Life on Earth: Cell Structure and Function

1. Chapter 2 Cells 0

2. 2.2 Life on Earth The Tree of Life and Evolutionary Theory All Earth organisms share many similarities: all cells have the same basic biochemistry with same types of macromolecules all organisms consist of cells known as the Cell Theory all cells are surrounded by a phospholipid bilayer plasma membrane

3. 2.2 Life on Earth The Tree of Life and Evolutionary Theory there is unity of life on planet Earth best explained by a tree of life with modern species having evolved from common ancestors organisms on this tree can be divided into 2 categories based on their cellular composition 1. Prokaryotic 2. Eukaryotic

4. 2.2 Life on Earth Prokaryotic and Eukaryotic Cells All cells on Earth are either prokaryotic or eukaryotic main difference is the lack of a nucleus

5. 2.2 Life on Earth Prokaryotic vs. Eukaryotic Cells Prokaryotic cells are smaller and simpler in structure Prokaryotes do not have a true nucleus have a region where their DNA is found = Nucleoid region Prokaryotes do not have organelles Prokaryotes do have cell wall

6. 2.2 Life on Earth Prokaryotic and Eukaryotic Cells Eukaryotic cells are much more complex. have a true nucleus surrounded by a membrane called the Nuclear envelope made up of two phospholipid bilayers also have membrane-bound organelles with specialized jobs e.g. endoplasmic reticulum – protein synthesis e.g. mitochondria – ATP synthesis

7. BioFlix: Tour of An Animal Cell

8. 2.2 Life on Earth Cell Structure all cells are surrounded by a plasma membrane. made of a phospholipid bilayer hydrophobic tails orient inside the membrane, away from water numerous proteins are embedded within the plasma membrane numerous functions the plasma membrane is said to have fluidity - lipids and proteins can move about within the membrane the plasma membrane is also semipermeable: some molecules can cross and some can’t WATER Hydrophilichead Hydrophobictail WATER

9. 2.2 Life on Earth Cell Structure Nucleus: site of genetic material surrounded by a nuclear membrane houses the DNA and RNA of the cell contains a small area called the nucleolus – for ribosome synthesis Cytoplasm: jelly-like “fluid” that surrounds the nucleus and organelles composed of two things: A. Cytosol: intracellular fluid of the cell B. Cytoskeleton: “framework” of the cell – protein filaments shape of the cell; movement by the cell Ribosomes: protein synthesis can be found attached to membranes or free floating Mitochondria: provide energy for the cell breakdown of glucose in the presence of oxygen involved in the synthesis of ATP

10. Cell Structure Rough Endoplasmic reticulum or RER: protein synthesis called “Rough” - has ribosomes attached to its membrane Smooth Endoplasmic reticulum or SER: lipid synthesis lacks ribosomes Golgi apparatus: modifies and sorts proteins and packages them into transport vesicles Lysosomes: contain digestive enzymes to break down substances Centrioles: moves genetic material during cell division one pair for every cell capable of dividing involved in Mitosis and Meiosis

11. Plant vs. Animal cells • very similar to animal cells • nucleus • plasma membrane • same organelles as animal cells • a few differences: • Cell wall: outside the plasma membrane • composed of complex carbohydrates • e.g. cellulose, lectin • Plastids: specialized organelles that perform unique functions • e.g. chloroplast – contains a light-absorbing pigment called chlorophyll • involved in photosynthesis • other plastids store starch and other chemicals important to plant viability • Central vacuole: found in plant cells and stores water

12. Function of the Plasma Membrane • plasma membrane is the boundary that separates the living cell from its surroundings • functions: • 1. integrity of the cell – size and shape • 2. controls transport = “selectively permeable” • 3. excludes unwanted materials from entering the cell • forms a physical barrier with the external environment • allows the cell to create different environments outside and inside • 4. maintains the inside environment of the cell • 5. forms contacts with neighboring cells = tissue • 6. sensitivity - first part of cell that is affected by changes in the • extracellular environment

13. Function of the Plasma Membrane Fibers of extra-cellular matrix (ECM) • scientists began building models of plasma membranes before they were seen with electron microscopes • RBC membranes were chemically analyzed in 1915 • found to be made of proteins and lipids • we now know that the plasma membrane is made of two phospholipid layers (i.e. phospholipid bilayer) with proteins embedded in the membrane or stuck on the surface • these proteins have numerous functions • one function is controlling transport in and out of the cell Glyco-protein Carbohydrate Glycolipid EXTRACELLULARSIDE OFMEMBRANE many of the phospholipids and proteins of the plasma membrane have sugars stuck to them = glycolipids and glycoproteins Cholesterol Microfilamentsof cytoskeleton Peripheralproteins Integralprotein CYTOPLASMIC SIDEOF MEMBRANE

