Biology Ch. 6

Cells

The simplest collection of matter that can be alive. All organisms are made of cells. Usually to small to see

Cell relation

Related by their descent from earlier cells, but can differ substantially from one another but share common features

Light microscope (LM)

Visible light is passed through a specimen and then through glass lenses. They refract (bend) the light so that the image is magnified

Three important parameters of microscopy

1. Magnification - ratio of an objects image to real size
2. Resolution - measure of the clarity of the image
3. Contrast - visible differences in brightness between parts of the sample

Light microscope magnification

Can magnify effectively to about 1,000 times the size of the specimen

Organelles

The membrane-enclosed structure in eukaryotic cells

Scanning Electron Microscope (SEM)

One of two basic types of electron microscopes. Focuses a beam of electrons onto the surface of a specimen providing images that look 3-D

Transmission Electron Microscope (TEM)

One of two basic types of electron microscopes. Focuses a beam of electrons through a specimen. Mainly used to study internal structure of cells

Recent advances in light microscopy

-Labeling individual cells with florescent markers
-Confocal microscopy and deconvolution microscopy provide a sharper image of 3-D tissue and cells
-Super-resolution microscopy allows us to distinguish structures as small as 10-20 nm across

Cell fractionation

Takes cells apart and separates the major organelles from one another

Centrifuges

Fractionate cells into their component parts

What does cell fractionation do?

Enable scientists to determine the functions of organelles

What is the basic structural and functional unit of every organism?

Prokaryotic or eukaryotic cells

What domains consist of Prokaryotic cells?

Archea and Bacteria

What domains consist of eukaryotic cells?

Protest, fungi, animals, and plants

Basic features of all cells

-plasma membrane
-semifluid substance called cytosol
-chromosomes (carry genes)
-ribosomes (make protein)

Prokaryotic cells characteristics

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

Eukaryotic cells characteristics

-DNA in a nucleus that is bounded by a double membrane
-Membrane-bound organelles
-Cytoplasm in the region between the plasma membrane and the nucleus

Which type of cell is larger?

Eukaryotic cells are generally much larger than prokaryotic cells

Plasma membrane

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

Size of cells

Metabolic requirements set upper limits on the cell size, as a cell grows in size its volume increases proportionately more than its surface area

Eukaryotic cell internal membranes

Has internal membranes that divide the cell into compartments-the organlles

Nucleus

Contains most of the cell's genes and is usually the most conspicuous organelle

Nuclear envelope

Encloses the nucleus, separating it from the cytoplasm. Is a double membrane consisting of lipid bi-layer

Pore complex

Pores lining a structure that regulate the entry and exit of molecules from the nucleus

Nuclear lamina

A netlike array of protein filaments lining the inner surface of the nuclear envelope; it helps maintain the shape of the nucleus.

Chromosomes

Threadlike structures made of DNA molecules that contain the genes

Chromatin

DNA molecule associated with proteins inside each chromosome

Chromatin condensation

Forms discrete chromosomes as a cell prepares to divide

Nuclolus

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

Ribosomes

Make proteins and are made of ribosomal RNA and protein

Ribosomes carry out protein synthesis in two locations

-The cytosol (free ribosomes)
-On the outside of the endoplasmic reticulum or the nuclear envelope (bound ribosomes)

Endomembrane system consists of

-Nuclear envelope
-Endoplasmic reticulum
-Golgi apparatus
-Lysosomes
-Vacuoles
-Plasma membrane.

Vesticles

Transports materials within the cell

Endoplasmic Reticulum (ER)

An extensive membranous network in eukaryotic cells, continuous with the outer nuclear membrane and composed of ribosome-studded (rough) and ribosome-free (smooth) regions.

Smooth ER

-Ribosome free
-Sythesizes lipids
-Metabolizes carbohydrates
-Detoxifies drugs and poison
-Stores calcium ions

Rough ER

-Has bound ribosomes which secrete glycoproteins
-Distributes transport vesticles
-Is a membrane factory for the cell

Glycoproteins

Proteins covalently bonded to carbohydrates

Transport vesticles

Secretory proteins surrounded by membranes

Golgi apparatus

Consists of flattened membranous sacs called cisternae

Golgi apparatus function

Modifies, sorts, and packages proteins and other materials and lipids for storage or transport out of the cell

Lysosome

A membranous sac of hydrolytic enzymes that can digest macromolecules

Where are hydrolitic enzymes and lysosomal membranes made?

By the rough ER and then transferred to the Golgi apparatus for further processing

Phagocytosis

A cell engulfing another cell forming a food vacuole

Phagocytosis process

- Attach to membrane
- Ingested (forms food vacuole)
- Food vacuole fuses with lysosome
- Enzymes digest
- Release

Autophagy

A process in which lysosomes decompose and recycle a cell's own organelles and macromolecules

Mitochondria

Sites of cellular respiration, a metabolic process that uses oxygen to generate ATP

Chloroplasts

Found in plants and algae and are the sites of photosynthesis

Similarities of mitochondria and chloroplasts

-Enveloped by a double membrane
-Contain free ribosomes and circular DNA molecules
-Grow and reproduce somewhat independently in cells

Endosymbiont theory

Suggest that an early ancestor of eukaryotes engulfed an oxygen-using nonphotosynthetic prokaryotic cell and formed a relationship with the host becoming an endosymbiont which evolve into mitochondria

Cristae

Infoldings of the inner membrane of a mitochondrion and provide a large surface area for enzyme catalyzing the synthesis of ATP.

Mitochondria characteristics

-have smooth outer membrand and an inner membrande folded into cristae
-inner membrane creates two compartments, intermembrane space and mitochondrial matrix
-found in nearly all eukaryotic cells

Mitochondrail matrix

One of two inner membrane compartments where some metabolic steps of cellular respiration are catalyzed

Chloroplast characteristics

Contain the green pigment chlorophyll. Also contain enzymes and other molecules that function in photosynthesis. Found in leaves and other green organs of plants and in algae

Peroxisomes

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