on the trans-side.
Mitochondria
Mitochondria are importnat for energy metabolism and fatty acid oxidation. They are the
main source of ATP production in the cell, and are very important for the citric acid cycle,
which is a key cycle of metabolism.
Lysosomes
Lysosomes are hydrolytic enzymes which are important in the degradation process of the
cells. They are also investigated to have influence on cell signalling and secretion
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Transport Vesicles
Transport vesicles are important for the transport between compartments in the cell. They
are crucial for the distribution of material and information. They are closely relate to the ER
and Golgi as in here they transport the most material
Cytoskeleton
The cytoskeleton is responsible for structuring of the cell, but it also has importance in cell
movement and transport within the cell. The cytoskeleton is mainly composed of
microtubuli, keratin, and actin fibres
Chloroplast
Chloroplasts are only present in photosynthetic organs, where they are responsible for the
capturing of energy from sunlight. From there, they can produce ATP to provide the cells
from energy.
Cytosol
The cytosol is a water-based gel which is located between the compartments of the cell. It
is composed of a broad range of molecules contributing to many chemical reactions central
in metabolism. The cytosol is extremely crowed, allowing effective concentrations of
molecules and reaction rates
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Energy Metabolism
CURRENCIES OF ENERGY
Cells need energy for metabolism, to allow biosynthesis, transport, and movement. Energy
for these processes are provided by the breakdown of carbohydrates, lipids and proteins.
Energy derived from diet molecules are stored according to the universal principles, which
are ATP and Ion motive forces across membranes.
ATP
ATP is used for energonic reactions. They can release an Pi group to yield ADP en free
energy.
Ion motive forces
Ion motive forces are formed by ion gradients across bio-membrane, which can drive
endergonic reactions. The proton motive is forced is driven by protons and is found in
bacteria, mitochondria and chloroplasts. A sodium motive force is driven by sodium ions
and is found in plasma membranes of eukaryotes.
ENERGY FROM NUTRIENTS
Energy can also be produced from nutrients, including substrate level phosphorylation
(glycolysis), the citric acid cycle, or oxidative phosphorylation.
Glycolysis
Glycolysis is the breakdown of carbohydrates as glucose into energy. It demands the input
of 2 ATP and it yields 4 ATP, giving it a total win of 2 ATP per molecule of glucose. The
glycolysis pathway is cytosolic and fast.
Glucose —> G6P —> F6P —> F16P —> Pyruvate
The final product of glycolysis is pyruvate. Via pyruvate dehydrogenase, this is converted
into Acetyl CoA. When this conversion has occurred, it cannot convert back anymore to
pyruvate. This step yields NADH
Citric Acid cycle (TCA cycle)
The function of the citric acid cycle is to harvest high-energy electrons from carbon fuels.
Acteyl Coa can be inserted from the glycolysis pathway into the TCA cycle at the step of a-
ketoglutarate —> succinyl CoA . The TCA cycle invests NAD+ and it yield NADH together
with 1 GTP, which is a form of ATP. Side products of the TCA cycle include CO2 and H+ .
The TCA cycle occurs in the bacterial cytosol and the mitochondrial matrix.
The TCA cycle is also important in biosynthesis pathways (eg. Amino acids),as they always
arise from an intermediate component of the TCA cycle
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