14. passive transport • active transport • diffusion • osmosis • facilitated • exocytosis • endocytosis • (pinocytosis • phagocytosis • receptor-mediated) Membrane Permeability and Transport • transport across the membrane may be: passive or active • http://programs.northlandcollege.edu/biology/Biology1111/animations/transport1.html

15. A. Diffusion = movement a solute from [high] to [low] • -random movement • -no energy needs to be synthesized • -three ways to diffuse: • 1. through the lipid bilayer: must be lipid soluble (non-polar) and small • -also capable: alcohol, gases, ammonia, fat-soluble vitamins • 2. through a membrane protein called a channel: charged ions (e.g. Na+, Ca2+) or small water-soluble (polar) molecules • 3. through a membrane protein called a transporter • -known as facilitated diffusion: larger, polar molecules too big for • channels Animation: Diffusion Right-click slide / select “Play”

16. Lowerconcentrationof solute (sugar) Higher concentrationof solute Same concentrationof solute • B. Osmosis = diffusion of water from [high] to [low] • OR movement of water from [low solute] to [high solute] -in osmosis – the membrane is permeable to water and NOT to the solutes -BUT it is the concentration of solutes that causes the water to move -WHY?? -the solutes are surround by water molecules -this decreases the amount of free water molecules available to move -so increased solute concentration decreases the concentration of free water molecules -through osmosis – additional free water will move toward that area of decreased free water concentration Sugarmolecule H2O Selectivelypermeablemembrane Osmosis

17. B. Osmosis = diffusion of water from [high] to [low] • OR movement of water from [low solute] to [high solute] -EXPERIMENT: U shaped tube divided by a membrane permeable to water only -increase the solute concentration in the right half of the tube -this decreases the free water concentration on the right side also -water rises on the side of the solutes – due to osmosis -if you counteract this rise in water by applying pressure = osmotic pressure (OP) -therefore increasing solute concentration increases osmotic pressure -water will move toward that area to decrease this OP -OP is important in determining how much fluid remains in your blood and how much leaves to surround the cells in your tissues

18. Water Balance of Cells Without Walls • How do cells behave in solutions? • must consider solute concentration and membrane permeability • the two things combine to create = TONICITY • Tonicity is the ability of a surrounding solution to cause a cell to gain or lose water • degree to which a the concentration of a specific solute surrounding a cell causes water to enter or leave the cell • Isotonic solution: Solute concentration is the same as that inside the cell = no net water movement across the plasma membrane • Hypertonic solution: Solute concentration is greater than that inside the cell = cell loses water • Hypotonic solution: Solute concentration is less than that inside the cell = cell gains water • Isotonicsolution • Hypertonicsolution • Hypotonicsolution • (a) Animal cell • H2O • H2O • H2O • H2O • Lysed • Normal • Shriveled • Cell wall • H2O • H2O • H2O • H2O • (b) Plant cell • Turgid (normal) • Flaccid • Plasmolyzed • Osmosis

19. Water Balance of Cells With Walls • Isotonicsolution • Hypertonicsolution • Hypotonicsolution • note things are different when there is a cell wall (i.e. in plant cells) • Isotonic solution: no water movement – plant cell is called flaccid • Hypertonic solution: plant cell loses water and shrinks  Plasmolysed • Hypotonic solution: plant cell gains water but does not burst due to the cell wall  Turgid • (a) Animal cell • H2O • H2O • H2O • H2O • Lysed • Normal • Shriveled • Cell wall • H2O • H2O • H2O • H2O • (b) Plant cell • Turgid (normal) • Flaccid • Plasmolyzed • Osmosis

20. Which organelle is not shared by both animal and plant cells? chloroplast mitochondrion lysosome Golgi apparatus

21. Which organelle is not shared by both animal and plant cells? chloroplast mitochondrion lysosome Golgi apparatus

22. What component would you not expect to find in both prokaryotic and eukaryotic cells? ribosomes nucleus plasma membrane cell wall

23. What component would you not expect to find in both prokaryotic and eukaryotic cells? ribosomes nucleus plasma membrane cell wall

24. Which organelle is responsible for protein synthesis? endoplasmic reticulum mitochondrion lysosome Golgi apparatus

25. Which organelle is not shared by both animal and plant cells? endoplasmic reticulum mitochondrion lysosome Golgi apparatus