General Biology 1: Exam 2 - Membrane Structure, Cellular Organization, Cellular Respiration, and Photosynthesis

Comprehensive practice flashcard set covering membrane structure and dynamics, passive and active transport, cellular anatomy and organelle functions, metabolic energetics, cellular respiration, fermentation, and photosynthetic pathways with plant adaptations.

According to the principles of cell theory, cells are considered the fundamental units of __________.

life

The cell theory principle stating that all cells arise from preexisting cells implies that all living organisms share a single __________ ancestor.

common

Every living cell is separated and physically demarcated from its external environment by a phospholipid __________.

cell membrane

The entire internal region of a cell, excluding the nucleus in eukaryotic cells, is designated as the __________.

cytoplasm

The organization of the plasma membrane as a dynamic phospholipid bilayer containing a shifting mosaic of proteins and carbohydrates is defined by the __________ model.

Fluid Mosaic

In a membrane bilayer, the polar, hydrophilic phosphate heads face outward toward water, while the nonpolar, hydrophobic __________ tails face inward away from water.

fatty acid

Phospholipids constitute approximately __________ of the total lipid composition of the plasma membrane, forming its primary structural permeability barrier.

$$75\%$$

Cholesterol accounts for approximately __________ of animal cell membrane lipids and functions directly to regulate membrane stability and fluidity.

$$20\%$$

Carbohydrates covalently attached to lipids found exclusively on the outer leaflet of the cell membrane for recognition are called __________, comprising roughly $5\%$ of membrane lipids.

glycolipids

Membrane proteins that are permanently embedded within the hydrophobic core of the phospholipid bilayer are classified as __________ proteins.

integral

Integral membrane proteins that span completely across the hydrophobic interior from one side of the bilayer to the other are called __________ proteins.

transmembrane

Membrane proteins that are covalently linked directly to internal fatty acid chains within the bilayer are termed __________ proteins.

anchored

Proteins positioned completely outside the membrane's hydrophobic core that attach weakly to polar heads via hydrophilic interactions are called __________ proteins.

peripheral

Carbohydrates covalently attached to proteins on the extracellular surface that facilitate cell-to-cell adhesion and signaling are known as __________.

glycoproteins

Membrane phospholipids with shorter fatty acid chain lengths exhibit less surface area for hydrophobic bonding, which causes membrane fluidity to __________.

increase

Membranes rich in saturated fatty acids pack together tightly because of their straight chains, which causes fluidity to __________.

decrease

Unsaturated fatty acid tails introduce carbon double-bond __________ that prevent tight packing and preserve membrane fluidity at lower temperatures.

kinks

At high temperatures, cholesterol acts as a buffer by restraining fatty acid movement to prevent the membrane from becoming excessively __________.

leaky

At low temperatures, cholesterol prevents the cell membrane from freezing solid by blocking fatty acid tails from __________.

packing together tightly

The spontaneous movement of solutes down their concentration gradient from high to low concentration without the expenditure of cellular energy is called __________.

simple diffusion

Passive transport of polar substances or charged ions down their concentration gradient via specialized integral transport proteins is termed __________.

facilitated diffusion

Hydrophilic tunnels spanning the membrane that permit the passive passage of specific ions or water molecules are known as __________ proteins.

channel

Transport proteins that physically bind to a specific substrate and undergo a conformational shape change to shuttle it across the membrane are __________ proteins.

carrier

The net movement of water across a semi-permeable membrane toward an area of higher solute concentration is defined as __________.

osmosis

Specialized channel proteins that facilitate the rapid, bulk movement of water molecules across cell membranes are called __________.

aquaporins

In terms of tonicity, water always moves net from a hypotonic solution toward a __________ solution.

hypertonic

When placed into a hypotonic solution where external solute concentration is lower than internal solute concentration, animal cells swell and __________.

lyse

When plant cells absorb water in a hypotonic environment, their rigid cell walls prevent lysis and generate internal __________ pressure.

turgor

In an __________ solution, solute concentrations inside and outside the cell are equal, resulting in no net water movement.

isotonic

Placing plant or animal cells into a __________ environment causes water to leave the cell, leading to cell shriveling.

hypertonic

Active transport forces solutes against their concentration gradient from low to high concentration and requires direct input of __________.

