MCAT The Cell

Prokaryote & Eukaryote - Commonalities Cytoskeleton - "Scaffolding" a) microfilaments

twisted double strand composed of the protein, actin; - are the thinnest elements of the cytoskeleton and are present in all cells; Functions: - used to generate movement (cytoplasmic streaming - "race track": in plants to move chloroplasts to areas with high exposure to sunlight, organelle arrangement in cell division, waste removal) and of amoeboids/white bloodcells (squeeze cytoplasm in direction to move aka psuedopodia); - provide mechanical support as in microvilli (make up core); - they anchor the cytoskeleton to integral proteins in the plasma; - involved in muscular contractions (via interactions with myosin motors; contraction forms cleavage furrow pinching diving cell into two daughter cells); - found mostly at the edge of the cell

The Eukaryotic Cell - The Parts Lysosomes: Formed by? Function

- A type of transport vesicle formed by the golgi apparatus that contain powerful enzymes that break down the cell - they break down harmful cell products, cells that are about to die, waste materials and cellular debris and forces it out of the cell

The Eukaryotic Cell - The Parts 3. Ribosomes - "Factories"

- Non-membrane bound organelles constructed in the nucleolus and functioning as the site of protein synthesis in the cytoplasm. - Consist of two subunits made up of rRNA and protein molecules. - Takes orders from the nucleus and ships protein to the ER. - Exist as free-floating or bound organelles.

The Eukaryotic Cell - The Parts Glyoxysomes

- Specialized peroxisomes found in fat-storing tissues of plant seeds that have enzymes for converting fatty acids to sugars; - used for energy UNTIL photosynthesis occurs to produce its own sugar.

Prokaryote

- a unicellular organism that has no nuclear membrane; - no organelles in the cytoplasm except ribosomes; - DNA in the form of nucleoids (single continuous strands forming coils or loops) and possibly plasmids(consist of a few genes that can replicate independently of the main chromosome); -characteristic of all organisms in the kingdom Monera; - includes bacteria and blue-green algae

Prokaryote & Eukaryote - Commonalities Cytoskeleton - "Scaffolding" b) microtubules

- hollow, polymers of tubulin proteins - radiate throughout cell providing superhighways for transport as well as structural support - involved in chromosome seperation during mitosis and meiosis - structural basis for cilia and flagella

The Eukaryotic Cell - The Parts 2. Nucleus - "City Hall & Library"

- membrane-bound organelle that contains the cell's DNA and that has a role in processes such as growth, metabolism, and reproduction - wrapped in a double phospholipid bilayer (nuclear envelope/membrane) which is perforated with holes (nuclear pores) that RNA exists through

The Eukaryotic Cell - The Parts Peroxisomes: made by? Function

- similar to lysosomes but have different enzymes; - made by the ER; - abundant in liver and kidney cells where they neutralize oxygen ions that can hurt cells and detoxify alcohol and drugs; - named for hydrogen peroxide because they produce it when breaking down alcohol and killing bacteria - they also break down fatty acids that mitochondria then use as energy

The Eukaryotic Cell - The Parts Microbodies

- smaller version of lysosomes with specific enzyme activities; - organelles that serve as specialized containers for metabolic reactions; - vesicles that are formed from incorporation of lipids and proteins and that contain oxidative and other enzymes; - isolate particular chemical activities from rest of cell include peroxisomes and glyoxysomes

The Eukaryotic Cell - The Parts 1. Cell Membrane - "city wall"

- surface of cell separating the inside from the surrounding extracellular fluid - controls the entry or elimination of ions, nutrients, and waste. - consist of phospholipid bilayer: proteins & lipids are the "city gates" - cholesterol: w/in determines rigidity - transport protiens: "border agents" allowing polar molecules and ions passage - cell adhesion molecules (CAM's): proteins that allow for cell recognition & development

Cell Theory

1. all living things are composed of cells 2. cells are the basic units of structure and function in living things 3. new cells are produced from existing cells 4. cells carry genetic information (DNA)

The Eukaryotic Cell - The Parts 4. Endoplasmic Reticulum - "Assembly Line - Manufacturers" a) rough ER b) smooth ER

4. attached to nuclear membrane and involved in chemical transport within the cell; made up of many channels a) rough "ER" has ribosomes on its surface, serves to store and deliver the proteins made by the attached ribosomes. - rough ER cisternae are involved in chemical modification of proteins b) smooth "ER" is free of ribosomes and is found in a variety of cells. Functions: - storage of enzymes and minerals - folding of proteins - detoxification of chemicals - metabolism of fats. - transport vesicles bud off smooth ER and are sent to the Golgi - triglycerides are produced here and storeed in adipocytes

Cell Organelles - "form follows function"

Cells that require a lot of locomotion (e.g. sperm cells) will have lots of mitochondria; cells involved in secretion (e.g. islet cells of pancreas) will have lots of golgi bodies; cells serving transport only (e.g. blood cells) have no organelles at all.

