Cells Dr. Gary Mumaugh

Transcription

1 Cells Dr. Gary Mumaugh

2 Introduction The cell is the basic unit of biological organization Basic composition protoplasm cell membrane Organelles uman cells vary in size, shape and function From microscopic to up to two feet long

3 There are trillion cells in the human body. Differentiation is when cells specialize. There are over 260 different kinds of human cells. As a result of differentiation, cells vary in size and shape due to their unique function

4 Anatomy of a Typical Cell

5

6 The Cell Membrane Double phospholipid layer with embedded proteins also called Plasma Membrane Protein functions of include forming channels or pores, transporters, receptor sites for hormones Cell membranes are selectively permeable membranes Only certain substances can get through Not everything is on the A list!

7 Cytoplasm of the Cell Mostly water with chemical compounds in solution or colloid Solution: atoms or ions distributed in medium Polar compounds go into solution Nonpolar compounds go into colloidal suspension

8 The Nucleus All human cells have a nucleus Except the RBC Control center of the cell Nuclear membrane has pores to allow substances passage Chromatin genetic material (long threads of chromosomes) are inside nucleoplasm Nucleolus - site of ribosome formation

9 Cytoplasm Is the watery solution of minerals, gases, organic molecules and cell organelles that is found between the cell membrane and the nucleus Cytosol is the water portion of the cytoplasm Many of the chemical reaction that occur in the cell happen in the cytoplasm

10 Endoplasmic Reticulum (ER) System of membranes that makes up channels Connects with outer nuclear and cell membranes Types of ER Rough: for protein synthesis attached ribosomes Smooth: fat transport and sex hormone synthesis

11 Ribosomes Very small structures made up of protein and ribosomal RNA Distributed throughout cytoplasm Attached to rough Endoplasmic Reticulum Site of protein synthesis

12 The Golgi Apparatus Secretion is the task of the Golgi apparatus They produce specific proteins to be used elsewhere in tissues To secrete a substance, small sacs of the membrane break off and fuse with the cell membrane, releasing the substance to the outside of the cell This is called exocytosis Collection of flat saclike cisternae Concentration and collection of cellular compounds Storage warehouses of the cell Carbohydrate synthesis site

13 The Mitochondria Powerhouses of the cell The aerobic (oxygen requiring) reactions of cell respiration take place here The site of ATP and energy production Cristae - inner folds where cellular respiration occurs Energy requirements of cell determine cristae number

14 Lysosomes Digestive enzyme packages When WBC engulf bacteria, the bacteria are digested and destroyed by lysosomal enzymes Worn out cell parts and dead cells are digested by the lysosomes Function digest stored food maintenance and repair of organelles suicide agents for old or weak cells

15 Centrioles Involved in cellular division and reproduction Form spindle fibers during cell division Guide duplicated chromosomes to daughter cells Centrosome - two centrioles at right angles to each other

16 Cilia and Flagella airlike protrusions from cell membrane Nine double fibrils around two single central fibrils Cilia move materials across cell surface Flagellum propels cell through a medium

17 Functions of Cell Organelles ER - Transport of materials in the cell Ribosomes Site of protein synthesis Golgi apparatus Cell secretion Mitochondria ATP production, cell powerhouse Lysosomes Digestive enzymes Centrioles Cell division Cilia Sweeps material across the cell surface Flagellum Enables a cell to move

18 Think of the Cell Factory Boss give orders to the rest of the factory (DNA in the nucleus surrounded by the nuclear membrane). The workers (ribosomes) on the assembly line are in the factory (cytosol) who receive orders for production from the boss s messanger (mrna). The raw materials are the amino acids. When things are sent to the mailroom for outside delivery (golgi apparatus), they are eventually shuttled to the gates of the factory (secretory vessels).the gate of the factory controls shipment in and out (cell membrane). The turbines provide power for the factory (mitochondria).

19 Movement of Materials Into and Out of Cells Passive (Physical) Processes Require no cellular energy and include: Simple diffusion Facilitated diffusion Osmosis Filtration Active (Physiological) Processes Require cellular energy and include: Active transport Endocytosis Exocytosis Transcytosis

20 Diffusion Movement of molecules from area of high concentration to low concentration Brownian movement - random collision of diffusing molecules Accelerated by increased temperature Gas exchange in the lungs of body tissue is an example O 2 - CO 2 exchange

21 .

22 Animation: ow Diffusion Works Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the Normal or Slide Sorter views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at 22

23 Facilitated Diffusion Facilitate means to help or assist Molecules move from an area of greater concentration to an area of lesser concentration, but they need help An example is glucose, which is need for ATP production. Glucose can t get through membranes by themselves, so they have a carrier enzyme or transporter to help facilitate diffusion

24 Animation: ow Facilitated Diffusion Works Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the Normal or Slide Sorter views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at 24

25 Animation: Diffusion Through Cell Membranes Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the Normal or Slide Sorter views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at

26 Osmosis Movement of water through semipermeable membrane from high water concentration to low water concentration Absorption of water by the small intestines and kidney is an example Isotonic solution - salt concentration is the same outside the cell as inside ypotonic solution - salt concentration inside cell is higher than outside cell ypertonic solution -salt concentration higher outside the cell than inside

27 Animation: ow Osmosis Works Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the Normal or Slide Sorter views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at 27

28 Osmotic Pressure ability of osmosis to generate enough pressure to move a volume of water. Osmotic pressure increases as the concentration of nonpermeable solutes increases Isotonic same osmotic pressure ypertonic higher osmotic pressure (water loss) ypotonic lower osmotic pressure (water gain) (a) (b) (c)

29 Active Transport The movement of molecules from and area of lesser concentration to an area of greater concentration Opposite of diffusion Requires the energy of ATP to do this An example in the body is sodium and potassium pumps in muscle and nerve cells

30 Filtration Water and dissolved materials are forced through a membrane from an area of higher pressure to an area of lower pressure In the body, blood pressure is an example of this, with filtration occurring through the capillaries

31 Phagocytosis and Pinocytosis Phagocytosis A moving cell engulfs something WBC engulfing bateria Think of pacman Pinocytosis A stationary cell engulfs something Kidney cells absorbing lost protein.

