Cell Structure & Function

1. Cell Structure & Function

2. Discovery of Cells • It wasn’t until the 1600s that scientists were able to use microscopes to observe living things.

3. Cells • In 1665, Robert Hooke observed cork cells under the microscope. He called them cells. • This is a drawing he made of the cork cells.

4. Leeuwenhoek’s Microscope Anton Van Leeuwenhoek used a single-lens microscope to view pond water and other things.

5. Light Microscope • Use light to view objects • Magnify up to 2000 times • Able to view living or preserved specimens

6. Electron Microscope Magnify up to 200,000 Takes place in a vacuum Not able to view live specimens

7. Cells • Smallest unit of life that can carry on functions of life • Diverse in size and structure • Shape is related to its function

8. Living Things can be Multicellular or Unicellular • Unicellular: made up of one cell • Multicellular: made up of many cells

9. The Cell Theory • Cells are the basic unit of life • All organisms are made of one or more cells • All cells arise from existing cells

10. Cell Size • The logistics of carrying out cellular metabolism sets limits on the size of cells • Small cells function more efficiently than large cells because they have a higher surface-area-to-volume ratio • Large cells would take too long to exchange need materials • Diffusion & Osmosis

11. Surface area increases while total volume remains constant 5 1 1 Total surface area (height  width  number of sides  number of boxes) 6 150 750 Total volume (height  width  length  number of boxes) 125 125 1 Surface-to-volume ratio (surface area  volume) 6 12 6 Cell Size

12. Common Features to All Cells • Some cell parts are common to all types of cells • Cell Membrane • Cytosol (Cell Fluid) Cytoplasm • Ribosomes • Chromosomes (DNA)

13. Types of Cells • Cells are classified as prokaryotic or eukaryotic. • Prokaryotic cells have genetic material that is not inside a nucleus (no nucleus). • Eukaryotic cells have genetic materials in a nucleus. (“true” nucleus)

14. Two Major Classes of Cells • Prokaryotic cells • The smallest, most simple cells. • They live in a broad range of environments. • Lack a nucleus and other organelles. • Have a single chromosome in a region called the nucleoid • Have a cell wall outside the membrane that provides structure and support. • Many use flagella (long, tail-like structures) for locomotion • Ex. Bacteria

15. Prokaryotic Cells • Gram-positive • Thick single layer wall that retains a violet dye from Gram stain procedure • Gram-negative • Multilayered wall does not retain dye • Susceptibility of bacteria to antibiotics depends on cell wall structure.

16. Cell Structures • Cells contain small structures called organelles. Each organelle has a specific task it performs in the cell.

17. Pili: attachment structures on the surface of some prokaryotes Nucleoid: region where the cell’s DNA is located (not enclosed by a membrane) Ribosomes: organelles that synthesize proteins Plasma membrane: membrane enclosing the cytoplasm Cell wall: rigid structure outside the plasma membrane Capsule: jelly-like outer coating of many prokaryotes Bacterialchromosome 0.5 µm Flagella: locomotion organelles of some bacteria (a) A typical rod-shaped bacterium (b) A thin section through the bacterium Bacillus coagulans (TEM) Figure 6.6 A, B

18. Two Major Classes of Cells • Eukaryotic cells • More complex, organized cells. • Posses a true nucleus and other organelles. • Ex. - plant and animal cells • The cells in our bodies are EUKARYOTIC!

19. Nuclear envelope ENDOPLASMIC RETICULUM (ER) NUCLEUS Nucleolus Rough ER Smooth ER Chromatin Flagelium Plasma membrane Centrosome CYTOSKELETON Microfilaments Intermediate filaments Ribosomes Microtubules Microvilli Golgi apparatus Peroxisome In animal cells but not plant cells: Lysosomes Centrioles Flagella (in some plant sperm) Lysosome Mitochondrion • A animal cell Figure 6.9

20. Nuclear envelope Rough endoplasmic reticulum Nucleolus NUCLEUS Chromatin Smooth endoplasmic reticulum Centrosome Ribosomes (small brwon dots) Central vacuole Tonoplast Golgi apparatus Microfilaments Intermediate filaments Microtubules Mitochondrion Peroxisome Plasma membrane Chloroplast Cell wall Plasmodesmata Wall of adjacent cell • A plant cell CYTOSKELETON In plant cells but not animal cells: Chloroplasts Central vacuole and tonoplast Cell wall Plasmodesmata Figure 6.9

21. Basic Cell Structures

22. Cell Membrane • Separates cells contents from its environment • Made up of 2 layers of phospholipids • Controls what enters and leaves the cell • Proteins are embedded in the membrane

23. Cell Membrane

24. Cytoskeleton • The cytoskeleton is a network of protein filaments that helps the cell maintain its shape. • It is also involved in movement.

25. Cytoplasm • The cytoplasm (AKA cytosol) is the fluid outside the nucleus. It contains the organelles. • Many chemical reactions occur here.

26. Nucleus • Control center of the cell • Contains genetic material • Surrounded by the nuclear envelope • Nucleolus: darkly stained portion of the nucleus that produces ribosomes

27. Ribosomes • Ribosomes are protein assembly organelles. • The ribosome connects the amino acids. • Ribosomes can be “free” in the cytoplasm or on the endoplasmic reticulum.

28. Endoplasmic Reticulum • The endoplasmic reticulum is the site where lipids of the cell membrane are assembled, along with proteins and other materials. • It can contain ribosomes and be Rough ER or have no ribosomes and be Smooth ER

29. Golgi Apparatus • The golgi apparatus modifies, sorts, and packages proteins and other materials from the ER. • These materials are then stored or secreted.

30. Lysosomes • Lysosomes are small organelles that contain enzymes. • These enzymes breakdown lipids, carbohydrates, and proteins into small molecules that can be used by the cell. • Lysosomes also remove “junk and clutter” in the cell.

31. Mitochondria • The mitochondria is the organelle that converts chemical energy from food into ATP to power cell processes.

32. Cell Wall • Inflexible structure that surrounds the plasma membrane • Made of different substances in different organisms • Found in plants, algae, and some bacteria and fungi

33. Central Vacuoles • Vacuoles are storage organelles. • They store water, salts, proteins, etc. • Plants have a large Central Vacuole that helps plants support leaves and stems.

34. Chloroplasts • Chloroplasts are organelles that capture sunlight energy and convert it into chemical energy in a process known as photosynthesis.