Cell Structure

1. Unit 3 Obj. 1.1.1, 1.1.2 Cell Structure

2. Place an “X” next to the things you think are made of cells • ___ flowers ___ hamburger ___ leaf • ___ skin ___ DNA ___ seeds • ___ proteins ___ calcium ___ water • ___ rocks ___ apples ___ sugar • ___ milk ___ sand ___ blood • ___ bone ___ worms ___ saliva • ___ lungs ___ bacteria ___ mushroom

3. What is a cell? • The smallest unit of life; the smallest thing biologists study • RECALL: Organization of Living Things: • Cell  Tissue  Organ  Organ system  Organism

4. What is a cell? • Cells have smaller parts inside of them called organelles • This means “little organ.” They perform special functions for the cell to keep it (and the organism) alive.

5. What is a cell? • Cells were discovered in 1665 by Robert Hooke • He thought they looked like the rooms monks lived in, so he called them “cells”

6. What is a cell? • Anton van Leeuwenhoek was the first to see living cells. He used a hand held microscope to look at pond scum and scrapings from his teeth in 1673. • He thought they look like little animals.

7. Cell Theory • Contributed to by Theodor Schwann and Matthias JakobSchleiden in 1839 and Rudolf Virchow in 1858. • Three main ideas: • 1. All living things are made of one or more cells. • Unicellular = one-celled organism • Multicellular = organism made from many cells • 2. Cells are the basic unit of structure and function in all living things. • 3. All new cells come from pre-existing cells.

8. Types of cells • 1. Prokaryotic (means “before nucleus”) • No nucleus, unbound DNA • No membrane-bound organelles • Small and simple; “older” type of cell • Examples: Bacteria • 2. Eukaryotic (means “true nucleus”) • Has a nucleus, DNA is inside nucleus • Has organelles • Larger and more complex; “younger” type of cell • Examples: Plants and Animals

9. Cell Membrane • Aka “plasma membrane” • Provides protection, helps cell communicate, transports substances in and out of cell, keeps the cell together • Made of a phospholipidbilayer (phosphate head, lipid tail, two layers) • The head is hydrophilic (loves water), the tails are hydrophobic (fears water) • Selectively permeable • Found in all cells

10. Cell Wall • Only found in plant cells • Shapes and supports the cell • Provides additional protection • Made of cellulose = humans cannot digest

11. Nucleus • Contains the genes that control the cell = DNA • Chromatin = uncoiled DNA • Chromosomes = coiled DNA • Surrounded by nuclear envelope = double membrane • The “information center” of the cell

12. Nucleolus • Makes rRNA and assembles ribosomes • Not surrounded by a membrane • Cells can have 1-3 • Disappears when the cell divides

13. Mitochondria • Where the cell performs respiration makes ATP, a molecule the cell can use as energy for work • Major site of metabolism • Folded inner membrane (cristae)  more surface area for chemical reactions

14. Chloroplast • Found only in plant cells • Contains chlorophyll = pigment that gives plants their green color • Traps sunlight to make glucose (food) • Site of photosynthesis

15. Ribosomes • Protein synthesis = making proteins using RNA from the nucleus to assemble amino acids into proteins • Can be floating in cytoplasm or attached to a membrane

16. Vacuole • Stores water, sugar, salts, nutrients, wastes, etc. • Large and central in plant cells • Small or not present in animal cells

17. Cytoplasm • Jelly-like substance that helps fill up the cell and suspend organelles • Site of many metabolic reactions

18. Centriole • Only found in animal cells • Made of microtubules • Help the cell divide

19. Golgi Apparatus • Processes and packages macromolecules that are synthesized by the cell in vesicles (membrane bound packages) • Secretion • Found in eukaryotes only

20. Rough endoplasmic reticulum • Rough ER • Called “rough” because it is studded with ribosomes • Makes proteins • The “highway” of the cell  transports proteins

21. Smooth endoplasmic reticulum • Smooth ER • Lacks ribosomes • Makes lipids • Also the “highway” of the cell  an interconnected network of tubules and vesicles

22. Cytoskeleton • Made of protein – microtubules and microfilaments • “Framework” of cell • Provides structural support

23. Lysosomes • Contain digestive enzymes • Digest food, worn out organelles, viruses, etc. • Can also act as a “self-destruct button” and cause the cell to lyse itself apoptosis • The “janitor,” “hit man,” and “suicide bomber” of the cell

24. Flagellum • Tail-like projection from cell • Helps cell move by whipping around in a circle  similar to helicopter blade

25. Cilia • Small, hair-like projections • Used to help cell move and sense environment

26. Pseudopodia • “False foot” • Temporary projections of eukaryotic cells • Usually found in amoeba • Cells use extension and contraction to move around

27. Plasmid • DNA molecule that is separate from and can replicate independently from chromosomal DNA • Usually found in prokaryotes

28. Eyespots • Photoreceptive organelle = can sense light • Usually found in unicellular photosynthetic cells, like green algae • Allows the organism to respond to light and swim towards it or away from it

29. Plant cells vs. Animal cells

30. To be or not to be… multicellular • What are some advantages? • Differentiation • More control over internal conditions • Greater motility  able to move around and avoid predators and find more food • Genetic diversity  greater chance for positive traits • What are some disadvantages? • Harder to reproduce  must find a mate first • Need more resources

31. Cell Specialization • When cells have different jobs or functions • Only multicellular organisms can have specialized cells

32. Specialized Animal Cells • Muscle, bone, brain, nerve, skin, hair= all different cells with different functions • Muscle cells: have more mitochondria than other cells= more metabolism! • Cool fact: Muscle cells have more than one nucleus! • Red Blood Cells: lose their nucleus and are donut-shaped to carry oxygen molecules • Remember: Hemoglobin is a protein

33. How do you get specialized cells? • Start as a stem cell= has the ability to become any cell in the body  a “blank slate” • Gets signals (usually hormones) to become a certain cell type (this is called differentiation)

34. Cell Communication - Chemical • Hormones = proteins that are used by both plant and animal cells to send messages • Produced in large amounts, usually in response to something environmental • Travel slowlythroughout the organism • Endocrine system (thyroid, testes, ovaries, pituitary gland, etc.) releases hormones into the blood stream • Affects only those cells with the right receptors= has effects on certain cells in the body

35. Cell Communication - Electrical • Neurons = cells in the nervous system that transmit information throughout the body. Animals only! • Sends messages that can be voluntary or involuntary • Send out neurotransmittersthat get passed from neuron to neuron • Neurons have two main parts: dendriteand axon