Unit 2 AP Biology Organelles

Endosymbiont Theory

The theory that an early eukaryotic cell engulfed a prokaryotic cell, which became an endosymbiont (a cell living inside another cell).

Evidence for Endosymbiont Theory

Double membrane, circular DNA, ribosomes, and ability to function independently.

Organelles supporting Endosymbiont Theory

Mitochondria and chloroplasts.

Function of mitochondria

Site of cellular respiration and ATP production.

Outer membrane of mitochondria

Smooth.

Cristae

Inner membrane folds that increase surface area for reactions.

Internal compartments of mitochondria

Intermembrane space and mitochondrial matrix.

Mitochondrial matrix

Krebs cycle; contains enzymes, DNA, and ribosomes.

Muscle cells and mitochondria

They have high metabolic activity and need more energy.

Function of chloroplasts

Site of photosynthesis.

Pigment in chloroplasts

Chlorophyll.

Thylakoids

Membranous sacs where light-dependent reactions occur.

Grana

Stacks of thylakoids.

Stroma

The fluid surrounding thylakoids; location of the Calvin cycle.

Contents of the stroma

Chloroplast DNA, ribosomes, and enzymes.

Cytoskeleton

A network of fibers in the cytoplasm providing structural and mechanical support.

Functions of the cytoskeleton

Support cell shape, anchor organelles, allow movement of vesicles/organelles and the whole cell.

Types of cytoskeletal fibers

Microtubules, microfilaments, and intermediate filaments.

Microtubules composition

The protein tubulin.

Growth of microtubules

The centrosome.

Functions of microtubules

Provide tracks for organelle movement, separate chromosomes during cell division, and allow cell motility (cilia & flagella).

Importance of microtubules in mitosis

They form spindle fibers that separate chromosomes.

Microfilaments composition

The protein actin.

Functions of microfilaments

Maintain cell shape, help in muscle contraction and cell motility, and assist in animal cell division (cleavage furrow).

Protein working with actin

Myosin.

Microfilaments in cell division

They form the contractile ring of the cleavage furrow.

Intermediate filaments composition

Fibrous proteins with varying subunits.

Intermediate filaments permanence

Permanent structural elements.

Functions of intermediate filaments

Maintain cell shape, anchor nucleus and organelles, and form the nuclear lamina lining the nuclear envelope.

Organelle detoxifying alcohol

Smooth Endoplasmic Reticulum (Smooth ER).

Organelle removing damaged parts

Lysosome.

Lysosome function

It fuses with the damaged organelle, releases hydrolytic enzymes to break it down, and recycles materials.