Cell Biology: Structure and Types

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

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 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

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 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

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

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

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.

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).

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.