172d ago

Chapter ll: Anatomy

Overview of Cells

  • Cells are the smallest living units in the human body.

  • The human body contains approximately 50 to 100 trillion cells.

Main Components of Cells

  • Nucleus: Contains genetic material (DNA) and controls cellular activities.

  • Cytoplasm: The space between the plasma membrane and nucleus, containing organelles and cytosol (fluid).

  • Plasma Membrane: Outer boundary of the cell, regulates what enters and exits the cell.

Types of Cells and Differentiation

  • Different cells exhibit various structures and functions due to gene expression.

  • All cells contain identical DNA, but different genes are expressed in different cell types, leading to cell differentiation.

Cell Sizes

  • Most plant and animal cells are between 10 to 100 micrometers.

  • Red blood cells are smaller, while some cells like human oocytes and muscle fibers can be quite large.

Organelle Functions

  1. Endoplasmic Reticulum (ER): Network of membranes; Rough ER has ribosomes for protein synthesis, while Smooth ER is involved in detoxification.

  2. Golgi Apparatus: Packages and distributes proteins and lipids synthesized in the ER.

  3. Lysosomes: Contain enzymes to digest cellular waste and debris.

  4. Peroxisomes: Contain enzymes that neutralize free radicals and detoxify substances.

  5. Mitochondria: The powerhouse of the cell; generates ATP through cellular respiration.

  6. Ribosomes: Sites of protein synthesis, made of rRNA and proteins.

  7. Cytoskeleton: Structural framework of the cell, aids in cell division and movement of organelles.

Membrane Structure

  • Fluids Mosaic Model: Plasma membrane consists of a phospholipid bilayer with embedded proteins, cholesterol, and carbohydrates.

  • Integral Proteins: Span the membrane and function in transport and cell signaling.

  • Peripheral Proteins: Attached loosely to the membrane and are involved in cellular signaling and structural support.

Transport Mechanisms

  1. Simple Diffusion: Movement of molecules down their concentration gradients without energy.

  2. Osmosis: Diffusion of water across a membrane.

  3. Facilitated Diffusion: Movement through protein channels; does not require energy.

  4. Active Transport: Movement of molecules against their concentration gradient, requires energy (e.g., sodium-potassium pump).

Exocytosis and Endocytosis

  • Exocytosis: Process to move materials out of the cell.

  • Endocytosis: Process of taking materials into the cell, including phagocytosis (cell eating) and pinocytosis (cell drinking).

Nucleus Structure and Function

  • Nuclear Envelope: Double membrane with pores that regulate the passage of molecules.

  • Nucleolus: Site of ribosome production within the nucleus.

  • Chromatin & Chromosomes: DNA exists as chromatin when the cell is not dividing and condenses into chromosomes during cell division.

The Cell Cycle

  • Interphase: Consists of G1 (growth), S (DNA synthesis), and G2 (preparation for division).

  • M Phase: Includes mitosis (division of nucleus) and cytokinesis (division of cytoplasm).

    • Stages of Mitosis: Prophase, Metaphase, Anaphase, Telophase.

Cell Aging and Death

  • Aging can result from various factors including wear and tear and a decrease in mitochondrial function.

  • Cell death can occur through necrosis (due to damage) or apoptosis (programmed cell death).


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Chapter ll: Anatomy

Overview of Cells

  • Cells are the smallest living units in the human body.

  • The human body contains approximately 50 to 100 trillion cells.

Main Components of Cells

  • Nucleus: Contains genetic material (DNA) and controls cellular activities.

  • Cytoplasm: The space between the plasma membrane and nucleus, containing organelles and cytosol (fluid).

  • Plasma Membrane: Outer boundary of the cell, regulates what enters and exits the cell.

Types of Cells and Differentiation

  • Different cells exhibit various structures and functions due to gene expression.

  • All cells contain identical DNA, but different genes are expressed in different cell types, leading to cell differentiation.

Cell Sizes

  • Most plant and animal cells are between 10 to 100 micrometers.

  • Red blood cells are smaller, while some cells like human oocytes and muscle fibers can be quite large.

Organelle Functions

  1. Endoplasmic Reticulum (ER): Network of membranes; Rough ER has ribosomes for protein synthesis, while Smooth ER is involved in detoxification.

  2. Golgi Apparatus: Packages and distributes proteins and lipids synthesized in the ER.

  3. Lysosomes: Contain enzymes to digest cellular waste and debris.

  4. Peroxisomes: Contain enzymes that neutralize free radicals and detoxify substances.

  5. Mitochondria: The powerhouse of the cell; generates ATP through cellular respiration.

  6. Ribosomes: Sites of protein synthesis, made of rRNA and proteins.

  7. Cytoskeleton: Structural framework of the cell, aids in cell division and movement of organelles.

Membrane Structure

  • Fluids Mosaic Model: Plasma membrane consists of a phospholipid bilayer with embedded proteins, cholesterol, and carbohydrates.

  • Integral Proteins: Span the membrane and function in transport and cell signaling.

  • Peripheral Proteins: Attached loosely to the membrane and are involved in cellular signaling and structural support.

Transport Mechanisms

  1. Simple Diffusion: Movement of molecules down their concentration gradients without energy.

  2. Osmosis: Diffusion of water across a membrane.

  3. Facilitated Diffusion: Movement through protein channels; does not require energy.

  4. Active Transport: Movement of molecules against their concentration gradient, requires energy (e.g., sodium-potassium pump).

Exocytosis and Endocytosis

  • Exocytosis: Process to move materials out of the cell.

  • Endocytosis: Process of taking materials into the cell, including phagocytosis (cell eating) and pinocytosis (cell drinking).

Nucleus Structure and Function

  • Nuclear Envelope: Double membrane with pores that regulate the passage of molecules.

  • Nucleolus: Site of ribosome production within the nucleus.

  • Chromatin & Chromosomes: DNA exists as chromatin when the cell is not dividing and condenses into chromosomes during cell division.

The Cell Cycle

  • Interphase: Consists of G1 (growth), S (DNA synthesis), and G2 (preparation for division).

  • M Phase: Includes mitosis (division of nucleus) and cytokinesis (division of cytoplasm).

    • Stages of Mitosis: Prophase, Metaphase, Anaphase, Telophase.

Cell Aging and Death

  • Aging can result from various factors including wear and tear and a decrease in mitochondrial function.

  • Cell death can occur through necrosis (due to damage) or apoptosis (programmed cell death).