1. Cells

2. Discovery of the Cell
In 1665, Robert Hooke was one of the first people to see and identify cells.
He used a microscope to look at thin slices of cork. The cork was made of thousands of tiny chambers.
He called the chambers “cells” b/c they reminded him of a monastery’s tiny rooms, called cells.

3. Robert Hooke

4. The Cell Theory Proposed by 3 scientists in the mid-1800’s
All living things are made of cells.
Cells are the basic unit of structure and function in living things.
New cells are produced from existing cells.
The cell theory applies to ALL living things!

5. Prokaryotes and Eukaryotes
Do not have a nucleus
Small and simple
Bacteria are prokaryotic
Eukaryotes
Have a nucleus
Larger and complex
Cells of protists, fungi, plants, and animals are eukaryotic

6. Prokaryotes and Eukaryotes
Prokaryotic Cell
Eukaryotic Cell

7. Cell Structure
Eukaryotic cells are divided into two major parts – the nucleus and the cytoplasm.
The cytoplasm is the portion of the cell outside the nucleus, but inside the cell membrane.

8. Cell Structure
Eukaryotic cells contain many structures, each with specialized functions. These specialized structures are called organelles.

9. Cell Structure - Nucleus
Contains almost all of the cell’s DNA; the DNA contains genetic info and instructions for making proteins
Controls the cell’s processes/activities
The DNA exists as chromatin when the cell isn’t dividing. Chromatin consists of DNA and protein.
Double membrane

10. Cell Structure - Nucleolus
Inside the nucleus is a structure called the nucleolus.
The nucleolus manufactures ribosomes.

11. Cell Structure - Ribosomes
Ribosomes are tiny organelles that manufacture proteins.
Ribosomes are located on rough endoplasmic reticulum and throughout the cytoplasm.

12. Cell Structure – Endoplasmic Reticulum
ER transports substances throughout the cell.
Rough ER has ribosomes on it, so it produces proteins.
Smooth ER lacks ribosomes

13. Cell Structure – Golgi Apparatus
Closely-stacked membranes
Modify, sort, and package proteins and other materials from the endoplasmic reticulum for storage in the cell, or secretion outside the cell.

14. Cell Structure - Lysosomes
Lysomes are small sacs filled with digestive enzymes.
These enzymes break down macromolecules into small molecules .
They also break down old, worn-out organelles. They “clean up” the cell.

15. Cell Structure - Vacuole
Large sac-like organelle in plant cells
Stores water, carbs, proteins, and salts
Is usually the largest organelle in plant cells

16. Cell Structure - Mitochondria
Convert the chemical energy stored in food into compounds that are more convenient for the cell to use.
“Powerhouse” of the cell
Double membrane

17. Cell Structure - Chloroplasts
Not found in animal or fungi cells
Capture energy from sunlight and convert it into chemical energy in a process called photosynthesis.
Double membrane

18. Cell Structure - Cytoskeleton
In all cells, the cytoskeleton maintains the shape of the cell
Cilia and flagella (extensions of the cytoskeleton) help some cells swim through water.

19. Cell Structure - Cytoskeleton
Cilia
Flagella
Numerous
Short and hair-like
Help unicellular organisms
Help multicellular organisms rid organs of dust and move mucous
Usually a cell only has one
Long and whip-like
Help unicellular organisms swim in liquids

20. Cell Structure – cell membrane
Regulates what enters and leaves the cell
Double layer of phospholipids
Fluid mosaic model (not rigid)
Selectively permeable

21. Cell Structure – Cell Wall
Not present on animal cells
Rigid; made of cellulose and protein
Support and protect the cell

22. Plant vs. Animal Cells Plant cells Animal Cells “boxy” Often green
Contain chloroplasts, vacuole, and cell wall
Variety of shapes depending on function
May contain structures for movement (cilia and flagella)

23. Plant Cells

24. Animal Cells

25. Transport Across Cell Membrane
Passive transport requires no energy input from cell (Ex. Osmosis, diffusion, facilitated diffusion)
Active transport requires energy input to move molecules across the cell membrane

26. Moving Across the Cell Membrane (Passive)
Diffusion is the movement of particles (solutes) from an area of greater concentration to an area of lesser concentration. When the concentration of solutes on both sides of the cell membrane is the same, equilibrium exists.
When equilibrium is reached, solute particles still continue to move across the membrane in both directions.

27. Moving Across the Cell Membrane

28. Moving Across the Cell Membrane
Osmosis is the diffusion of water across a membrane.

29. Isotonic if concentration of dissolved particles is the same outside of cell compared to inside
Hypertonic if concentration of dissolved particles is higher outside of cell compared to inside
Hypotonic if concentration of dissolved particles is lower outside of cell compared to inside

30. Moving Across the Cell Membrane
Osmotic Pressure
What would happen to a cell if it were placed in an isotonic solution?
What would happen to a cell if it were placed in a hypertonic solution?
What would happen to a cell if it were placed in a hypotonic solution?

31. Moving Across the Cell Membrane

32. Movement Across the Cell Membrane
During facilitated diffusion, molecules that cannot cross the cell membrane by themselves b/c they are too big, get help from protein channels in the membrane. Uses transport protein

33. Endocytosis and Exocytosis

34. Movement Across the Cell Membrane
Sometimes, cells must move substances in the opposite direction of diffusion against the concentration gradient To move substances from a low concentration to a higher concentration requires energy. This requires active transport. Uses transport protein

35. Cell Diversity Unicellular Organisms Multicellular Organisms
Made of only one cell
Made of many cells

36. Cell Diversity
Multicellular organisms are made of many, many specialized cells. In cell specialization, the cells of a multicellular organism develop in different ways to perform different tasks in the organism.

38. Levels of Organization
In multicellular organisms, the levels of organization of the body are (from simplest to most complex):
Cells
Tissues - a group of similar cells that perform a particular function (ex: nervous, connective, epithelial, and muscle)
Organs - a group of tissues working together to perform a specific function (ex: heart, pelvis, uterus)
Organ systems – group of organs working together to perform a specific function (ex: cardiovascular system, reproductive system)`