1. Section 1.2 – 1.4 in your textbook
Cell Structures
Section 1.2 – 1.4 in your textbook

2. Overview
From the cell theory we know that cells are living units that make up living organisms
2 main types of cells:
Prokaryotic  bacteria
Eukaryotic  plants & animals
Prokaryotic cells are much simpler
than eukaryotic cells

4. Cell Structures in common…
Cell membrane: (membrane means “thin skin”)
Barrier/boundary  security guard
Keeps all of the “stuff” inside the cell
Lets nutrients & water in, lets waste out
Keeps harmful stuff out

5. More about the cell membrane…
Also called the “plasma membrane”
Selectively permeable
If it was impermeable  no movement of materials from inside of the cell to out & vice versa
If it was completely permeable  anything could get in & out!
“Lipid bi-layer” – two layers of fat molecules
Hydrophilic heads (love water)
Hydrophobic tails (hate water)
Embedded proteins – help move materials across the membrane

7. Nucleus Control center of the cell Contains DNA
Prokaryote  no “true” nucleus  DNA is floating free in the cell
Eukaryote  has a true nucleus, surrounded by the nuclear membrane  DNA in the nucleus

9. DNA Genetic information Deoxyribonucleic acid
“nucleic” means: found in the nucleus
Long chain molecule organized into threads called chromosomes, which have genes, which contain instructions for making proteins.
DNA can make copies of itself so the cell can divide!
Also found in the nucleus: RNA….
More about that later!

10. More terminology…
Protoplasm: all of the “stuff inside of the cell membrane.
Cytoplasm: everything inside of the cell membrane except the nucleus
where all the “action” happens...
Fluid + cell organelles + nutrients + waste
2 external structures:
Flagella  whip-like tails, used for propulsion
Cilia  short, hair-like, used for propulsion & to move materials around outside the cell

12. Cellular organelles
Small, specialized structures found in the cytoplasm
Visible only under an electron microscope

13. Mitochondria “Power Plant” of the cell
Provide the cell with energy through cellular respiration.
2 membranes: smooth outer & folded inner
Folds on the inner are called “cristae”
Enzymes on cristae speed up cellular respiration

14. Cellular respiration Happens in the mitochondria
Energy is released as ATP (adenosine triphosphate) & used by the cell for necessary processes of life
More active cells (like muscles) have more mitochondria than less active ones (like fat cells).

15. Ribosomes Site of protein synthesis Composed of RNA & proteins
Smallest organelles in the cytoplasm
Large number
Mainly found on the endoplasmic reticulum & the nuclear envelope

16. Endoplasmic reticulum
Network of interconnected parallel canals
Rough ER: has ribosomes attached, aids in production of proteins
Smooth ER: no ribosomes, where lipids are synthesized

17. Golgi apparatus
Looks like a stack of flattened balloons (membranous sacs)
Processes proteins from the Rough ER
Ends pinch off to form vesicles – last step before ejecting proteins from the cell to be used by the organism

18. Exocytosis
Vesicles from the Golgi apparatus fuse with the cell membrane and their contents (waste, hormones, enzymes, proteins) are released into the extracellular fluid.

19. Endocytosis Opposite of exocytosis
Vesicles formed for transport purposes.
Two types of endocytosis:
Pinocytosis refers to small particles (cell drinking)
Phagocytosis refers to ingestion of large molecules (cell eating)

21. Lysosomes Surrounded by a membrane Formed by the Golgi apparatus
Contain enzymes to break down molecules and discarded cell parts – “cellular digestion”
A build up of waste products (that are not broken down) can cause brain damage
Only found in animal cells

22. Microfilaments and microtubules
Microfilaments: fibrous structures that provide support, shape and movement for the cell
Microtubules: tiny tubes that transport materials in the cytoplasm
Collectively called the “cytoskeleton”

23. Chloroplasts
Plant cells produce and store their own food through the process of photosynthesis
Chloroplasts drive the process of photosynthesis
Contain a green pigment called chlorophyll
Only found in plant cells

24. Cell Wall Not found in animal cells Composed of cellulose
Protects and supports plant cells
Differing degrees of rigidity: flowers have thin cell walls, trees have thicker, secondary cell walls

25. Vacuole Plant cells have a large fluid filled space called a vacuole
Storage space: sugars, minerals, proteins, water
Found in the cytoplasm
Provides physical support for the cell: turgor pressure
Animal cells have smaller vacuoles (not used for physical support)