1. The Cellular Level of Organization
Anatomy & Physiology – Honors

2. Essential Question
What are the essential functions of cells and cell organelles?
What is the basic function of the cell nucleus?

3. Contemporary Cell Theory
Cells are the building blocks of all plants and animals
Cells are produced by the division of pre-existing cells
Cells are the smallest units that perform all vital physiological functions
Each cell maintains homeostasis at the cellular level
Homeostasis at the tissue, organ, organ system, and organism levels reflect the combined and coordinated actions of many cells.

4. Studying Cells
Cytology is the study of the structure and function of cells
It is part of cell biology
The human body contains two types of cells
Sex cells
Sperm
oocytes
Somatic cells
All other cells

6. Cytoplasm – material between plasma membrane and the nucleus
Cytosol – largely water with dissolved protein, salts, sugars, and other solutes
Cytoplasmic organelles – metabolic machinery of the cell
Inclusions – chemical substances such as glycosomes, glycogen granules, and pigment

7. The Cytoplasm The Cytosol
The cytoplasm contains the fluid cytosol and the organelles the cytosol surrounds

8. Organelles Non-membrane organelles Not enclosed by membranes
Always in contact with the cytosol
Include the following:
Cytoskeleton
Microvilli
Centrioles
Cilia
Flagella
Ribosomes

9. Membranous organelles
surrounded by lipid membranes
Isolates them from the cytosol
Include the following:
Endoplasmic reticulum
Golgi apparatus
Lysosomes
Peroxisomes
Mitochondria

10. Cytoskeleton The “skeleton” of the cell
Gives cytoplasm strength & flexibility
Dynamic, elaborate series of rods running through the cytosol
Consists of microtubules, microfilaments, and intermediate filaments

11. Microfilaments Dynamic strands of the protein actin
Attached to the cytoplasmic side of the plasma membrane
Braces and strengthens the cell surface
Attach to CAMs and function in endocytosis and exocytosis
Functions of microfilaments
Anchor the cytoskeleton to integral membrane proteins
Interact with other filaments to produce cellular movement

12. Intermediate Filaments
Tough, insoluble protein fibers with high tensile strength
Resist pulling forces on the cell and help form desmosomes
Functions of intermediate filaments:
Provide strength
Stabilize position of other organelles
Transport materials within the cytoplasm

13. Microtubules
Dynamic, hollow tubes made of the spherical protein tubulin
Determine the overall shape of the cell and distribution of organelles
Functions of microtubules:
Provide cell strength, rigidity and anchoring organelles
Alter shape of cell, perhaps assisting with cell movement
Can relocate organelles within the cell
Form the spindle apparatus for cell division
Form centrioles, cilia and flagella

14. Thick filaments – made of myosin

15. Motor Molecules Protein complexes that function in motility
Powered by ATP
Attach to receptors on organelles

17. Microvilli Small projections of the cell membrane
Increase the surface area exposed to the extracellular environment
Usually located on cells that are involved in transporting substances across the cellular membrane from extracellular fluid
Microvilli contain microfilaments

18. Centrioles
Small barrel-shaped organelles located in the centrosome near the nucleus
Pinwheel array of nine triplets of microtubules
Organize mitotic spindle during mitosis
Direct movement of chromosomes during cell division
Organize the cytoskeleton
Centrosome is the cytoplasm surrounding the centrioles
Form the bases of cilia and flagella

20. Cilia Anchored by a Basal Body
Beat rhythmically to move fluids or secretions across the cell surface
Whiplike, motile cellular extensions on exposed surfaces of certain cells
Move substances in one direction across cell surfaces

22. Flagella
Move a cell through surrounding fluid rather than moving fluid past a stationary cell

23. Ribosome Intracellular factory Manufactures proteins
Composed of small and large ribosomal units
ribosomal RNA (rRNA)
Free Ribosomes are in the cytoplasm
Free ribosomes synthesize soluble proteins

24. Fixed Ribosomes are attached to the rough Endoplasmic Reticlum
Granules containing protein and rRNA
Site of protein synthesis
Membrane-bound ribosomes synthesize proteins to be incorporated into membranes

