Parts of the Cell

nucleus

central organelle of a eukaryotic cell that contains most of the cell's genetic material in the form of DNA

nuclear envelope

the double membrane structure that surrounds the nucleus, separating its contents from the cytoplasm of the cell

nuclear pores

openings in the nuclear envelope that allow the passage of large macromolecules, such as RNA and proteins, between the nucleus and the cytoplasm

nuclear lamina

network of protein filaments that lines the nuclear side of the nuclear envelope, providing structural support to the nucleus and helping maintain its shape

chromosomes

discrete units of DNA

histones

help coil the DNA molecule of each chromosome, reducing its length and allowing it to fit into the nucleus

chromatin

combination of DNA and histones

transcription

synthesis of RNA from DNA

translation

process where ribosome subunits clamp to RNA to create new protein

ribosomes

site of protein synthesis

endomembrane system

continuous membrane system including the nuclear envelope, the endoplasmic reticulum, the Golgi apparatus, lysosomes, various kinds of vesicles and vacuoles, and the plasma membrane

cisternae

fluid-filled spaces in the endoplasmic reticulum

rough ER

abundant in cell that secrete proteins

smooth ER

responsible for the synthesis of lipids, oil, phospholipids and steroids

transport vesicles

parts of the ER that bud off to carry proteins

Golgi apparatus

modifies, stores, then sends products of the ER to other destinations

Golgi apparatus

abundant in cells specialized for the secretion of glycoproteins

cis side

receiving side of Golgi apparatus

trans side

shipping side of Golgi apparatus

lysosomes

perform phagocytosis and autophagy

autophagy

process where lysosomes recycle damaged organelles

phagocytosis

process where lysosomes join food vacuole and digest food particles

contractile vacuoles

pump excess water out of the cell

central vacuole

enlarge as they absorb water so investment in new cytoplasm is minimized as plant cell grows

tonoplast

membrane surrounding the central vacuole

mitochondria

site for cellular respiration

chloroplasts

site of photosynthesis

mitochondria and chloroplasts

organelles apart from the nucleus that has genes

cristae

foldings of the mitochondria which provide ample surface area for enzymes

mitochondrial matrix

fluid space in the mitochondria filled with DNA, ribosomes, and enzymes

amyloplasts

plastid that store starch

chromoplasts

plastid that store carotene

peroxisomes

degrade hydrogen peroxide

microtubules, microfilaments, intermediate filaments

components of the cytoskeleton

microtubules

largest component of the cytoskeleton

alpha and beta tubulin dimers

protein subunits of microtubules

microtubules

central support for cilia and flagella

microtubules

provides track for cell streaming

pseudopodia

cellular extensions in amoeboid movement

microfilaments

responsible for muscle contraction and pseudopodia in amoeba

microfilaments

responsible for cleavage furrow during cell division

intermediate filaments

tension-bearing element of cytoskeleton

actin

protein subunit of microfilaments

keratin

protein subunit of intermediate filaments

microfilament

smallest component of cytoskeleton

cell wall

protects the plant cell, maintains its shape, and prevents excessive uptake of water

primary cell wall

thin and flexible wall made of cellulose

middle lamella

gap between cell walls

secondary cell wall

hard wall made of lignin

pectins

sticky polysaccharides which compose middle lamella

plasmodesmata

channel that allows cytosol to pass between plant cells

tight junctions

fuse adjacent cells and prevents leakage of extracellular fluid

desmosomes

fasten cells together into strong sheets reinforced by intermediate filaments

gap junctions

provide cytoplasmic channels from one cell to an adjacent cell

lateral or flip-flop

movement performed by phospholipids

aquaporins

transport proteins that allow polar molecules to pass through lipid bilayer

passive transport

diffusion of a substance across a membrane with no energy investment

osmosis

diffusion of free water across a selectively permeable membrane

osmoregulation

control of solute concentrations and water balance

tonicity

ability of a surrounding solution to cause a cell to gain or lose water

normal

isotonic (animal cell)

flaccid

isotonic (plant cell)

shriveled

hypertonic (animal cell)

plasmolyzed

hypertonic (plant cell)

lysed

hypotonic (animal cell)

turgid

hypotonic (plant cell)

active transport

diffusion of a solution against its gradient that requires energy

exocytosis

exports product

endocytosis

macormolecules are taken in

pinocytosis

cellular drinking

receptor-mediated endocytosis

binding of ligands to receptors triggering vesicle formation

ligand

any molecule that binds specifically to a receptor site of another molecule