1. Cell Structure and Function
Chapter 4

2. 4.1 What is a Cell?
Each cell has a plasma membrane, cytoplasm, and a nucleus (in eukaryotic cells) or a nucleoid (in prokaryotic cells)

3. Components of Cell Membranes
Lipid bilayer

4. extracellular environment one layer of lipids one layer of lipids
membrane
protein
cytoplasm
Fig. 4.4, p. 53

5. Cell Size and Shape
Surface-to-volume ratio limits cell size

6. 4.2 How Do We See Cells? Three key points of the cell theory:
All organisms consist of one or more cells
The cell is the smallest unit that retains the capacity for life
A cell arises from the growth and division of another cell

7. Microscopes
Different microscopes use light or electrons to reveal details of cell shapes or structures

8. Five Different Views

9. 4.3 Membrane Structure and Function
Each cell membrane is a boundary (lipid bilayer) that controls the flow of substances across it
Fluid mosaic model
Membrane is composed of phospholipids, sterols, proteins, and other components
Phospholipids drift within the bilayer
Many proteins are embedded in or attached to cell membrane surfaces
Receptors, transporters, communication proteins, and adhesion proteins
Plasma (outer) membrane also incorporates recognition (marker) proteins
Animation:

10. Common Membrane Proteins

11. Membrane Structure Studies

12. 4.4 Introducing Prokaryotic Cells
Bacteria and archaeans
The simplest cells
The groups with greatest metabolic diversity
Cell wall
Surrounds plasma membrane in nearly all prokaryotic organisms
Flagella
Used for motion by prokaryotes that are motile
Capsule
Protects cells from immune destruction
Pili
Protein filaments in some that are used for attachment to surfaces
“Sex” pilus transfers genetic material

13. Prokaryote Structure

14. Prokaryote Structure

15. 4.6 Introducing Eukaryotic Cells
Start with a nucleus and other organelles
Carry out specialized functions inside a cell

16. Components of Eukaryotic Cells

17. 4.7 Components of The Nucleus
Nucleus separates DNA from cytoplasm
Chromatin (all chromosomal DNA with proteins)
Chromosomes (condensed)
Nucleolus assembles ribosome subunits
Nuclear envelope encloses nucleoplasm
Pores, receptors, transport proteins

18. Organization of DNA Image from: http://micro. magnet. fsu

19. Nucleus and Nuclear Envelope

20. Nucleus and Nuclear Envelope

21. 4.8 The Endomembrane System
Endoplasmic reticulum (ER)
An extension of the nuclear envelope
RER modifies new polypeptide chains
SER makes lipids; other metabolic functions
Transport vesicles
used to move proteins through the cytoplasm
Golgi bodies
Further modify polypeptides
Assemble lipids
Plasma membrane
Where transport vesicles attach to “secrete” cell products

22. Endomembrane System Image From: http://www. phschool

23. The Endomembrane System
Vesicles
Endocytic and exocytic: Transport or store polypeptides and lipids
Peroxisomes: Digest fatty acids and amino acids; break down toxins and metabolic by-products
Lysosomes: Intracellular digestion (animals)
Central vacuole: Storage; fluid pressure (plants)

24. Endomembrane System

25. Endomembrane System

26. 4.9 Mitochondria and Chloroplasts
Break down organic compounds by aerobic respiration (oxygen-requiring)
Produce ATP
Chloroplasts
Produce sugars by photosynthesis
Origins of mitochondria and chloroplasts:

27. Mitochondria image from: http://pingrybiology. pbworks

28. Chloroplasts

29. 4.10 Visual Summary: Plant Cells

30. Visual Summary: Animal Cells

31. 4.11 Cell Surface Specializations
Most prokaryotes, protists, fungi, all plant cells have a cell wall around their plasma membrane
Protects, supports, maintains cell shape
Primary and secondary cell walls in some plants
Plasmodesmata across cell walls connect plant cells

32. Plant Cell Walls

33. Plant Cell Walls

34. Plant Cuticle
Protective surface secretion, limits water loss

35. Extracellular Matrixes
Surrounds cells of specific tissues –
some are hard (bone) and some are liquid (blood)

36. Animal Cell Junctions Connect cells of animals
Adhering junctions, tight junctions, gap junctions

37. 4.12 The Dynamic Cytoskeleton
Components of the cytoskeleton
Microtubules
Microfilaments
Intermediate filaments (in most)

38. Components of the Cytoskeleton

39. Cytoskeleton Function
Organizes and moves cell parts
Reinforces cell shape
Interactions between motor proteins and microtubules in cilia, flagella, and pseudopods can move the whole cell/organism
Paramecium image from:

40. Motor Protein: Kinesin
Moves vesicles along microtubules
Animation:

41. Flagellum and Pseudopods

42. Eukaryotic Flagella and Cilia: Dynein

43. Eukaryotic Flagella and Cilia: Dynein

44. Microtubule organizing center
Responsible for the organization/formation of microtubules that function during cell division
Contain centrioles in animal cells