Unit 3 - Week 1

7 universal challenges of life

Energy use; exchange with environment; transport inside body; coordinating responses; defense; reproducing; developing/growing/maturing

Things exchanged with the environment

Energy, nutrients, gases, water, wastes, other molecules

What shapes how evolution acts on organisms?

The environment (abiotic and biotic)

Cell

Simplest self-reproducing unit of life

Cell theory

All living things are made of cells; cells come from pre-existing cells

What do cells do? (3 things)

Separate/regulate internal environment; store/transmit information; acquire, transform, and use energy

Cell membrane function

Controls exchange and communication with the environment

Cell membrane structure

Phospholipid bilayer with embedded proteins

Hydrophilic head vs. hydrophobic tail

Heads face the watery inside/outside; tails face inward, away from water

Selectively permeable

Lets some molecules through freely, some only under certain conditions, and blocks others

Why is the membrane selectively permeable?

The phospholipid bilayer (hydrophilic heads and hydrophobic tails) blocks large, polar molecules while allowing small, non-polar substances to pass. Also, because embedded proteins regulate the movement of specific ions and molecules.

Nucleus

Houses DNA in chromosomes

Cytoplasm

Everything inside the cell membrane but outside the nucleus

Prokaryote

No nucleus (bacteria and archaea)

Eukaryote

Has a nucleus (animals, plants, fungi, protists)

Central dogma

DNA to RNA to protein

Transcription

DNA to RNA (in the nucleus in eukaryotes)

Translation

RNA to protein (in the cytoplasm)

DNA

Molecule of heredity; polymer of nucleotides. Provides information that influences cellular processes.

RNA

Complement of DNA template; involved in protein synthesis

Proteins do what?

Speed up/regulate metabolism, give structure, transport, defense, signaling, coordination, reproduction

Gene expression

DNA transcribed to RNA, translated to protein, producing traits

Why does regulating transcription matter?

Allows different functions in different contexts

Homeostasis

Active maintenance of a stable internal state despite a changing environment

Diffusion

Net movement from high to low concentration

Passive transport

Movement across membrane with NO energy (diffusion)

Active transport

Movement against the gradient (low → high); REQUIRES energy

Simple diffusion

Small molecules pass directly through the bilayer

Facilitated diffusion

Moves down gradient through channel or carrier proteins (no energy, passive transport)

How does O2 get from alveoli to blood?

Passive diffusion driven by a partial pressure gradient

Nutritional mode

How an organism obtains energy AND carbon

Phototroph

Energy from sunlight

Chemotroph

Energy from chemical compounds

Autotroph

Carbon from inorganic source (CO2); makes own food

Heterotroph

Carbon from organic compounds made by others

Photoautotroph

Energy: sunlight. Carbon: CO2. Ex: plants, cyanobacteria

Photoheterotroph

Energy: sunlight. Carbon: organic. Ex: heliobacteria, green nonsulfur bacteria

Chemoautotroph

Energy: inorganic chemicals. Carbon: CO2. Ex: sulfur-oxidizing and hydrogen bacteria

Chemoheterotroph

Energy: chemicals. Carbon: organic from other organisms. Ex: animals, most bacteria, Salmonella

Humans are what nutritional mode?

Chemoheterotrophs

Why do autotrophs lack sensory organs, muscles, and nervous systems?

Their nutrients don't need to be hunted or captured. Survival strategy does not require detecting environmental changes, moving actively, or coordinating complex internal responses

Sponges and corals get nutrients by...

Absorbing them from the surrounding environment (like autotrophs)

What is a major determinant of body plan?

Mode of nutrition

Ultimate energy source for almost all life

Sunlight

Metabolism

All chemical reactions in cells that convert molecules and transfer energy

Catabolism

BREAKS DOWN molecules, RELEASES energy (makes ATP). Ex: cell respiration

Anabolism

BUILDS molecules, USES energy (ATP). Ex: photosynthesis, biosynthesis

Photosynthesis: anabolic or catabolic?

Anabolic (stores energy in glucose, makes O2)

Cell respiration: anabolic or catabolic?

Catabolic (breaks down glucose, releases energy)

Photosynthesis equation

6 H2O + 6 CO2 + light → 6 O2 + glucose

Respiration equation

6 O2 + glucose → 6 H2O + 6 CO2 + heat (+ ATP)

ATP

Adenine + ribose + 3 phosphates; the cell's usable energy currency

Why does heat get released during respiration?

Only ~66% of glucose energy is captured as ATP; the rest is lost as heat (2nd law of thermodynamics)

Why do compost piles steam?

Lots of cellular respiration releasing heat

Primary way organisms make ATP

Aerobic respiration

Aerobic metabolism

Makes ATP using oxygen

Anaerobic metabolism

Makes energy without oxygen (fermentation; ends in lactic acid in animals)

Metabolic rate

An animal's overall rate of energy use

Recovery metabolism

Elevated oxygen use after activity

Glycolysis

Cytoplasm (cytosol). Glucose to 2 pyruvate; makes 2 ATP, 2 NADH

Pyruvate oxidation

Occurs in mitochondrial matrix. Pyruvate to acetyl-CoA; makes NADH, CO2

Citric acid cycle

Mitochondrial matrix. Makes CO2, NADH, FADH2, 2 ATP

Electron transport chain + oxidative phosphorylation

Inner mitochondrial membrane. Uses NADH, FADH2, O2; makes H2O and most of the ATP

What do NADH and FADH2 do?

Deliver electrons to power ATP synthesis at the electron transport chain

Which step needs oxygen?

Electron transport chain / oxidative phosphorylation (O2 is the final electron acceptor, making H2O)

Endotherm

Makes own body heat (mammals, birds); HIGHER metabolic rate

Ectotherm

Gets heat from environment (most reptiles, amphibians, fish); LOWER metabolic rate

Bigger animal: overall metabolic rate?

Higher

Bigger animal: mass-specific metabolic rate (per gram)?

Lower (small animals burn more energy per gram)

What does oxygen consumption indicate?

Rate of aerobic ATP production

Metabolic rate and activity

Metabolic rate increases with activity

Short bursts of activity are powered mostly by...

Anaerobic pathways

Surface area to volume ratio: large cells

LOWER ratio and longer diffusion distances

What do cell size and shape affect?

Surface-area-to-volume ratio and diffusion distance (exchange)

How do cells increase surface area to volume ratio?

Forming microvilli, projections, folds, flattened shape, metabolism at the edges

Sponges and jellyfish and the diffusion problem

Body structure keeps cells close to the environment