Chapter 6-Lecture Notes Flashcards by Sara Richmond

All organisms are made of _____________

cells
The cell is the simplest collection of matter
that can be alive
All cells are related by their descent from earlier cells
Cells can differ substantially from one another but share common features

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Cells are usually too small to be seen by the naked eye we use

Microscopy

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In a l\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ visible light is passed through a specimen and then through glass lenses
Lenses refract (bend) the light, so that the image is magnified

light microscope (LM),

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Three important parameters of microscopy
________________ the ratio of an object’s image
size to its real size
_____________ the measure of the clarity of the image, or the minimum distance of two distinguishable points
____________________ visible differences in brightness between parts of the sample

Magnification,

Resolution,

Contrast,

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Light microscopes can magnify effectively to about_______________________________
Various techniques enhance contrast and enable cell components to be stained or labeled

1,000 times the size of the actual specimen

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The resolution of standard light microscopy is too low to study_________________, the membrane-enclosed structures in eukaryotic cells

organelles

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Two basic types of electron microscopes (EMs) are used to study subcellular structures

_____________________ focus a beam of electrons onto the surface of a specimen, providing images that look 3-D

___________________ focus a beam of electrons through a specimen
TEMs are used mainly to study the internal structure of cells

Scanning electron microscopes (SEMs)

Transmission electron microscopes (TEMs)

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provide sharper images of three-dimensional tissues and cells
New techniques for labeling cells improve resolution

Confocal microscopy and deconvolution microscopy

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takes cells apart and

separates the major organelles from one another

Cell fractionation

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Centrifuges fractionate cells into their

component parts

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_____________have
internal membranes that compartmentalize
their functions

Eukaryotic cells

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Only organisms of the domains Bacteria and Archaea consist of

prokaryotic cells

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Protists, fungi, animals, and plants all consist of

eukaryotic cells

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The basic structural and functional unit of every organism is one of two types of cells:

prokaryotic or eukaryotic

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Basic features of all cells

Plasma membrane
Semifluid substance called cytosol
Chromosomes (carry genes)
Ribosomes (make proteins)

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Prokaryotic cells are characterized by having

No nucleus
DNA in an unbound region called the nucleoid
No membrane-bound organelles
Cytoplasm bound by the plasma membrane

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Eukaryotic cells are characterized by having

DNA in a nucleus that is bounded by a membranous nuclear envelope
Membrane-bound organelles
Cytoplasm in the region between the plasma membrane and nucleus
Eukaryotic cells are generally much larger than prokaryotic cells

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is a selective barrier that allows sufficient passage of oxygen, nutrients, and waste to service the volume of every cell

plasma membrane

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has internal membranes that partition the cell into organelles
The basic fabric of biological membranes is a double layer of phospholipids and other lipids
Plant and animal cells have most of the same organelles

A eukaryotic cell

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layers in prokaryotic cells

plasma membrane
cell wall
capsule

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

The nucleus

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The nuclear membrane is a double membrane; each membrane consists of a

lipid bilayer fluid mosaic

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encloses the nucleus, separating it from the cytoplasm

The nuclear envelope

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The nuclear size of the envelop is lined by the ________ , which is composed of proteins and maintains the shape of the nucleus

nuclear lamina

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n the nucleus, DNA is organized into discrete units called

chromosomes

Each chromosome is composed of a single DNA molecule associated with proteins The DNA and proteins of chromosomes are together called

chromatin

Chromatin condenses to form discrete __________________ as a cell prepares to divide

chromosomes

is located within the nucleus and is the site of ribosomal RNA (rRNA) synthesis Ribosomes: Protein Factories

