Chapter 4: A Tour of the Cell

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1 Chapter 4: A Tour of the Cell
CELLS Chapter 4: A Tour of the Cell Cells

2 Cell Theory A. What is it? 1. All living things are made of cells.
2. Existing cells have come from other cells.

3 Evidence for cell theory 1
Evidence for cell theory 1. When observed, all living things consistently appear to be composed of cells. 2. Made of organelles, but cooperation of all organelles required for life processes. 3. Cell division is evident where spontaneous generation or abiogenesis is not. Some organisms test our std. definition of cell – muscle cells have many nuclei; fungal hyphae are multiunit with many nuclei and continuous cytoplasm, walls of chitin (exoskeleton material)

4 Answer in Notebooks: #2. Define the following: Spontaneous Generation: Abiogenesis:

5 membrane thickness ~10 nm viruses ~ 100 nm bacteria ~1 μm
B. Cells are small and their components even smaller molecules ~1 nm membrane thickness ~10 nm viruses ~ 100 nm bacteria ~1 μm organelles – up to 10 μm most cells – up to 100 μm * remember that cells are 3D objects

6 scale of universe HW: Briefly describe 6 types of light microscopy and 2 electron microscopy

7 Figure 4.1e-0 10 m Human height 1 m Length of some nerve and muscle cells 100 mm (10 cm) Chicken egg Unaided eye 10 mm (1 cm) Frog egg 1 mm Paramecium Human egg 100 μm Most plant and animal cells Figure 4.1e-0 The size range of cells and related objects Light microscope 10 μm Nucleus Most bacteria Mitochondrion 1 μm Electron microscope Smallest bacteria 100 nm Viruses Ribosome 10 nm Proteins Lipids 1 nm Small molecules 0.1 nm Atoms

8 C. Cell size is limited by ratio of surface area to volume. 1
C. Cell size is limited by ratio of surface area to volume. 1. as the size of structure increases the SA:V ratio decreases Why might this ratio be so significant, what happens at the surface of the cell?

9 The rate of exchange of heat, waste and fuel is a function of Surface Area
Use oxygen/glucose or urea as seeds for discussion on why this matters  gas exchange of oxygen for respiration. A cell which respires aerobically demands oxygen for the process. Oxygen is obtained form the surrounding environment such as water or blood (depends on the cell). Oxygen diffuses across the cell membrane. More membrane more diffusion (Surface area= increases by the 2). Bigger cell (Volume = increases by the 3). However the ratio of surface area2 : volume 3 is decreasing Therefore the volume of oxygen obtained for each unit of cell volume is actually decreasing Cells must not get too big because they cannot obtain sufficient oxygen to satisfy the demands of the cell. why cells are small (reasoning): Size as a limiting Factors for cell because: A big cell needs more oxygen than a little cell Big cells need to have more oxygen diffusion across the cell membrane. But the big cell has relatively small surface area compared to its volume i.e. the surface area: volume ratio is small. What ever other benefits a cell might gain from being big, it cannot become larger than is limited by the rate of gas exchange.

10 Answer in Notebooks: #3. Why is it important to have a larger surface area to volume ratio in cells?

11 2. Two types of cells: Prokaryotic and Eukaryotic
- all cells have plasma membrane, cytoplasm, DNA and ribosomes A. prokaryotic (before nucleus - kernal) 1. no membrane bound organelles such as nucleus to separate DNA from rest of cell a. nucleoid – region of coiled DNA 2. bacteria and archaea (extremely plentiful and diverse) 3. reproduce (divide) via binary fission a. DNA replicates then cell splits in two each containing the DNA # of prokaryotes in handful of soil is greater than the # of people that have ever lived Collective biomass of prokaryotes is at least 10X that of all eukaryotes

12 A colorized TEM of the bacterium Escherichia coli
Figure 4.3-0 Fimbriae Ribosomes Nucleoid Plasma membrane Cell wall Bacterial chromosome Figure A diagram (left) and electron micrograph (right) of a typical prokaryotic cell Capsule A colorized TEM of the bacterium Escherichia coli A typical rod-shaped bacterium Flagella

13 B. Eukaryotic Cells (good/true nucleus) 1
B. Eukaryotic Cells (good/true nucleus) 1. contain membrane bound organelles such a nucleus 2. generally larger than prokaryotic

