Bio Test 2

Cell theory

The idea that all organisms are made of cells, cells are the smallest living things, and cells arise only from pre-existing cells.

Principle 1 of cell theory

All organisms are composed of cells.

Principle 2 of cell theory

Cells are the smallest living things.

Principle 3 of cell theory

Cells arise only from pre-existing cells.

Robert Hooke

Scientist credited with discovering cells in 1665.

Schleiden and Schwann

Scientists who helped propose cell theory after studying plants and animals.

Why cells are usually small

higher surface area-to-volume ratio, making diffusion and exchange of materials more efficient.

Surface area-to-volume ratio

A comparison of a cell's outer surface area to its internal volume; smaller cells have a more favorable ratio.

Cell size limitation

volume increases faster than surface area, making diffusion less efficient.

Diffusion and cell size

Cells rely on diffusion for movement of substances, so shorter distances inside small cells are an advantage.

Resolution

The minimum distance two points can be apart and still be distinguished as two separate points.

Light microscope

uses visible light and magnifying lenses; useful for viewing cells and large organelles.

Compound light microscope

A light microscope used to view thin or small specimens at higher magnification.

Dissection microscope

A light microscope used to view larger, thicker specimens, often in 3D at lower magnification.

Electron microscope

uses a beam of electrons and has much higher resolution than a light microscope.

TEM

Transmission electron microscope; sends electrons through a specimen to produce detailed 2D images of internal structures.

SEM

Scanning electron microscope; scans the specimen surface to produce detailed 3D-like surface images.

Basic features common to all cells

All cells have DNA in a nucleoid or nucleus, cytoplasm/cytosol, ribosomes, and a plasma membrane.

Cytoplasm

The semifluid interior of a cell that includes cytosol and cellular structures.

Cytosol

The fluid portion of the cytoplasm.

Plasma membrane

The phospholipid bilayer surrounding the cell that controls movement in and out.

Ribosomes

Cell structures that synthesize proteins; found in all types of cells and not membrane-bound.

Two major cell types

Prokaryotic cells and eukaryotic cells.

Prokaryotic cells

Cells that lack a membrane-bound nucleus and lack other membrane-bound organelles.

Eukaryotic cells

Cells that contain a nucleus and other membrane-bound organelles.

Two domains of prokaryotes

Bacteria and Archaea.

Nucleoid

The region in a prokaryotic cell where DNA is located.

Prokaryotic DNA

Usually double-helical, circular DNA located in the nucleoid.

Prokaryotic ribosomes

Ribosomes present in prokaryotes that make proteins even though the cell lacks membrane-bound organelles.

Bacterial cell wall

A strong outer structure made of peptidoglycan that protects the cell, maintains shape, and prevents excess water movement.

Peptidoglycan

A complex molecule made of carbohydrates attached to small polypeptides; a major component of bacterial cell walls.

Plant cell wall

A eukaryotic cell wall made mainly of cellulose, not peptidoglycan.

Fungal cell wall

A eukaryotic cell wall made mainly of chitin.

Flagella

Long structures used for locomotion; prokaryotic flagella rotate, while eukaryotic flagella undulate using microtubules.

Prokaryotic flagella

Flagella that move by rotary motion to propel the cell.

Distinguishing features of eukaryotes

Eukaryotes are typically larger and have a nucleus, linear chromosomes, and membrane-bound organelles.

Nucleus

A membrane-bound organelle in eukaryotic cells that houses DNA and is the site of transcription.

Nuclear envelope

A double membrane made of two phospholipid bilayers that surrounds the nucleus.

Nuclear pores

Openings in the nuclear envelope that control movement of materials in and out of the nucleus.

Nucleolus

The region of the nucleus where ribosomal RNA synthesis occurs.

Eukaryotic DNA organization

DNA is organized into multiple linear chromosomes inside the nucleus.

Chromatin

DNA plus proteins that make up eukaryotic chromosomes.

Transcription

The process of synthesizing RNA from a DNA template.

Ribosome composition

made of ribosomal RNA (rRNA) and protein.

mRNA

carries genetic information from DNA for protein synthesis.

tRNA

carries amino acids during translation.

rRNA

Ribosomal RNA; part of the structure and function of ribosomes.

Free ribosomes

located in the cytoplasm that often make proteins used inside the cell.

Bound ribosomes

attached to internal membranes, such as rough ER, that make proteins for secretion, lysosomes, or membranes.

Endomembrane system

A series of membranes in eukaryotic cells that divides the cell into compartments for different functions.

Rough ER

Endoplasmic reticulum with ribosomes attached; synthesizes proteins to be secreted, sent to lysosomes, or inserted into membranes.

Smooth ER

Endoplasmic reticulum with few or no ribosomes; involved in carbohydrate and lipid synthesis, Ca2+ storage, and drug detoxification.

Rough ER vs smooth ER

Rough ER has ribosomes attached; smooth ER has few bound ribosomes and performs lipid/carbohydrate synthesis and detox functions.

