Biology Lecture: Photosynthesis and Chromosomes

This set of flashcards covers the introductory concepts of photosynthesis, the detailed mechanics of light-dependent and light-independent reactions, and the basic organization of eukaryotic chromosomes and genes.

Chloroplast

The organelle in eukaryotes where photosynthesis occurs, identified by having an outer membrane, inner membrane, and a third green membrane called the thylakoid.

Thylakoid

The third membrane inside a chloroplast that is responsible for absorbing sunlight.

Stroma

The region inside the chloroplast analogous to the matrix of the mitochondria where light independent reactions take place.

Oxidation

The loss of electrons; in photosynthesis, water is oxidized into oxygen.

Reduction

The gain of electrons; in photosynthesis, carbon dioxide is reduced to form carbohydrates.

Light dependent reactions

The first step of photosynthesis that absorbs sunlight, oxidizes water into oxygen, and reduces $NADP^+$ into $NADPH$, while also producing $ATP$.

NADP

The electron carrier typically used in anabolic (building up) reactions, such as photosynthesis, as opposed to $NAD$ used in catabolic reactions.

Glyceraldehyde 3-phosphate

The specific carbohydrate and immediate product of the Calvin cycle that can be used to make glucose, starch, or cellulose.

Chlorophyll

A hydrophobic green dye that lives in the thylakoid membrane and absorbs light energy.

Fluorescence

A nonbiological process where chlorophyll, when isolated, releases absorbed energy as light and heat.

Photosystem

A scaffold of proteins that organizes units of chlorophyll to collect and focus light energy like an antenna.

Reaction center

A special pair of chlorophyll molecules at the bottom of a photosystem where the chlorophyll is actually oxidized and an electron is lost.

Resonance energy transfer

The mechanism where chlorophyll molecules pass energy to neighbors via a wave of electron promotion and falling, focusing energy toward the reaction center.

Photosystem II

The first photosystem in the series of light dependent reactions; it was named after Photosystem I because it was described second by scientists.

Oxygen generating complex

A cluster of proteins at the reaction center of Photosystem II that oxidizes water into oxygen gas and hydrogen ions.

ATP synthase

A protein that uses the hydrogen ion gradient to allow ions to diffuse from high to low concentration, capturing energy to produce $ATP$ from $ADP$ and inorganic phosphate.

Calvin cycle

The light independent reactions where carbon dioxide is reduced to a carbohydrate using a preexisting intermediate.

Ribulose 1,5-bisphosphate

A five-carbon carbohydrate that serves as the preexisting intermediate in the Calvin cycle to which carbon dioxide is attached.

Rubisco

The most common enzyme on the planet; it is responsible for sticking carbon dioxide to ribulose 1,5-bisphosphate, despite being relatively ineffective at its job.

Chromosomes

Finite internal bodies into which DNA is organized; the name literally means "colored body."

Centromere

The central structure of a eukaryotic chromosome that joins two strands.

Telomeres

The special structures found at the ends of a chromosome.

Diploid

The state of having two copies of every chromosome and every gene, typically one from each biological parent.

Allele

A variation of a specific gene.

Homologous chromosomes

Also known as sister chromosomes, these are a pair of chromosomes (one from each parent) that contain the same genes but likely different alleles.

Autosomal chromosomes

In humans, these are chromosomes 1 through 22, which behave normally and contain the same sets of genes in pairs.

Sex chromosomes

In humans, chromosome pair 23 (X and Y), which determines biological sex.

SRY gene

The gene found on the degenerate Y chromosome that, when activated in utero, causes an individual to become biologically male.

Sister chromatids

Two identical strands of DNA that are produced during DNA replication and remain attached to each other at the centromere until cell division.