Prokaryote & Eukaryote - Commonalities Cytoskeleton - "Scaffolding" c) intermediate filaments

Diverse fibrous proteins (from keratin family) supercoiled into thicker cables; - Functions: - maintaining cell shape - the anchoring of some organelles such as the nucleus, - formation of the nuclear lamina - ( In the middle in terms of size) 8-12 nm; - More permanent than the other filaments

Gram Postive Prokaryote

Have a thick cell wall of petidoglycan.

Gram Negative Prokaryote

Have a thin peptidoglycan layer sandwiched between layers of periplasm and coated with a layer of lipopolysaccharide and protein.

The Eukaryotic Cell - The Parts Vacuoles - "Storage"

Membrane-bound liquid-filled spaces found in most cells in variable numbers. Plant cells typically have large fluid-filled vacuoles, containing cell sap, that provide physical support (turgidity) and storage. In other cells, vacuoles may be involved in intracellular digestion (food vacuoles) or water balance (contractile vacuoles).

The Eukaryotic Cell - The Parts Mitochondria - "Power Plant": Function Inner Membrane Outer Membran Inner Matrix Where does ETC occur? Where does the Kreb cycle occur? How do mitochondria replicate? Apoptosis

Once the food is made into smaller pieces by the lysosome, the mitochondria breaks it down further to produce ATP for cellular functions. -Surrounded by two highly folded membranes: - the outer is a wall that lets in molecules based on size, -the inner contains the molecules and enzymes used in the e- transport chain (cristae w/in increase surface area for ETC) and surrounds the inner mitochondrial matrix (site of Krebs/TCA Cycle) which contains the mitochondria's DNA and ribosomes - Replicates via binary fission; thought to have risen from ingestion by prokaryote in a symbiotic relationship. - In apoptosis, release the enzymes from the ETC that kill the cell.

Prokaryotes vs Eukaryotes

PROKARYOTES ("pro" = before, "karyon" = nucleus) 1. Unicellular: Bacteria and blue-green algae 2. No nucleus; nucleiod region with single circular DNA; single chromosome; 3. Smaller 4. Cell wall in all 5. Ribosomes (30 & 50S) 6. No membrane-bound organelles 7. Transcription and Translation in cystosol EUKARYOTES ("eu" = true, "karyon" = nucleus) 1. Unicellular or Multicellular: protists, fungi, plants & animals 2. Nucleus; consist of mutiple chromosomes 3. Bigger 4. Cell wall ONLY in fungi & plants 5. Ribosomes (40 & 60S) 6. Membrane-bound organelles 7. Transcription in nucleus; Translation in cytosol BOTH 1. Cytoplasm 2. DNA 3. Cell membrane 4. ribosomes 5. Activities of living things

The Eukaryotic Cell - The Parts Chloroplasts - "Solar Power Plant"

Plant cell organelle that contains the pigment chlorophyll that absorbs light energy for use in of photosynthesis (CO2 + H2O = carbs) - Chlorophyll is located within parallel stacks of membranes called grana. are characteristic of plant and algae cells; animal cells do not have these; - Contain their own DNA and may have evolved second by symbiotic relationship with primitive eukaryote.

The Eukaryotic Cell - The Parts 5. Golgi Apparatus - "Post Office"

Stack of membranes in the cell that modifies (glycoslyation: add carbo chains or remove AA's), sorts, and packages proteins from the ER - Vesicles are either excreted from the cell via exocytosis, released to mature into lysosomes in the cytosol, or transported to other organelles within the cell. - Vesicles may contain enzymes, growth factors, extracellular matrix, or membrane integral proteins & lipids.

Prokaryote & Eukaryote - Commonalities Cytoskeleton - "Scaffolding": Function 3 Components

a network of fibers extending throughout the cytoplasm that are easy to dismantle and move; - gives the cell mechanical support (e.g. provides track from ER to golgi for vesicles, pulls on membrane in phagocytosis), maintains shape, provides anchorage for organelles,and motility; - composed in all cells (recent discovery in prokaryotes) - 3 components: microfilaments, microtubules, intermediate filaments

The Eukaryotic Cell - The Parts 2. Nucleus - "City Hall & Library" a) Nucleolus b) Nucleoplasm

a) A region within the nucleus not seperated by a membrane where rRNA is transribed (synthesized) and ribosomes are partially assembled. b) Semifluid medium of the nucleus containing chromatin ("the soup").

The Eukaryotic Cell - The Parts

cell membrane, nucleus, nuclear membrane, cytoskeleton, ribosomes, lysosomes, peroxisomes, golgi apparatus, endoplasmic reticulum (rough ER, smooth ER), centrioles, vacuoles, chloroplasts, cytoplasm * See fig. 1.5 on pg 12 in Kaplan Bio Notes

The Eukaryotic Cell - The Parts Centrioles - "Spindle Spinsters": Function Who has them? Where are they located?

specialized microtubles involved in spindle organization/chromosome seperation during cell division (prophase); - not bound by a membrane; - animal cells usually have 2 centrioles at right angles to each other and lie in the centrosome near nuclear envelope; - plant cells do not have them