Golgi apparatus

Flattened stacks of membranes that modify, package, and distribute molecules made elsewhere in the cell.

Cis-Golgi face

The receiving side of the Golgi apparatus where vesicles from the ER arrive.

Trans-Golgi face

The shipping side of the Golgi apparatus where molecules are sent to their destinations.

Vesicles

Small membrane-bound sacs that transport materials within the cell.

Protein trafficking pathway

DNA is transcribed into RNA, ribosomes translate the RNA into protein, protein enters ER, moves to Golgi, and is packaged in vesicles for delivery.

Lysosomes

Membrane-bound digestive vesicles from the Golgi that contain enzymes to break down macromolecules and engulfed materials.

Lysosomal enzymes

Proteins made by ribosomes that catalyze breakdown of macromolecules inside lysosomes.

Microbodies

Small enzyme-bearing, membrane-enclosed vesicles found in eukaryotic cells.

Peroxisomes

Microbodies that contain enzymes involved in fatty acid oxidation and detoxify hydrogen peroxide using catalase.

Catalase

An enzyme in peroxisomes that converts harmful hydrogen peroxide into safer molecules.

Vacuoles

Membrane-bound structures with functions such as storage, water balance, or maintaining pressure in plant cells.

Central vacuole

Large plant-cell vacuole that stores materials and helps maintain turgor pressure.

Contractile vacuole

A vacuole in some protists that ejects excess water from the cell.

Mitochondria

Membrane-bound organelles in eukaryotes that carry out oxidative metabolism and produce ATP.

Mitochondrial structure

outer membrane, intermembrane space, inner membrane with cristae, and matrix.

Cristae

Folds of the inner mitochondrial membrane that increase surface area for oxidative metabolism.

Matrix

The inner fluid-filled space of a mitochondrion.

Chloroplasts

Organelles in plants and some eukaryotes that contain chlorophyll and perform photosynthesis.

Chloroplast structure

two membranes, thylakoids, grana, and chlorophyll.

Thylakoids

Membranous sacs inside chloroplasts where photosynthesis-related reactions occur.

Grana

Stacks of thylakoids inside chloroplasts.

Animal cells vs plant cells

Plant cells have chloroplasts, a central vacuole, and cell walls; animal cells lack cell walls and usually have an extracellular matrix.

Prokaryotes vs eukaryotes

Prokaryotes lack a nucleus and membrane-bound organelles; eukaryotes have a nucleus, membrane-bound organelles, and linear chromosomes.

Endosymbiosis

The theory that mitochondria and chloroplasts evolved when ancestral cells engulfed free-living bacteria that became organelles.

Evidence for endosymbiosis

Mitochondria and chloroplasts have their own bacterial-like DNA, bacterial-like ribosomes, and replicate by binary fission.

Binary fission

A cell division process used by bacteria and also by mitochondria and chloroplasts to replicate.

Cytoskeleton

A dynamic network of protein fibers that supports cell shape, movement, and internal transport.

Three cytoskeletal fibers

Microfilaments, microtubules, and intermediate filaments.

Microfilaments

The smallest cytoskeletal fibers; made of actin monomers and involved in cell crawling, muscle contraction, and cell division pinching.

Actin

The protein monomer that makes up microfilaments.

Microfilament polarity

Microfilaments have polarity with plus (+) and minus (-) ends.

Microtubules

The largest cytoskeletal fibers; hollow tubes made of alpha- and beta-tubulin dimers.

Tubulin

The protein subunit that makes up microtubules as alpha/beta dimers.

Microtubule function

move organelles and macromolecules, help move chromosomes during cell division, and form cilia and flagella.

Microtubule polarity

have plus (+) and minus (-) ends.

Intermediate filaments

Cytoskeletal fibers of intermediate size that are tough, stable, ropelike, and provide strong attachment structures.

Intermediate filament polarity

do not have polarity.

Centrosome

A microtubule-organizing center made of two centrioles in animal cells and most protists.

Centriole

A cylindrical structure that helps nucleate or initiate microtubule assembly.

Motor proteins

Proteins that use ATP to move along actin filaments or microtubules.

Motor proteins and intermediate filaments

Motor proteins do not move on intermediate filaments.

Cilia

Short, numerous cell projections made of microtubules that help move cells or move fluid across cell surfaces.

Eukaryotic flagella

Long cell projections made of microtubules that move by undulation, not rotation.

9 + 2 arrangement

The microtubule pattern found in eukaryotic flagella, with nine outer pairs and two central microtubules.

Four major types of eukaryotic cells

Animal cells, plant cells, fungal cells, and protist cells.

Extracellular matrix

A mixture outside animal cells made of glycoproteins and fibrous proteins such as collagen, fibronectin, laminin, and elastin.

Integrins

Transmembrane proteins that link the extracellular matrix to the cell's cytoskeleton and influence cell behavior.