Lesson Topic 1.3: Structural and Functional Organization of Cells Flashcards
Cell Structure
Plasma membrane
Cytoplasm: cytosol + organelles
Nucleus
Cell Membrane Function
Barrier between inside and outside of cell
Controls entry of materials: transport
Receives chemical and mechanical signals
Transmits signals between intra- and extra- cellular spaces
Body Fluid Pools
Intracellular (ICF)
Within cells: 2/3 of total
Extracellular (ECF):
Between cells = Interstitial
In blood vessels = Plasma
In lymphatic vessels = Lymphatic
Solvent:
the liquid doing the dissolving
Usually water
Solute:
the dissolved material (particles or gas)
Concentration
Amount of solute in a given amount of solvent
Concentration gradient
Passive Transport
Requirements for simple diffusion
Concentration gradient of solute present
Solute can diffuse across a membrane if membrane is present
Passive transport
Pathways of simple diffusion:
Pass across lipid bilayer if lipid-soluble (O2, CO2, N2, fatty acids, steroids, fat-soluble vitamins), or if polar molecules (H2O, urea)
Pass through ion channels (which may be gated: gates open and close) if ions such as K+, Ca2+, Cl–
Facilitated Diffusion
Requires a carrier in membrane but not ATP
Solute goes down concentration gradient
Maximum transport speed depends on number of carriers
insulin increases number of carriers for glucose in
plasma membrane
Osmosis
Diffusion of water across selectively permeable membrane:
Permeable to solvent
Impermeable to solute
Types of solutions surrounding human RBCs
Isotonic: solution outside RBC has same concentration of solute as RBC: 0.9% NaCl
Hypotonic: solution outside of RBC has lower concentration: 0% NaCl hemolysis
Hypertonic: solution outside of RBC has higher concentration: 4% NaCl crenation
Active Transport
Requires a carrier (called a pump)
Requires energy (ATP)
Can transport up a concentration gradient
Critical for moving important ions
Major active transport in most cells is sodium-potassium (Na+/K+) pump
Transport in Vesicles
Requires energy (ATP)
Involves small membrane sac
Endocytosis: importing materials into cell
-Phagocytosis: ingestion of particles such as bacteria into white blood cells (WBCs)
-Pinocytosis: ingestion of fluid
Exocytosis: exporting materials
Cell Organelles: Table 3.2 Pg. 86
Cytoskeleton
Flagella, cilia & centrioles
Endoplasmic reticulum
Golgi apparatus
Mitochondrion
Nucleus, nucleolus, nuclear envelope
Vesicles, e.g. lysosome
Cytoplasm
Cell contents
Includes organelles and cytosol
Excludes nucleus
Cytoskeleton
Maintains shape of cell
Positions organelles
Changes cell shape
Includes: microfilaments, intermediate filaments, microtubules
Centrosome
Structure:
Two centrioles arranged perpendicular to each other
-Composed of microtubules: 9 clusters of 3 (triplets)
-Pericentriolar material
Composed of tubulin that grows the mitotic spindle
Function: moves chromosomes to ends of cell during cell division
Cilia and Flagella
Specialized for motion
Flagellum: single tail like structure on sperm
-Propels sperm forward in reproductive tract
Cilia: in groups
-Found in respiratory system: move mucus
Ribosomes
Made within the nucleus (in nucleolus)
Sites of protein synthesis (on E.R. or freely within cytoplasm)
Consist of ribosomal RNA (rRNA) + proteins
Contain large and small sub-units
Can be attached to endoplasmic reticulum or free in cytosol
Endoplasmic Reticulum (E.R.)
Structure: network of folded membranes
Functions: synthesis, intracellular transport
Types of E.R.
-Rough E.R.: studded with ribosomes (sites of protein synthesis)
-Smooth E.R. lacks ribosomes. Functions:
lipid synthesis
release of glucose in liver cells into bloodstream
drug detoxification (especially in liver cells)
storage and release of Ca2+ in muscle cells (where smooth E.R. is known as sarcoplasmic reticulum or SR)
Golgi Complex
Structure:
Flattened membranes (cisterns) with bulging edges (like stacks of pita bread)
Functions:
Modify proteins glycoproteins and lipoproteins that:
-Become parts of plasma membranes
-Are stored in lysosomes, or
-Are exported by exocytosis
Small Bodies
Lysosomes: contain digestive enzymes
-Help in final processes of digestion within cells
-Carry out autophagy (destruction of worn out parts of cell) and death of old cells (autolysis)
-Tay-Sachs: hereditary disorder; one missing lysosomal enzyme leads to nerve destruction
-Peroxisomes: detoxify; abundant in liver
-Proteasomes: digest excess or faulty proteins
Faulty proteins accumulate in brain cells in
persons with Parkinson or Alzheimer disease.
Mitochondria
Structure:
-Sausage-shaped with many folded membranes (cristae) and liquid matrix containing enzymes
-Have some DNA, ribosomes (can make proteins)
Function:
-Nutrient energy is released and trapped in ATP; so known as “power houses of cell”
-Chemical reactions require oxygen
Abundant in muscle, liver, and kidney cells
-These cells require much ATP
Nucleus
Round or oval structure surrounded by nuclear envelope with nuclear pores
Contains nucleolus: makes ribosomes that pass into cytoplasm through nuclear pores
Store genetic material (DNA) in genes arranged in 46 chromosomes (the human genome containing 30,000 genes!)
DNA contains information for directing protein synthesis:
-In this cell
-In new cells (formed by cell reproduction)
Cell Size and Shape
The body of an average human adult is composed of nearly 100 trillion cells. Cells vary considerably in size
The sizes of cells are measured in units called micrometers.
The largest cell, a single oocyte, has a diameter of about 140 μm and is barely visible to the unaided eye.