ATP

The $Na^+/K^+-ATPase$ pump is a classic example of __________ active transport because it relies directly on ATP hydrolysis to alter transporter shape.

primary

Secondary active transport does not consume ATP directly; instead, it harnesses energy stored in an established __________ gradient.

ion

The process by which internal membrane-bound vesicles fuse with the plasma membrane to secrete bulk materials outside the cell is called __________.

exocytosis

The highly specific ingestion of extracellular targets triggered when external ligands bind to dedicated surface receptors is __________ endocytosis.

receptor-mediated

In human blood vessels, receptor-mediated endocytosis is specifically utilized for the cellular uptake of __________ cholesterol.

low-density lipoprotein (LDL)

The non-specific, routine cellular sampling and inward folding of plasma membrane to ingest surrounding fluids is called __________ or 'cell drinking.'

pinocytosis

The specialized bulk uptake process where a cell engulfs large particulate matter or whole bacterial cells is called __________ or 'cell eating.'

phagocytosis

The four universal cellular structures shared by all living cells on Earth are the plasma membrane, cytoplasm, DNA, and __________.

ribosomes

Unicellular organisms that lack internal membrane-bound compartments belong to the domains Bacteria and __________.

Archaea

In prokaryotic organisms, genomic DNA floats freely in an un-enclosed internal cytoplasmic region known as the __________.

nucleoid

Bacterial cells maintain their structural integrity and cell shape using an external cell wall constructed from a __________ matrix.

peptidoglycan

Eukaryotic cells can be up to __________ times larger than prokaryotes and maintain efficiency through extensive membrane-bound compartmentalization.

$$100$$

The eukaryotic nucleus is surrounded by a double-membrane nuclear envelope equipped with __________ that permit the transit of mRNA.

nuclear pores

Within the nucleus, the specialized dense region responsible for the assembly and construction of ribosomal subunits is the __________.

nucleolus

The __________ endoplasmic reticulum consists of interconnected membrane sheets studded with ribosomes dedicated to folding and modifying proteins.

rough

The smooth endoplasmic reticulum lacks ribosomes and specializes in the synthesis of lipids, phospholipids, and steroid hormones such as __________ and testosterone.

estrogen

The Golgi apparatus consists of a stack of flattened membrane sacs called __________ that sort, modify, and package materials for cellular shipment.

cisterns

Organelles containing hydrolytic enzymes that use internal proton pumps to maintain a low internal pH for digestion are called __________.

lysosomes

The powerhouses of eukaryotic cells that generate chemical ATP from metabolic fuels via aerobic respiration are the __________.

mitochondria

Photosynthetic plastids found in plants and algae that harvest solar photons to synthesize carbohydrates are called __________.

chloroplasts

The theory stating that mitochondria and chloroplasts originated as free-living prokaryotic bacteria engulfed by an ancestral eukaryote is the __________ theory.

endosymbiotic

Supporting the endosymbiotic theory, mitochondria and chloroplasts divide independently inside eukaryotic cells via __________.

binary fission

In the cytoskeleton, the thinnest protein filaments responsible for maintaining cell shape and driving cytokinesis pinching are microfilaments made of __________.

actin

Microtubules are composed of polymerized dimers of the protein __________ and serve as directional tracks for motor proteins and vesicle transport.

tubulin

Long, whip-like microtubule-propelled projections that power cellular locomotion in human sperm cells are called __________.

flagella

Microtubule triplet barrels that organize the mitotic spindle apparatus to pull chromosomes apart during animal cell division are __________.

centrioles

Freshwater protists prevent osmotic lysis in hypotonic aquatic environments by using active __________ vacuoles to pump out excess water.

contractile

While plant cell walls are constructed primarily of cellulose, fungal cell walls are made of __________.

chitin

The extracellular matrix (ECM) secreted by animal cells consists of a meshwork of glycoproteins including proteoglycans and __________.

collagen

Intercellular junctions that stitch adjacent animal cell membranes tightly together to form an impermeable barrier preventing fluid leakage are __________ junctions.

tight

Intercellular connections that act like mechanical spot-welds or rivets to resist strong shearing forces in skin tissues are called __________.

desmosomes

Open cytoplasmic channels that permit direct, immediate passage of ions, water, and signaling molecules between adjacent animal cells are __________ junctions.

gap

Metabolic pathways that synthesize complex macromolecules from smaller building blocks and require an input of energy are defined as __________.

anabolism

Spontaneous chemical reactions that tear down complex structures and release free energy into their surroundings are categorized as __________.

exergonic

Living cells drive non-spontaneous endergonic reactions forward by pairing them directly with exergonic reactions in a strategy known as energy __________.

coupling

An ATP molecule is chemically composed of an adenine nitrogenous base, a ribose pentose sugar, and __________ negatively charged phosphate groups.

$$3$$

Hydrolysis of ATP releases usable energy to power cellular work by cleaving its unstable terminal phosphate bond, leaving behind inorganic phosphate and __________.