14

15 Animal Cell Micrograph

16 C. Comparing prokaryotic cells to eukaryotic cells
Small cells (<5 um) Larger cells (>10 um) Always unicellular Often multicellular No nucleus, DNA in nucleoid in cytoplasm DNA in membrane bound nucleus No membrane bound organelles Contains membrane bound organelles No mitochondria Mitochondria present Small ribosomes (70 s) s = svedberg unit of measure of size of organelles Larger ribosomes (80 s) Cell division via binary fission Cell division via mitosis Mostly asexual reproduction though some gene exchange via conjugation Asexual and sexual reproduction

17 Answer in Notebooks: #4. Compare and Contrast Prokaryotic vs. Eukaryotic Cells Use a Venn Diagram Pro Both Eu

18 Genetic Control - Houses DNA - Brain
Nucleus

19 Ribosomes Protein Synthesis Made of rRNA and protein, make proteins
Free (suspended in cytosol) or attached (to ER or nuclear envelope)  identical and can alternate roles

20 Endoplasmic Reticulum
Rough ER: Transports materials and ribosomes produce proteins in cisternae Smooth ER: No ribosomes. Makes proteins and lipids that are exported, controls Calcium level in muscles, and detoxifies poisons, alcohol, and drugs Endoplasmic Reticulum Smooth = no ribosomes Synthesis of lipids, metabolism of carbs and detox of drugs and poisons. Sex hormones of vertebrates are made here as well as steroid hormones of adrenal glands Detox (usually adding OH to make them soluble in water and flushable from system) – presence of certain drugs can cause body to create more smooth ER thereby increasing tolerance to the drug (and in some cases other drugs) Smooth ER also stores Ca Rough ER = with ribosomes Proteins formed by ribosomes move through ER (e.g. insulin from pancreas), move via transport vessicles

21 Golgi Body (Apparatus or Complex)
Modifies and packages proteins and carbohydrates for export. Post Office of cell – transport vessicles arrive from ER with products (proteins, etc.) where they are modified, stored and eventually shipped to another destination. Each stacklike cisternae’s internal environ is separate from cytosol, each cisterna contains different enzymes. The Golgi App distributes its products by budding vessicles from trans face where they are sorted for target areas of cell (the products even get tags, like a phosphate grp, to act as a zip code)

22 Breaks down fatty acids and rids body of toxic peroxides
Vesicles Lysosomes Digestive enzymes – digests nutrients and old cell organelles to be recycled Transport Lysosome – membranous sac of hydrolytic enzymes (digestion) Autophagy – hydrolytic enzymes recycle cell’s parts Peroxisomes Breaks down fatty acids and rids body of toxic peroxides

23 Phagocytosis – eating cell (engulfing and digesting large food particles)
Amoebas and in humans immunce cells (macrophages – white blood cells) engulf bacteria and other invaders

24 Vacuoles Fill with food being digested and Substances being removed from cell Vacuoles – membrane bound organelles with varying functions: food vacuoles (phagocytosis), contractile vacuoles – pump out excess water

25 Energy processing - Powerhouse of the Cell
Mitochondria

26 Chloroplast Contain Chlorophyll that traps sunlight for energy

27 4. Plant cells vs. animal cells (eukaryotic)
Feature Plant Animal Cell wall Present with plasma membrane Not present, only plasma membrane Chloroplasts Present in cells that photosynthesize Not present Carbohydrate storage Starch Glycogen Vacuoles Large and fluid filled Not usually present (sometimes small temporary vacuoles found) Shape Fixed, though often irregular Varied, usually rounded

28 Rough endoplasmic reticulum Chromatin CYTOSKELETON Microtubule
Figure 4.4a NUCLEUS Nuclear envelope Nucleolus Rough endoplasmic reticulum Chromatin CYTOSKELETON Microtubule Microfilament Intermediate filament Ribosomes Peroxisome Figure 4.4a An animal cell Smooth endoplasmic reticulum Plasma membrane Golgi apparatus Centrosome with pair of centrioles Lysosome Mitochondrion

29 Rough endoplasmic reticulum Nuclear envelope
Figure 4.4b NUCLEUS Rough endoplasmic reticulum Nuclear envelope Smooth endoplasmic reticulum Nucleolus Chromatin Mitochondrion CYTOSKELETON Microfilament Microtubule Central vacuole Ribosomes Figure 4.4b A plant cell Chloroplast Cell wall Plasmodesma Cell wall of adjacent cell Golgi apparatus Peroxisome Plasma membrane

30 Answer in Notebooks: #8. Compare and Contrast Animal vs. Plant Cells Use a Venn Diagram Animal Both Plant