Protein Structure, Photosynthesis, and Genetic Mutations: A Comprehensive Overview

Posted on Aug 19, 2024 in Biology

June 5th – Biological Concepts

B1OA – Protein Structure and Function

1. Protein Structure

The composition and shape of a protein are defined by four hierarchical structures of increasing complexity: primary, secondary, tertiary, and quaternary.

Primary Structure: The linear sequence of amino acids, determining the number and order in which they occur. Peptide bonds between amino acids stabilize this structure.

Secondary Structure: The regular and periodic arrangement of the polypeptide chain in space. This results from the alpha carbon’s ability to self-turn. Two main types exist:

  • Helix
  • β-Sheet

Tertiary Structure: The three-dimensional arrangement of the secondary structure. Common conformations include globular and filamentous. A protein’s biological function depends on its tertiary structure.

Quaternary Structure: The arrangement of multiple polypeptide chains (subunits) to form the active protein (e.g., hemoglobin). Subunits are joined by hydrogen bonds and disulfide bonds.

2. Importance of Protein Structure and Denaturation

Altering a protein’s structure can determine its importance for biological function. An extreme disturbance is denaturation, the complete disruption of the three-dimensional structure. This can be caused by heat, extreme pH changes, organic solvents, and detergents.

Denaturation typically leads to loss of biological activity. However, some proteins can undergo renaturation, regaining their structure and function under favorable conditions.

3. Biological Roles of Proteins

Proteins are versatile biomolecules with diverse functions. Key roles include:

  • Reserve of compounds
  • Transport of substances
  • Defense mechanisms
  • Contractile function
  • Enzymatic function
  • Homeostatic function
  • Hormonal function
  • Structural function

B2OA – Photosynthesis and Chemosynthesis

1. The Calvin Cycle

The Calvin cycle is the metabolic pathway responsible for fixing CO2 during photosynthesis, providing the carbon needed for building organic biomolecules. This cycle represents the dark phase or biosynthesis stage, utilizing ATP and NADPH from the light phase to reduce CO2 and synthesize carbohydrates.

Phases of the Calvin Cycle:

  1. Carboxylation Stage: CO2 is incorporated into ribulose-1,5-bisphosphate, producing two molecules of 3-phosphoglycerate. This reaction is catalyzed by the enzyme ribulose-1,5-bisphosphate carboxylase-oxygenase (RUBISCO).
  2. Reduction Phase: The incorporated CO2 in 3-phosphoglycerate is reduced using ATP and NADPH from the light phase.
  3. Regeneration Phase: Glyceraldehyde-3-phosphate is converted to glucose-6-phosphate and partly into ribulose-1,5-bisphosphate to restart the cycle.

Overall Reaction:

6 CO2 + 18 ATP + 12 NADPH + 12 H+ + 12 H2O → glucose + 18 ADP + 18 Pi + 12 NADP+

The high ATP consumption reflects the highly oxidized state of CO2.

The Calvin cycle takes place in the chloroplast stroma.

2. Chemosynthesis

Chemosynthesis is an anabolic process similar to photosynthesis, but it uses energy from exothermic chemical reactions instead of light. This process is characteristic of certain bacteria that oxidize inorganic compounds for energy.

Phases of Chemosynthesis:

  • Oxidation of inorganic compounds: ATP is produced, and electrons are used to reduce NAD+ to NADH.
  • Formation of organic compounds: ATP and NADH are used to reduce inorganic molecules, similar to the dark phase of photosynthesis.

3. Temperature and Photosynthesis

Photochemical reactions of the light phase are temperature-independent, while dark phase reactions are temperature-dependent. However, excessive temperature increases can denature enzymes and decrease photosynthetic efficiency. An optimum temperature for photosynthesis is around 35°C.

B3OA – Chromatin, Genetic Recombination, and Mutations

1. Chromatin and Chromosomes

Chromatin is the fundamental substance of the eukaryotic cell nucleus. During mitosis, chromatin condenses into chromosomes. Each chromosome consists of two chromatids joined at the centromere. Each chromatid contains a single DNA molecule.

