Basic Cell Info. Cell diameter range: 7.5 micrometers (RBC) 150 micrometers (ovum)

Transcription

1 Unit 2: Cells 1

2 Basic Cell Info Cell Theory - the cell is the fundamental organizational unit of life Schleidon & Schwann first to suggest that all living things are composed of cells Human body 100 trillion cells Cell diameter range: 7.5 micrometers (RBC) 150 micrometers (ovum) Composite cell generalized cell illustration we study that exhibits most important characteristics of many different dinstinctive cell types; no such cell exists in the body 3 Main Cell Structures: plasma membrane cytoplasm (with organelles) nucleus 2

3 Cytoplasm Chromatin Nuclear pore Plasma membrane 3

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5 Cell Structures Plasma membrane Outer boundary of cell Made of lipids, proteins, and other molecules Fluid mosaic model molecules slowly float around the membrane molecules bound tightly to form continuous sheet molecules bound loosely to slip past one another Chemical attractions / forces hold membrane together Phospholipid bilayer hydrophilic heads - polar hydrophobic tails - nonpolar Without cholesterol (steroid lipid), membranes would break easily 5

6 Plasma Membrane cont. Selectively permeable Lipid-soluble molecules pass through easily Water-soluble molecules can not pass through Membrane proteins: how the cell controls movement of molecules gates that open and close to allow things into and out of the cell Carbohydrates attached glycoproteins identification markers allow to distinguish between normal and abnormal cells attack bacteria, cancer, blood transfusions Enzymes attached catalyze cellular reactions Other proteins attached form connections between cells Receptors react to hormones, etc. to trigger metabolic changes; signal transduction 6

7 Hydrophilic Phospholipid head Integral protein Hydrophobic Phospholipid tail Peripheral protein 7

8 Types of Membrane Proteins 8

9 Nucleus One of largest cell structures Occupies central portion of cell Shape and number in a cell vary (most common is one spherical nucleus) Nuclear membrane - double membrane with pores contains nucleoplasm pores called nuclear pore complex (NPCs) selectively permit molecules to enter or leave nucleus extensions of the ER Contains genetic material forms 46 chromosomes in dividing cells Remains as chromatin in non-dividing cells Dictates structure and function of the cell Contains nucleolus nonmembranous contains RNA synthesizes ribosomal RNA (rrna) to combine with proteins to make ribosomes cells that make more protein have bigger nucleolus 9

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11 Cytoplasm Gel-like substance that makes up inside of cell Contains various organelles suspended in cytosol (intracellular fluid) Membranous organelles - specialized sacs or canals made of cell membrane Endoplasmic reticulum Golgi apparatus Lysosomes Peroxisomes Mitochondria Nucleus Nonmembranous organelles - not made of a membrane; made of microscopic filaments Ribosomes Cytoskeleton Fibers microfilaments; intermediate filaments Centrosome Cell extensions microvilli, cilia, flagella Nucleolus 11

12 Organelles Endoplasmic Reticulum Flat, curving sacs in parallel rows Two types Rough ER Contains ribosomes Extends from nucleus Protein synthesis and intracellular transportation proteins move through canals to the golgi Smooth ER Synthesizes lipids and carbohydrates steroid hormones, glycoproteins, membrane lipids 12

13 Organelles cont. Golgi Apparatus Membranous Cisternae (sacs) stacked near nucleus Processes and packages molecules for export from cell Steps to processing and packaging 1. ER delivers protein via vesicles 2. Enters first cisternae 3. Chemical modifications 4. Sent to next cisternae via vesicle 5. Further modification 6. Repeated until last cisternae 7. Packaged in secretory vesicle 8. Migrates to cell surface 9. Combines with membrane 10.Secretes contents 13

14 Organelles cont. Lysosomes & Peroxisomes Lysosomes Membraneous sac Vesicles that pinched off from Golgi Size and shape change depending on activity Contains enzymes that if bust can kill the cell Destroy bacteria, etc. digestive bags, cellular garbage disposals Peroxisomes membraneous sac Smaller than lysosome Contains enzymes (peroxidase, catalase) Detoxify harmful substances Seen in kidney and liver cells 14

15 Organelles cont. Mitochondria Membraneous Double membrane Form a sac within a sac Cristae inner membrane folds contain enzymes make ATP Membranes same structure as plasma membrane power house Liver mitochondria Sperm cell 25 mitochondria Exercise increases number of mitochondria 15

16 Organelles cont. Ribosome Every cells contains thousands rer and free in cytoplasm Nonmembranous Protein synthesis (cell s protein factory ) Ribosomes on ER export and cell membrane use Free ribosomes make proteins for domestic use make structural and functional proteins (enzymes) Large and small subunits each has RNA bonded to protein rrna 16

17 Cytoskeleton 1. Cell s internal supporting network 2. Made of rigid, rodlike pieces (support and movement) 3. Muscle-like groups of fibers 4. Twisted protein molecules 17

