Biology Exam 2 (Chapters 4, 5, 6, 7)

Includes chapters 4, 5, 6, and 7.

Microtubules

Straight, hollow tubes composed of globular proteins called tubulins, they elongate by the addition of tubulin proteins.

Eukaryote

Every living thing other than bacteria and arachaea are eukaryotic, the cell is more complex.

Glycoprotein

Made of short chains of sugar linked to the polypeptide.

Mitochondrial Matrix

The inner membrane of the mitochondria, it contains mitochondrial DNA and ribosomes, as well as enzymes that catalyze some of the reactions in cellular respiration.

Microfilaments

Form a three dimensional network that helps maintain a cell’s shape, composed of proteins called actin twisted into a double chain.

Stroma

The compartment within the inner membrane of chloroplasts, holds a thick fluid that contains chloroplast DNA, ribosomes and enzymes.

Chromatin

Complex of proteins and DNA, composed of chromosomes.

Thylakoids

A network of interconnected sacs that are suspended from the storms, they are stacked like poker chips.

Prokaryote

Consists of the domains bacteria and archaea, simple cells.

Substrate

The specific reactant that an enzyme acts on.

Active transport

A cell must expend energy to move a solute against its concentration gradient.

Passive transport

When a cell doesn’t have to work to diffuse molecules across its membrane.

Exergonic

A reaction that releases energy.

Endergonic

A reaction that requires a net input of energy and yields products that are rich in potential energy.

Phosphorylation

Transferring a phosphate group from ATP to another molecule.

Feedback inhibition

When a cell is producing more of that product than it needs, the product may act as an inhibitor of one of the enzymes early in the pathway.

Chemiosmosis

The potential energy of the concentration gradient is used to make ATP.

Oxidation

The loss of electrons from one substance in a redox reaction.

Reduction

The addition of electrons to another substance.

Photosystem

Contains two kinds of complexes: a reaction-center complex surrounded by a number of light harvesting complexes.

Phospholipid

Spontaneously self-assemble into single membranes.

Diffusion

The tendency of particles to spread out evenly in an available space. It doesn’t require energy, meaning it’s passive transport.

Osmosis

Diffusion of water across a selectively permeable membrane.

Facilitated diffusion

Polar substances move across membranes with help of specific transport proteins. It doesn’t require energy and relies on the concentration gradient.

Plasmolysis

The process in which cells lose water when they are placed in a hypertonic solution.

Endosymbiosis

Two organisms living together, with one inside the other.

Endocytosis

Used to take in large molecules.

Exocytosis

Used to export bulky molecules, such as proteins or polysaccharides.

Cell theory

All living things are composed of cells and all cells come from other cells.

Surface to volume ratio

The microscopic size of most cells provides a large surface to volume ratio, ensuring the exchange of resources and waste occurs quickly enough for the cell to survive.

Plasma membrane

A phospholipid bilayer with embedded proteins. Some proteins form channels that shield ions and other hydrophilic molecules as they pass through the hydrophobic center of the membrane. Other proteins serve as pumps, using energy to actively transport molecules in/out of the cell.

Nucleus

Houses the cells DNA, which directs protein synthesis via messenger RNA.

Nucleolus

Where subunits of ribosomes are assembled.

Ribosomes

Composed of ribosomal RNA and proteins and synthesize proteins according to directions from DNA. Cells that make a lot of proteins have a large number of ribosomes.

Endoplasmic Reticulum

A membranous network of tubes and sacs. The smooth ER synthesizes lipids and processes toxins, the rough ER produces membranes and ribosomes on its surface make membrane and secretory proteins.

Golgi apparatus

Consists of stacks of sacs in which products of the ER are processed and then sent to other organelles or to the cell surface.

Lysosome

Houses enzymes that break down ingested substances and damaged organelles, the clean up crew.

Vacuoles

Large vesicles that have a variety of functions. Some protists have contractile vacuoles, plant cells contain a large central vacuole that stores molecules and wastes and facilitates growth.

Peroxisome

Metabolic compartments that do not originate from the endomembrane system.

Mitochondria

Organelles that carry out cellular respiration in nearly all eukaryotic cells. Intermembrane space is the narrow region between the inner and outer membranes. The mt matrix contains mitochondrial DNA, ribosomes, and many enzymes that catalyze some of the reactions of cellular respiration.

