Bio 1009 - Cells and Membranes

Week 2

Magnification

Ratio between the size of an image produced by a microscope and its actual size

Resolution

Ability to observe two adjacent objects as distinct from one another

Contrast

How one structure looks different from another

– enhanced by dyes

Light microscopes

Uses light for illumination

○ Resolution 0.2 µm

Electron microscopes

Uses an electron beam

○ Resolution 2 nm

Transmission electron microscopy (TEM)

○ An electron beam passes through the sample

○ Thin slices are stained with heavy metals

○ Some electrons are scattered, while others pass through to form an image

Scanning electron microscopy (SEM)

○ Sample coated with heavy metal

○ Beam scans the surface to make a 3D image

Prokaryotes

Does not have a membrane-bound nucleus; Bacteria and Archaea

Eukaryotes

Contain a membrane-bound nucleus: Animals, Plants, Fungi, Protists

Smooth Endoplasmic Reticulum (SER)

● Lipid-handling center and storage facility

● Synthesizes needed lipids (e.g., phospholipids, cholesterol)

● Breaks down poisonous ones.

● Stores calcium

● Helps break down glycogen into glucose-6-phosphate when energy is needed

Rough Endoplasmic Reticulum (RER)

● Protein synthesis and processing.

● Attached ribosomes insert proteins into the ER lumen cotranslationally.

● Proteins are packed into vesicles and shipped to:

○ plasma membrane

○ cell exterior

○ specific organelles

Golgi apparatus

● Vesicles from the ER deliver proteins to Golgi.

● Proteins progress from the cis-cisternae to the trans-cisternae

● Proteins are posttranslationally modified

● Proteins are delivered to the plasma membrane or organelles.

Lysosomes

● Found only in animal cells

● Function as digestive centers.

● Proton pumps keep the lysosome lumen acidic (pH 5.0)

● Lysosomes contain 40+ enzymes for breaking up macromolecules.

Peroxisomes

● Originate from ER

● Centers for redox reactions to break down molecules by removing hydrogen or adding oxygen.

● Catalase converts Hazardous byproduct, H2O2 , back to oxygen and water.

Mitochondria

● Primary role is to make ATP

● Outer and inner membranes

● Intermembrane space and mitochondrial matrix

● Also involved in the synthesis, modification, and breakdown of several types of cellular molecules

Chloroplasts

● Photosynthesis: Turns solar energy into chemical energy

● Present in most plants and algae

● Three membranes: Outer, Inner, Thylakoid

Central vacuoles

in plants for storage (water, ions, proteins, pigments, noxious compounds) and support.

Contractile vacuoles

in protists for expelling excess water

Phagocytic vacuoles

in protists and white blood cells for degradation

To have a more fluid membrane

Shorter tails, more double bonds, high temperature, less cholesterol

To have a less fluid membrane

Longer tails, less double bonds, low temperature, more cholesterol

Passive transport

No energy, down the gradient

Active transport

requires energy, against the gradient

Secondary Active Transport

Uses a pre-existing gradient, pumps with gradient

Primary Active Transport

Uses ATP-powered pump, pumps against gradient

Uniporter

A transporter that moves a single solute in one direction

Symporter or cotransporter

A transporter that moves two solutes in the same direction

Antiporter

Two solutes move in opposite directions