18 Cytoskeleton Cell Fibers Microfilaments smallest fibers serve as cellular muscles muscle cells proteins slide past each other Intermediate filaments slightly thicker than microfilaments supporting framework dense arrangement in cells on outer skin layer connects everything in the cell Microtubules thickest cell fiber engines of the cell move things around in cell cause movement of entire cell movement of vesicles movement of chromosomes in mitoses 18

19 Cytoskeleton cont. Centrosome Non-membraneous Very active site Near nucleus Coordinates building and breaking of microtubules microtubule organizing center (MOC) Important role in cell division Centrioles found here form microtubular cell extensions form spindle in cell division 19

20 Cytoskeleton cont. Cell extensions Microvilli found in areas where absorption is important increases surface area of cell allows faster rate of absorption found in epithelial cells that line intestines cover surface of cell contain microfilaments 100s/cell Cilia contain microtubules main purpose movement cilia shorter and more numerous than flagella line respiratory tract; cilia moves mucus to be swallowed Flagella contain microtubules main purpose movement Only present in sperm cells 20

21 Cell to cell contact Gap junctions It directly connects the cytoplasm of two cells, which allows various molecules and ions to pass freely between cells. Channel proteins connect plasma membranes Desmosomes Intermediate filaments connect plasma membranes specialized for cell-to-cell adhesion Ex. Skin cells Tight junctions join together the cytoskeletons of adjacent cells. Xb0PFFGblI 21

22 PASSIVE Cellular Transport with concentration gradient Moves from areas of HIGH to low concentration Simple diffusion movement of particles through bilayer from high to low concentration 3 main categories Dialysis diffusion of small solute particles through selectively permeable membrane Osmosis diffusion of water Facilitated diffusion diffusion of particles through membrane with help of carrier proteins 22

23 Diffusion how_diffusion_works.html 1. molecules densely packed when enter water 2. molecules collide in high conc. 3. gradually move away from each other 4. toward low conc. 5. eventually evenly distributed 1.semipermeable membrane 2.left unbalanced 3.right - homeostasis

24 Dialysis

25 Osmosis Osmotic pressure / tonicity water pressure that develops in the solution with the higher concentration of impermeable solute (low water concentration) how_osmosis_works.html

26 Osmosis cont. Hypotonic Isotonic Hypertonic Pressure Low Same High Solute conc Low Same High Water conc High Same Low Cell change Swells Same Shrinks plasmolysis crenation

27 Facilitated Diffusion how_facilitated_diffusion_works.html 1. Carrier mediated 2. Attracts solute to binding site 3. Carrier protein changes shape 4. Solute can move to other side of memb

28 ACTIVE Cellular Transport against concentration gradient From low to HIGH concentration Non-vesicular membrane transport uses carrier protein & ATP ATPases ex. Sodium-Potassium pump Vesicular membrane transport Endocytosis Phagocytosis - taking in of solute particles by vesicles fusing with plasma membrane cellular eating Pinocytosis taking in of dissolved particles (fluid) by vesicles fusing with plasma membrane cellular drinking Exocytosis movement of particles out of the cell via secretory vesicles fusing with plasma membrane 28

29 Active Transport Carrier protein uses ENERGY to move solute AGAINST conc gradient 3 Na + /2K +

30 Endocytosis

31 Name Type of Transport Direction Of Movement Examples Facilitated Diffusion passive Towards Lower concentration Osmosis passive Towards Lower concentration Dialysis passive Towards Lower concentration Non-vesicular active Towards Higher concentration Vesicular (phagocytosis) active Towards Higher concentration Water, glucose, and amino acids. (polar or large) Water only. Small solute particles Na-K pump, Ions, sugars, amino acids. Cellular eating, large particles Vesicular (pinocytosis) active Towards Higher concentration Cellular drinking, small dissolved particles/fluid

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33 Enzymes Functional proteins Catalyst Lowers activation energy to start chemical reaction Not changed in reaction or used up Tertiary/quaternary proteins Cofactor inorganic, non protein Coenzyme organic, non protein Active site part of enzyme where binds to substrate Lock-and-key model 33

34 Enzyme Function Allosteric Effect Allosteric effector molecule binds to allosteric site Active site s shape is changed Inhibition or Activation of enzymes Factors that have allosteric effect ph Temp Cofactors being added/removed Proenzymes inactive enzymes Kinases synthesize enzymes Convert proenzyme to enzyme

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36 Cell Metabolism 1. Catabolism a. net output of energy b. Breaks down large molecules into smaller ones c. ie. cellular respiration 2. Anabolism a. net input of energy b. Build large molecules from smaller ones c. ie. synthesizing DNA 36

37 Cellular Disease 1.Cystic fibrosis a. Cl - pumps in membrane missing b. Secretions (sweat, mucus) salty c. Thick mucus causes lung infection d. Respiratory & digestive problems 2.Diabetes mellitus/type 2 a. Adult onset b. Non-insulin dependent c. Obesity onset d. Reduces insulin receptors in memb 3.Cancers a. Abnormalities in mitosis b. Cause tumors c. Hyperplasia: increase in number of cells/proliferation of cells 4.Genetic Disorders a. Sickle-cell anemia: mutation in hemoglobin protein

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