Unit 2 Quiz Flashcards (Organelles + Membranes)

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Cells

• The basic structural and functional units of every organization

All cells…

1. Bound by a plasma membrane

2. Contains cytosol, chromosomes, and ribosomes

• Two types: Prokaryotes and Eukaryotes

Prokaryote

• Domains bacteria and archaea

• DNA is the nucleotide region (NO NUCLEUS)

• Generally smaller in size than eukaryotes

• Single-celled

Eukaryote

• Protists, fungi, animals, and plants

• DNA is in the nucleus

• Contain membrane-bound organelles

Organelles

• Membrane-bound structures in eukaryotes.

• Two classifications: Endomembrane organelles and energy organelles

Endomembrane Organelles

A group of organelles in eukaryotic cells that work together to modify, package, and transport lipids and proteins.

• Nuclear envelope

• Endoplasmic reticulum

• Golgi complex/apparatus

• Lysosomes

• Vesicles/vacuoles

• Plasma membrane

Energy organelles

Perform energy production

• Mitochondria

• Chloroplasts

Compartmentalization

• Divides cells into different parts

• Allows for different metabolic reactions to occur in different locations

• Increases surface area for reactions to occur

• Prevents interfering reactions from occurring in the same location

Unique Components

Plants:

• Chloroplasts

• Central vacuole

• Cell wall

• Plasmodesmata

Animals:

• Lysosomes

• Centrosomes

• Flagella

Nucleus

• Contains chromosomes (genetic information)

• Enclosed by the nuclear envelope (double membrane)

• Has pores that regulate the entry and exit of materials from the cell

• Contains a nucleolus

Nucleolus

• A dense region of the nucleolus where ribosomal RNA (rRNA) is synthesized

• rRNA is combined with proteins to form the large and small subunits of ribosomes

• Subunits exit via nuclear pores → assemble into ribosomes

• Ribosomes translate messages from mRNA into the primary structure of polypeptides

Ribosomes

• Comprised of ribosomal RNA and proteins

• Synthesize proteins

• Not bound by a membrane, so they’re not always considered an organelle

Can be found in…

1. Cytosol: Proteins produced here only function within the cytosol (ex. enzymes)

• “free ribosomes”

2. Bound to the ER or nuclear envelope

• Proteins produced here can be secreted from the cell

• Leave via transport vesicles

Endoplasmic Reticulum

• A network of membranous sacs and tubes

Functions…

• Synthesize membranes

• Compartimentalize the cell to keep proteins formed in the rough ER from those of free ribosomes

Two types:

Rough ER: Contains ribosomes bound to the ER membrane

Smooth ER: Contains no ribosomes

• Synthesize lipids, metabolizes, carbohydrates, and detoxifies carbohydrates, and detoxifies the cell

Golgi Complex

• Contains flattened membranous sacs called cisternae

• Separate the sacs from the cytosal

• Each cisternae is not connected (has directionality)

Cis face: Receives vesicles from the ER

Trans face: Sends vesicles back out into the cytosol to other locations or to the plasma membrane for secretion.

Functions:

1. Receives transport vesicles with materials from the ER

2. Modifies the materials

3. Ensures newly formed proteins are folded correctly or modified correctly

4. Sorts the materials

5. Adds molecular tags

6. Packages materials into new transport vesicles that exit the membrane via exocytosis

Lysosomes

• A membranous sac with hydrolytic enzymes

• Function: Hydrolyzes macromolecules in animal cells

Autophagy

Lysosomes can recycle their own cell’s organic materials

• allows the cell to renew itself

Peroxisomes

• Similar to lysosomes

• Membrane-bound metabolic compartment

• Catalyze reactions that produce H202 (hydrogen peroxide)

• Enzymes in peroxisomes then break down H20 to water

Vacuoles

• Large vesicles that stem from the ER and Golgi (Selective in transport)

Types of Vacuoles:

• Food vacuole: Form via phagocytosis (cell eating) and are then digested by lysosomes.

• Contractile vacuole: Maintains water levels in cells

• Central vacuole:

1. Found in plants

2. Contains inorganic ions and water

3. Important for turgor pressure

Endosymbiont Theory

• The theory that explains the similarities between mitochondria and chloroplasts has to a prokaryotic cell.

