CELLS
1. Study of Life:
Difference between atoms, elements, molecules, and compounds:
-Atoms are the basic units of matter, consisting of protons, neutrons, and electrons.
-Elements are pure substances made up of only one type of atom. -
Molecules are formed when two or more atoms bond together, while compounds are molecules that
contain at least two different types of atoms.
Organic molecules in the human body:
The main organic molecules include carbohydrates, proteins, lipids, and nucleic acids.
Structure and function:
PROTEINS: Composed of amino acids; they perform a wide variety of functions, including catalyzing
reactions (enzymes), providing structure (collagen), and regulating processes (hormones).
CARBOHYDRATES: Made of sugar molecules; they provide energy (glucose) and structural support
(cellulose in plants).
LIPIDS: Composed of fatty acids and glycerol; they store energy, make up cell membranes, and serve as
signaling molecules (hormones).
NUCLEIC ACIDS: DNA and RNA, composed of nucleotides; they store genetic information and are involved
in protein synthesis.
2. NUCLEUS AND DNA:
o Cell components: A cell consists of a plasma membrane (outer boundary), cytoplasm (fluid inside),
nucleus (contains DNA), and organelles (specialized structures like mitochondria).
o Structure and function of the nucleus:
§ The nucleus contains the cell’s genetic material (DNA) and is responsible for
regulating gene expression and cell division.
o Structure of DNA:
§ DNA is a double helix composed of nucleotides, with a sugar-phosphate backbone
and nitrogenous bases (adenine, thymine, cytosine, guanine). DNA is stored as
chromatin within the nucleus.
DNA vs. RNA: DNA is double-stranded and contains deoxyribose
sugar; RNA is single-stranded and contains ribose sugar. RNA plays a
role in protein synthesis.
Protein generation process:
Transcription: The process of copying DNA to produce messenger
RNA (mRNA).
Translation: The process of decoding mRNA to assemble amino acids
into proteins.
, 3. CELLULAR ORGANELLES:
Cytoplasm structure and function:
The cytoplasm is a jelly-like fluid that fills the cell and contains organelles; it supports cellular structures and
facilitates biochemical reactions.
Roles of organelles:
-Ribosomes: Sites of protein synthesis.
-Endoplasmic reticulum (ER): Rough ER synthesizes
proteins, while Smooth ER synthesizes lipids and
detoxifies substances.
-Golgi apparatus: Modifies, sorts, and packages proteins
and lipids for secretion or use within the cell.
-Vacuoles/vesicles: Storage and transport of materials
within the cell.
-Mitochondria: Powerhouses of the cell; produce ATP
through cellular respiration.
-Lysosomes: Contain enzymes for digestion of waste
materials and cellular debris.
-Cytoskeleton: A network of protein filaments that provide structural support, aid in cell movement, and
play roles in intracellular transport.
4. CELL MEMBRANE:
Plasma membrane structure: Composed of a lipid bilayer with embedded proteins; it is selectively
permeable.
Roles of the plasma membrane: Protects the cell, facilitates communication, and regulates the movement
of substances in and out of the cell.
5. CELLULAR COMMUNICATION:
o Significance of cellular communication:
§ Essential for coordinating cellular activities, responding to environmental changes,
and maintaining homeostasis.
o Receptors and ligands:
§ Receptors are proteins on the cell surface that bind to signaling molecules (ligands)
to initiate a cellular response.
o Types of receptors and ligands:
§ Include ion channel receptors, G-protein coupled receptors, and enzyme-linked
receptors.
o Cellular signaling mechanisms:
§ Contact-dependent: Direct interaction between cells.
§ Autocrine: Cells respond to their own signals.
§ Paracrine: Signals affect nearby cells.
§ Endocrine: Hormones travel through the bloodstream to distant cells.
1. Study of Life:
Difference between atoms, elements, molecules, and compounds:
-Atoms are the basic units of matter, consisting of protons, neutrons, and electrons.
-Elements are pure substances made up of only one type of atom. -
Molecules are formed when two or more atoms bond together, while compounds are molecules that
contain at least two different types of atoms.
Organic molecules in the human body:
The main organic molecules include carbohydrates, proteins, lipids, and nucleic acids.
Structure and function:
PROTEINS: Composed of amino acids; they perform a wide variety of functions, including catalyzing
reactions (enzymes), providing structure (collagen), and regulating processes (hormones).
CARBOHYDRATES: Made of sugar molecules; they provide energy (glucose) and structural support
(cellulose in plants).
LIPIDS: Composed of fatty acids and glycerol; they store energy, make up cell membranes, and serve as
signaling molecules (hormones).
NUCLEIC ACIDS: DNA and RNA, composed of nucleotides; they store genetic information and are involved
in protein synthesis.
2. NUCLEUS AND DNA:
o Cell components: A cell consists of a plasma membrane (outer boundary), cytoplasm (fluid inside),
nucleus (contains DNA), and organelles (specialized structures like mitochondria).
o Structure and function of the nucleus:
§ The nucleus contains the cell’s genetic material (DNA) and is responsible for
regulating gene expression and cell division.
o Structure of DNA:
§ DNA is a double helix composed of nucleotides, with a sugar-phosphate backbone
and nitrogenous bases (adenine, thymine, cytosine, guanine). DNA is stored as
chromatin within the nucleus.
DNA vs. RNA: DNA is double-stranded and contains deoxyribose
sugar; RNA is single-stranded and contains ribose sugar. RNA plays a
role in protein synthesis.
Protein generation process:
Transcription: The process of copying DNA to produce messenger
RNA (mRNA).
Translation: The process of decoding mRNA to assemble amino acids
into proteins.
, 3. CELLULAR ORGANELLES:
Cytoplasm structure and function:
The cytoplasm is a jelly-like fluid that fills the cell and contains organelles; it supports cellular structures and
facilitates biochemical reactions.
Roles of organelles:
-Ribosomes: Sites of protein synthesis.
-Endoplasmic reticulum (ER): Rough ER synthesizes
proteins, while Smooth ER synthesizes lipids and
detoxifies substances.
-Golgi apparatus: Modifies, sorts, and packages proteins
and lipids for secretion or use within the cell.
-Vacuoles/vesicles: Storage and transport of materials
within the cell.
-Mitochondria: Powerhouses of the cell; produce ATP
through cellular respiration.
-Lysosomes: Contain enzymes for digestion of waste
materials and cellular debris.
-Cytoskeleton: A network of protein filaments that provide structural support, aid in cell movement, and
play roles in intracellular transport.
4. CELL MEMBRANE:
Plasma membrane structure: Composed of a lipid bilayer with embedded proteins; it is selectively
permeable.
Roles of the plasma membrane: Protects the cell, facilitates communication, and regulates the movement
of substances in and out of the cell.
5. CELLULAR COMMUNICATION:
o Significance of cellular communication:
§ Essential for coordinating cellular activities, responding to environmental changes,
and maintaining homeostasis.
o Receptors and ligands:
§ Receptors are proteins on the cell surface that bind to signaling molecules (ligands)
to initiate a cellular response.
o Types of receptors and ligands:
§ Include ion channel receptors, G-protein coupled receptors, and enzyme-linked
receptors.
o Cellular signaling mechanisms:
§ Contact-dependent: Direct interaction between cells.
§ Autocrine: Cells respond to their own signals.
§ Paracrine: Signals affect nearby cells.
§ Endocrine: Hormones travel through the bloodstream to distant cells.
