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Cell Structure and Function

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Presentation on theme: "Cell Structure and Function"— Presentation transcript:

1 Cell Structure and Function

2 What Cell Theory tells us
A cell is the basic unit of life All living things are made up of cells New cells arise from preexisting cells

3 Why are most cells small?
Consider the cell surface-area-to-volume ratio: Small cells have a larger amount of surface area compared to the volume An increase in surface area allows for more nutrients to pass into the cell and wastes to exit the cell more efficiently There is a limit to how large a cell can be and be an efficient and metabolically active cell

4 Thinking about surface area to volume in a cell

5 common microscopes (used to view cells)
Compound light microscope Lower magnification Uses light beams to view images Can view live specimens Transmission electron microscope 2-D image Uses electrons to view internal structure High magnification, no live specimens Scanning electron microscope 3-D image Uses electrons to view surface structures

6 Light Microscope Blood cells Bacteria

7 Transmission Electron Microscope
Blood cell Bacteria

8 Scanning Electron Microscope
Blood cells Bacteria

9 Two main groups of cells . . .
Prokaryotic cells Thought to be the first cells to evolve Lack a nucleus Represented by bacteria and archaea Eukaryotic cells Have a nucleus that houses DNA Many membrane-bound organelles

10 What prokaryotic and eukaryotic cells have in common
A plasma membrane that surrounds and delineates the cell A cytoplasm that is the semi-fluid portion inside the cell that contains organelles DNA

11 Where did eukaryotic cells come from?

12 What do eukaryotic cells look like?

13 Characteristics of the plasma membrane
It is a phospholipid bilayer It is embedded with proteins that move in space It contains cholesterol for support It contains carbohydrates on proteins and lipids Selectively permeable

14 What does selectively permeable mean?
The membrane allows some things in while keeping other substances out

15 How things move across the plasma membrane
1. Diffusion 2. Osmosis 3. Facilitated transport 4. Active transport 5. Endocytosis and exocytosis

16 Diffusion and osmosis 1. Diffusion is the random movement of molecules from a higher concentration to a lower concentration 2. Osmosis is the diffusion of water molecules

17 Tonicity Hypertonic solutions have more solute than the inside of the cell and lead to crenation (shrinking) Hypotonic solutions have less solute than the inside of the cell and lead to lysis (bursting) Isotonic solutions have equal amounts of solute inside and outside the cell and thus does not affect the cell

18 Facilitated diffusion and active transport
3. Facilitated transport is the transport of molecules across the plasma membrane from higher concentration to lower concentration via a protein carrier 4. Active transport is the movement of molecules from a lower to higher concentration using ATP as energy; requires a protein carrier

19 What are endocytosis and exocytosis?
5. Endocytosis transports molecules or cells into the cell via invagination of the plasma membrane to form a vesicle 6. Exocytosis transports molecules outside the cell via fusion of a vesicle with the plasma membrane

20 Which of the following require cellular energy?
Diffusion Osmosis Facilitated transport Active transport Selective permeability

21 The cytoskeleton A series of proteins that maintain cell shape as well as anchors and/or moves organelles in the cell Made of 3 fibers: large microtubules, thin actin filaments and medium-sized intermediate filaments

22 The cytoskeleton Actin filaments – maintain cell shape
Intermediated filaments – anchor organelles Microtubules – movement move structures within cells movement of cilia and flagella

23 What are cilia and flagella?
3.5 The cytoskeleton and cell movement What are cilia and flagella? Movable hair like structures on the surface of cells Both are made of microtubules Cilia – short and multiple Flagellum - long and single

24 Cell junctions Junctions between the cells in a human tissue Three main types Adhesion junctions: mechanically attach adjacent cells (common in skin cells) Tight junctions: waterproof connections between cells Gap junctions: communication channels between cells.