The nucleolus

``` Nuclear envelope Endoplasmic reticulum Golgi apparatus Lysosomes Vacuoles Plasma membrane ```

The endomembrane system consists of

These components are either continuous or connected via transfer by

vesicles

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

The endoplasmic reticulum (ER) two types smooth and rough ER

Smooth ER, | Rough ER,

which lacks ribosomes | whose surface is studded with ribosomes

The smooth ER

Synthesizes lipids Metabolizes carbohydrates Detoxifies drugs and poisons Stores calcium ions

The rough ER

Has bound ribosomes, which secrete glycoproteins (proteins covalently bonded to carbohydrates) Distributes transport vesicles, secretory proteins surrounded by membranes Is a membrane factory for the cells

Has bound ribosomes, which secrete _____________________(proteins covalently bonded to carbohydrates)

glycoproteins

Distributes _______, secretory proteins surrounded by membranes

transport vesicles

--------------------------------- consists of flattened membranous sacs called cisternae Functions of the Golgi apparatus Modifies products of the ER Manufactures certain macromolecules Sorts and packages materials into transport vesicles

The Golgi apparatus

________________________ is a membranous sac of hydrolytic enzymes that can digest macromolecules Lysosomal 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

A lysosome

Some types of cell can engulf another cell by _________________ this forms a food vacuole A lysosome fuses with the food vacuole and digests the molecules

phagocytosis;

Some types of cell can engulf another cell by ------------------------------; this forms a food vacuole A lysosome fuses with the food vacuole and digests the molecules

phagocytosis

are large vesicles derived from the ER and Golgi apparatus

Vacuoles

are the sites of cellular respiration, a metabolic process that uses oxygen to generate ATP

Mitochondria

found in plants and algae, are the sites of photosynthesis Peroxisomes are oxidative organelles The Evolutionary Origins of Mitochondria and Chloroplasts Mitochondria and chloroplasts have similarities with bacteria

Chloroplasts,

suggests that an early ancestor of eukaryotes engulfed an oxygen-using nonphotosynthetic prokaryotic cell

The endosymbiont theory s

They have a smooth outer membrane and an inner membrane folded into

cristae

Chloroplast structure includes

Thylakoids, membranous sacs, stacked to form a granum Stroma, the internal fluid The chloroplast is one of a group of plant organelles, called plastids

membranous sacs,

Thylakoids,

is one of a group of plant organelles, called plastids

The chloroplast

stacked to form a ___________ | _______________________ the internal fluid

geranium | Stroma,

are specialized metabolic compartments bounded by a single membrane Peroxisomes produce hydrogen peroxide and convert it to water

Peroxisomes

perform reactions with many different functions | How peroxisomes are related to other organelles is still unknown

Peroxisomes

is a network of fibers extending throughout the cytoplasm | It organizes the cell’s structures and activities, anchoring many organelles

The cytoskeleton

It is composed of three types of molecular structures Microtubules Microfilaments Intermediate filaments

The cytoskeleton helps to support the cell and maintain its shape

It interacts with motor proteins to produce motility | Inside the cell, vesicles can travel along tracks provided by the cytoskeleton

________________ are the thickest of the three components of the cytoskeleton ___________________ also called actin filaments, are the thinnest components ______{___________are fibers with diameters in a middle range

Microtubules Microfilaments, Intermediate filaments

___________________ are hollow rods about 25 nm in diameter and about 200 nm to 25 microns long Functions of microtubules Shaping the cell Guiding movement of organelles Separating chromosomes during cell division

Microtubules

In animal cells, microtubules grow out from a -----------------------------near the nucleus In animal cells, the centrosome has a pair of _______________ each with nine triplets of microtubules arranged in a ring

centrosome centrioles,

Microtubules control the beating of ________________________microtubule-containing extensions that project from some cells they differ in their beating patterns

flagella and cilia,

_____________________ that anchors the cilium or flagellum | A motor protein called _________________ which drives the bending movements of a cilium or flagellum

A basal body dynein,

__________________are solid rods about 7 nm in diameter, built as a twisted double chain of actin subunits The structural role of microfilaments is to bear tension, resisting pulling forces within the cell They form a 3-D network called the _____________ inside the plasma membrane to help support the cell’s shape Bundles of microfilaments make up the core of microvilli of intestinal cells

Microfilaments cortex just

that function in cellular motility contain the protein myosin in addition to actin In muscle cells, thousands of actin filaments are arranged parallel to one another Thicker filaments composed of myosin interdigitate with the thinner actin fibers

Microfilaments

is a circular flow of cytoplasm within cells This streaming speeds distribution of materials within the cell In plant cells, actin-myosin interactions and sol-gel transformations drive cytoplasmic streaming

Cytoplasmic streaming

___________________ range in diameter from 8–12 nanometers, larger than microfilaments but smaller than microtubules They support cell shape and fix organelles in place

Intermediate filaments r

____________________ are more permanent cytoskeleton fixtures than the other two classes

Intermediate filaments

is an extracellular structure that distinguishes plant cells from animal cells

cell wall

The cell wall protects the plant cell, maintains its shape, and prevents excessive uptake of water Plant cell walls are made of cellulose fibers embedded in other polysaccharides and protein

Prokaryotes, fungi, and some unicellular eukaryotes also have cell walls

Plant cell walls may have multiple layers

Primary cell wall: Relatively thin and flexible Middle lamella: Thin layer between primary walls of adjacent cells Secondary cell wall (in some cells): Added between the plasma membrane and the primary cell wall

Relatively thin and flexible

Primary cell wall:

Thin layer between primary walls of adjacent cells

Middle lamella:

Added between the plasma membrane and the primary | cell wall

Secondary cell wall (in some cells):

Animal cells lack cell walls but are covered by an elaborate extracellular matrix (ECM)

The ECM is made up of glycoproteins such as collagen, proteoglycans, and fibronectin

are channels that perforate plant cell walls | Through plasmodesmata, water and small solutes (and sometimes proteins and RNA) can pass from cell to cell

Plasmodesmata

3 types of cell junctions are common in epithelial tissues

Tight Junctions, Desmosomes, and Gap Junctions in Animal Cells

membranes of neighboring cells are pressed together, preventing leakage of extracellular fluid

At tight junctions,

) fasten cells together into strong sheets

Desmosomes (anchoring junctions

(communicating junctions) provide cytoplasmic channels between adjacent cells

Gap junctions

The Cell: A Living Unit Greater Than the Sum of Its Parts | Cells rely on the integration of structures and organelles in order to function

For example, a macrophage’s ability to destroy bacteria involves the whole cell, coordinating components such as the cytoskeleton, lysosomes, and plasma membrane