• An early eukaryotic cell engulfed a prokaryotic cell

• The prokaryotic cell became a (a cell that lives in another cell)

Evidence: 

1. Double membrane

2. Ribosomes

3. Circular DNA

4. Can function on their own

Mitochondria

• Site of cellular respiration

• Structure of the double membrane: Smooth outer membrane and folds called cristae in the inner membrane that divide the mitochondria into 2 internal compartments and increase the surface area.

• Intermembrane: Space between the inner and outer membranes

• Mitochondrial Matrix: enclosed by the inner membrane (Location for the Krebs cycle)

Contains:

1. Enzymes that catalyze cellular respiration and produce ATP

2. Mitochondrial DNA

3. Ribosomes

• The number of mitochondria in a cell correlates with metabolic activity

• Cells with high metabolic activity have more mitochondria (Cells that move/contract)

Chloroplasts

• Specialized organelles in photosynthetic organisms

• Site of photosynthesis

• Contains the green pigment chlorophyll

Inside it’s double membrane…

• Thylakoids: Membranous sacs that can organize into stacks called grana

• Light-dependent reactions occur in grana

• Stroma: Fluid around thylakoids

• Location for the Calvin Cycle

• Contains: Chloroplast DNA, Ribosomes, Enzymes

Microfilaments

• Thin, solid rods made of the protein actin

Functions:

1. Maintain cell shape: Bear tension

2. Assist in muscle contraction and cell motility: Actin works with another protein called myosin to cause a contraction

3. Division of animal cells: Contractile ring of the cleavage flow

Intermediate filaments

• Fibrous proteins are made up of varying subunits

• Permanent structural elements of cells

Functions:

1. Maintain cell shape

2. Anchor nucleus and organelles

3. Forms the nuclear lamina: Lines the nuclear envelope

Cell size

• Cellular Metabolism depends on cell size.

• Cellular waste must leave

• Dissipate thermal energy

• Nutrients and other resources/chemical materials must enter

• At a certain size, it begins to be too difficult for a cell to regulate what comes in and what goes out of the plasma membrane

• The size of a cell will dictate the function

• Cells need a high SA to V ratio to optimize the exchange of material through the plasma membrane.

Cell size 2

• Cells tend to be small

• Small cells have a high SA: V ratio which optimizes the exchange of materials at the plasma membrane

• Large cells have a lower SA: V ratio, so they lose efficiency when exchanging materials ↴

1. The cellular demand for resources increases

2. The rate of heat exchange decreases

Plasma Membrane

• Separates the internal cell environment from the external environment

• Comprised primarily of amphipathic phospholipids

• Forms a bilayer

• Selective permeability: The ability of membranes to regulate the substances that enter and exit.

• Hydrophilic heads: Oriented towards aqueous environments

• Hydrophobic tails: Facing inwards AWAY from aqueous environment

Fluid Mosaic Model

• A model to describe the structure of cell membranes

• Fluid: Membrane is held together by weak hydrophobic interactions and can therefore move and shift

• Temperature affects fluidity

• Unsaturated hydrocarbon tails help maintain fluidity at low temps (Kinked tails prevent tight packing of phospholipids)

• Cholesterol: Helps maintain fluidity at high and low temperatures

• High temps: reduces movements

• Low temps: reduces the tight packing of phospholipids

• Mosaic: Comprised of many macromolecules

Membrane Proteins

• Proteins in the membrane

• Integral Proteins: Amphiphatic proteins that are embedded into the lipid bilayer (AKA Transmembrane proteins)

• Peripheral Proteins: Proteins that are not embedded into the lipid bilayer and loosely bound to the surface

Membrane Carbohydrates

• Important for cell-to-cell recognition

• Glycolipids: Carbohydrates bonded to lipids

• Glycoproteins: Carbohydrates bonded to proteins (most abundant)

Plant cells

• Plants have a cell wall that covers their plasma membranes

• Extracellular structure (not found in animal cells)

• Provides: Shape/structure, protection, regulation of water intake

• The cell wall is composed of cellulose (thicker than plasmodesmata)

• Hole-like structures in the cell wall filled with cytosol that connect adjacent cells.