DNA Transcription, Cell Membrane and Cell transport

Physio 1 study for Moving exam

When a cell divides, it creates one copy of its genetic information — in the form of:

DNA molecules

This factor helps ensure precise replication, the double-helical structure of DNA. TRUE OR FALSE

TRUE

DNA is constructed from just four different chemical building blocks (four nucleotides), what are these:

Adenine (A), Thymine (T), Cytosine (C), Guanine (G)

DNA strands bond according to a strict complementary pattern. Specifically, Adenine (A) always pairs with: _____

Thymine (T)

Cytosine (C) always pairs with:_____

Guanine (G)

During cell division, does paired strands unravel or no?

They unravel

Nerve cells express genes to synthesize an abundance of______ They use these chemical signals to send rapid messages to other cells.

Neurotransmitters

Muscle cells express specific genes to load themselves with: ________ These

structures provide the mechanical force necessary for contraction.

Protein-based filaments

This is the fundamental first step in decoding a cell's genetic information.

Transcription

During transcription process, specialized enzymes called ______ bind to DNA and synthesize RNA molecules

RNA polymerases

Unlike the rigid DNA double helix, RNA is typically_____stranded and highly flexible

Single stranded

RNA utilizes ________ in its backbone instead of the deoxyribose sugar found in DNA

Ribose sugar

In RNA, Thymine (T) is replaced by _______ as the complementary base pairing partner.

Uracil (U)

Being single-stranded, RNA does not fold into intricate shapes stabilized by internal base-pairing. TRUE or FALSE

FALSE, RNA folds

What are the THREE major classes of RNA?

mRNA (messenger RNA), rRNA(Ribosomal RNA), tRNA (Transfer RNA)

In eukaryotic cells, __________ has its own dedicated polymerase enzyme. This division of labor allows for highly specialized and distinct transcription pathways.

each class of RNA

Prokaryotic cells rely on a __________ to synthesize all different classes of RNA across the genome.

single RNA polymerase

Alternative RNA types play crucial _________roles in gene expression and act as vital defense systems protecting against invading viruses.

regulatory roles

This is the most variable class or RNA.

mRNA

Certain mRNA molecules are highly abundant, numbering in the hundreds or thousands. TRUE OR FALSE?

TRUE

Some mRNAs are extremely rare, often existing as a single copy. Transcripts for signaling proteins are highly unstable and are typically degraded in less than

______

10 minutes

In eukaryotes, transcripts for essential structural proteins are highly stable and long-lived. These vital mRNA molecules can remain completely intact for over _______

10 hours

This is the complete spectrum of mRNA molecules in a cell. its active molecular profile varies widely based on specific cell type and physiological function.

Transcriptome

The transcriptome serves as a __________of genes actively expressed at any given point in time.

Precise temporal catalog

They are complexes of rRNA molecules and proteins, which can be clearly observed in electron micrographs of cells.

Ribosomes

Sometimes, ribosomes are visible as active clusters called ________ working together to translate genetic instructions.

Polyribosomes

In eukaryotes (but not prokaryotes), some ribosomes are physically attached to __________ they actively synthesize proteins destined to either reside within those membranes or be targeted for outward cellular secretion.

Internal membranes

Although only a few rRNA molecules are present in each ribosome, these molecules make up about half of the ribosomal mass. TRUE OR FALSE?

TRUE

The remaining mass consists of a large number of

diverse proteins.

● Nearly _____ proteins in prokaryotic cells.

● Over ______ proteins in eukaryotic cells.

60, 80

This forms a highly selective, flexible barrier protecting the cell. It acts as a gateway, precisely regulating the entry and exit of molecules to maintain internal cellular homeostasis.

Plasma membrane

Eukaryotic cells contain specialized internal membrane systems, what are these?

● The complex network of the Endoplasmic Reticulum

● The inner and outer membranes of mitochondria

● The double-layered nuclear envelope

These structures are exceedingly thin, measuring just 6-8 nanometers (nm) across.

This is composed of a bilayer of phospholipids and globular protein molecules.

Plasma membrane

The proteins are suspended and float dynamically within a double layer of phospholipids, acting as a highly selective barrier

Fluid mosaic model

(function) The plasma membrane is a _______ barrier that defines the cell's limits. It physically separates the cellʼs internal components from the external environment, protecting vital intracellular structures.

Flexible and elastic

(plasma membrane composition) Externally facing proteins and

lipids carry _______essential for cellular recognition and interactions.

Sugar chains

(plasma membrane composition) Dispersed _________

stabilizes the fluid bilayer, while specialized proteins govern the membrane's antigenicity.

Cholesterol

(plasma membrane transport) The membrane exhibits _________ and leaves the cell. Movement occurs via passive pathways or through active transport, where the cell must expend energy.

Selective permeability

(biomembranes: Compartmentalization Physical Separation & Microenvironments) The cell membrane, for instance,__________ from its surroundings, permitting the intracellular environment to maintain distinct properties from the outside.

Separates the inside of a cell

(Biomembranes: Dynamic Systems Active Cellular Participation) Far from being inert barriers, biomembranes are ______and________ structures. They play vitally essential roles by actively articipating in a wide array of crucial cellular and subcellular functions necessary for life.

Highly dynamic and adaptive

(permeable species) Certain substances can penetrate biomembranes directly without the assistance of membrane proteins. ________ and _______ pass freely through the lipid bilayer.

Small, uncharged molecules and oily (lipophilic) molecules

(Impermeable Species: needs protein assistance) ________ do not pass through due to the highly hydrophobic inner core of the bilayer.

Large polar molecules (with net electrical imbalances and MW > 100 Da) cannot pass readily on their own

Charged particles & ions

(Cell Membrane:primary outer barrier) Protein molecules are structurally embedded in the lipid bilayer. The fluid mosaic illustrates the alignment of these membrane components. TRUE OR FALSE

True

(Intracellular Membranes: Internal Organelle Boundaries)

the fundamental structure of the various intracellular membranes matches the outer cell membrane

● ________ Functions as the core

structural foundation for internal organelle

boundaries.

● _________Features protein

molecules embedded within to support

specialized functions.

Phospholipid Bilayer and Protein Integration

(The Molecular Logic) _______ dictates how molecules interact,

giving rise to critical hydrophilic and hydrophobic behaviors that form biological barriers.

Polarity

Vinegar consists of acetic acid and water. Because acetic acid is

polar, it intermingles freely and remains completely in solution with the water molecules. HYDROPHILIC OR HYDROPHOBIC?

Hydrophilic

When vinegar-and-oil dressing sits still, the oil separates entirely. Nonpolar oil molecules repel the polar water, forcing the oil to form a distinct, separate layer. HYDROPHILIC OR HYDROPHOBIC?

Hydrophobic

(UNEVEN DISTRIBUTION) The distribution of electrons in a molecule determines whether it is polar or nonpolar. Within a polar molecule, electrons gather ________, creating distinct, relatively negative and positive regions.

Unevenly

(THE POLAR STANDARD) _______ is a classic polar molecule with pronounced charge imbalances. This permanent polarity enables it to act as an highly active medium for charge-based molecular interactions.

Water

(SOLUTION FORMATION) Other polar molecules, such as acetic acid and ions ________ freely with water. By engaging in continuous charge interactions, these substances disperse completely, forming stable solutions.

Intermingle