Exploring Cell Structure and Function: A Comprehensive Guide

1. The Cell Unit B Chapter 3

3. The Cell Theory • All living things are made up of one or more cells • The cell is the functional unit of life • All living cells interact with the environment, use energy, grow and come from pre-existing cells

4. The cell as a factory: • The parts of a cell can be compared to the workers and jobs in a factory • Each department in a factory has specific jobs that need to be done or else the factory becomes less efficient and eventually shut down. • The same idea is true for the cell, if one of its components stops working efficiently then the cell or the organism could die.

5. Cell Membrane: • The “gate keeper” or “bouncer” of the cell • Decides which materials enter, which ones stay and which ones leave a cell. • Keeps the good ones in and bad ones out. • Every cell has a cellular membrane (including both animal and plant cells). • It is a phospholipid bilayer with protein molecule inside it. • More about the cell membrane will be seen in section D

6. Cytoplasm • The rest of the cell material that is inside the cell membrane but outside the nucleus • Organelles and vacuoles are considered part of the cytoplasm • Usually the cytoplasm is referred to as the semi-liquid material that surrounds the organelles of a cell

7. Nucleus • The “control center” or the “Boss” • With few exceptions all plant and animal cells possess a nucleus (plural form is nuclei). • Dark mass usually seen in the middle of the cell • Contains the DNA or chromatin of the cell which are the instructions for all the activities of the cell. • It also contains nucleoplasm.

8. Chromatin • Floats in the nucleoplasm • Made of DNA and Protein • Is known as chromosomes when it is coiled up for cell division

9. Nuclear Envelope • The membrane that encloses the contents of the nucleus. • “the Boss’ office” • Protects DNA • It has pores in it for larger materials to pass in and out. Nuclear pore

10. Nucleolus • A visible darker staining region inside the nucleus. • It is where RNA and the materials for ribosomes are made. nucleolus

11. Cell Organelles • Like your body which has organs to perform the necessary functions for life, similarly cells have organelles which perform the necessary function of particular cells. • Many organelles are bound by their own membrane(s) • The proportion of the different organelles inside a particular cell depends on the function of the cell. • For example a cell that produces a lot of hormones will have a large amount of golgi apparatus which is the organelle responsible for packaging the products of a cell.

12. Vacuole • “long term Storage Containers” • Vacuoles serve a variety of functions, including storing nutrients, wastes and water. • Irregular shape • They are usually much larger in plant cells than in animal cells. • Example: in the plant cell they take up almost the entire cell. • They help maintain the shape of the cell

13. Ribosomes • The “workers” that put together the products of the cell. • Non-membranous, and consists of two unequal sized subunits. • The location of protein synthesis • Made from RNA from the nucleolus

14. Ribosomes • Some are free in the cytoplasm or become loosely clustered together to form Polysomes • A polysome is a cluster of ribosomes attached to the same mRNA molecule; each ribosome is producing a copy of the same enzyme/protein. • The proteins produced by free ribosomes in cytoplasm are generally used within the cell • Other ribosomes are embedded in the rough endoplasmic reticulum (RER). • The products of ribosomes in the RER are often secreted from the cell

15. Endoplasmic Reticulum: There are two types of endoplasmic reticulum: • The “assembly line” for the products of the cell • Consists of membranous channels that wind through the cytoplasm usually close to the nucleus 1) Rough endoplasmic reticulum 2) Smooth endoplasmic reticulum

16. Rough Endoplasmic Reticulum: • AKA “rough ER” or “RER” • The ER that has ribosomes embedded in it. • Manufactures proteins for other cells • Assists in the movement of molecules from one area of the cell to another

17. Smooth Endoplasmic Reticulum • Aka : Smooth ER or “SER” • Lack ribosomes • Manufactures steroids • Example: testicle cells which produce testosterone have abundant amounts of smooth ER.

18. Transporting products • When products of the RER and the SER accumulate, sections of the ER filled with these products break free in a process known as blebbing or budding • The result is a collection of small membrane bound sacs called vesicles which contain the biochemicals.

19. Vesicle • “transport containers” • Double membrane bound sacs carrying different products and substances from one part of the cell to another. • Sometimes called transition or transport vesicles as they are used to bring the products to the golgi apparatus for further processing or to the cell membrane for secretion out of the cell. • They can also carry food, waste products, digestive enzymes.

