1. REVIEW-Cell Structure and Function
Chapter 3
REVIEW-Cell Structure and Function

2. Cell Characteristics Plasma Membrane Cytoplasm Organelles
Outer cell boundary
Cytoplasm
Cytosol
Cytoskeleton
Cytoplasmic inclusions
Organelles
Specialized structures that perform specific functions

3. Functions of the Cell Basic unit of life Protection and support
Movement
Communication
Cell metabolism and energy release
Inheritance

5. Plasma Membrane Intracellular versus extracellular Membrane potential
Glycolipids and glycoproteins
Fluid-mosaic model

6. Membrane Lipids Phospholipids form a lipid bilayer
Hydrophilic (water-loving) polar heads
Hydrophobic (water-fearing) nonpolar heads
Cholesterol: Determines fluid nature of membrane

7. Membrane Proteins Integral or intrinsic Peripheral or extrinsic
Extend from one surface to the other
Peripheral or extrinsic
Attached to either the inner or outer surfaces of the lipid bilayer

8. Marker Molecules
Allow cells to identify one another or other molecules
Glycoproteins
Glycolipids
Examples:
Immune system
Recognition of oocyte by sperm cell

9. Channel Proteins Non-gated ion channels Ligand-gated ion channel
Always open
Ligand-gated ion channel
Open in response to small molecules that bind to proteins or glycoproteins
Voltage-gated ion channel
Open when there is a change in charge across the plasma membrane

10. Receptors Receptor molecules Linked to channel proteins
Exposed receptor sites
Linked to channel proteins
Acetylcholine
Linked to G proteins
Alter activity on inner surface of plasma membrane

11. Enzymes and Carrier Proteins

12. Movement through the Plasma Membrane
Diffusion
Osmosis
Filtration
Mediated transport mechanisms
Facilitated diffusion
Active transport
Secondary active transport

13. Diffusion
Movement of solutes from an area of higher concentration to an area of lower concentration in solution
Concentration (or density) gradient
Difference between two points
Viscosity
How easily a liquid flows

14. Diffusion

15. Osmosis
Diffusion of water (solvent) across a selectively permeable membrane
Important because large volume changes caused by water movement disrupts normal cell function
Cell shrinkage or swelling
Isotonic: cell neither shrinks nor swells
Hypertonic: cell shrinks (crenation)
Hypotonic: cell swells and bursts (lysis)

16. Osmosis

17. Osmosis

18. Filtration Works like a sieve
Depends on pressure difference on either side of partition
Small particles move through holes with liquid
Larger particles cannot move beyond partition
Moves from side of greater pressure to lower
Example: In kidneys in urine formation
BP moves fluid from blood through filtration membrane
Water, ions, small molecules pass through partition; most proteins and blood cells remain in blood

19. Mediated Transport Mechanisms
Involve carrier proteins
Characteristics
Specificity
To a single type of molecule
Competition
Saturation
Rate of transport limited to number of available carrier proteins

20. Saturation of a Carrier Protein

21. Mediated Transport Mechanisms
Facilitated diffusion
Higher to lower concentration without metabolic energy
Active transport
Requires ATP
Moves against gradient
Secondary active transport
Ions or molecules move in same (symport) or different direction (antiport)

22. Secondary Active Transport

23. Endocytosis Internalization of substances by formation of a vesicle
Types
Phagocytosis
Pinocytosis
Receptor-mediated endocytosis

24. Pinocytosis and Receptor-Mediated Endocytosis

25. Exocytosis Accumulated vesicle secretions expelled from cell Examples
Secretion of digestive enzymes by pancreas
Secretion of mucus by salivary glands
Secretion of milk by mammary glands

28. Cytoplasm Cellular material outside nucleus but inside plasma membrane
Half cytosol, half organelles
Cytosol: Fluid portion
Cytoskeleton: Supports the cell
Microtubules
Microfilaments
Intermediate filaments
Cytoplasmic inclusions
Melanin, hemoglobin, lipid droplets

29. Organelles Small specialized structures for particular functions
Most have membranes that separate interior of organelles from cytoplasm
Related to specific structure and function of the cell

