Introduction to Biochemistry Overview

Course Information

• Course title: Introduction to Biochemistry & Cell Medical Biochemistry
• Instructor: Dr Lina Yousif Mohammed
• Email: [email protected]
• Academic Year: 2024-2025
• Semester: First

Session One: Introduction to Biochemistry - Aims

• The course provides a basic understanding of biochemistry's core principles and experimental basis.
• Students will gain specialized knowledge and understanding of selected aspects through branch lecture series.

Learning Outcomes

• Students demonstrate advanced knowledge and understanding in these core areas:
  • Structures and functions of prokaryotic and eukaryotic cells, focusing on macromolecules, membranes, and organelles.
  • Utilization of cellular components for energy generation and utilization.
  • Cellular components underlying mitotic cell division.

What is Biochemistry?

• Biochemistry, also called biological chemistry, is the study of chemical processes within and relating to living organisms.
• Biochemical processes create life's complexity.
• Biochemistry is divided into three fields: Molecular genetics, Protein science, and Metabolism.

What Types of Molecules Do Biochemists Study?

• Biochemists study the structures, functions, and interactions of biological macromolecules (proteins, nucleic acids, carbohydrates, and lipids).
• These molecules form the structure of cells and perform vital life functions.

Introduction to Cells

• The word "cell" comes from the Latin "cellula," meaning "small room."

• The study of cells is called cytology.

  • Robert Hooke first used the term "cell."
  • Robert Brown discovered the nucleus in 1833.
  • Theodor Schwann discovered that animals are made of cells in 1838.

• Cell Theory:

  • All living things are made of cells.
  • Cells are the smallest functional units of living things.
  • All cells come from pre-existing cells through cell division.

Examples of Cells

• Cells are the smallest units capable of performing life functions. Examples include Amoeba Proteus, Plant Stem, Bacteria, Nerve Cell, and Red Blood Cell are shown.

Types of Cells

• The biological world includes two cell types:
  • Prokaryotic cells: Single, closed compartments with plasma membranes; lack a defined nucleus; simple internal organization; examples include Bacteria and Blue-green algae.
  • Eukaryotic cells: Contain a defined membrane-bound nucleus and extensive internal membranes enclosing compartments; examples include fungi, plants, and animals (including unicellular yeast).
  • Cytoplasm: The region between the plasma membrane and the nucleus, composed of cytosol (liquid) and organelles. Eukaryotic cells have more complex internal organization.

Biological Membranes

• Membranes form the boundaries of cells/organelles.
• Plasma membranes are selectively permeable, controlling movement of molecules into and out of the cell.
• The structure is a phospholipid bilayer with embedded proteins. Protein structure/arrangement dictates cell function. Specific proteins may be embedded entirely (transmembrane) or attached in various ways.

Components of Biological Membranes - Lipids

• Lipids are the most abundant membrane component (40-80%).
• Phospholipids are the prevalent lipid type, having both hydrophilic "heads" and hydrophobic "tails."
  • The hydrophilic portion contains a phosphate and an attached alcohol.
  • The hydrophobic portion is composed of fatty acid tails (hydrocarbons).
• Cholesterol: An amphipathic molecule that intercalates (inserts) between phospholipids.
  • Cholesterol's polar hydroxyl group faces the phospholipid head groups.
  • The steroid ring and hydrocarbon tails are oriented parallel to the phospholipids, modifying the membrane's fluidity.
• Glycolipids: Lipids with attached carbohydrates (found in lower concentrations); carbohydrates project into the environment and mediate cell-cell interactions.

Components of Biological Membranes - Proteins

• Proteins are involved in many membrane functions.
• Types of membrane proteins vary by cell type.
  • Transmembrane proteins: Span the membrane; hydrophilic portions face the inner and outer environments, and hydrophobic portions interact with the fatty acid tails.
  • Lipid-anchored proteins: Covalently attached to lipids in the membrane. They are integral membrane proteins.
  • Peripheral membrane proteins: Located on the cytosolic side of the membrane; bound to other proteins attached to lipids.

Cell Wall

• Bacteria and plant cells have cell walls outside their plasma membranes.

• Structure:

  • Outermost, nonliving layer.
  • Secreted by the cell itself
  • Plant cell walls are mainly cellulose, sometimes with other components like pectin and lignin.

• Functions

  • The cell wall protects internal parts and gives the cell its shape.
  • It allows for the passage of water and chemicals in and out of the cell.

Transport across Membranes

• Substances like glucose, amino acids, water, and mineral ions can be transported across a cell's plasma membrane by diffusion, osmosis, and active transport.
  • Diffusion: Movement of molecules from high to low concentration (no energy required).
  • Osmosis: Movement of water from high to low concentration (across a semipermeable membrane; no energy required).
  • Active transport: Movement of molecules against a concentration gradient (energy required).

