Notes, abstracts, papers, exams and problems of Biology

21) Osmosis can be defined as

the diffusion of water.

22) A cell that neither gains nor loses water when it is immersed in a solution is

isotonic to its environment.

23) Which of the following processes can move a solute against its concentration gradient?

active transport

24) Which of the following is a typical feature of an ATP-driven active transport mechanism?

The solute moves against the concentration gradient.

25) The process of a white blood cell engulfing a bacterium is

phagocytosis.

26) Which of the following examples is classified as a metabolic pathway?

protein synthesis

27) Which of the following most accurately describes selective permeability?

Only certain molecules can cross a cell membrane.

28) Which of the following would likely move through... Continue reading "Cellular Processes and Energy Production" »

Key Properties of Proteins

• Their molecular weight ranges from 1,000 to several hundred thousand.
• Generally water-soluble, with the exception of hydrophilic membrane proteins.
• Absorb light in the UV range, with maximum absorption at 280nm due to the presence of aromatic amino acids.
• Have a specific isoelectric pH (pI). Positively charged below pI, negatively charged above pI.
• Proteins are charged, which depends on the buffer.
• Move under the electric charge and can be separated by electrophoresis.
• Give a color reaction with reagents, such as a blue color with ninhydrin.

Classification of Proteins

Basis of Structure

1. Globular: All enzymes and intracellular proteins are globular, such as myoglobin and hemoglobin.
2. Fibrous: Mostly extracellular, such as collagen.

Auto or Self Antigens

Antigens present in one's own cells.

Altered by the action of bacteria, viruses, chemicals, or drugs as a non-self.

Auto antibody

Altered cell (Auto Ag) - elicits the production of Antibody.

Autoimmunity (misnomer, alternative = auto allergy)

Immune response of auto Ab against self Ag.

Humoral or cell-mediated immune response against the constituents of the body's own tissues.

There are more than 80 different kinds of diseases caused by autoimmunity.

Causes of Autoimmune Diseases

Sequestered or Hidden antigens

Ag in the secluded places - are not accessible to the immune system.

Neo antigens

Altered or Modified Antigens – by physical (irradiation), chemical (drugs), or microbial agents (intracellular viruses).

Cessation of Tolerance

It... Continue reading "Auto or Self Antigens: Causes and Effects of Autoimmunity" »

Behind the iris is a lens which changes shape in order to focus the image.

Photosynthesis and Cellular Respiration

Photosynthesis

Photosynthesis is the process by which plants convert carbon dioxide and water into glucose and oxygen, using light energy. This endothermic reaction can be summarized by the following equation:

6CO₂ + 6H₂O -> C₆H₁₂O₆ + 6O₂

The rate of photosynthesis is influenced by several factors, often referred to as limiting factors. These include:

• Light intensity: Increased light levels generally lead to a higher rate of photosynthesis until an optimum level is reached.
• Carbon dioxide concentration: Higher levels of carbon dioxide can enhance the rate of photosynthesis, up to a certain point.
• Temperature: Plants in their ideal temperature range perform photosynthesis more efficiently than those outside

Microbial Secretion Systems

Matching

Which secretion system:

• Moves protein from the periplasmic space to the exterior? 2, 4, 5
• Moves DNA from one cell to another through conjugation? 4
• Moves protein from cytoplasm to exterior (not into another cell)? 1, 3
• Relies on Sec to do the first step of transportation? 2, 4, 5
• Requires ATP? All
• A domain of the protein itself forms a beta-barrel that inserts into the outer membrane (i.e., forming a pore), allowing the rest of the protein to pass through? 5
• The protein being transported carries a C-terminal signal peptide? 1
• The preprotein (before final folding) being transported carries an N-terminal signal peptide? Sec

Viral Multiplication

Six Steps to Viral Multiplication:

1. Attachment to host cell
2. Entry
3. Uncoating of

Plant Nutrition Fundamentals

Photosynthesis Definition

Photosynthesis is the process by which plants manufacture carbohydrates from raw materials using energy from light.

Photosynthesis Word Equation

The word equation for photosynthesis is: carbon dioxide + water → (in the presence of light and chlorophyll) → glucose + oxygen.

Photosynthesis Balanced Equation

The balanced chemical equation for photosynthesis states that the combination of carbon dioxide, water, and light energy produces a carbohydrate (glucose) and oxygen.

The chemical formula is: 6CO₂ + 6H₂O + Light Energy → C₆H₁₂O₆ + 6O₂.

Chlorophyll's Role in Energy Transfer

Chlorophyll transfers light energy into chemical energy stored in molecules, enabling the synthesis of... Continue reading "Plant Nutrition and Photosynthesis Essentials" »

Cellular Respiration

1. Definition and Chemical Equation

Cellular respiration is the chemical reaction in which glucose and oxygen are converted into water, carbon dioxide, and energy (ATP). The balanced chemical equation for cellular respiration is: C₆H₁₂O₆ + 6 O₂ --> 6 CO₂ + 6 H₂O + ATP

2. Location of Respiration

Cellular respiration takes place in the mitochondria of living cells.

3. Phases of Respiration and ATP Production

Cellular respiration occurs in three stages: glycolysis, the Krebs cycle, and electron transport. Glycolysis takes place in the cytoplasm and results in a net gain of two ATP molecules.

4. ATP and Energy Production

ATP provides energy to the cell when it is broken down into ADP (adenosine diphosphate) and inorganic phosphate,... Continue reading "Cellular Respiration and Cell Cycle: Key Concepts and Processes" »

6. Fill in the gaps with words from the box

1. Viruses are a type of microorganisms which are not affected by antibiotics

2. We couldn’t           the experiment because the machine didn’t work come up 

3. Any national government has been able to       with effective measures to lower COVID expansion.

4. The results are inconclusive and that’s why scientists haven’t been able to find a cure yet

5. These tomatoes have been genetically modified 

6. Remember to turn off all the machinery before leaving the laboratory

7. The samples need to be poured into test tubes after being processed

8. Some women receive hormone treatment to control irregular periods