Bio Chapter 2

Prokaryote

No nucleus, no internal organelles, special movement structures, and smaller.

Eukaryotes

Nucleus, many membranes bound organelles, advanced cytoskeleton and bigger.

What are prokaryotes good at?

Effective at rapid growth and simple tasks.

What are Eukaryotes good at?

Effective at specialization and do more complex jobs at once.

What is the Nucleus?

Stores chromosomes, DNA replication, and transcription DNA to mRNA.

Why does structure matter to the Nucleus?

Double membrane with nuclear pores controls what enters/leaves. DNA is physically separated to precisely regulate gene expression.

What do Ribosomes do?

They manufacture proteins. They do NOT make up proteins.

What does Rough Endoplasmic Reticulum / Rough Er do?

helps forming, folding, and modifying proteins, and it also assists in quality control to ensure proteins are properly folded before they are sent to their final destinations within or outside the cell.

Smooth Endoplasmic Reticulum / Smooth ER 

Makes lipids, stores calcium and detoxes the cell

What does the Golgi Apparatus do?

Acts as packing center for proteins by applying finishing chemical touch ups and putting the protein in a vesicle to be shipped into/outside the cell

Lysosomes are only found in

only found in animal cells

Vacuoles are only found in 

only found in plant/fungi cells.

Lysosomes are

are acidic organelles with hydrolytic enzymes

What do lysosomes do?

they digest big molecules, old organelles, and destroy foreign objects inside of the cell

What are Vacuoles?

Large storage compartment for water and ions. In some cases, hold pigments, toxins and proteins. Help rigidify plant cells.

What are Peroxisomes?

Small organelles where oxidative reactions happen. Help break down fatty acids and detoxify compounds.

What does the Mitochondria do?

produce ATP via oxidative phosphorylation

Why do Mitochondria have folds?

increases surface area for ATP machinery. Own DNA & ribosomes support endosymbiotic origin

What do chloroplasts do?

Photosynthesis site

How does a Chloroplast work?

Multiple membranes partition light capture from sugar-synthesis steps. Own DNA & ribosomes

Why does the cell have a Cytoskeleton?

Shape, movement, intracellular transport, and cell division — acts as scaffolding + tracks for motor proteins.

How many structures are in the Cytoskeleton?

: 3 fiber systems (actin, intermediate filaments, microtubules).

What does the Cell Wall do?

Protects, supports, and prevents excessive water uptake.

Endosymbiotic theory

Mitochondria and chloroplasts evolved from free-living bacteria that were engulfed by an ancestral eukaryotic cell and formed a mutually beneficial relationship.

How cells target proteins to different compartments?

Proteins are delivered precisely because they carry addresses — short amino-acid sequences or chemical tags that are recognized by cellular machinery.

How the nucleus gets proteins?

How the nucleus gets proteins

Actin filaments (microfilaments)

movement & shape; intermediate filaments

intermediate filaments

structural strength

microtubules

transport & mitosis

Motor proteins

myosin (on actin) or kinesin/dynein (on microtubules).

Plasma Membrane

membrane proteins or secreted proteins are fused to the surface or released.

Analogy

Intermediate filaments are the building’s steel rebar — provide tensile strength.

Microtubules Composition

Hollow tubes of α- and β-tubulin heterodimers stacked into protofilaments

Microtubules Size

Largest cytoskeletal filaments

Microtubules Polarity

Plus end (fast-growing) and minus end (slow-growing).

Microtubules

Microtubule organizing center (MTOC); in animal cells this is the centrosome (with centrioles).

Microtube Dynamics

Dynamic instability — periods of growth and rapid shrinkage (catastrophe/rescue) regulated by GTP-binding to tubulin.

Desmosomes

Links the cytoskeletons of adjacent cells

Desmosomes are good

Resist pulling and shearing forces

Desmosomes are common in 

·       Common in epithelial and muscle tissue

Desmosomes make

·       Integral membrane proteins form bridges between anchoring proteins inside adjacent cells

Gap Junction

The airlock tubes between cells – connects the cytoplasm of adjacent animal cells together

Plasmodesmata

: Narrow thread of cytoplasm that passes through the cell wall of adjacent plant cells

Distant cells can communicate through signaling molecules such as

Neurotransmitters and Hormones

Neurotransmitters allow

the brain to control the body

Hormones are

are information carrying molecules secreted by plant and animal cells into bodily fluids to act on distant target cells

