MCAT B/B Section Full Content Review

Ofc, I need to manually edit this, but this is generally pretty good!

Cell theory

The cell is the fundamental unit of life; all living organisms are composed of cells; cells arise from preexisting cells; cells contain genetic material passed to daughter cells

Fundamental unit of life

The cell is the smallest unit capable of carrying out all life processes

Are viruses considered living?

No; viruses are not made of cells, lack metabolism, cannot reproduce independently, and require a host cell

But, they can evolve, have DNA/RNA, and can respond to environmental stimuli

Genetic material in living organisms

Living organisms use DNA as their genetic material

Genetic material in viruses

Viruses may contain DNA or RNA, but not both

Eukaryotic cells

Cells that contain a nucleus and membrane-bound organelles

Prokaryotic cells

Cells that lack a nucleus and membrane-bound organelles

Plasma membrane

Phospholipid bilayer that separates the cell from its environment and regulates transport

Fluid mosaic model

The plasma membrane consists of a fluid phospholipid bilayer with embedded proteins

Phospholipid structure

Hydrophilic phosphate head and hydrophobic fatty acid tails

Selective permeability. Describe how small nonpolar molecules, small polar molecules, large nonpolar molecules, large polar molecules, and charged molecules cross.

The plasma membrane allows some substances to pass while restricting others.

Small nonpolar molecules diffuse passively, small polar molecules diffuse passively but more slowly, large nonpolar molecules diffuse passively but not as favorable as small molecules, large polar molecules need to use channels and transporters, and charged molecules need a channel.

Integral membrane proteins. In nonpolar environments, the nonpolar amino acids on the transmembrane protein will be facing inwards/outwards, while the charged amino acids will be facing inwards/outwards.

Proteins embedded within the lipid bilayer.

Outwards; inwards. Of course in polar environments, the opposite happens

Peripheral membrane proteins

Proteins loosely associated with the membrane surface

Cholesterol in membranes. What is the effect of high vs low temperatures on fluidity?

Regulates membrane fluidity in animal cells

Higher temperatures increase fluidity, while low temperatures decrease fluidity

Membrane carbohydrates

Serve in cell recognition and signaling

Nucleus (in biology not chemistry)

Organelle that houses DNA and controls gene expression

Nuclear envelope

Double membrane surrounding the nucleus

Nuclear pores

Regulate transport of RNA and proteins between nucleus and cytoplasm

Nucleolus

Site of rRNA synthesis and ribosome assembly inside the nucleus

Chromatin

DNA-protein complex within the nucleus

Euchromatin

Loosely packed chromatin that is transcriptionally active

Heterochromatin

Densely packed chromatin that is transcriptionally inactive

Ribosomes

Site of protein synthesis

Free ribosomes

Synthesize proteins that function in the cytosol

Bound ribosomes

Synthesize proteins for secretion, membranes, or lysosomes

Rough endoplasmic reticulum

Organelle involved in protein folding and modification; contains membrane-bound ribosomes

Smooth endoplasmic reticulum

Organelle involved in lipid synthesis, detoxification, and calcium storage (no ribosomes)

Golgi apparatus

Modifies, sorts, and packages proteins and lipids

Cis face of Golgi

Receives vesicles from the endoplasmic reticulum

Trans face of Golgi

Ships vesicles to final destinations

Vesicles

Membrane-bound sacs used for transport within the cell

Lysosomes

Organelles containing hydrolytic enzymes for intracellular digestion

Lysosomal enzymes

Function optimally at acidic pH

Peroxisomes

Organelles involved in fatty acid oxidation and detoxification. Can do beta oxidation, phospholipid synthesis, and can do parts of the PPP (Pentose Phosphate Pathway, similar to glycolysis but generates NADPH)

Hydrogen peroxide metabolism

Peroxisomes both generate and degrade hydrogen peroxide

Mitochondria

Double-membrane organelles responsible for ATP production via oxidative phosphorylation

Mitochondrial DNA

Circular DNA inherited maternally

Inner mitochondrial membrane

Contains electron transport chain proteins

Cristae

Folds of the inner mitochondrial membrane that increase surface area

Matrix of mitochondria

Contains enzymes for the citric acid cycle (it’s like the cytosol of hte mitochondria)

