BSCI Unit 2

Plasma Membrane

Defines the cell, outlines its border, and determines the nature of its interaction with its environment

Phospholipids

Hydrophilic areas in contact with aqueous fluid. Hydrophobic molecules interact with other non-polar molecules. Forms a lipid bilayer that seperates water and other materials.

Integral proteins

Integrate completely into the membrane structure, hydrophobic membrane-spanning regions interact with the phospholipid bilayers hydrophobic region

Peripheral proteins

On membranes exterior and interior, may serve as enzymes, structural attachments for cytoskeletons fibers or as part of the cells recognition sites

Carbohydrates

Always on the cells’ exterior surface and are bound to either proteins or lipids. They form specialized sites on the cells surface that allow cells to recognize each other

What are the factors that maintain the fluid characteristic

Unsaturated phospholipids - Contain double bonds that result in a bend in the carbong string and when they get compressed the kinks maintain some space which helps maintain fluidity. Cholesterol - Tends to dampen temp effects on the membrane, preventing lower temps from inhibiting fluidity.

Selective Permeability

Amphiphilic characteristic helps move some materials through the membrane and hinders the movement of others. Polar molecules and small ions cannot pass through easily.

Diffusion

Single substance moves from a high concentration to a low concentration area until the concentration is equal across a space - expends no energy - Passive

Facilitated Transport

Materials diffuse across the plasma membrane with the help of membrane proteins - a concentration gradient exists that would allow these materials to diffuse into the cell without expending cellular energy - Passive

Transport proteins

function as either channels for the material or carriers

Channel proteins

Have hydrophilic domains exposed to intra and extracellular fluids. Allows rapid movement of ions+water

Carrier proteins

Binds a substance and triggers a change of its own shape, moving the bound molecule from the cells outside to its interior

Osmosis

movement of free water molecules through a semi permeable membrane - Passive. From higher concentration to lower concentration if no energy is added. From lower concentrations to higher if energy is added

Tonicity

How an extracellular solution can change a cells volume by affecting osmosis

Osmolarity

Describes the solutions total solute concentration - low osmolarity = greater number of water molecules

Hypertonic solutions

Fluid contains less water than the cell does - water will leave the cell

Hypotonic solutions

Extracellular fluid has a higher water concentration than the cell - water enters the cell

Active Transport

Requires the cells energy to transport substances against their gradients. Only carriers

Electrochemical gradient

Combined concentration gradient and electrical charge that affects an ion

Sodium potassium pump

Moves K+ into the cell while moving Na+ out at the same time

Primary active transport

Energy from ATP hydrolysis is used to pump something across a membrane to a region of higher concentration. Active, transports sodium, potassium, and calcium. ATP hydrolysis can provide the energy to actively move two substances in two different directions.

Secondary active transport

Active, transports amino acids, lactose. Energy supplied by ATP hydrolysis to transport one ion can be stored in an ion gradient - stored potential energy can drive the active transport of another solute with a seperate cotransport protein.

Endoycytosis

Type of active transport that moves particles into a cell. The cell plasma membrane invaginates, forming a pocket around the target particle

Phagocytosis

Process by which a cell takes in large particles, active

Pinocytosis

“Cell drinking” process that takes in molecules, including water, which the cell needs from the extracellular fluid.

Oxidation

Removal of an electron from a molecule that results in decrease in potential energy

Electron Carriers

They bind and carry high energy electrons between compounds in biochemical pathways

NAD

Electron carrier that is dervied from niacin

NAD+

Oxidized from of NAD

NADH

Reduces form NAD after it has accepted two electrons and a proton

Reduction

Gain of electrons (hydrogen or oxygen) which decreases its charge

ATP

Primary energy currency of the cell that consists of adenine, ribose, and three phosphate groups and provides a direct link between exergonic and endergonic pathways.

