Cell Biology: Structure and Types

Cells

• Cell Structure:
  • Cell membrane: semi-permeable membrane that separates the cell from its environment
  • Cytoplasm: jelly-like substance inside the cell membrane where metabolic processes occur
  • Nucleus: control center of the cell where DNA is stored
  • Mitochondria: organelles responsible for generating energy for the cell
  • Endoplasmic reticulum: organelle involved in protein synthesis and transport
• Cell Types:
  • Prokaryotic cells: lack a true nucleus, typically found in bacteria
  • Eukaryotic cells: have a true nucleus, found in plants, animals, fungi, and protists
• Cell Functions:
  • Metabolism: cells carry out chemical reactions to sustain life
  • Growth and development: cells grow, divide, and differentiate to form tissues and organs
  • Response to stimuli: cells respond to internal and external stimuli
  • Reproduction: cells divide to produce new cells

Genetics

• DNA Structure:
  • Double helix model: two strands of nucleotides twisted together
  • Nucleotides: building blocks of DNA, composed of sugar, phosphate, and nitrogenous bases
  • Nitrogenous bases: adenine (A), guanine (G), cytosine (C), and thymine (T)
• Genetic Code:
  • Triplet code: sequence of three nucleotides that codes for an amino acid
  • Codons: sequences of nucleotides that specify amino acids
  • Start and stop codons: regulate protein synthesis
• Genetic Inheritance:
  • Mendel's laws: laws of segregation, independent assortment, and dominance
  • Dominant and recessive alleles: different forms of a gene
  • Genotype: genetic makeup of an individual
  • Phenotype: physical expression of an individual's genotype
• Genetic Variation:
  • Mutation: change in the DNA sequence
  • Genetic recombination: shuffling of genetic material during reproduction
  • Gene expression: process by which genetic information is converted into a phenotype

Cell Structure and Functions

• Cell membrane is semi-permeable, separating the cell from its environment
• Cytoplasm is a jelly-like substance inside the cell membrane where metabolic processes occur
• Nucleus is the control center of the cell where DNA is stored
• Mitochondria are organelles responsible for generating energy for the cell
• Endoplasmic reticulum is an organelle involved in protein synthesis and transport
• Cells carry out chemical reactions to sustain life through metabolism
• Cells grow, divide, and differentiate to form tissues and organs through growth and development
• Cells respond to internal and external stimuli through response to stimuli
• Cells divide to produce new cells through reproduction

Cell Types

• Prokaryotic cells lack a true nucleus and are typically found in bacteria
• Eukaryotic cells have a true nucleus and are found in plants, animals, fungi, and protists

DNA Structure and Genetic Code

• DNA is structured as a double helix model with two strands of nucleotides twisted together
• Nucleotides are the building blocks of DNA, composed of sugar, phosphate, and nitrogenous bases
• Nitrogenous bases are adenine (A), guanine (G), cytosine (C), and thymine (T)
• The genetic code is based on a triplet code, where a sequence of three nucleotides codes for an amino acid
• Codons are sequences of nucleotides that specify amino acids
• Start and stop codons regulate protein synthesis

Genetic Inheritance

• Mendel's laws of segregation, independent assortment, and dominance explain how genes are inherited
• Dominant and recessive alleles are different forms of a gene
• Genotype refers to the genetic makeup of an individual
• Phenotype refers to the physical expression of an individual's genotype

Genetic Variation

• Mutation is a change in the DNA sequence
• Genetic recombination is the shuffling of genetic material during reproduction
• Gene expression is the process by which genetic information is converted into a phenotype

Cell Structure

• Plasma Membrane: a semi-permeable membrane that surrounds the cell, regulating what enters and leaves the cell, and maintaining cell shape.
• Cytoplasm: a jelly-like substance inside the cell membrane, comprising water, salts, sugars, and various organelles, providing a medium for metabolic reactions.
• Cytosol: the fluid component of cytoplasm, where many metabolic reactions occur, such as protein synthesis and degradation.
• Organelles: specialized structures within the cell that perform specific functions, including:
  • Nucleus: contains genetic material (DNA), controlling cell growth and reproduction, and regulating gene expression.
  • Mitochondria: generates energy for the cell through cellular respiration, using oxygen to convert glucose into ATP.
  • Endoplasmic Reticulum (ER): involved in protein synthesis, folding, and transport, with two types: rough ER (with ribosomes) and smooth ER (without ribosomes).
  • Ribosomes: site of protein synthesis, reading mRNA sequences to assemble amino acids into polypeptide chains.
  • Lysosomes: contains digestive enzymes, breaking down and recycling cellular waste and foreign substances, maintaining cellular homeostasis.
  • Golgi Apparatus: involved in protein modification, sorting, and transport, adding carbohydrates and lipids to proteins and lipids to form glycoproteins and lipoproteins.

Cell Functions

• Metabolism: chemical reactions that occur within the cell, including energy production (catabolism) and consumption (anabolism), such as glycolysis, Krebs cycle, and fatty acid oxidation.
• Growth and Development: cell growth, division, and differentiation, involving DNA replication, mitosis, and cytokinesis.
• Response to Stimuli: cells respond to changes in their environment, such as light, temperature, and touch, through signal transduction pathways and gene expression.
• Reproduction: cells divide to produce new cells, ensuring the continuation of life, through mitosis (somatic cells) and meiosis (gametes).

Cell Types

• Prokaryotic Cells: lack a true nucleus, typically small and simple, with a single circular chromosome, e.g., bacteria, archaea, and blue-green algae.
• Eukaryotic Cells: have a true nucleus, typically larger and more complex, with linear chromosomes, e.g., plants, animals, fungi, and protists.
• Stem Cells: undifferentiated cells that can develop into different cell types, having the ability to self-renew and differentiate into specialized cells.
• Specialized Cells: cells that have specific functions, such as:
  • Nerve Cells: transmit and process information through electrical and chemical signals.
  • Muscle Cells: contract and relax to produce movement, maintaining posture, and regulating body temperature.
  • Blood Cells: transport oxygen, nutrients, and waste products, and play a role in immune responses.