The Structural Organization of Human cells (Cytoplasm)

Cytoplasm

Cytosol, Inclusions, Organelles. Includes all materials between plasma membrane and nucleus.

Cytosol

A viscous fluid containing water and many dissolved substances such as: ions, nutrients, proteins, carbohydrates, lipids, other small molecules

Inclusions

Some cells store this in their cytosol

Inclusions include chemicals like

Pigments (melanin in skin cells), nutrient stores (glycogen in muscle cells), protein crystals (dissolve proteins)

Organelles

Structures in cells that perform specific functions (the type and number of organelles reflect the cells’s function)

Membrane-bound organelles

Endoplasmic reticulum, golgi apparatus, lysosomes, peroxisomes, mitochondria. Contents are separate form cytosol

Non membrane-bound organelles

Ribosomes, cytoskeleton, centrosomes, centrioles, cilia, flagella, microvilli. Contents are in direct contact with cytosol

Specific Organelles

Endoplasmic Reticulum (ER), smooth ER (SER), rough ER (RER), golgi Apparatus, lysosomes, peroxisomes, mitochondria, ribosomes, cytoskeleton, centrosome and centrioles, cilia and flagella, microvilli

Endoplasmic Reticulum

Network of intracellular membrane bound tunnels. Enclosed spaces are called cisternae

Two types of Endoplasmic Reticulum

Smooth endoplasmic reticulum (SER), Rough endoplasmic reticulum (RER)

Smooth ER (SER)

Smooth due to lack of ribosomes, continuous with rough ER. Functions: Synthesis, transport, and storage of lipids including steroid hormones. Metabolism of carbohydrates, Detoxification of drugs, alcohol, and poisons.

Rough ER (RER)

Rough due to attachment of ribosomes outside membrane. RER receives newly synthesized proteins from ribosomes. Proteins will be secreted, inserted into plasma membrane or included in a lysosome. RER modifies proteins and package them into transport vesicles.

Golgi Apparatus

Receive material from ER for modification, sorting, and packaging (not producing anything just sending it off)

Lysosomes

Vesicles generated by golgi apparatus, contain enzymes used to digest and remove waste products and damaged organelles within the cell, when a cell is dying it releases lysosomal enzymes that digest the cell. (Job: Break down, cut or break down)

Peroxisomes

Sacs formed by pinching off from RER, smaller than lysosomes, detoxify harmful molecules in a cell, abundant in liver cells.

Mitochondria

Organelles with double membranes (Crisae), produce ATP, cells that require more energy (ex: muscle cells) have more mitochondria

Ribosomes

Responsible for protein synthesis, free ribosomes float in the cytosol, fixed ribosomes are attached to RER

Cytoskeleton

Proteins organized in the cytosol as solid filaments or hollow tubes. Three cytoskeleton components: Microfilament, intermediate filaments, microtubules

Centrosome

Centrosome: Contains centrioles. Non membranous, spherical structure adjacent to nucleus. Contains pair of centrioles at right angles to each other

Centriole

Attached to chromosomes during cell division causing chromosomal migration

Cilia and Flagella

Projections from cell containing cytoplasm and microtubules capable of movement

Cilia

On exposed surfaces of certain cells, move objects across their surface. (Ex: Cells of respiratory passage use cilia to move mucus

Flagella

Longer than cilia, usually singular whiplike tails (Ex: sperm)

Microvilli

Tiny projections from plasma membrane increase surface area for membrane transport (Ex: Small intestine - increase absorption of nutrients)