Unit 2 Quiz Flashcards (Organelles + Membranes)

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Cells

• The basic structural and functional units of every organism

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)

• Smaller 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 that have specific functions

• Two classifications: Endomembrane organelles and energy organelles

Endomembrane Organelles

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 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

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

• Contains a nucleolus

Nucleolus

• A dense region of the nucleolus where rRNA is synthesized

• rRNA is combined with proteins to form the 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 rRNA 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

• Can be secreted from the cell 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 the free ribosomes

Two types:

Rough ER: Contains ribosomes bound to the ER membrane

Smooth ER: Contains no ribosomes

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

Golgi Complex

• Contains flattened membranous sacs called cisternae that separate the sacs from the cytosol

• 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/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

• Catalyze reactions that produce H202 (hydrogen peroxide)

• Enzymes then break down H202 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 (pressure against cell wall)

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 an endosymbiont (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)

• Mitochondria have their own DNA and energy source

Contains:

1. Enzymes that catalyze cellular respiration and produce ATP

2. Mitochondrial DNA

3. Ribosomes

• The number of mitochondria 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 myosin to cause a contraction

3. Contractile ring of the cleavage furrow in the division of animal cells

Intermediate filaments

• Fibrous proteins 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

• Size dictates 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

• 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)

Cellulose

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