20. Golgi Apparatus • AKA “Golgi bodies” • May looks similar to smooth ER, but it is a set of about 7 or 8 flattened saccules between ER and the cell membrane • “Packages, processes and labels” the products from the ER • Makes concentrated packages of proteins • Put carbohydrate chains (labels) on the packages of proteins so that specific cells recognize them once they are released in the blood. • Makes lysosomes

21. Golgi Apparatus: • New vesicles called secretory vesicles with the newly modified products form by blebbing from the golgi apparatus. • The vesicles move towards and join the cell membrane so that their contents are expelled from the cell. • This process is know as exocytosis which will be taught later in this section.

22. Secretory Pathway • Shows the interrelationships between cell organelles

23. Lysosomes • “Janitors or quality control” • Vesicle-like structures that contain hydrolytic enzymes used for digestion of molecules in the cells. • Have a double membrane • Multicellular organisms use them to digest unwanted cells (dying cells) and cell parts that are defective (autodigestion) • Think of them as the quality control or health board, that can shut down the cell at any time.

24. Mitochondrion: • “The Generator” or “power house” of the cell • Plural form “mitochondria” • Performs Cellular Respriation • Fluid filled, with a complex internal membrane • The inner fluid is called the matrix • The inner membrane which folded in the matrix is called the cristae.

25. Cellular Respiration • A series of chemical reactions that give the cell all the energy it needs • The energy is saved in the high energy bonds of an ATP (adenosine triphosphate) molecule. Net Chemical Reaction: Glucose + oxygen → Carbon dioxide + water + energy Balanced Chemical Reaction: C6H12O6 + 6O2→ 6CO2 + 6H2O + 38 ATP

26. Chloroplasts • Chloroplasts are specialized organelles found in all higher plant cells and some photosynthetic protists. • The place where photosynthesis takes place. • These organelles contain the plant cell's chlorophyll, which enable them to capture sunlight energy

27. Chloroplasts • They have a double outer membrane. • Inside the inner membrane the fluid filled space is called the stroma • Within the stroma are other membrane structures including the thylakoids. • Thylakoids are flattened sacs that contain chlorophyll and are piled up like a stack of coins, each stack is called a granum (plural is grana) • There are membranous connections between the grana called lamellae

28. Photosynthesis Net Chemical Reaction: Carbon dioxide + water + energy → Glucose + oxygen Balanced Chemical Reaction: 6CO2 + 6H2O →C6H12O6 + 6O2 Sunlight + Chlorophyll

29. Cell Wall • The cell wall provides and maintains the shape of these cells and serves as a protective barrier. • Made of cellulose • Has large pores that allow many molecules to enter. • Not found in animal cells • Restricts the size and shape of a cell.

30. Cytoskeleton: • Helps maintain the cell’s shape • Anchors the organelles • Allows the cell and its organelles to move • Constist of two basic types of structures: • Microtubules: assembled by the Microtubule organizing center (MTOC) which is found near the nucleus. Form spindle fibers during cell division and make cillia and flagella. • Actin filaments (AKA microfilaments): long thin protein fibers, usually found in bundles. Capable of contracting. Found especially in muscle cells and microvilli. Both canassemble and disassemble.

31. Centriol: • “Traffic Cop” • Organizes organelles and chromosomes during cell reproduction • Microtubules arranged in a specific pattern. • Found in the MTOC at right angles to each other.

32. There are some structures that plant cells possess that animal cells do not. Including: Cell wall Chloroplasts Also, plant cells have larger vacuoles (that sometimes appear to take up the entire cell). Plant cell do not have a centriole! Plant cells vs Animal cells

33. Cell membrane Centriol Cytoplasm Lysosome Rough ER Nucleus Nucleolus Smooth ER Nuclear Envelope Ribosomes Vacuole Golgi Apparatus Mitochondrion

34. Cytoplasm Cell Wall Lysosome Cell membrane Vacuole Nucleus Rough ER Nucleolus Smooth ER Nuclear Envelope Ribosomes Chloroplast Golgi Apparatus Mitochondrion