Cellular Structures & Functions

CYTOPLASM (Between nucleus and cell membrane) Includes ORGANELLES- small structures with a specific function CYTOSOL-semi-fluid “goo” Image from: Image from:

NUCLEUS Surrounded by DOUBLE membrane (Nuclear envelope) Nuclear pores- allow molecules in & out Contains DNA Control center Replication (DNA → DNA) Transcription (DNA → RNA) Image from:

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings NUCLEAR ENVELOPE Figure 6.10 Nucleus Nucleolus Chromatin Nuclear envelope: Inner membrane Outer membrane Nuclear pore Rough ER Pore complex Surface of nuclear envelope. Pore complexes (TEM). Nuclear lamina (TEM). Close-up of nuclear envelope Ribosome 1 µm 0.25 µm

NUCLEOLUS Dark spot in nucleus Produces ribosomal RNA Assembles ribosomes (RNA & proteins) Image from:

DNA CHROMATIN- spread out in NON-dividing cells to access info CHROMOSOMES- condensed in dividing cells for easier transport

Cytoskeleton Network of protein fibers supporting cell shape and anchoring organelles – Microtubules – Microfilaments

RIBOSOMES Composed of two subunits that join and attach to messenger RNA Made of r-RNA & proteins Site of protein synthesis (~translation of genetic instructions to yield specific polypeptides)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings ENDOMEMBRANE SYSTEM Regulates protein traffic and performs metabolic functions in the cell Includes: Plasma membrane Nuclear membrane Endoplasmic reticulum Golgi apparatus Vacuoles Lysosomes

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings CELL MEMBRANE (also called plasma membrane) PHOSPHOLIPID BILAYER with PROTEINS Hydrophobic tails face in Hydrophilic heads face out Outside of cell Inside of cell (cytoplasm) Cell membrane Proteins Protein channel Lipid bilayer Carbohydrate chains Membrane Image from: © Pearson Education Inc, Publishing as Pearson Prentice Hall; All rights reserved Phospholipid image from: SEE HOW MEMBRANES FORM

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings FLUID MOSAIC MODEL Molecules in cell membranes are constantly moving and changing Click here to See Fluidity Animation from:

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings CELL MEMBRANES act as boundary selectively permeable ~ gases & hydrophobic molecules can pass through ~ large, ionic, OR polar molecules need help (facilitated diffusion, ion channels, Na+-K+ pump, endocytosis & exocytosis)

ENDOPLASMIC RETICULUM (ER) Lipid bilayer continuous with nuclear envelope Smooth ER no ribosomes synthesis of lipids Rough ER with ribosomes synthesis of secretory proteins (glycoproteins) membrane production compartmentalizes: serves as mechanical support, site specific protein synthesis with membrane bound ribosomes, and intracellular transport Image from:

Golgi apparatus ( collection of Golgi bodies) Consists of a series of flattened membrane sacs called cisternae “UPS” of cell Modify, sort, & package molecules from ER for storage OR transport out of cell via vesicles Produces lysosomes Image from: Image from:

Animation from: See a Golgi movie

EVERYTHING’S CONNNECTED!

18 LYSOSOMES (common in animal cells but rare in plant cells) Contain hydrolytic enzymes for intracellular digestion Food (Phagocytosis) Damaged organelles AUTOPHAGY ~ “eating self” Bacteria Recycles cell’s organic materials Helps in APOPTOSIS See movie

“PROGRAMMED CELL DEATH” APOPTOSIS Embryo development Cell maintenance Signal to self destruct lost in cancer cells

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LYSOSOMES: Uncontrolled release of lysosome contents into the cytoplasm can also cause cell death (necrosis) APOPTOSIS (self-destruct mechanism) “cell suicide” Embryonic development Removes damaged cells Immune response Cancer cells and AIDS virus override self-destruct signals

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings WHITE BLOOD CELLS USE LYSOSOMES TO DIGEST ENGULFED BACTERIA (Phagocytosis)

CENTRIOLES Made of microtubules Appear during cell division in animal cells to pull chromosomes apart

CENTRIOLES/MITOTIC SPINDLE Made of MICROTUBULES (Tubulin) Image from:

MITOCHONDRIA DOUBLE MEMBRANE Creates compartmentalization within mitochondria Outer membrane is smooth inner membrane highly convoluted to (increase surface area) forming cristae that contain enzymes that make ATP Images from:

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings MITOCHONDRIA Has own DNA Powerplant of cell ~ site of cellular respiration – ~ burn glucose – ~ store energy as ATP Specializes in energy capture and transformation

CHLOROPLASTS DOUBLE MEMBRANE Compartmentalize structures Contains thylakoid sacs with chlorophyll (key light trapping molecules in photosynthesis and reason why plants are green) for photosynthesis= energy capturing reactions in thylakoids produce ATP and NADPH which fuel C fixing reactions in Calvin Cycle. C fixation occurs in the stroma where molecules of CO 2 are converted to carbohydrates. Has own DNA

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Who else has a circular chromosome not found within a nucleus?

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Endosymbiotic Theory Originally proposed in early 1900’s Idea reintroduced in 1963 by Lynn Margulis Suggests that engulfed prokaryotes shared symbiotic relationship with host cell Advantages for both: ~ one supplies energy ~ other raw materials & protection

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings ENDOSYMBIOTIC THEORY See a movie about ENDOSYMBIOTIC THEORY

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Evidence for Endosymbiotic theory 1. Mitochondria and chloroplasts have circular DNA like bacteria. 2. Mitochondria and chloroplasts have ribosomes whose size and structure resemble bacterial ribosomes. 3. Mitochondria and chloroplasts replicate independently of cell division using binary fission like bacteria. 4. Inner membranes of mitochondria and chloroplasts have a composition similar to bacterial membranes.

Move substances past cells Help move cells FLAGELLA & CILIA Made of microtubules

CILIA Many short FLAGELLA Few Long WHAT’S THE DIFFERENCE? Animation from:

WHAT’S SPECIAL ABOUT PLANT CELLS? Cell wall HUGE vacuoles Chloroplasts No centrioles

CELL WALL Outside cell membrane Supports and protects cell Plants- Cellulose makes it “sturdy” Bacteria- have peptidoglycan instead

VACUOLES Huge in plants Storage space for water, food, enzymes, waste Helps with intracellular digestion with release of cellular waste products Image from:

Freshwater organisms have contractile vacuoles to control excess water in cells (HOMEOSTASIS)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PLANT VACUOLES (Central Vacuole) Surrounded by membrane = Selectively permeable – controls what goes in & out STORAGE Water Stockpile proteins/inorganic ions Deposit metabolic byproducts Store pigments Store defensive compounds against herbivores

WHAT’S DIFFERENT ABOUT BACTERIAL CELLS? Cell wall NO NUCLEAR MEMBRANE DNA is circular No membrane bound organelles

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

WHICH IS BIGGER? _________ > _____________ > ___________ Plant cellAnimal cell bacteria