AP BIO Chapter 6

Describe light microscopes

• visible light is passed through the specimen and then through the glass lense

• lense bends the light so the image gets magnified

• Can magnify up to about 1k times of the actual size

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Describe the 3 important parameters of microscopes

1) magnification: ratio of the object’s image to its real size

2) resolution: image clarity

3) contrast: visible differences between light and dark

Describe an electron microscope

• Used to study subcelluar structures

• Two types: Scanning and transmission

• Scanning is used to study the TOPOGRAPHY of the specimen. It scans the surface and the electrons get detected by a device that translates these patterns

• Transmission studies the INSIDE of the cells. The electron beam goes into the specimen.

Advances in light microscopy

• Fluorescent marker labeling makes it easier to with detail

• Confocal and deconvolution allow us to distinguish tiny structures! It makes the images sharper

• Cryoelectron microscopy allows specimens to be preserved at low temperatures.

• Cytology is the study of cell structure

What is cell fractionation?

• Used to study cell structure and function

• It basically takes the cell apart and seperates major organelles and subcelluar structures.

• The centrifuge spins test tubes holding disrupted mixtures at increasing speeds (differential centrifugation). At each speed, the force causes cell components to settle at the bottom of the tube, forming a pellet. At lower speeds this pellet is made up of larger components and at higher speeds its made up of smaller components

• Biochem and cytology work together!

What kinds of cells are prokaryotic and eukaryotic?

• Prokaryotic: single celled organisms that belong to Bacteria and Achaea

• Eukaryotic: animals, plants, fungi, protists

What do both cells have in common?

• Plasma Membrane

• Cytosol (fluid part of the cytoplasm. Tiny structures of cell are here!)

• Chromosomes (or DNA)

• Ribosomes

Describes ALL differences between the two cells

Eukaryotic cells have DNA in the nucleus while prokaryotic cells carry DNA in the nucleoid (more on this later!). For Eukaryotic cells, the cytoplasm is between the nucleus while for prokaryotic cells it fills the whole interior space. In Eukaryotes all the organelles are suspended in cytosol but Prokaryotes have no organelles (membrane bounded). Eukaryotes are bigger while Prokaryotes are smaller (smallest cells are bacteria called mycoplasmas).

Describe the plasma membrane

• It is a selective barrier

• Cells need to have a tiny volume with a big SA to keep things moving in and out. SA can be increased with microvilli (thin projections that increase SA).

What is in a prokaryotic cell?

A prokaryotic cell has:

• Fimbriae (short and hair-like)

• Glyoclayx (outer coating)

• Cell wall

• plasma membrane

• nucleoid

• ribosomes

• flagella

Name the things that plant cells have but animal cells do not

• Cell wall

• Central Vacuole

• Chloroplast

• Plasmodesmata

Describe the parts of the nucleus (nucleus in general, nuclear envelope, chromatin, chromosomes, and the nucleolus).

The Nucleus

• Genes are mostly in the nucleus, but they can also be found in the mitochondria and the chloroplasts

• Stores and protects DNA

• Regulates gene expression

The Nuclear Envelope

• A double membrane

• Embedded in the nuclear envelope is the protein complex, which regulates the entry and exit of proteins, RNAs, as well as large complexes of macromolecules

• Beneath the inner membrane is the nuclear lamina. Protein filaments maintain the shape of the nucleus by supporting the envelope.

Chromosomes

• Each consists of one long DNA strand with multiple proteins. Some of these proteins help coil the DNA. The proteins are called chromatin, a mixture of DNA, RNA, and proteins that make up the chromosomes.

Nucleolus

• Ribosome synthesis

• rRNA is created from the genes in the DNA. Proteins are imported from the cytoplasm and get assembled with rRNA into large and small subunits of ribosomes. These then exit the nucleus through the pores into the cytoplasm. Smaller and larger subunits come together to make a ribosome.

• mRNA will carry the info from DNA. mRNA is escorted out by proteins to the cytoplasm through the nuclear pores. Ribosomes then translate the genetic information into the polypeptide structure.

describe ribosomes.

• Ribosomes are made up of rRNA and proteins

• NOT a membrane bound organelle!

They carry out protein synthesis in TWO places

• In the cytosol (free ribosomes)

• Attached to the outside of the ER or nuclear envelope. These are generally proteins made for insertion into membranes, packaging, export (secretion) from the cell, and more.

What are the parts of the Endomembrane System

• ER

• Golgi Apparatus

• Lysosomes

• Vacuoles

• Plasma Membrane

Connected by vesicles (made up of lipid bilayer membranes)

Describe the ER, the Rough ER, and the Smooth ER

ER

• Made up of membranous tubules and sacs called cisternae

• Internal compartment of the ER is called the ER lumen or the cisternal space

• Cont. with the nuclear envelope

Rough ER

• Proteins produced by ribosomes are attached to the Rough ER

• As a polypeptide chain grows from a bound ribosome, the chain is threaded into the lumen through a pore formed by a protein complex in the ER membrane.

• Most secretory proteins are glycoproteins, proteins with carbohydrates covalently bonded to them. Enzymes attach them.

Smooth ER

• No ribosomes on the outer surface

• Synthesize lipids, metabolism of carbohydrates, detoxification and storage of Ca+

• detoxification: adding a hydroxl group to drug molecules make them water soluable (flush away easily).