Endosymbiotic theory

Mitochondria originated from free-living prokaryotes

Chloroplasts

Organelles responsible for photosynthesis in plants

Thylakoids

Membrane sacs where light-dependent reactions occur

Grana

Stacks of thylakoids

Stroma

Fluid surrounding thylakoids where the Calvin cycle occurs

Cell wall

Rigid structure providing support and protection

Cell wall in plants

Composed primarily of cellulose

Cell wall in bacteria

Composed primarily of peptidoglycan

Cell wall in fungi

Composed primarily of chitin

Cytoskeleton

Network of protein filaments providing structure and transport

Microfilaments

Actin filaments involved in cell shape and movement

Intermediate filaments

Provide tensile strength and mechanical stability

Microtubules

Tubulin-based structures involved in transport and cell division

Centrosome

Microtubule organizing center in animal cells

Centrioles

Paired structures involved in spindle formation

Cilia

A hair-like structure that cause cellular movements/sweeping motions of the surroundings (like the mucociliary escalator)

Flagella

Long projections used for cell motility (what we think of as tails)

9+2 microtubule arrangement

Structure of cilia and flagella in eukaryotes

Describe the prokaryotic flagella

Made of a protein called flagellin, which is anchored and rotated by the basal body, and both are connected to each other via a hook.
This is powered by a proton gradient, which is a motive force

Cytoplasm

Fluid matrix inside the cell containing organelles

Cytosol

Aqueous component of the cytoplasm

Prokaryotic nucleoid

Region containing DNA in prokaryotic cells

Prokaryotic ribosomes

Made of 30S and 50S subunits, which forms a 70S ribosomes (think odd numbers: 3, 5, and 7). This is smaller than eukaryotic ribosomes

Prokaryotic plasma membrane

Performs many functions of eukaryotic organelles

Capsule

Bacterial outer layer that enhances virulence and protection

Pili

Hair-like structures used for attachment and conjugation

Fimbriae

Short pili involved in adhesion

Binary fission

Method of prokaryotic cell division (also how mitochondria reproduce)

Gram-positive bacteria

Thick peptidoglycan cell wall, retain crystal violet stain

Gram-negative bacteria

Thin peptidoglycan layer and outer membrane, do not retain crystal violet

Lipopolysaccharide

Endotoxin found in gram-negative bacterial outer membranes

Archaea

Prokaryotes with distinct membrane lipids and metabolic pathways

Virion

Complete virus particle

Capsid

Protein coat surrounding viral genetic material

Envelope

Lipid membrane surrounding some viruses

Lytic cycle

Viral replication cycle resulting in host cell lysis

Lysogenic cycle

Viral genome integrates into host genome

Retrovirus

Virus that uses reverse transcriptase to convert RNA into DNA

Bacteriophage

Virus that infects bacteria

Prions

Infectious protein particles lacking nucleic acids

Viroids

Infectious RNA molecules affecting plants

Subviral particles

Include prions and viroids

Passive diffusion

Movement of molecules down their concentration gradient

Facilitated diffusion

Passive transport using membrane proteins

Active transport

Movement of substances against gradient using ATP

Primary active transport

Uses ATP directly

Secondary active transport

Uses ion gradients to drive transport

Symport

Transport of two substances in the same direction

Antiport

Transport of two substances in opposite directions

Endocytosis

Uptake of material into the cell via vesicles

Exocytosis

Release of material from the cell via vesicles

Phagocytosis

Engulfment of large particles. Goal is to ingest particles and degrade them (either for defense or recycling of materials)

Pinocytosis

Engulfment of extracellular fluid (it’s like cell drinking)

Receptor-mediated endocytosis

Specific uptake using membrane receptors

Osmosis

Movement of water across a semipermeable membrane

Hypotonic solution

Lower solute concentration than the cell

Hypertonic solution

Higher solute concentration than the cell

Isotonic solution

Equal solute concentration as the cell

Tonicity

Effect of a solution on cell volume

Gene

A sequence of DNA that encodes a functional product