Transport of Large Molecules (Bulk Transport)

• Endocytosis: The cell takes in large molecules.
• Exocytosis: The cell releases large molecules.
  • Phagocytosis: Ingesting solid particles.
  • Pinocytosis: Ingesting liquid droplets.

Organelles

• Organelles are complex intracellular compartments, enclosed by membranes, where processes essential for eukaryotic cell life take place.
• The membranes have the same basic components as plasma membranes.
• Organelles are fixed in place supported by the cytoskeleton.

Nucleus

• All eukaryotic cells (except mature red blood cells) have a nucleus.
• The nucleus stores the cell's genomic DNA.
• The nuclear envelope is a double lipid bilayer with pores that allow material exchange between the nucleus and the cytosol.
• The inside is the nucleoplasm where DNA is located.
• The nucleolus is a suborganelle that produces ribosomes.

Ribosomes

• Ribosomes are protein synthesis machinery.
• Composed primarily of proteins and ribosomal RNA (rRNA).
• Found within the cytosol (free ribosomes) or attached to the endoplasmic reticulum (bound ribosomes).

Endoplasmic Reticulum (ER)

• ER forms a network of membranous sacs; interacts with the nuclear envelope.
  • Rough ER (rER): Has ribosomes attached and is involved in protein production and modification.
  • Smooth ER (sER): Lacks ribosomes and performs tasks like lipid synthesis and carbohydrate addition to proteins (glycosylation).

Golgi Complex

• Golgi complex appears as flat, stacked, membrane-bound sacs.
• Three regions: cis (closest to ER), medial, trans (closest to plasma membrane).
• Modifies and packages proteins

Mitochondria and Chloroplasts (Energy Transformers)

• Mitochondria:
  • Double phospholipid bilayer membrane.
  • Inner membrane folds (cristae) increase surface area for ATP production.
  • Site of cellular respiration for ATP production from breakdown of carbohydrates and lipids.
• Plastids (plants only):
  • Chloroplasts: Sites of photosynthesis; found in green plant cells.
  • Outer and inner membranes.
  • Thylakoid sacs (inside) to trap solar energy.

Microbodies (Tiny But Important)

• Small, sac-like organelles enclosed by a membrane. Examples include lysosomes, peroxisomes, and glyoxysomes.
  • Lysosomes: Contain acid hydrolases (digestive enzymes). Break down macromolecules (proteins, lipids, carbohydrates).
  • Peroxisomes: Contain enzymes for various metabolic reactions, including the breakdown of fatty acids and detoxification.
  • Glyoxysomes: Primarily in plant cells; contain enzymes for converting lipids to carbohydrates; critical during germination.

Cilia and Flagella (Organelles for Mobility)

• Short, hair-like projections (cilia) or longer whip-like extensions (flagella).
• Move cells/move substances along cell surface (such as mucus).
• Composed of contractile protein tubulin (microtubules).
• Arrangements of microtubules (9 + 2) are a key structure feature.

Centrioles

• Cylindrical structures in animal cells (not in Amoeba)
• 9 sets of 3 microtubules arranged.
• Involved in cell division to help form mitotic spindle.

Vacuoles

• Membrane-bound sacs in cells.
• Help plants maintain structure and shape.
• Store substances; can have catalytic/digestive functions. Plant cells often have a large central vacuole.

Cytoskeleton

• Complex network of protein filaments (actin, intermediate filaments, microtubules).
• Provides support, structure, and facilitates cell transport.

Molecules of the Cell

• The cell and its structures consist of different types of molecules including water and minerals in addition to organic molecules like proteins, carbohydrates, nucleic acids and fats.

Elements Necessary for Life

• Necessary for organic compound formation within cells.
• Act as cations and anions.
• Critical for energy transfer and enzyme function.

Carbohydrates

• Main function: Energy source or storage, or structural components.
• Most common: Glucose
• Polysaccharide examples: starch (plants), glycogen (animals), and cellulose (plant cell walls)

Proteins

• Composed of amino acids linked by peptide bonds.
• Numerous diverse roles; structural components, enzymes, transport proteins

Nucleic Acids

• Deoxyribonucleic acid (DNA), ribonucleic acid (RNA)
• DNA: Stores genetic information; RNA: Processes genetic information for protein synthesis. Their chemical components and structures are explained.

Lipids

• Composed of C, H, O - low amounts of oxygen.
• Include fats, oils, and phospholipids.
• Primary function is energy storage, but also significant component of cell membranes. These key molecules are vital components of life.

This quiz will assess your understanding of the fundamental principles and concepts covered in the introduction to biochemistry course. You will explore cellular structures, functions, and the chemical processes that occur within living organisms. Test your knowledge on macromolecules, energy utilization, and cell division mechanisms.