Describe the Golgi Apparatus

• Vesicles go to the Golgi

• Products of the ER are modified and stored and sent here.

• Consists of flattened membranous sacs cisternae

• Manufactures some macromolecules. Many polysaccharides that secreted by cells are made in the Golgi

• When a vesicle secretes protein it gets incorporated into the plama membrane, making the SA go up.

• There are two sides of the Golgi

Cisface

• Recieving

Transface

• Shipping

• Products of the ER are usually modified during transition from cis to trans.

Lysosomes

• Hydrated enzymes that are used to hydrolyze macromoleucles

• Hydrolitic enzymes and the lysosomal membranes are made by the rough er and transferred to the Golgi. 3d protein shape of proteins o the inner surface of the lysosmal and digestive enzymes are protected from an eenzymatic attack.

• Autophagy: hydrolytic enzymes recycle the cell’s organic materials. A damaged organelle or a small amount of cytosol becomes surround by a double membrane and a lysosome fuses with the ouer membrane, dismantles the inner membrande, and the enclosed ting and releases it into the cytosal for reuse.

• Inheritied Lysosomal Storage Disease: no functioning hydrolytic enzymes so the lysosomes become full of indigestibale things

Vacuoles

• From the ER and the Golgi

• Many functions:

  • Contractile vacuoles pump excess water out of the cell

  • The central vacuole is made up of smaller vacuoles. The solution inside is called cell sap, which stores inorganic ions. Absorbs water, and the plant gets big

  • Food vacuoles formed by phagocytosis

Endosymbiont Theory

• Early ancestor of a eukaryotic cell engulfed an oxygen using no photosynthetic bacteria and became endosymbiont.

• Mitochondria and chloroplast both have ribosomes and are autonomous

Mitochondria

• 2 Membranes

• Inner membrane has folding called cristae

• ATP is built in the inner membrane

• Two parts:

Membrane space and mitochondrial matrix

Chloroplasts

• Thykaloids: coin like compartments. A stack is called a granum and the fluid is called stroma

• Contains chloroplast and ribosomes and other enyzmes

• Three parts: intermembrane space, stroma, and thykaloid.

• Member of plastids

Perioxisomes

• Single Membrane

• Contains enzymes that remove the H atoms from various substrates and transfers them to O2 making H2O2 as a by product.

• Break down fatty acids, detoxify alcohol, and can be convereted into water.

• Glyoxysomes are found in fat storage tissues of plants and can convert fat to sugar.

• Grow bigger by incorporatig proteins made in the cytosol and ER as well as lipids in the ER and in peroxisome itself.

Cytoskeleton

• supports and maintains cell shape

• Can change cell shape

• Cell motility (ability to move).

• Interacts with motor proteins

Microtubules

• Thickest

• Hollow tubes

• Protein = Tublin (alpha and beta)

• Cell motility, chromosome movements in cell division. Organelle movements.

• Each tublin protein is a dimer. Made up of two parts. alpha and beta polypeptides. They grow in length by adding tublin dimers, can be diassembled and can be used to build microtubules elsewhere.

• One end releases or accuulates dimers at a much higher rate so it grows and shrinkes alo during cell activity.

• Guides vesicles from the ER to the GA and from the plasma membrane centrosoms and centrioles.

Centrisomes and Centrioles

• Microtubules grow out of the centrosome

• Each centriolel has a set of triplet microtubules

• Not very common

Cilia and Flagella

• Extensions that contain microtubules

• A special arrangement of the microtubules is for moving back and forth

• Unicelluar protsits are propelled by cilia and flagella

• Flagella usually have less than one and are quite long with wave like movements

• Each have a group of microtubules. A microtubule pairs on th ousid and 2 in the middle

Microfilaments

• Form structural networks when proteins bind with.

• Bears tension

Intermediate filaments

• Bear tension

• Only in eukaryotes

• Use different building blocks depending on cell type

• Can survive after cell dies

• Stops cell from tearing apart

• Forms nuclear lamina

Cell wall of plants

• thicker than plasma membrane

• Though fibers made of cellulose and an enzyme called cellulose synthase makes these fibers and pushes them out of the cell

• 3 layers:

1) thin and flexible

2) sticky and full of pectin

3) second cell wall: strong and thick

ECM of Animal Cells

• Made of glycoproteins and carbohydrates containing molecules secreted by the cell.

• Collagen: most abundant. Makes strong fibers outside of cell.

• Proteoglycons: small proteins with carbo chains attached. Collagen fiber are embedded in an etwork of proteins

• Fibranectin: ECM glycoproteins that attach to the matrix

• Integring: cell surface receptors proteins built in plasam membrane

Cell Junctions

• neighboring cells adhere , interact, and comm thru direct contact via junctions

• Plant: plasmodesta: membrane lined channels thru plant cells that connect cytoplasm of adj cell

• Allow water, small solutes and ceertain proteins/RNA to pass freely btwn cells.

• In animals:

• Tight: plasma membranes of a neighboring cell are pressed tightly against each other bound by proteins creating water tight seals.

• Desmosomes: act like rivets, fastening cells togeter into strong sheets.

• Gap Junctions: provide cytoplasmic channels from one cell and an adj cell sim to plasmodes in plants.