Dephosphorylation

Process of removing one or more phosphate groups from ATP which releases significant amount of free energy for cellular work

ATP Hydrolysis

A reaction where water is used to split ATP into ADP and an inorganic phosphate, which results in the release of energy

Phosphorylation

Addition of a phosphate group to a molecule. ATP transfers its third phosphate to a substrate to make it more reactive

Intermediate complex

A temporary structure where an enzyme binds to substrates allowing them to react more readily before forming a final product

Glycolysis

First step of glucose breakdown, occuring in the cytoplasm. It is an anaerobic process and converts one 6-carbon glucose into two 3-carbon pyruvates

Energy Investment Phase (Part 1)

First half of glycolysis where cell spends 2 ATP to phosphorylate glucose, which traps it in the cell and makes it unstable enough to split into two 3-carbon molecules (G3P)

Energy payoff phase (part 2)

The second half of glycolysis where the cell earns 4 ATP and 2 NADH. Because 2 ATP were spent earlier, the net gain is 2 ATP

Pyruvate oxidation

Occurs in the mitochondria. Pyruvate is decarboxylated (loses CO2) and oxidized to form an Acetyl group, which attaches to Coenzyme A and becomes Acetyl CoA

Citric Acid Cycle (Krebs)

A series of 8 reactions in the mitochondrial matric that completes the breakdwon of glucse. Per glucose molecule (2 turns), it produces 4 CO2, 6 NADH, 2 FADH2, and 2 ATP/GTP

Oxaloacetate

The 4-carbon molecule that joins with Acetyl CoA at the start of the Citric Acid cycle to form Citrate and is regenerated at the end of the cycle

Amphibolic Pathway

Metabolic pathway that is both catabolic and anabolic

Electron Transport Chain

Series of four protein complexes in the inner mitochondrial membrane that use electrons from NADH and FADH2 to pump protons (H+) into the intermembrane space

Chemiosmosis

The movement of hydrogen ions down their electrochemical gradient through ATP synthase, which provides mechanical energy to generate ATP

ATP Synthase

Complex enzyme/protein that acts like a molecular generator, spinning as protons flow through it to phosphorylate ADP into ATP

Final Electron Acceptor

Oxygen. At the end of the ETC, oxygen accepts spent electrons and joins with protons to form Water.

Oxidative phosphorylation

The combines process of the ETC and Chemiosmosis. It generates about 90% of the ATP made during glucose catabolism

Fermentation

An anaerobic process that allows glycolysis to continue by regenerating NAD+ from NADH. It uses an organic molecule as the final electron acceptor

Lactic Acid Fermentation

Used by animals and some bacteria. Pyruvate is reduced to lactate to recyle NAD+. In humans, lactate can be sent to the liver and converted back to pyruvate

Alcohol Fermentation

Used by yeast. Pyruvate is converted into CO2 and Acetaldehyde, and then Acetaldehyde is reduced to Ethanol to recyle NAD+

Photoautotrophs

Organisms capable of capturing sunlight and converting it into chemical energy

Chemoautotrophs

A group of bacteria that syntehsize sugars using energy from inorganic chemical compounds rather than sunlight

Mesophyll

Middle layer of leaf tissues where photosynthesis primarily occurs

Stomata

Small regulated openings on the underside of leaves that allow for gas exchange and help minimize water loss

Chloroplast

Organelle in autotrophic eukaryotes where photosyntehsis takes place. It contains disc shaped structures called thylakoids stacked into grana

Light dependent reactions

First stage of photosynthesis occuring in the thylakoid membranes. It converts solar energy into chemical energy in the form of ATP and NADPH, releasing O2 as a byproduct

Chlorophyll

The primary pigment that absorbs blue and red light but reflects green. It resides in the photosystems to capture photons

Photosystem II

The first protein complex in the LDR that captures light to excited electrons and splits watter to replace those electrons, releasing oxygen gas

Photosystem I

Second protein complex in the LDR that re-energizes electrons using light and transgers them to NADP+ to form NADPH

Cytochrome Complex

A group of proteins between PSII and PSI that uses electron energy to pump H+ ions into the thylakoid lumen, creating a proton gradient

Light independent reactions

Occurs in the stroma and uses the ATP and NADPH produced in the light reactions to fix CO2 into organic sugar molecules

RuBisCO

The enzyme catalyzes the first step of the Calvin Cycle by attaching CO@ to RuBP. It is considered one of the most important enzymes on Earth for its role in carbon fixation

Carbon Fixation

Process of converting inorganic CO2 gas into organic compounds that the cell can use

Reduction (Calvin cycle Phase 2)

Stage where ATP and NADPH are used to convert 3-PGA into the high-energy sugar molecule G3P

Regeneration (Calvin Cycle Phase 3)

Stage where most of the G3P molecules are rearranged back into RuBP so the cycle can continue

G3P

Direct product of the Calvin Cycle. Some is sued to regenerate RuBP and some is leaves the cycle to be converted into glucose and other carbohydrates

ATP Synthase

An enzyme in the thylakoid membrane that uses the flow of H+ ions to power the addition of a phosphate to ADP, creating ATP