Cytoskeleton

Contains micro filaments, intermediate filaments and microtubules.

Cilia

Work like oars on a boat, they have common structure and mechanism of movement.

Flagella

Longer than cilia, propel cell by an undulating, whiplike motion.

Endosymbiont theory

States that mitochondria and chloroplasts were formerly small prokaryotes that began living within larger cells.

Hypertonic

Cells shrink, there’s higher solute levels, both plant and animal cells shrivel.

Hypotonic

Cells swell, there’s lower solute levels, animal cells become lysed (explode) and plant cells are turgid (normal).

Isotonic

There’s equal solute levels, cells are normal in animal cells and flaccid in plant cells.

Gap junctions

Clusters of intercellular channels that allow direct diffusion of ions and small molecules between adjacent cells.

Tight junctions

Multifunctional and dynamic protein complexes that connect adjacent cells by sealing the intercellular space between cells preventing the paracellular movement of solutes, ions and water.

Anchoring junctions

Hold cells together in tissue, they attach cytoskeletal proteins of one cell to cytoskeletal proteins of neighboring cells or extracellular matrix.

Plasmodesmata

A channel through the plant cell wall that allows molecules and substances to move in and out of the cell.

Enzymes

Protein catalysts that decrease the activation energy needed to begin a reaction.

Enzyme structure

1. The enzyme is available with an empty active site.

2. The substrate enters the active site, which enfolds the substrate with an induced fit.

3. The substrate is converted to products.

4. The products are released.

Enzyme denatured

When an enzyme becomes denatured the substrate can’t fit in the active site, preventing the substrate from forming the products.

Competitive inhibitor

Competes with the substrate for the active site.

Non competitive inhibitor

Alters an enzymes function by changing its shape.

Laws of Thermodynamics

Total energy in a closed system is neither lost nor gained and entropy constantly increases in a closed system.

cellular respiration equation

C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + ATP + Heat

Glycolysis

• Stage 1

• Occurs in the cytosol

• ATP is used to prime a glucose molecule, which is split in two

• Three-carbon intermediates are oxidized to two molecules of pyruvate, yielding a net of 2 ATP and 2 NADH

• ATP is formed by substrate level phosphorylation, in which a phosphate group is transferred from an organic molecule to ADP

Pyruvate oxidation and the citric acid cycle

• Stage 2

• Takes place in the mitochondria

• Yields acetyl, CoA, CO2 and NADH

For each turn of the citric acid cycle:

• two carbons from acetyl CoA are added

• 2 CO2 are released

• 3 NADH and 1 FADH2 are produced

Oxidative phosphorylation and chemiosmosis

• Stage 3

• NADH and a related electron carrier, FADH2, shuttle electrons to electron transport chains embedded in the inner mitochondrial membrane.

• Most of the ATP produced by cellular respiration is generated by oxidative phosphorylation.

• The electrons are finally passed to oxygen, which is reduced to H2O

Lactic acid fermentation

A common type of fermentation, allows your muscle cells and certain bacteria to regenerate NAD+.

Alcohol fermentation

Yeasts and certain bacteria recycle their NADH back to NAD+ while converting pyruvate to CO2 and ethanol.

Photosynthesis equation

Energy + 6 CO2 + 6 H2O → C6H12O6 + 6 O2

Where do the stages of photosynthesis occur?

The light reactions occur in thylakoids, producing ATO and NADPH for the Calvin Cycle, which takes place in the stroma. Both the thylakoid and stroma are located in chloroplasts.

Light reactions

• Electrons shuttle from photo system II to photo system I, providing energy to make ATP, and then reduce NADP+ to NADPH

• Photosystem II regains electrons as water is split and O2 is released

• In phosphorylation, the electron transport chain pumps H+ into the thylakoid space

• The concentration gradient drives H+ back through ATP synthase, powering the synthesis of ATP

Calvin Cycle

Using carbon from CO2, electrons from NADPH, and energy from ATP, the cycle constructs G3P, which is used to build glucose and other organic molecules.

Photosynthetic reactions in C3, C4 and CAM plants

• In C3 plants a drop in CO2 and rise in O2 when stomata close divert the Calvin Cycle to photo respiration.

• C4 and CAM plants first fix CO2 into four-carbon compounds that provide CO2 to the Calvin Cycle even when stomata close on hot, dry days