2. Genetic Recombination

is a direct result of the exchange of
genetic information that occurs at chromosomal crossing-over
meiotic. In this phenomenon the homologous chromosome pairs are
closely matched and adhere to certain points called
chiasmata. In this situation the sister chromatids are intertwined and are
transversely fragment giving rise to an exchange of DNA between them.
This process, together with the mutation leads to increased variability
genetics. Thus, an individual can acquire the most favorable mix
characters of their parents and so, in unfavorable conditions, reproduction
sex can facilitate adaptation to the environment.
3. a) Gene mutations, also known point, are those which affect
to the nucleotide sequence. We can distinguish two types of gene mutations
by:
– Replacement of bases: They account for around 20% of gene mutations and
consist of a base change of DNA by another.
– Shift in the reading frame: They can be consist of inserts when
the addition of any nucleotide in the DNA molecule or deletions when
involve the loss of a nucleotide in the DNA molecule.
b) Chromosome mutations are also called chromosomal variations
structural. The variation or alteration affecting a chromosome segment that
includes several genes and therefore some are detectable under the microscope thanks
the chromosome banding technique for specific stains. Alterations in
the organization of genes on chromosome produced by breakage during
germ cells to reproduce, so to put back the
lead to broken chromosomes other than the originals. There are several types
mutations caused by chromosomal deletion, inversion,duplication and
translocation of fragments in the chromosomes.
c) The genomic mutations affect the number of chromosomes. These are of
several types:
1 .- Polyploidy: These mutations consist in increasing the number of normal
sets of chromosomes or chromosomes of each species (for example, 2n
to 4n).
2 .- Haploidy: Are the mutations that cause a decrease in the number of
sets of chromosomes of the species.
3 .- Aneuploidies: are the mutations that affect only the number of copies of a
chromosome, or more, but not into the whole game.
B4OA
The degree of pathogenicity of a microorganism known as virulence and is
quantifiable. Is a pathogen that is capable of producing a
disease pathogenicity refers to the ability of parasites to
penetrate the host and anatomical and physiological changes occur as the
disease.
A toxin is a substance of protein nature of the specific causative
functional in some bacteria. The toxins are characterized by their ability to
cause damage to your host, actually being the cause of disease
bacteria. There are two types of toxins:
– The exotoxins of proteinaceous, thermolabile and secreted abroad
Gram-positive bacteria, which possess high toxicity.
– Endotoxin, structural components of Gram-negative bacteria, and
toxigenic capacity of which is much smaller than that of endotoxin.
2. HIV belongs to the family of retroviruses. These viruses are characterized by
carry genetic information in an RNA molecule that must be copied to DNA
during its replication cycle, through the action of an enzyme’s own
virus, reverse transcriptase or retrotrancriptasa.
The cycle begins when the retrovirus HIV interacts with a glycoprotein
of the host cell membrane. This interaction triggers the fusion of
membranes of the virus and the cell with the consequent entry of the retrovirus to
cell interior. After the loss of the coat protein is initiated
reverse transcription of viral RNA through reverse transcriptase, resulting in a
Duplex DNA. Induces an enzyme called integrase integration
Viral DNA into the host cell chromosome. The next step is the
expression of viral DNA that leads to the formation of viral RNA, which
translate to cause structural and enzymatic proteins of the virus. After
assembly of virions, they can be released to restart a new cycle
Retroviral infecting new target cells.
The cycle of HIV is represented in the following schedule:
3. The AIDS virus infects T 4 lymphocytes causing their destruction and
Therefore, disabling the immune response, both cellular and humoral. In the
Eventually, the body can not produce an immune response against the cells or
T 4-infected or against the virus itself, or even against other
opportunistic invading organisms or malignant cells that may be
present and develop. As the system becomes weaker, the patient is more
vulnerable to other diseases, most notably pneumonia caused
Pneumocystis carinii, Kaposi’s sarcoma and other cancers.
Pathological situations and immunodeficiency are produced as a result of
the absence, or failure, the role of one or more elements of the system
immune. Considering the origin of the spoils, there are: immunodeficiency
congenital or primary and secondary or acquired immunodeficiency.
The i nmunodeficiencias secondary or acquired are those that are acquired after
birth, and are due to extrinsic or environmental factors, such as
be most drugs used in cancer chemotherapy, the
radiation, malnutrition or infections. Among the immunodeficiencies
we might cite the high produced by HIV, which causes AIDS.