Cell Exchange and Transport

Edexcel AS level Biology revision cards, based on the information needed to cover the specification. 

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  • Created by: Jas
  • Created on: 02-11-11 21:16



 200nm    1400x

the specimen has to be thin and transparent.


0.5nm   300,000x

2-dimensional specimens stained with heavy metals and hard to prepare.


just over 0.5nm   300,000x

3-dimensional, colour can be added to images. 

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magnification, resolution and staining.


the process of enlarging an image.


how much you can distinguish between two objects close together. 


different stains used to highlight and enhance visualization of certain parts of a cell, eg the nucleur or cell wall. 

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calculating magnification.


      M         x       O

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group of compunds, include fats, oil and waxes.

dont mix with water.

two types -> triglycerides which store energy and phospholipids which form membrane.

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small sphere of membrane.

contain digestive enzymes.

break down substances/ cell organelle/ whole cell. 


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where aerobic respiration takes place. 

smooth outer membrane, with folded inner membrane.

the more folds, the more metabically active.


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rough er.

extensive membrane system, connected to the nucleur membrane.

transport system = collects > stores > packages

transports proteins made on ribosomes. 

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golgi apparatus

found close to the rough er.

synthesises/modifies proteins before secreting them from cell. 

flat stack of membrane. 


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small and dense like a giant enzyme.

no membrane.

site of translation. 

attached to rough er or in cytoplasm.

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smooth er

synthesis of lipids and some steroids. 

small patches found in cytoplasm. 

membrane system with no cavaties. 

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slimy capsule.

stores waste.

stops cells from drying out. 

harder for white blood ells to engulf cells. 

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small circular piece of DNA, contains extra genes such as antiibiotic resistant genes. 

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where respiration takes place in prokaryotic cells.

a bit like mitochondria. 

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eukaryotic cell.

plant / animal / fungi

relatively complex.

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prokaryotic cell.

no nucleus.

single celled organism = bacteria.

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plasma membrane or fluid mosaic model.


hydrophilic head and hydrophobic tail.


outside, inside or throughout the bilayer, can have carbohydrates attached called glycoproteins and cell recognition.

(http://t1.gstatic.com/images?q=tbn:ANd9GcT0xC2ShaX6i1U3ZhpMgCuNoOMRiruWfVGSHOQ6I95_H4-wI6pxKg)PARTIALLY PERMEABLE!!!!!

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purpose of plasma membrane.

to seperate organelles and cells from intercellular fluid. 

to control the movement of substances in and out of cells. 

to allow communication between cells. 

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passive transport - diffusion.

all substances have natural movement. 

they all try to reach an equillibrium. 

substances will spread from somewhere with a high concentration to somewhere with a low concentration. 

no energy is required.

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passive transport - facilitated diffusion.

molecules move from high to low concentration gradient. 

molecules have to be moved through the membrane by a special carrier protein if it is difficult for them to pass though the bilayer.

specific membrane proteins have to be used. 

molecules like sugar and amino acids.

doesnt require and energy.

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active transport.

for cells such as ions and large molecules that are repelled or are too big to pass through the membrane.

works against a concentration gradient.

specific membrane proteins have to be used. 

example of this is the Na/K pump.

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osmosis and water potential.

water potential = measure of the amount of water in a substance in a solution > pure water has the potential of 0, if something is added to the water then the potential decreases. 

osmosis is a special type of diffusion where water diffuses through a partially permeable membrane. 

it is the movement of water down a concentration gradient, from high to low. 

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