B1: Cell Structure Flashcards
What is magnification?
How many times larger the image is than the object.
What is the equation for magnification?
Image size / object size
What is resolution?
The shortest distance between two points on an object that can still be distinguished at two separate entities
What is the pathway of light through a microscope?
Light source, stage, microscope slide, object, objective lens, body tube, eyepiece lens, eye
What are advantages of light microscopes?
Easy to use and relatively cheap
What is a disadvantage of light microscopes?
Low resolution
What are disadvantages of electron microscopes?
Very expensive and hard to use
What are advantages of electron microscopes
Have a high resolution
What is the function of the cell wall?
The cell wall is made of cellulose, and this helps to strengthen the cell
How are nerve cells specialised for their functions?
They have dendrites, which make connections with other cells, an axon, which carries nerve impulse from one place to another and synapses, which pass impulses from one place to another
How are muscle cells specialised for their functions?
Contain special proteins that slide over each other, many mitochondria to transfer energy needed for chemical reactions and can store glycogen
How are sperm cells specialised for their functions?
Long tail to help sperm move, many mitochondria for tail to move and the acrosome which stores enzymes to break through egg’s outer layer
How are root hair cells specialised for their functions?
Have a high surface area for water to move into the cell, permanent vacuole to speed movement of water by osmosis and mitochondria to carry out active transport
How is the xylem specialised for its functions?
Dead cells which form hollow tubes for water and minerals to pass. Lignin makes the cell walls strong, helping them withstand pressure
How is the phloem specialised for its functions?
Sieve plates allow water carrying dissolved food to move up tubes. Companion cells keep them alive and contain mitochondria for energy to move dissolved food
What is diffusion?
The net movement of particles from an area of high concentration to an area of low concentration
Give examples of when diffusion occurs
Oxygen and carbon dioxide in gas exchange and the waste product of urea from cells into the blood plasma for excretion in kidneys
What 3 factors affect the rate of diffusion?
Concentration gradient, temperature and surface area of membrane
What 4 factors increase the effectiveness of exchange surfaces?
A large surface area, thin membrane, which provides a short diffusion distance, having an efficient blood supply and being ventilated
What is osmosis?
The net movement of water molecules from a dilute solution to a concentrated solution through a semi-permeable membrane
What is osmosis?
The net movement of water molecules from a dilute solution to a concentrated solution through a semi-permeable membrane
What is active transport?
The net movement of particles from an area of low concentration to an area of high concentration (against the concentration gradient) requiring energy
Which molecules are able to diffuse into and out of cells? Why?
Amino acids, water and glucose because they are small molecules
True or false: Active transport can only take place across a membrane
True
How are the lungs and intestines adapted to increase surface area?
Lungs have millions of alveoli and intestines have villi
Give examples of exchange systems
Gills in fish and the leaves in root hair cells
What are 4 general features that exchange surfaces have in common?
Large surface area so more particles can pass at once. Thin membranes, reduce distance and membranes are ventilated as well as a diffusion gradient
Explain 3 ways alveoli make good exchange surfaces
Lots of alveoli, increasing the surface area which allows more molecules to diffuse across in a given time, substances are thin, which decrease diffusion distance and a good blood supply, which maintains a strong concentration gradient as blood is constantly replaced
Which adaptation in plants contributes to the efficient exchange of gases?
The flattened shape of leaves
