Cell Biology Quiz

Chapter Objectives

• Students will be able to describe the structure and function of the cell membrane, including its regulation of materials into and out of the cell
• Students will be able to describe the functions of various cytoplasmic organelles
• Students will be able to explain the structure and contents of the nucleus, along with the process of DNA replication
• Students will be able to explain the process by which a cell builds proteins using the DNA code
• Students will be able to list the stages of the cell cycle in order, including the steps of cell division in somatic cells

Mitosis Cell

• A lung cell from a newt was studied.
• The green stain reveals mitotic spindles.
• The red stain corresponds to the cell membrane and part of the cytoplasm.
• The light blue structures are chromosomes.
• The cell is in anaphase of mitosis.

The Cell Membrane

• The cell membrane is a phospholipid bilayer.
• Includes proteins, cholesterol, and carbohydrates.
• Contains many molecular components.

Phospholipid Structure

• The phospholipid molecule consists of a polar phosphate "head" (hydrophilic).
• The phospholipid molecule has a nonpolar lipid "tail" (hydrophobic).
• Unsaturated fatty acids result in kinks in the hydrophobic tails.
• Allows the cell membrane to be selectively permeable.

Phospholipid Bilayer

• The bilayer consists of two adjacent sheets of phospholipids arranged tail to tail
• Hydrophobic tails associate with each other, forming the membrane's interior
• Polar heads contact the fluid inside and outside the cell.

Cell Membrane - Proteins

• Channel proteins allow large and charged molecules to pass through the membrane
• Integral proteins anchor the cell membrane
• Glycoproteins are involved in cell recognition and signaling

Cell Membrane - Cholesterol

• Helps with cell fluidity, stability, and flexibility.

Cell Membrane - Carbohydrates

• Enables cell-to-cell recognition and signaling
• Glycocalyx is important in cell protection against pathogens.
• Formed by glycoproteins and glycolipids.

Simple Diffusion

• Non-polar substances like oxygen and carbon dioxide, and lipids diffuse down their concentration gradient.
• No helper proteins or ATP are needed.

Facilitated Diffusion

• Helper proteins, such as channel proteins, facilitate the movement of large and charged molecules like ions, amino acids, and glucose down their concentration gradient.
• No ATP is required.

Active Transport

• Requires a helper protein and ATP.
• Substances such as sodium and potassium move against their concentration gradient.
• The sodium-potassium pump is a typical example of active transport.

Endocytosis

• A form of active transport where a cell envelopes extracellular materials using its cell membrane.
• Phagocytosis is a non-selective process for engulfing large particles .
• In pinocytosis, the cell takes in small particles in fluid .
• Receptor-mediated endocytosis is a specific process.

Exocytosis

• Exocytosis is essentially endocytosis in reverse.
• Material destined for export is packaged into vesicles within the cell.
• The vesicle membrane fuses with the cell membrane.
• The contents of the vesicle are then released into the extracellular space.

Osmosis

• The diffusion of water (movement) through a semipermeable membrane down its concentration gradient.
• Water follows solute through the membrane

Tonicity

• Hypertonic solution has a higher solute concentration than another
• Isotonic solution has an equal solute concentration to another
• Hypotonic solution has a lower solute concentration than another

The Cytoplasm and Cellular Organelles

• The cytoplasm is the fluid portion of the cell, excluding organelles.
• The cytoplasm is involved in cell structure and metabolic reactions
• The cytoplasm contains cytoskeleton

Prototypical Human Cell

• Includes mitochondria, plasma membrane, ribosomes, rough endoplasmic reticulum, nucleus, nucleolus, chromatin, Golgi apparatus, Golgi vesicles, cytoplasm, vacuole and others
• A prototypical example of a cell with primary organelles and internal structures.

Cytoskeleton

• Consists of microtubules, microfilaments, and intermediate filaments.
• Plays a crucial role in maintaining cell shape, promoting cellular movement, and aiding cell division.

Endoplasmic Reticulum (ER)

• A winding network of thin membranous sacs found in close association with the cell nucleus.
• Rough ER makes protein, with ribosomes attached.
• Smooth ER makes lipids.
• No ribosomes are attached to the smooth ER.

Golgi Apparatus

• Manipulates products from the rough ER and produces new organelles (e.g., lysosomes)
• Organizes, modifies, packages, and tags proteins and other products.
• Some products are transported to other parts of the cell; others are exported via exocytosis.

Mitochondrion

• Powerhouse of the cell.
• Bilayer membrane, inner membrane contains various molecules to produce ATP.

Membrane-bound Structures

• Peroxisomes contain enzymes for detoxifying harmful substances and lipid metabolism.
• Lysosomes break down waste products.
• Vacuoles store nutrients and waste

Ribosome

• Made in the nucleus and synthesizes proteins.
• Works with mRNA and tRNA.
• Can be found in the RER or in cytosol

The Nucleus and DNA Replication

• The nucleus is the control centre of the cell.
• Contains genetic material to control structure and function.

Nucleus

• Control center of the cell
• Contains the genetic material (DNA) determines the entire structure and function of the cell.
• DNA & proteins in chromatin are stored
• Site of ribosome production (nucleolus)

Nucleic acids

• RNA (key to protein synthesis): mRNA, rRNA, tRNA
• mRNA delivers instructions to ribosomes
• tRNA carries amino acids to ribosomes
• rRNA forms part of the ribosome structure

Transcription

• In the first stage of protein synthesis, a gene on the DNA molecule is transcribed into a complementary mRNA molecule.

Translation

• mRNA transcript is read by a functional complex (ribosome and tRNA molecules).
• tRNAs bring the appropriate amino acids.

Cell Growth and Division

• The cell cycle consists of mitosis (cell division) and interphase (cell growth and normal functions).
• Diploid cells have 23 pairs of chromosomes (46 chromosomes total)

Meiosis

• A cell divides twice to form four cells with half the genetic information (2n → n).
• Meiosis forms sperm and egg.

Anaerobic vs Aerobic Respiration

• Anaerobic respiration occurs in the absence of oxygen and converts glucose into two lactate molecules.
• Aerobic respiration takes place in the presence of oxygen, converting glucose into two pyruvate molecules

Glycolysis

• Two ATPs are consumed in glycolysis’ energy-consuming phase.
• Transforms glucose into two pyruvate molecules.

Krebs Cycle

• Each pyruvate is oxidized to a two-carbon acetyl-CoA molecule.
• Acetyl-CoA is processed through the cycle.

Oxidative Phosphorylation

• Includes electron transport chain and ATP synthesis, using H+ concentration gradient to generate ATP.
• Oxygen is the final electron acceptor.

ETC Key Takeaway

• NADH and FADH2 donate electrons and protons to the electron transport chain.
• Protons from the electron transport complexes move into the intermembrane space.
• This creates a gradient needed to power ATP synthase, leading to ATP production.
• Oxygen is the final electron acceptor., producing water.

Carbohydrate Metabolism Summary

• Involves glycolysis, Krebs cycle, and the electron transport system.
• Total ATP production varies with efficiency.