Chapter 4 Cell Structure

1. Chapter 4Cell Structure

2. I. Cell Theory (4.1) • Hooke first observed cells 1665 • Leeuwenhoek first observed live cells. • 1838-9 Schleiden and Schwann.

3. A. Cell theory is the unifying foundation of cell biology • All organisms are made of cells. • Cells are the basic units of life. • Cells are made through division of preexisting cells.

4. B. Cell size is limited • Surface area – to – volume ratio: molecules can more through the membrane quickly if they are close in small cells; surface area = r2 but volume = r3.

6. C. Microscopes allow visualization of cells and components 1. Resolution: clarity; minimum distance 2 can be apart and still seen as 2 separate points.

7. 2. Types of Microscopes • Light: uses light and 2 lenses • Compound: uses multiple lenses

8. Electron: electron beams • Transmission electron: see through specimen • Scanning electron: look at surface of specimen

9. 3. Using stains to view cell structure • Stains: cause some structures to become darker for contrast helping resolution.

10. D. All cells exhibit basic structural similarities • Nucleus or nucleoid • Cytoplasm • Ribsomes • Plasma membrane

11. 1. Centrally located genetic material i. Prokaryotes: simple organisms, most genetic material is circular DNA ii. Nucleoid: area near center of cell where genetic material found (no membrane separating it) iii. Eukaryote: complex organisms, contain nucleus and organelles. iv. Nucleus: organelles w/ DNA

13. 2. Cytoplasm • Cytoplasm: jelly-like matrix that fills inside of cell • Organelle: membrane-bound structure w/ specific job • Cytosol: part of cytoplasm with organic molecules (like proteins, sugars) and ions

14. O R G A N E L L E S Cytoplasm

15. 3. Plasma Membrane • Phospholipid bilayer: 2 layers of lipids around cell, separate contents from surroundings • Transport proteins: help move material across membrane • Receptor proteins: help cells communicate, send and receive messages

17. II. Prokaryotic Cells (4.2) • No nucleus • No organelles

18. A. Prokaryotic cells have relatively simple organization 1. Cell wall: provides structure; outside of cell membrane and cytoplasm 2. Ribosomes: carry out protein synthesis 3. 2 types: archaea and bacteria 4. Cell membrane can take on other jobs 5. Functions as 1 whole unit

20. B. Bacterial cell walls consist of peptidoglycan 1. Peptidoglycan: made of a carbohydrate that provides structure, protection, and water balance 2. Gram-positive: group of bacteria w/ single layer of cell wall that holds violet dye 3. Gram-negative: group of bacteria with multilayer cell wall that does NOT hold violet dye.

22. C. Archaea lack peptidoglycan

23. D. Some prokaryotes move by means of rotating flagella 1. Flagella: threadlike structures made of protein fibers used for locomotion

24. III. Eukaryotic Cells (4.3) 1. Endomembrane system: membrane bound sections carrying out chemical processes 2. Central vacuole: large organelle that stores proteins, pigments, and waste 3. Vesicles: small transport sacs 4. Chromosomes: DNA tightly pack around proteins 5. Cytoskeleton: proteins supporting the shape and structure of a cell

26. A. The nucleus acts as the information center 1. Nucleus: large organelle holding genetic information 2. Nucleolus: area in nucleus synthesis of ribosomal RNA 3. The nuclear envelope: membrane around nucleus i. nuclear pores: holes in nuclear envelope that allow passage of RNA and proteins

28. 4. Chromatin: DNA wrapped around proteins called histones to form chromosomes i. chromatin ii. nucleosomes iii. histones

29. 5. The nucleolus: Ribosomal subunit manufacturing i. Ribosomes are made of rRNA and protein. ii. These parts are synthesized in the nucleolus.

30. B. Ribosomes are the cell’s protein synthesis machinery 1. ribosomal RNA (rRNA): along with proteins they form ribosomes which make or synthesize proteins 2. messenger RNA (mRNA): carries info from DNA to ribosome 3. transfer RNA (tRNA) : carries amino acids to ribosomes

32. IV. The Endomembrane System (4.4) • Endoplasmic Reticulum (ER): phospholipid bilayer w/ proteins makes this folded internal membrane w/ channels. • Cisternal space/Lumen: inner region of ER

34. A. The Rough ER is a site of protein synthesis • Rough ER: Rough b/c it is covered w/ ribosomes. Makes proteins. • Glycoproteins: Proteins w/ short carbohydrate chains.

36. B. Smooth ER has multiple roles • Smooth ER (SER): network of enzymes that synthesize carbohydrates and lipids. Stores Ca2+ Modify foreign substances so they are less toxic, liver. cells would have a long SER

37. C. The Golgi apparatus sorts and packages proteins • Golgi body: flattened stack of membranes • Golgi apparatus: collection of Golgi bodies that collect, package and distribute molecules sometimes from ER. Cis entrance; leave through trans face in vesicles. Finally it synthesizes the cell wall. • Cisternae: stacked membrane that can pinch off to form vesicles for transport.

40. D. Lysosomes contain digestive enzymes • Lysosomes: membrane bound digestive vesicles that break down and recycle proteins, lipids, nucleic acids and carbohydrates.

41. Phagocytosis: Cells can take in large molecules of food in vesicles which fuse w/ lysosomes for digestion.

43. E. Microbodies: vesicles w/ enzymes • Peroxisomes: microbodies w/ digestive and detoxifying enzymes that produce and break down hydrogen peroxide and remove electrons. • Glyoxysome: microbody found in plants that convert fats to carbs.

45. F. Plants use vacuoles for storage and water balance • Vacuoles: Stores useful molecules like sugar, ions, pigments and water as well as waste. The large central vacuole in plants allows the cell to contract and expand through water channels. Different types of vacuoles exist. 2. Tonoplast: membrane around vacuole that contains water channels to maintain water levels.

47. V. Mitochondria and Chloroplasts: Cellular Generators A. Mitochondria metabolize sugar to make ATP 1. Mitochondria: organelle involved in cellular respiration. It has its own DNA. They can divide to reproduce but this process is dependent upon DNA in the nucleus.

48. 2. Cristae: inner membrane of mitochondria increasing surface area. 3. Matrix: solution in the interior of cristae involved in respiration 4. Intermembrane space: outer compartment of mitochondria.

49. 5. ATP: energy storing molecule produced during cell respiration

50. B. Chloroplasts use light to generate ATP and sugars 1. Chloroplasts: organells that carry out photosynthesis. They make their own food thanks to Chlorophyll (green pigment). Consist of membrane, grana and own DNA.