Cell Cycle and Its Phases Quiz

Cell Biology I - Course Notes

• This course is for third-level biochemistry students at Helwan University
• Course code: BCh3105
• Lecturer: Dr. Rania EL-Lethy Abdelhamed EL-Lethy
• Department of Biochemistry, Chemistry Department
• Faculty of Science, Helwan University

Cell Biology - Definition

• Cell biology, also known as cytology or cytobiology, is a branch of biology
• It studies the different structures and functions of cells
• It focuses on the cell as the basic unit of life
• It explains cell structure, organization of organelles, physiological properties, metabolic processes, and signaling pathways
• It studies the life cycle and interactions with the environment
• This field includes both microscopic and molecular levels.
• The scope encompasses both prokaryotic and eukaryotic cells

Cell Structure and Function

• Cells are the fundamental and functional units of all living organisms
• The body contains trillions of cells, organized into over 200 major types
• Cells carry out various jobs at any given time
• The cells have highly skilled jobs, which include covering (skin cells), preventing sloshing (bone cells), and eliminating toxins (liver cells).
• Others include making essential products such as sweat, saliva, enzymes, hormones, and antibodies.
• Cells carry out various functions depending on their type (e.g., red blood cells carry oxygen; white blood cells fight infection).

Blood

• Blood is the most important fluid in the body
• It's bright red when oxygenated, due to hemoglobin
• Blood circulates throughout the body via blood vessels, pumped by the heart
• Blood accounts for 7% of the human body weight and the average adult has a blood volume of approximately 5 litres
• Blood pH is kept within a narrow range (7.35 to 7.45), slightly basic
• Blood below 7.35 is acidic, while above 7.45 is basic

Functions of Blood

• Delivers oxygen to tissues, bound to hemoglobin in red blood cells
• Transports nutrients such as glucose, amino acids, and fatty acids
• Removes waste products, including carbon dioxide, urea, and lactic acid
• Has immunological functions (white blood cells and antibodies)
• Involved in coagulation (blood clotting)
• Transports hormones

Constituents of Human Blood

• Blood is composed of plasma and blood cells
• Plasma is the liquid component (~55% of blood), mainly water, with dissolved proteins and nutrients such as glucose, amino acids
• Blood cells include red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes)

Erythrocytes (Red Blood Cells)

• The most numerous blood cells in humans
• Lack a nucleus and have a biconcave shape in mammals
• Responsible for transporting oxygen to tissues
• Have a lifespan of approximately 120 days

Leukocytes (White Blood Cells)

• Responsible for the body's defense mechanisms
• Less numerous than red blood cells
• Classified into granulocytes (neutrophils, basophils, eosinophils) and agranulocytes (lymphocytes, monocytes)
• Each type has specific functions in the immune system

Platelets (Thrombocytes)

• Smallest blood cells
• Involved in blood clotting by converting fibrinogen to fibrin
• Short lifespan (a few hours)

Plasma

• The liquid component of blood (about 55%)
• Primarily water (92%), with plasma proteins (8%) and trace amounts of other materials
• It carries dissolved nutrients, such as glucose, amino acids, etc
• Plays a crucial role in transporting essential materials throughout the body

Counting Red Blood Cells (RBCs)

• Hemocytometer is a device used to count RBCs
• It consists of a thick glass microscope slide with a rectangular indentation that creates a chamber. This is divided into nine 1.0 mm squares. A cover glass is supported over the chambers for counting.

Cell Biology: Additional Information

• The cell, in biological terms, is the fundamental unit of life encompassing all living things.
• It plays a critical role as a self-contained unit, capable of metabolizing its own nutrients, synthesizing various types of molecules, providing energy, and replicating itself.
• Within multicellular organisms, cells exhibit high levels of specialization through differentiation into different specialized cells
• Cells interact with each other, forming tissues, organs, and, ultimately, entire organisms, all organized to carry out specific tasks.

Organelles

• Key components found within cells
• Mitochondria are responsible for energy transactions
• Lysosomes digest unwanted materials within the cell.
• Endoplasmic reticulum and golgi apparatus play key roles in the internal organization of the cell, including synthesis, sorting of molecules.
• In plant cells, chloroplasts are used for photosynthesis (converting CO2 and H2O into carbohydrates using sunlight energy).
• The cytosol, the liquid part of cytoplasm, contains an organized cytoskeleton, giving the cell shape and enabling movement, is crucial for various metabolic pathways.
• Cells, whether animal, plant, or bacterial, demonstrate variations in their constituent organelle, which is well illustrated by diagrams and figures.

Cell Membrane

• The cell membrane is a crucial component of cell biology, serving as a protective boundary.
• It is primarily a phospholipid bilayer, controlling the passage of materials into and out of the cell.
• The membrane is semipermeable.

Nucleus

• The nucleus is a membrane-bound organelle that houses the cell's genetic material.
• The nucleus is a crucial component, including the nucleolus, chromosomes and chromatin
• Its major role is containing the genetic information necessary for cell growth and reproduction.

Endoplasmic Reticulum (ER)

• Rough ER contains ribosomes (sites of protein synthesis)
• Smooth ER plays a role in various metabolic processes such as lipid synthesis, detoxification.

Ribosomes

• Ribosomes are the protein synthesis machinery of a cell.
• They are responsible for reading mRNA and synthesizing proteins.

Golgi Apparatus

• Golgi complex plays a role in processing and sorting of molecules within cells
• Processes and modifies proteins, including the addition of sugar groups for proper function.

Lysosomes

• Membrane bound sacs which contain various hydrolytic enzymes.
• Responsible for breaking down and recycling cellular components.

Mitochondria

• Membranes contain folds (cristae), providing a large surface area for the cellular activities that take place inside the organelle.
• Contain their own DNA and ribosomes.
• Energy production is a major role of these organelles - Cellular respiration is used to convert nutrient energy into a usable energy form called ATP.

Centrosome (Centrioles)

• This is the central microtubule-organizing center, involved in cell division and movement.

Chloroplasts

• Found in plant cells
• Involved in photosynthesis, transforming light energy into chemical energy.

Peroxisomes

• Contain enzymes that detoxify harmful substances.
• Involved in breaking down fatty acids and certain amino acids.

Cell Cycle and Checkpoints

• The series of events a cell goes through to divide and produce two identical daughter cells
• Interphase, a preparatory phase that encompasses the G₁, S, and G₂ steps before mitosis.
• Mitosis, the division of the nucleus, and cytokinesis, the division of the cytoplasm.
• These phases include prophase, metaphase, anaphase and telophase
• Checkpoints are critical control mechanisms that ensure the cell cycle proceeds accurately.

Cell Death

• Apoptosis is a highly organized type of programmed cell death, crucial for development and maintaining homeostasis
• Necrosis is a more disordered form of cell death, often resulting from external factors—such as injury or damage.

Genes

• Oncogenes
• Genes that promotes cell division
• Tumor suppressor genes
• Genes that inhibit cell division

Enzymes

• Enzymes are protein catalysts that accelerate the rate of chemical reactions without being consumed in the process in the body.
• The presence of enzymes is critical for directing metabolic events and facilitating numerous biochemical pathways.
• They have an active site, which is a special pocket or cleft uniquely designed to bind substances (substrates) in specific ways, thus promoting reaction between the substrate molecules, that result in products.
• Enzymes exhibit a high level of specificity
• Enzymes usually have a specific coenzyme that facilitates proper function and is involved in the process.