Cell Structure and Function Overview

1. Chapter 3, part 1 An Introduction to The Cellular Level of Organization

2. Learning Objectives • List the main points of the cell theory. • Describe the chief structural features of the cell membrane, and note their broad importance. • Describe the organelles of a typical cell, and give their specific functions.

3. SECTION 3-1An Introduction to Cells

4. The cell theory states: • Cells are the building blocks of all plants and animals • Cells are produced by the division of preexisting cells • Cells are the smallest units that perform all vital physiological functions • Each cell maintains homeostasis at the cellular level • Homeostasis at higher levels reflects combined, coordinated action of many cells

5. Figure 3.1 The Diversity of Cells in the Human Body Figure 3.1

6. Cell biology • Cytology, the study of the structure and function of cells • The human body contains both somatic and sex cells

7. Figure 3.2 The Anatomy of a Representative Cell Figure 3.2

8. A typical cell • Is surrounded by extracellular fluid, which is the interstitial fluid of the tissue • Has an outer boundary called the cell membrane or plasma membrane

9. SECTION 3-2The Cell Membrane

10. Cell membrane functions include: • Physical isolation • Regulation of exchange with the environment • Structural support

11. Figure 3.3 The Cell Membrane • The cell membrane is a phospholipid bilayer with proteins, lipids and carbohydrates. Figure 3.3

12. Phospholipids—forming the bilayer of the membrane

13. Cholesterol helps give structural integrity to cell membrane Also cholesterol serves diverse functions such as: it is converted to vitamin D (if irradiated with Ultra Violet light), modified to form steroid hormones, and is modified to bile acids to digest fats.

14. Membrane proteins include: • Integral proteins • Peripheral proteins • Anchoring proteins • Recognition proteins • Receptor proteins • Carrier proteins • Channels

15. Figure 3.4 Membrane proteins Figure 3.4

16. Membrane carbohydrates form the glycocalyx All 3 carbohydrate types extend beyond the cell membrane into the extracellular matrix • Proteoglycans • Glycolipids • Glycoproteins Helps lubricate and protect cell membrane Can anchor cells in place, and plays a role in the locomotion of certain specialized cells

17. SECTION 3-3The Cytoplasm

18. The cytoplasm contains: • The fluid (cytosol) • The organelles the cytosol surrounds

19. Organelles • Nonmembranous organelles are not enclosed by a membrane and always in touch with the cytosol • Cytoskeleton, microvilli, centrioles, cilia, ribosomes, proteasomes • Membranous organelles are surrounded by lipid membranes • Endoplasmic reticulum, Golgi apparatus, lysosomes, peroxisomes, mitochondria

20. Figure 3.2 The Anatomy of a Representative Cell Figure 3.2

21. Cytoskeleton provides strength and flexibility • Microfilaments • Intermediate filaments • Microtubules • Thick filaments Microvilli increase surface area

22. Figure 3.5 The Cytoskeleton Figure 3.5

23. Centrioles • Direct the movement of chromosomes during cell division • Organize the cytoskeleton • Cytoplasm surrounding the centrioles is the centrosome

24. Cilia • Is anchored by a basal body • Beats rhythmically to move fluids across cell surface

25. Figure 3.6 Centrioles and Cilia Figure 3.6

26. Ribosomes • Are responsible for manufacturing proteins • Are composed of a large and a small ribosomal subunit • Contain ribosomal RNA (rRNA) • Can be free or fixed ribosomes

27. Figure 3.7 Ribosomes Figure 3.7

28. Proteasomes • Remove and break down damaged or abnormal proteins • Require targeted proteins to be tagged with ubiquitin

29. Endoplasmic reticulum • Intracellular membranes involved in synthesis, storage, transportation and detoxification • Forms cisternae • Rough ER (RER) contains ribosomes • Forms transport vesicles • Smooth ER (SER) • Involved in lipid synthesis

30. Figure 3.8 The Endoplasmic Reticulum Figure 3.8

31. Golgi Apparatus • Forms secretory vesicles • Discharged by exocytosis • Forms new membrane components • Packages lysosomes

32. Figure 3.9 The Golgi Apparatus Figure 3.9

33. Figure 3.10 Functions of the Golgi Apparatus Figure 3.10

34. Lysosomes and Peroxisomes • Lysosomes are • Filled with digestive enzymes • Responsible for autolysis of injured cells • Peroxisomes • Carry enzymes that neutralize toxins

35. Figure 3.11 Lysosome Functions Figure 3.11

36. Membrane flow • Continuous movement and recycling of membranes • ER • Vesicles • Golgi apparatus • Cell membrane

37. Mitochondria • Responsible for ATP production through aerobic respiration • Matrix = fluid contents of mitochondria • Cristae = folds in inner membrane