25 Cell Junctions plasma membranes cytoplasmic plaque plasma membranes
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. plasma membranes cytoplasmic plaque plasma membranes plasma membranes tight junction proteins membrane channels filaments of cytoskeleton intercellular filaments intercellular space intercellular space intercellular space a. Adhesion junction b. Tight junction c. Gap junction

26 Enzymes are important for cellular respiration and many activities in the cell
Enzymes correctly orient molecules to speed up (catalyze) chemical reactions in the body. They can catalyze synthesis reactions They can catalyze hydrolysis reactions

27 Enzymes are important for cellular respiration and many activities in the cell
Most enzymes are proteins Enzymes are often named for the molecule that they work on (substrates) Enzymes are specific to what substrate they work on Enzymes have active sites where a substrate binds Enzymes are not used up in a reaction but instead are recycled Some enzymes are aided by non-protein molecules called coenzymes

28 Structures involved in protein production
3.4 The nucleus and the production of proteins Structures involved in protein production Nucleus – Contains DNA, the blueprint for making proteins Ribosomes – A structure made of RNA that is the site of protein synthesis Endomembrane system – where proteins are manufactured, utilized, modified and packaged for use

29 The structure and function of the nucleus
3.4 The nucleus and the production of proteins The structure and function of the nucleus Bound by a porous nuclear envelope Houses DNA and associated proteins called chromatin Contains nucleoplasm Nucleolus region(s) that contain ribosomal RNA (rRNA)

30 The structure and function of ribosomes
3.4 The nucleus and the production of proteins The structure and function of ribosomes Organelles made of RNA and protein Found bound to the endoplasmic reticulum and free floating in the cell Site of protein synthesis

31 The endomembrane system
3.4 The nucleus and the production of proteins The endomembrane system A series of membranes in which molecules are transported in the cell It consists of the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes and vesicles

32 How does the endomembrane system function and appear?
3.4 The nucleus and the production of proteins How does the endomembrane system function and appear?

33 Summary of the parts of the endomembrane system
3.4 The nucleus and the production of proteins Summary of the parts of the endomembrane system Rough endoplasmic reticulum – studded with ribosomes used to make proteins Smooth endoplasmic reticulum – lacks ribosomes but aids in making carbohydrates and lipids Golgi apparatus – flattened stacks that process, package and deliver proteins and lipids from the ER Lysosomes – membranous vesicles made by the Golgi that contain digestive enzymes Vesicles – small membranous sacs used for transport

34 Mitochondria A highly folded organelle in eukaryotic cells
3.6 Mitochondria and cellular metabolism Mitochondria A highly folded organelle in eukaryotic cells Produces energy in the form of ATP They are thought to be derived from an engulfed prokaryotic cell

35 Cellular respiration Production of ATP in a cell Includes: Glycolysis
3.6 Mitochondria and cellular metabolism Cellular respiration Production of ATP in a cell Includes: Glycolysis Citric acid cycle 3. Electron transport chain

36 Glycolysis – step 1 of cellular respiration
3.6 Mitochondria and cellular metabolism Glycolysis – step 1 of cellular respiration Glycolysis Occurs in the cytoplasm Breaks glucose into 2 pyruvate NADH and 2 ATP molecules are made Does not require oxygen

37 Citric acid (Krebs) cycle – step 2 of cellular respiration?
3.6 Mitochondria and cellular metabolism Citric acid (Krebs) cycle – step 2 of cellular respiration? Citric acid cycle A cyclical pathway that occurs in the mitochondria Produces NADH and 2 ATP Requires oxygen

38 Electron transport chain – step 3 of cellular respiration
3.6 Mitochondria and cellular metabolism Electron transport chain – step 3 of cellular respiration Electron transport chain Series of molecules embedded in the mitochondrial membrane NADH made in steps 1 and 2 carry electrons here 32-34 ATP are made depending on the cell Requires oxygen as the final electron acceptor in the chain

39 Other molecules besides glucose can be used in cellular respiration
3.6 Mitochondria and cellular metabolism Other molecules besides glucose can be used in cellular respiration Other carbohydrates Proteins Lipids

40 Cell make ATP without oxygen
3.6 Mitochondria and cellular metabolism Cell make ATP without oxygen Fermentation Occurs in the cytoplasm Does not require oxygen Involves glycolysis Makes 2 ATP and lactic acid in human cells Is important in humans for a burst of energy for a short time but build up of acids limit its use

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