25. Endoplasmic Reticlum (ER)
Network of intracellular membranes that function in
Synthesis of proteins, carbohydrates and lipids
Storage of materials
Transport of materials within the cell
Detoxification of drugs or toxins
Forms
Hollow tubes
Flattened sheets
Round chambers called cisternae
Continuous with the nuclear membrane
Two varieties – rough ER and smooth ER

27. Rough Endoplasmic Reticulum (RER)
External surface studded with ribosomes
Manufactures all secreted proteins
Responsible for the synthesis of integral membrane proteins and phospholipids for cell membranes
Contains
ribosomes on its outer surface
forms transport vesicles
Functions specific to the RER
Synthesis and modification of proteins
Packaging proteins for transport to the Golgi

28. Tubules arranged in a looping network
Catalyzes the following reactions in various organs of the body
In the liver – lipid and cholesterol metabolism, breakdown of glycogen and, along with the kidneys, detoxification of drugs
In the testes – synthesis of steroid-based hormones
In the intestinal cells – absorption, synthesis, and transport of fats
In skeletal and cardiac muscle – storage and release of calcium

29. Smooth Endoplasmic Reticulum (SER)
Functions specific to the SER
- Synthesis of phospholipids and cholesterol
- Synthesis of steroid hormones, in gonads and adrenals
- Synthesis of storage of glycerides, in liver and fat cells
- Detoxification of drugs, in liver and kidney cells
- Synthesis and storage of glycogen, in muscle and liver cells

30. Golgi Apparatus Stacked and flattened membranous sacs
Functions in modification, concentration, and packaging of proteins
Transport vessels from the ER fuse with the cis face of the Golgi apparatus
Proteins then pass through the Golgi apparatus to the trans face
Secretory vesicles leave the trans face of the Golgi stack and move to designated parts of the cell

32. Secretions are discharged from the cell by exocytosis
Forms
secretory vesicels
new membrane components
packages lysosomes
Secretions are discharged from the cell by exocytosis
Functions of the Golgi include
Synthesis and packaging of secretions for exocytosis
Renewal or modification of the cell membrane
Packaging of enzymes for use in the cytosol

34. Lysosomes Spherical membranous bags containing digestive enzymes
Digest ingested bacteria, viruses, and toxins
Degrade nonfunctional organelles
Breakdown glycogen and release thyroid hormone
Breakdown nonuseful tissue
Breakdown bone to release Ca2+
Secretory lysosomes are found in white blood cells, immune cells, and melanocytes

36. Peroxisomes Membranous sacs containing oxidases and catalases
Carry enzymes that neutralize toxins
Neutralize dangerous free radicals
Free radicals – highly reactive chemicals with unpaired electrons (i.e., O2–)

37. Mitochondria Double membrane structure with shelflike cristae
Responsible for 95% of the ATP production in a typical cell
The matrix, or fluid contents of a mitrochondrion, lie inside the cristae, or folds of an inner membrane
Contain their own DNA and RNA

39. Nucleus
Contains nuclear envelope, nucleoli, chromatin, and distinct compartments rich in specific protein sets
Gene-containing control center of the cell
Contains the genetic library with blueprints for nearly all cellular proteins
Dictates the kinds and amounts of proteins to be synthesized

40. Nucleoli Dark-staining spherical bodies within the nucleus
Site of ribosome production

42. Nuclear Envelope
Selectively permeable double membrane barrier containing pores
Encloses jellylike nucleoplasm, which contains essential solutes
Outer membrane is continuous with the rough ER and is studded with ribosomes
Inner membrane is lined with the nuclear lamina, which maintains the shape of the nucleus
Pore complex regulates transport of large molecules into and out of the nucleus

43. Chromatin Threadlike strands of DNA and histones
Arranged in fundamental units called nucleosomes
Form condensed, barlike bodies of chromosomes when the nucleus starts to divide

44. Endomembrane System System of organelles that function to:
Produce, store, and export biological molecules
Degrade potentially harmful substances
System includes:
Nuclear envelope, smooth and rough ER, lysosomes, vacuoles, transport vesicles, Golgi apparatus, and the plasma membrane