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the smallest unit that shows properties of life which means it has the capacity for metabolism, homeostasis, growth, and reproduction. All start out with a plasma membrane, a DNA-containing region, and cytoplasm.


Eukaryotic Cell

Is divided into various functional compartments, including the nucleus.


Prokaryotic Cells

Are smaller and simpler cells; they do not have a nucleus.


Plasma Memebrane

A cells outer membrane. It separates metabolic activities from events outside the cell, but does not isolate the cells interior. Water, carbon dioxide, and oxygen can still pass freely across it. Some substances can cross through with assistance from membrane proteins however others are kept out entirely.



A double-membraned sac which hold an eukaryotic cell's DNA.



The region where the DNA inside a prokaryotic cell is concentrated inside the cytoplasm.



Is the semifluid mixture of water, ions, sugars, and proteins between the plasma membrane and the region of DNA.Cell compartments and other components are suspended in cytoplasm.



Structures on which proteins are built.


Lipid bilayer

the structural foundation of the cell membranes. It is double layer of lipids organized so that their hydrophobic tails are sandwiched between their hydrophilic heads. Proteins in the bilayer carry out the membranes functions.



The most abundant type of lipid in the cell membrane. Each has a phosphate-containing head an two fatty acid tails. The polar head is hydropholic (attracts water molecules) and the non polar tails are hydrophobic (repel water molecule). This causes the hydrophobic tails to be sandwiched between their hydrophilic heads making up the cell membrane.


Examples of cells that can be seen from naked eye?

Egg yolk, watermelon tissues, and amphibian and fish eggs.


Surface-to-volume ratio

An objects volume increases with the cube of its diameter, but it's surface area increases only with the square. So it's volume increases faster then surface area and the plasma membrane must handle exchanges with much more cytoplasm slowing down the inward and outward flow of nutrients. If this slows down too much the cell may die. Many cells find ways to increase their surface area (long and thin or frilly with folds) to keep up with an actives cells metabolism.


The Cell Theory

1. All organisms consist of one or more cells 2. The cell is the smallest nit that retains the properties of life 3. Each new cell arises from another cell.


Light Microscopes

They rely on visible light to illuminate objects. Light is focused and magnified with curved glass lenses. Light passes through the specimen so only cells that are thin enough for light to pass through them will be enhanced.



Photos of images enlarged by microscopes.


Fluorescence Microscope

The cell or molecule is the light source and it emits energy (fluoresces) in the form of light when a laser beam is focused on it. Chlorophyll's fluoresce naturally.



The distance from the peak of one wave to the peak of the one behind it. This limits the power of any light microscope because structures which are smaller then one half of the wave length are too small to scatter light waves.


Electron Microscopes

Reveals smaller details because instead of using light to illuminate samples they use electrons which travel in smaller wave lengths.


Transmission Electron Microscopes

Electrons form an image after they pass through a thin specimen. The internal details appear as shadows.


Scanning Electron Microscope

Direct beam of electrons back and froth across a specimen which has been coated with a thin layer of gold or another metal. The metal emits both electrons and x-rays which re converted into an image of the surface.


Fluid Mosaic Model

describes the organization of cell membranes.


Passive Transporters

Allows ions r small molecules to cross a membrane to the side where they are less concentrated. Open or grated channels. Ex. Porins; glucose transporter.


Active Transporters

Pump ions or molecules through membranes to the side where they are ore concentrated. Requires energy input as ATP. Ex. Calcium pump; serotonim transporter



Initiate change in cell activity by responding to an outside signal. Ex. Insulin receptor; B cell receptor


Cell Adhesion Molecules

Help cells stick to one another and to protein matrixes tat are part of tissues. Ex. Integrins; cadherins


Recognition proteins

Identity cells as self (belonging to one's own body or tissue) or non-self (foreign to the body)


Communication Proteins

Join together and form cytoplasm-to-cytoplasm junctions through which ions and small molecules pass freely and quickly between adjacent cells. Ex. Connexins in gap junctions.


Membrane compostition

Membrane composition differs dependent on the cell's functions. The two surfaces of the lipid bilayer are even different.


Two domains of prokaryotic cells

Bacteria and Archea


Cell Wall

Found in prokaryotic and plant cells. Surrounds the plasma membrane and is a rigid yet porous structure.