Cell Structure and Function Quiz

Structure of the Cell

• Composed of a cell membrane, cytoplasm, and various organelles.
• Organelles classified into two categories:
  • With limiting membrane: nucleus, mitochondria, Golgi apparatus, lysosomes, peroxisomes, endoplasmic reticulum (smooth and rough), secretory vesicles.
  • Without limiting membrane: ribosomes, centrosome, cytoskeleton.

Cell

• Defined as the basic structural and functional unit of all living organisms.
• Each cell displays all characteristics of life.

Tissue

• Tissue consists of groups of similar function cells.
• Four primary tissue types:
  • Epithelial: includes squamous, columnar, cuboidal cells.
  • Connective: encompasses connective tissue proper, cartilage, bone, and blood.
  • Muscle: made up of skeletal, smooth, and cardiac muscle.
  • Nervous: formed by neurons and supporting cells.

Organ

• Comprises two or more types of primary tissues.
• Organs can be tubular (like intestines) or hollow (like the stomach).

System

• A system is a group of organs that collaborate to perform specific functions.
• Major body systems:
  • Digestive system: digestion of food.
  • Cardiovascular system: transport of substances.
  • Respiratory system: oxygen supply and carbon dioxide removal.
  • Endocrine system: growth regulation and maintenance of body functions.
  • Nervous system: controls movement and intellectual tasks.

Cell Membrane

• Serves as a protective barrier for the cell.
• Separates extracellular fluid (ECF) from intracellular fluid (ICF).
• Semipermeable, allowing selective exchange of substances.

Composition of Cell Membrane

• Constructed as a three-layered unit membrane:
  • Central electron-lucent lipid bilayer.
  • Flanked by two electron-dense protein layers.
• Surface features carbohydrate molecules contributing to cell signaling.

Lipid Layer of the Cell Membrane

• Composed mainly of phospholipids and cholesterol.
• Phospholipids are amphipathic, featuring a hydrophilic head and hydrophobic tails.

Protein Layers of the Cell Membrane

• Protein types:
  • Integral proteins: span the membrane, provide structural integrity.
  • Peripheral proteins: partially embed in the membrane, offering flexibility.

Functions of Protein Layers

• Facilitate transport of substances.
• Integral proteins maintain membrane structure.
• Channel and carrier proteins assist in active and passive transport.

Carbohydrates of the Cell Membrane

• Located on the membrane surface, forming glycoproteins and glycolipids.
• Role in cell signaling, adhesion, and forming a protective glycocalyx.

Functions of Cell Membrane

• Acts as a barrier, protects internal components.
• Regulates entry and exit of nutrients and wastes.
• Facilitates gas exchange.
• Maintains cell shape and size.

Cytoplasm

• Contains a fluid medium (cytosol) within cells.
• Hosts organelles crucial for cell function and metabolism.

Organelles in Cytoplasm

• Rough Endoplasmic Reticulum (RER): involved in protein synthesis.
• Smooth Endoplasmic Reticulum (SER): lipid synthesis, detoxification, calcium storage.
• Golgi Apparatus: processes, packages, and transports proteins and lipids.
• Lysosomes: degrade macromolecules and worn-out organelles.
• Peroxisomes: break down fatty acids, detoxify harmful substances.
• Mitochondria: produce energy (ATP) through respiration.

Functions of Major Organelles

• Rough Endoplasmic Reticulum: synthesizes proteins, engages in autophagy.
• Smooth Endoplasmic Reticulum: synthesizes lipids, detoxifies harmful substances.
• Golgi Apparatus: processes, sorts, and ships cellular products.
• Lysosomes: digest macromolecules and recycle cellular components.
• Mitochondria: powerhouse of the cell, generating ATP.

Nucleus

• Largest organelle, controls cellular activities.
• Enclosed by a double-layered nuclear membrane, contains nucleoplasm and chromatin.
• Chromatin condenses into chromosomes during cell division.
• Responsible for storing genetic material and regulating gene expression.

Chromosomes and Genes

• Chromosomes carry hereditary information, formed from DNA.
• Diploid cells contain 23 pairs of chromosomes; haploid cells have 23 single chromosomes.
• Genetic material includes sex chromosomes (X, Y) and autosomes (22 pairs).

Functions of the Nucleus

• Coordinating cellular activities, such as growth and reproduction.
• Storing and transmitting genetic information.

Summary

• The cell is the fundamental unit of life, organized into tissues, organs, and systems performing specialized functions.
• Organelles have distinct structures and roles, essential for maintaining cellular health and functionality.### Functions of Nucleus
• Controls cellular activities such as metabolism, protein synthesis, growth, and reproduction (cell division).
• Synthesizes ribonucleic acid (RNA) and forms subunits of ribosomes.
• Sends genetic instructions to cytoplasm via messenger RNA (mRNA) for protein synthesis.
• Regulates cell division through genes.
• Stores hereditary information in genes and transfers it across generations.

Structure of Nucleus

Nuclear Membrane

• Composed of a double-layered membrane, known as the nuclear membrane.
• Encloses nucleoplasm, allowing communication with the cytoplasm due to its porous and permeable nature.

Nucleoplasm

• A viscous fluid similar to cytoplasm, surrounding chromatin and nucleolus.

Chromatin

• Thread-like material made from deoxyribonucleic acid (DNA).
• DNA is compacted with histone proteins, forming the bulk of nuclear material.
• Condenses into chromosomes during cell division.

Deoxyribonucleic Acid (DNA)

• Nucleic acid that carries genetic information, forming the basis of hereditary traits.
• Contains instructions for protein synthesis; genes are segments of DNA.
• Composed of two strands forming a double helix, with a backbone of deoxyribose and phosphate.
• Base pairs include adenine (A) with thymine (T) and cytosine (C) with guanine (G).

Gene

• Basic hereditary unit that encodes for specific proteins, acting as a "book" for protein synthesis.

Ribonucleic Acid (RNA)

• A long chain of nucleotides formed from DNA, used to carry genetic information.

Types of RNA

• Messenger RNA (mRNA): Carries the code for protein synthesis.
• Transfer RNA (tRNA): Transfers the code from mRNA to ribosome.
• Ribosomal RNA (rRNA): Integrates into ribosome structure and aids in assembling proteins.

Genetic Disorders

• Result from absent or defective genes or chromosomal abnormalities, examples include hemophilia, cystic fibrosis, and diabetes.

Chromosomal Disorders

• Arise from chromosomal abnormalities, either structurally or numerically.

Gene Expression

• Process where genetic information is converted into functional products (RNA/proteins).
• Comprises two main phases: transcription and translation.

Transcription of Genetic Code

• Involves copying DNA code to form mRNA, essential for protein synthesis in ribosomes.

Translation of Genetic Code

• Process where ribosomes synthesize proteins using instructions from mRNA, interpreting the genetic code.

Cell Death

• Occurs through programmed methods and accidental damage; main types include:
  • Apoptosis: Programmed cell death, essential for normal development.
  • Necrosis: Uncontrolled cell death due to injury or other external factors, leading to inflammation.

Cell Junctions

• Connections between neighboring cells and the extracellular matrix, categorized into:
  • Occluding Junctions: Prevent passage of molecules, primarily tight junctions.
  • Communicating Junctions and Anchoring Junctions are other classifications.

Tight Junctions

• Formed by fusion of adjacent cell membranes, creating a seal to prevent molecule passage.
• Found in epithelial cells, renal tubules, and choroid plexus, involving proteins like JAMs and cingulin.

Test your understanding of cell structure, including the various components like the cell membrane, organelles, and genetic material. This quiz covers essential concepts related to the building blocks of life and their functions within living organisms.