32 Endocytosis Cell engulfs a substance by forming a vesicle around the substance Three types: Pinocytosis substance is mostly water Phagocytosis substance is a solid Receptor-mediated endocytosis requires the substance to bind to a membrane-bound receptor Cell membrane V esicle Nucleus Nucleolus

33 Endocytosis Cell membrane Particle Phagocytized particle Vesicle Nucleus Nucleolus Molecules outside cell Receptor-ligand combination Receptor protein V esicle Cytoplasm Cell membrane Cell membrane indenting (a) (b) (c) (d) 33

34 Exocytosis Reverse of endocytosis Substances in a vesicle fuse with cell membrane Contents released outside the cell Release of neurotransmitters from nerve cells Endoplasmic reticulum Golgi apparatus Nucleus 34

35 DNA and the Genetic Code DNA is a double helix strand of nucleotides, looking like a spiral ladder The rungs of the ladder are made up of four different bases, arranged in different orders and sequences These sequences are the genetic code The DNA of our 46 chromosomes is the genome which contains 20,000 to 30,000 genes If there is a mistake in the DNA, the result is genetic or hereditary disease

36 RNA and Protein Synthesis Protein Functions structure, enzymes or catalysts, immune response Transcription Messenger RNA copies DNA code, leaves nucleus Translation (trna) picks up amino acids

37 Cell Division Cell division is the process by which a cell reproduces itself Two types of cell division Mitosis Meiosis

38 Mitosis One cell with the diploid number of chromosomes divides once to form two cells, each with the diploid number of chromosomes (46) Stages of mitosis Prophase, metaphase, anaphase, telophase Mitosis is essential for growth and for repair and replacement of damaged cells Most nerve and muscle cells seem unable to divide and their loss may involve permanent loss of function

39 Meiosis: A Reduction Division Reduces genetic material from diploid to haploid Two divisions resulting in four cells Occurs only in the gonads In women, meiosis takes place in the ovaries and is called oogenesis In men, meiosis takes place in the testes and is called spermatogenesis Fertilization is the egg uniting with the sperm

40 Comparison of Mitosis and Meiosis Mitosis Two daughter cells with exact same genetic material Cellular division for growth, maintenance and repair Meiosis Four daughter cells with half the genetic material Cellular division for reproduction

41 3.5: Control of Cell Division Cell division capacities vary greatly among cell types Skin and blood cells divide often and continually Neuron cells divide a specific number of times then cease Chromosome tips (telomeres) that shorten with each mitosis provide a mitotic clock Cells divide to provide a more favorable surface area to volume relationship Growth factors and hormones stimulate cell division ormones stimulate mitosis of smooth muscle cells in uterus Epidermal growth factor stimulates growth of new skin Contact (density dependent) inhibition Tumors are the consequence of a loss of cell cycle control 41

42 Tumors Two types of tumors: Benign usually remains localized Malignant invasive and can metastasize; cancerous Two major types of genes cause cancer: Oncogenes activate other genes that increase cell division Tumor suppressor genes normally regulate mitosis; if inactivated they are unable to regulate mitosis Cells are now known as immortal Normal cells (with hairlike cilia) Cancer cells

43 Cellular Metabolism Metabolic processes all chemical reactions that occur in the body There are two (2) types of metabolic reactions: Anabolism Larger molecules are made from smaller ones Requires energy Catabolism Larger molecules are broken down into smaller ones Releases energy

44 Anabolism Anabolism provides the materials needed for cellular growth and repair C 2 O Dehydration synthesis Type of anabolic process Used to make polysaccharides, triglycerides, and proteins. Produces water C 2 O C 2 O C 2 O O O O O O O O O O O O O O O O 2 O O O O O Monosaccharide + Monosaccharide Disaccharide + Water

45 Catabolism Catabolism breaks down larger molecules into smaller on ydrolysis A catabolic process Used to decompose carbohydrates, lipids, and protei Water is used to split the substances Reverse of dehydration synthesis C 2 O C 2 O C 2 O C 2 O O O O O O O O O O O O O O O O 2 O O O O O Monosaccharide + Monosaccharide Disaccharide + Water

46 Control of Metabolic Reactions Enzymes Control rates of metabolic reactions Lower activation energy needed to start reactions Not consumed in chemical reactions. Substrate molecules Product molecule Active site Enzyme Enzyme-substrate molecule complex (a) (b) (c) Unaltered enzyme molecule 46

47 Animation: ow Enzymes Work Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the Normal or Slide Sorter views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at 47

48 Factors That Alter Enzymes Factors that alter enzymes: eat Radiation Electricity Chemicals Changes in p

49 Energy for Metabolic Reactions Energy is the capacity to change something; it is the ability to do work Common forms of energy: eat Light Sound Electrical energy Mechanical energy Chemical energy 49