ADP

In biological redox chemistry, the loss of electrons is oxidation, whereas the gain of electrons is defined as __________.

reduction

During cellular respiration, dehydrogenase enzymes strip electrons and protons from food substrates, reducing the coenzyme $NAD^+$ into high-energy __________.

$$NADH$$

The complete oxidation of a single glucose molecule through aerobic cellular respiration yields a theoretical maximum net output of approximately __________ ATP.

$$32$$

The balanced chemical summary equation for aerobic cellular respiration is $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{\_\_\_\_\_\_\_\_\_\_}$.

ATP

In the aerobic respiration overview shown, the metabolic stage occurring in the cytosol that splits glucose into pyruvate is __________.

Glycolysis

Glycolysis takes place entirely in the cytoplasm and requires __________ molecules of oxygen gas to function.

$$0$$

Glycolysis splits one 6-carbon molecule of glucose into two 3-carbon molecules of __________.

pyruvate

Although glycolysis produces 4 gross ATP during its payoff phase, it consumes 2 ATP upfront, yielding a net gain of __________ ATP per glucose.

$$2$$

During the investment and payoff phases of glycolysis, a single glucose molecule yields a net total of __________ $NADH$ electron carriers.

$$2$$

Pyruvate generated by glycolysis is actively transported into the central fluid compartment of the mitochondrion, which is the mitochondrial __________.

matrix

During pyruvate oxidation, each pyruvate molecule is decarboxylated, releasing a carbon atom as waste __________ gas.

$$CO_2$$

The remaining 2-carbon fragment from pyruvate oxidation is bonded to Coenzyme A to create the entry substrate __________ for the Citric Acid Cycle.

Acetyl-CoA

In the first step of the Citric Acid Cycle, 2-carbon Acetyl-CoA donates its acetyl unit to 4-carbon oxaloacetate to synthesize 6-carbon __________.

citric acid

A single turn of the Citric Acid Cycle generates 1 ATP, 1 $FADH_2$, and __________ molecules of $NADH$.

$$3$$

Because one glucose molecule produces two Acetyl-CoA molecules, the Citric Acid Cycle turns twice, producing a total of __________ ATP via substrate-level phosphorylation.

$$2$$

In oxidative phosphorylation, the multiprotein electron transport chain uses the energy of falling electrons to pump protons ($H^+$) into the mitochondrial __________.

intermembrane space

At the very end of the mitochondrial electron transport chain, __________ serves as the terminal electron acceptor, binding electrons and protons to yield water.

$$O_2$$

During chemiosmosis, protons rush back down their electrochemical gradient into the matrix through the catalytic rotor enzyme __________.

ATP Synthase

Long fatty acid chains from catabolized lipids are chopped into 2-carbon pieces that enter respiration directly as Acetyl-CoA via the process of __________.

beta-oxidation

Before amino acids can enter cellular respiration pathways, their toxic nitrogenous __________ groups ($NH_3$) must be removed.

amino

Prokaryotes achieve a higher maximum net yield of 38 ATP per glucose because they do not have to expend energy pumping pyruvate across internal __________ membranes.

mitochondrial

Under anaerobic conditions, the ultimate biological objective of fermentation is to oxidize $NADH$ back into __________ to keep glycolysis operating.

$$NAD^+$$

In animal muscle cells deprived of oxygen during intense exertion, pyruvate acts as an electron dump for $NADH$, directly producing __________.

lactic acid

During alcoholic fermentation in yeasts, pyruvate is decarboxylated to release $CO_2$, and the remaining fragment is reduced to form __________.

ethanol

According to the comparison table of metabolic features, in the photosynthesis pathway, __________ is oxidized while $CO_2$ is reduced.

$$H_2O$$

The complete chemical equation for photosynthesis demonstrates that it is an __________ process requiring kinetic input from light.

endergonic

Inside chloroplasts, flattened membrane discs called thylakoids are stacked into organized vertical columns termed __________.

grana

While the light-dependent reactions occur in the thylakoid membranes, the light-independent Calvin cycle occurs in the fluid-filled __________.

stroma

Chlorophyll is the primary photosynthetic pigment and appears green because it absorbs blue and red wavelengths while __________ green light.

reflecting

Photosystem II (PSII) contains a specialized reaction-center chlorophyll a pair known as __________ because its absorbance peak is at 680 nm.

P680

The reaction-center chlorophyll pair inside Photosystem I (PSI) has an optimal light absorption peak at 700 nm and is designated __________.

P700

The process by which an enzyme complex splits water molecules to donate electrons to $P680^+$ while releasing oxygen gas is called __________.

photolysis