Tour of the Cell

Cell Structure

Plasma Membrane

all cells are bounded by

Double Layer

phospholipid bilayer, with various proteins attached to or embedded

hydrophobic parts

phospholipids and proteins are foundf in the interior of the membrane where the fatty acid tails are

hydrophilic parts

are in contact with the aqueous solution on either side; water loving region

carbohydrate chain

may be attached to proteins or lipids in the outer surface of the plasma membrane

cytosol / cytoplasm

semi-fluid or jelly-like substance inside the cell; where subcellular components are suspended

Nucleus

contains most of the cell’s genes and is usually the most conspicuous organelle

Nucleus

has several parts: nuclear envelope, nuclear pores and nuclear lamina

Nucleus

where DNA replication occurs

Nuclear envelope

encloses the nucleus, separating it from the cytoplasm

Pores

regulate the entry and exit of molecules from the nucleus

Nuclear Lamina

lines the nuclear envelope

Nuclear Lamina

composed of proteins and maintains the shape of the nucleus

Chrmosomes

In the nucleus, DNA is organized into discrete units

Chromatin

DNA and proteins of chromosomes 

Nucleolus

located within the nucleus and site of ribosomal RNA (rRNA) synthesis

Nucleolus

usually in the middle of nucleus

Ribosomes

complexes made of ribosomal RNA and proteins

Ribosomes

build proteins into cytoplasmic regions at any given time

Ribosomes

protein synthesis (translation) takes place in ribosomes

Ribosomes carry out protein synthesis in two locations:

Cytosol (Free Ribosomes) and Outside the Endoplasmic Reticulum or the Nuclear Envelope (Bound Ribosomes)

Free Ribosomes

Cytosol

Bound Ribosomes

Outside the endoplasmic reticulum or the nuclear envelope

Endoplasmic Reticulum

accounts for more than half of the total membrane in many eukaryotic cell

Endoplasmic Reticulum

extensive network of membranes, accounts for more than half of the membrane in many eukaryotic cells

Endoplasmic Reticulum

consists of membranous tubules and sacs (cisternae)

Endoplasmic Reticulum

Continuous with the nuclear envelope

Two distinct regions of ER

Smooth ER and Rough ER

Smooth ER

outer surface lacks ribosomes

Smooth ER

synthesizes lipids, metabolizes carbohydrates, detoxifies drugs and poison, stores calcium ions

Rough ER

outer surface is studded with ribosomes

Rough ER

membrane factory for the cell

Rough ER

has bound ribosomes which secrete glycoproteins

Rough ER

distributes transport vesicles, secretory proteins surrounded by membranes

Golgi Apparatus

consists of cisternae

Cisternae

flattened membranous sacs

Golgi Apparatus

modifies products of the ER

Golgi Apparatus

manufactures certain macromolecules

Golgi Apparatus

sorts and packages materials into transport vesicles

Lysosomes

membranous sac of hydrolytic enzymes that digest macromolecules

Lysosomes

carry out intracellular digestion in a variety of circumstances

Lysosome enzymes

work best in the acidic environment inside the lysosome

Hydrolytic enzymes and Lysosomal membranes

are made by rough ER and then transferred to the Golgi apparatus for further processing

Phagocytosis

which cells engulf other cells; forms food vacuole

Lysosomes

fuse with the food vacuole and digests the molecules

Nutrients

Once it enters plasma membrane, it is enclosed in a food vacuole then fuses with lysosomes and digest molecules

Lysosmes

use enzymes to recycle the cell’s own organelles and macromolecules through **autophagy** 

Lysosomes

digest organelles that are no longer functioning

Molecular Composition and Metabolic Functions

are modified as molecules move from ER to Golgi Apparatus

Mitochondria

nearly all eukaryotic cells have one

Mitochondrion and Chloroplast

organelles that convert energy to form stem cells for work

Mitochondria

sites of cellular respiration

Cellular Respiration

metabolic process that uses oxygen to drive the generation of ATP by extracting energy from sugars, fats and other fuels

Mitchondria

have smooth other membrane and inner membrane folded into cristae

Cristae

large surface area for enzymes that synthesize ATP

Intermembrane Space and Mitochondrial Matrix

Inner membrane of mitochondria creates two compartments

Mitchondrial Matrix

where some metabolic steps of cellular respiration are catalyzed

Peroxisomes

specialized metabolic compartments bounded by a single membrane

Peroxisomes

produce hydrogen peroxide and convert it to water

Peroxisomes

perform reactions with many different functions

Peroxisomes

some use oxygen to break fatty acids into smaller molecules to transport it to mitochondria and use as fuel for cellular respiration

Peroxisomes

in the liver, it detoxifies alcohol and other harmful compounds by transferring hydrogen from the poisonous compounds to oxygen

Cytoskeleton

network of fibers that organizes structures and activities in the cell

Cytoskeleton

a network of fibers extending throughout the cytoplasm

Cytoskeleton

composed of three types of molecular structures: **microtubules**, **microfilaments** (actin filaments), and **intermediate filaments**

Cytoskeleton

most obvious function is to give support to the cell and maintain it shape which is important in the animal cells which lack cell walls

Cytoskeleton

is involve in some cell motility and movement

Cytoskeleton

helps to support the cell and maintain its shape

Cytoskeleton

interacts with motor proteins to produce motility

Vesicles

can travel along the tracks provided by the cytoskeleton

Microtubules

function as compression resisting girders of the cytoskeleton

Microtubules

in animal cells it grows out from a **centrosome** near the nucleus

Centrosome

has a pair of **centrioles**, each with nine triplets of microtubules arranged in a ring

Microtubules

control the beating of **flagella and cilia**

Cilia and Flagella

microtubule-containing extensions that project from some cells

Cilia and Flagella

differ in their beating pattern but share a common structure

Plasma Membrane

sheathes the core of microtubules

Basal Body

anchors the cilium or flagellum

Dynein

motor protein that drives the bending movements of a cilium or flagellum

Dynein

has two feet that walk along the microtubule the adjacent doublet using ATP for energy

Dynein

Cross-links

prot

Microfilaments

function in cellular motility contain the protein myosin in addition to actin

Actin Filaments

in muscle cells, thousands of it are arranged parallel to one another

Thicker Filaments (Myosin)

initerdigitates with thinner actin fibers

Intermediate filaments

formation of nuclear lamina

Intermediate Filaments

Fibrous proteins coiled into cables

Intermediate Filaments

anchorage of nucleus and certain other organelles

Intermediate Filaments and Microfilaments

maintenance of cell shape (tension-bearing elements)

Microfilaments

Two intertwined strands of actin

Microfilaments

functions in changes in cell shape

Microfilaments

function: cell motility (as in amoeboid movement)

Microfilaments

function: muscle contraction

Microtubules

hollow tubules

Tubulin

 a dimer consisting of a-tubulin and B-tubulin

Microtubules

maintenance of cell shape (compression-resisting “girders”)

Microtubules

functions in cell motility (as in cilia or flagella)

Microtubules

function: chromosome movements in cell division

Fibroblasts

in each structure of interest has been tagged with fluorescent molecules

Extracellular Components

connection between cells that help coordinate cellular activities