The Nucleus and Cytoplasmic Organelles

organelles

small specialized structures with particular functions; most have membranes that separate interior from cytoplasm

nucleus

large membrane-bound structure containing DNA

nucleus composition

nucleoplasm surrounded by nuclear envelope which is a double membrane with many fused areas called nuclear pores that regulate movement into/out of nucleus

DNA in nucleus

specifies the structure of proteins

RNA in nucleus

serves as an intermediate during protein synthesis and consists of mRNA, rRNA, and tRNA

nucleolus

dense regions within the nucleus where ribosomes are made

chromosome structure

DNA is found in nucleus, associated with proteins called histones to form chromosomes

nucleosomes

structural units of chromosomes

chromatin

what chromosomes are dispersed as during cell cycle; condenses into compact chromosomes

ribosomes

site of protein synthesis, composed of a large and a small subunit, composed of rRNA and proteins

free ribosome

synthesize proteins used inside of cell

attached ribosome

to ER, produce integral proteins and proteins secreted from the cell

endoplasmic reticulum

organelle consisting of a network of membranes that is continuous with outer membrane of nuclear envelope; internal spaces are cisternae

rough ER

has attached ribosomes; where proteins are produced and modified

smooth ER

no attached ribosomes; manufactures lipids, participates in detoxification, and calcium ion storage

Golgi apparatus

flattened membrane sacs, containing cisternae, stacked on each other

Golgi apparatus function

modifies, packages, and distributes proteins and lipids for secretion or internal use; substances packed into transport vesicle

lysosomes

form at golgi, contain hydrolytic enzymes that function in digesting cellular material

peroxisomes

smaller than lysosomes, contain enzymes to break down fatty acids and amino acids, hydrogen peroxide is a by-product of breakdown, also contain the enzyme catalase which breaks down hydrogen peroxide into water and oxygen

proteasomes

consist of large protein complexes that are not surrounded by membranes, proteins fold to form a barrel-like structure with enzymatic regions on the inside surface that break down and recycle proteins in cell, proteins at the ends of the barrel regulate which proteins are taken in for breakdown and recycling

mitochondria

major site of ATP synthesis, increase in number when cell energy requirements increase, contain DNA that codes for some of the proteins needed for production

cristae

in-foldings of inner mitochondria membrane, contain enzymes of the electron transport chain

matrix

substance located in space formed by inner mitochondria membrane, contains the enzymes for the critic acid or Krebs cycle

centrosome

center of microtubule information that are involved in cell shape and movement

centrioles

located in centrosome

spindle fibers

made before cell division, when centrioles divide and move to ends of cell and organize these

cilia and flagella

appendages projecting from cell surfaces; capable of movement

cilia

move materials over the surface of cells

flagella

used for movement by sperm cells

microvilli

extension of plasma membrane that increases surface area; some modified as sensory receptors; normally many on every cell; 1/10-1/20 the size of cilia, don’t move, supported by actin filaments