30. Centrioles
In specialized zone of microtubule formation near nucleus: Centrosome
Each unit consists of 9 triplet microtubules
Before cell division, centrioles divide, move to ends of cell and become spindle fibers

31. Cilia Short appendages projecting from cell surfaces
9 + 2 microtubule arrangement
Capable of movement
Moves materials over the cell surface

32. Flagella Similar to cilia but longer Usually only one exists per cell
Moves the cell itself in wavelike fashion
Example: Sperm cell

33. Microvilli Extensions of plasma membrane Normally many on each cell
Increase the cell surface
One tenth to one twentieth size of cilia
Do not move

34. Ribosomes Sites of protein synthesis
Composed of a large and small subunit, each consisting of rRNA
Types
Free
Attached to endoplasmic reticulum

35. Endoplasmic Reticulum
Types
Rough
Has attached ribosomes
Proteins produced and modified for secretions
Smooth
Not attached ribosomes
Manufacture lipids
Cisternae: Interior spaces isolated from rest of cytoplasm

36. Golgi Apparatus
Modification, packaging, distribution of proteins and lipids for secretion or internal use
Flattened membrane sacs stacked on each other

37. Function of Golgi Apparatus

38. Action of Lysosomes Membrane-bound vesicles that pinch off from Golgi
Hydrolytic enzymes for intracellular digestion, autophagia
WBC’s have many lysosomes to digest bacteria
Important in bone remodeling; digesting damaged cells

39. Peroxisomes and Proteasomes
Membrane-bound vesicles smaller than lysosomes
Contain enzymes to break down fatty acids and amino acids
Hydrogen peroxide is a toxic by-product of breakdown; catalase breaks it down to water and oxygen
Proteasomes
Consist of large protein complexes
Include several enzymes that break down and recycle proteins in cell

40. Mitochondria Provide energy for cell Major site of ATP synthesis
Membranes
Cristae: Infoldings of inner membrane
Matrix: Substance located in space formed by inner membrane

41. Nucleus DNA dispersed throughout Consists of :
Nuclear envelope: Separates nucleus from cytoplasm and regulates movement of materials in and out
Chromatin: Condenses to form chromosomes during cell division
Nucleolus: Assembly site of ribosomal units

45. Chromosome Structure

46. Overview of Cell Metabolism

47. Overview of Protein Synthesis

48. Protein Synthesis cont’d
Transcription
Transcription
DNA copied to make mRNA
Translation
Synthesis of a protein
Requires mRNA, ribosomes, and tRNA
Ribosomes align mRNA codons with tRNA anticodons

50. Translation

51. Cell Life Cycle Interphase Mitosis: Division of nucleus
3 Phases between cell divisions: G1, S, G2
Mitosis: Division of nucleus
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis: Division of cytoplasm
Immediately follows mitosis

52. Mitosis
Interphase
Prophase
Metaphase

53. Mitosis
Anaphase
Telophase
Cytokinesis

54. MEIOSIS
Sex cells are formed by meiosis
Nucleus undergoes 2 divisions (Meiosis I and Meiosis II)
Resulting in 4 nuclei
Each nuclei has half the number of chromosomes as parent cell
Called haploid; 23 chromosomes in human sex cells
Resulting daughter cells differentiate into gametes or sex cells
Sperm cells in males; oocytes (egg cells) in females
During fertilization, a sperm cell fuses with the oocyte
This restores the normal number of 46 chromosomes in the human zygote

55. MEIOSIS

56. Meiosis

58. Comparison of Mitosis and Meiosis

59. Cellular Aspects of Aging
Aging involves lipids, proteins, and nucleic acids within the cell
35% or more factors are genetic
Cellular clock: death of cell line after a certain number of cell divisions
Death genes: turn on late in life
DNA damage: results in cell degeneration and death
Free radicals: direct damage (by atoms with unpaired electrons) to DNA in somatic cells
Results in somatic mutations, cellular dysfunction, and cell death
Mitochondrial damage: loss of energy to cell and cell death