cell theory / structure

Leeuwenhoek's contribution to microscopes

Built single-lens microscopes; first to observe blood cells, bacteria, sperm cells, and protozoa (animalcules); his evidence refuted spontaneous generation

Unifying properties of all cells

Plasma membrane, cytosol, cytoskeleton, genome (DNA chromosomes), ribosomes

Plasma membrane (unifying property)

All cells are bounded by a membrane of phospholipids

Cytosol (unifying property)

Thick, jelly-like, polar fluid inside all cells that cell components are suspended in

Cytoskeleton (unifying property)

Protein-based filaments in the cytoplasm that maintain cell structure

Genome (unifying property)

All cells have one or more chromosomes carrying genes made of DNA

Ribosomes (unifying property)

Tiny structures that build proteins according to instructions from the genes

3 main points of Cell Theory

1) Cells are the smallest unit of life 2) All life is composed of cells 3) All cells arise from other cells

Matthias Schleiden

Concluded all plants are made of cells

Theodor Schwann

Concluded all animals are made of cells

Rudolf Virchow

Concluded all cells come from previous cells

Why are cell membranes important?

Control what enters/exits the cell, maintain homeostasis, allow compartmentalization in eukaryotes, and facilitate communication with the environment

What are membranes composed of?

A phospholipid bilayer embedded with proteins, cholesterol, and carbohydrates

Amphipathic (phospholipids)

Having both a hydrophilic polar head and hydrophobic nonpolar fatty acid tails

How do phospholipids form a bilayer in water?

Polar heads face outward toward the watery inside and outside of the cell; nonpolar tails hide on the inside

Why is the membrane a "fluid" mosaic?

Lipids and proteins can drift sideways within the plane of the membrane

Why is the membrane a fluid "mosaic"?

Diverse pattern of protein molecules embedded through the phospholipid bilayer

Extracellular matrix: contents

Glycoproteins, proteoglycans, and fibronectin

Extracellular matrix: job

Supports, anchors, and mediates signaling between cells

What is inside a nucleus?

Nucleoplasm, chromatin (DNA + proteins), nucleolus, nuclear bodies

Nucleolus

Where ribosomes are made

Chromatin

DNA and proteins

Chromosome

Structure of tightly wound DNA with histone proteins carrying genetic information

mRNA significance

Mobile copy of instructions transcribed from DNA; travels from nucleus to ribosomes; blueprint for assembling amino acids into proteins

Ribosomes: what and where

Molecular machines of rRNA and proteins that synthesize proteins; found free in cytoplasm or bound to rough ER

Which cells have ribosomes?

Prokaryotes, plant cells, and animal cells (all three)

Are enzymes found in prokaryotes?

Yes; crucial for metabolism, found in the cytoplasm and associated with the cell membrane

Endoplasmic reticulum function

Synthesizes lipids, processes proteins, and acts as a major manufacturing and transport network

Rough ER

Studded with ribosomes on outer surface; synthesis, folding, and modification of proteins for membranes, secretion, or organelles

Smooth ER

Lacks ribosomes; lipid synthesis, carbohydrate metabolism, calcium storage, detoxification of drugs/poisons

Is the ER found in prokaryotes?

No; only in eukaryotes

Transport vesicles and the ER

Bud off the ER membrane and carry newly made proteins and lipids to the Golgi apparatus

Golgi apparatus function

Modifies, sorts, and packages proteins and lipids from the ER for transport to final destination (not found in prokaryotes)

Surface protein pathway: step 1 (nucleus)

DNA is transcribed into mRNA

Surface protein pathway: step 2 (rough ER)

mRNA is translated by ribosomes into a protein chain, which is folded and packaged into a transport vesicle

Surface protein pathway: step 3 (transport vesicle)

Carries protein from rough ER to the cis face of the Golgi

Surface protein pathway: step 4 (Golgi)

Protein is modified and sorted from cis to trans face, then packaged into a secretory vesicle

Surface protein pathway: step 5 (exocytosis)

Secretory vesicle fuses with the cell membrane, releasing the protein to the exterior

Chloroplast function

Photosynthesis: converts light energy, CO2, and water into glucose and oxygen

Where are chloroplasts found?

Plant cells and some protists only (not animals or bacteria)

Lysosome contents

Digestive enzymes that break down macromolecules, old cell parts, and invaders under acidic conditions

Example of a lysosomal storage disease

Tay-Sachs disease

Organelle

Specialized, membrane-bound structure within a eukaryotic cell with a specific function

Which came first, prokaryotes or eukaryotes?

Prokaryotes

Prokaryote and eukaryote similarities

Both have a plasma membrane, cytoplasm, DNA, and ribosomes

Prokaryote characteristics

Smaller, unicellular, no true nucleus, no membrane-bound organelles, cannot form multicellular organisms

Eukaryote characteristics

Larger, unicellular or multicellular, true nucleus, membrane-bound organelles, can form complex multicellular organisms

Bacterial cell components

Capsule, cell wall, plasma membrane, cytoplasm, nucleoid (circular DNA), ribosomes, flagella/pili

Animal cell components

Nucleus, nucleolus, nuclear membrane, rough and smooth ER, Golgi, mitochondria, ribosomes, cytoplasm, lysosomes, centrioles, plasma membrane

Plant cell components

Nucleus, nucleolus, rough and smooth ER, Golgi, mitochondria, ribosomes, central vacuole, chloroplasts, cell wall, plasma membrane

Key differences among bacterial, plant, and animal cells

Plants: cell wall, chloroplasts, large central vacuole. Animals: lysosomes and centrioles. Bacteria: no internal membrane-bound compartments

Mitochondria function

Cellular respiration: converts glucose and oxygen into ATP, CO2, and water

Where are mitochondria found?

Plants and animals; absent in bacteria (they use the cell membrane for respiration)

Components of the cytoskeleton

Microfilaments (actin), intermediate filaments, and microtubules

Functions of the cytoskeleton

Maintains cell shape, anchors organelles, enables cell movement, powers intracellular transport and chromosome separation

Plant central vacuole vs. regular vacuole

Central vacuole is a massive, permanent single organelle that maintains turgor pressure, stores water/nutrients, degrades waste; regular vacuoles are smaller and temporary

Uses of regular vacuoles

Storage of food, water, waste, or toxins; contractile vacuoles regulate water in freshwater protists

Cilia

Short, numerous hair-like microtubule extensions of the cell membrane; move substances along cell surfaces

Flagella

Long, whip-like microtubule extensions of the cell membrane; propel the cell forward

Endosymbiont theory

Mitochondria and chloroplasts originated as free-living prokaryotes engulfed by a larger anaerobic host cell, forming a mutually beneficial symbiosis

Cytoskeleton's role in endosymbiont theory

Its dynamic nature let the host cell engulf smaller prokaryotes without destroying them

Which was incorporated first: mitochondria or chloroplasts?

Mitochondria; all eukaryotes have them, but only photosynthetic eukaryotes have chloroplasts

Advantage of mitochondria for eukaryotes

ATP production via aerobic respiration

Advantage of chloroplasts for eukaryotes

Harvest solar energy to make their own food (autotrophy)