Signal Receptors

·       Change shape and activity after binding to a hormone

·       Are Dynamic and the number of receptors/ability of receptors may change

Signal binds

and triggers a signal transduction(cascade): (extracellular-->intracellular signal)

G-Protein

Coupled receptors trigger the production of a second messenger

Enzyme-Linked Receptors trigger

a Phosphorylation Cascade of Protein Kinases

Kinase

An enzyme that attaches a phosphate group to a protein (TURNS PROTEIN ON)

Phosphatase

An enzyme that removes a phosphate group from a protein (TURNS PROTEIN OFF)

Amino groups

found in proteins

Carboxyl groups

 proteins

Carbonyl groups

sugars

Hydroxyl groups

sugars/alcohols

Phosphate groups

 nucleic acids

Sulfhydryl groups

 proteins (disulfide bonds)

Monosaccharides

(CH₂O)n → "simple sugars"

4 ways sugars vary structurally:

Number of carbon atoms, Location of carbonyl group (C=O), Arrangement of hydroxyl (–OH) groups, and Form: linear vs. ring.

Monosaccharides could form

 under early Earth conditions

Disaccharides

2 sugars linked

Condensation reaction links sugars form

 forms glycosidic bond

Hydrolysis reactions….

break bonds back into monosaccharides.

Different bond structures =

different functions.

Polysaccharides & Evolution

Likely not important for the origin of life (need enzymes to form). Don’t self-replicate or catalyze reactions

Carbohydrates decorate

 the outer surface of cells

Glycoproteins =

 carbs + proteins

Glycolipids

= carbs + lipids

Roles of Carbohydrates on outer cell

• Cell recognition → ID as "self" and Cell signaling → communication

Photosynthesis

plants store energy in carbohydrate bonds

Starch is found in 

found in plants

Glycogen is found in

found in animals

Starch (plants) & Glycogen (animals)

Both use α-glycosidic linkages → easy to hydrolyze

Glycogen is broken by

phosphorylase

Starch is broken by

amylase

Glucose breakdown is 

energy captured in ATP

ATP

 powers cell work (endergonic reactions, movement, etc.)

Three Types of Lipids Found in Cells

Steroids, Fats and Phospholipids

Lipids are…

Carbon compounds found in organisms Largely nonpolar and hydrophobic

Lipids many comprise

Hydrocarbons

Hydrocarbons

molecules that contain only C & H They are hydrophobic Electrons are shared equally
in C-H bonds

Lips function as

pigments, scents, vitamins, sex hormone precursors

A fatty acid (simple lipid)

is a hydrocarbon chain bonded to
a carboxyl (-COOH) functional
group
• Contain 14–20 carbon atoms
• Can be saturated or unsaturated

Steroid examples are

Cholesterol and Sex hormones like testosterone and estrogen

Fats (Triglycerides)

Butter, lard, cod liver oil,
margarine
• Cow’s milk (myristic acid)
• Palm oil (stearic acid)
• Omega-3-fatty acids

Phospholipids

2 fatty acids linked to glycerol linked to a phosphate group

Lipid micelles 

Hydrophilic head make a circle with hydrophilic heads out and hydrophobic tails in.

w sheets of phospholipids align

sheets of
phospholipids align
• Hydrophilic heads
in face out
• Hydrophobic tails
face in

lipid bilayer with short and unsaturated tails are

higher permeability and fluidity

Lipid bilayer with long and saturated tails

are lower permeability and fluidity

Cholesterol

Cholesterol orients in the membrane
with its hydrophobic steroid rings
buried deeply in the hydrocarbon tails
of the phospholipids
• Bulky cholesterol rings force the
phospholipid tails closer to each other,
increasing their packing density
• When cholesterol was added to the
experimental membranes, the closer
packing of the tails caused the
membranes to become less
permeabl

osomsis

water only moving from low concentration to high concentrations

Hypertonic solution

Solute concentration is HIGHER outside vs. inside
Water will move out of the cell by osmosis
CELL WILL SHRINK

Hypotonic solution

Solute concentration is LOWER outside vs. inside
Water will move into the cell by osmosis
CELL WILL EXPAND

Isotonic solution

Solute concentration is = outside vs. inside
No net water movement
The cell size will remain the same

protocells

Simple vesicle-like structures that harbor nucleic acids are called

Two prevailing theories for composition of plasma membranes

Sandwich model and Fluid mosaic model

Two types of proteins in the membrane

integral and membrane proteins