B1 Flashcards
Why microscopes are used
To see things that are unable to be seen without assistance
What is the unit conversion chart?
1km= 1000m 1m=100cm 1cm=10mm 1mm=1000um 1um=1000nm
When was the light microscope invented?
Mid 17th century
What are the features of a light microscopes?
- used a lot in school
- forms a beam of light that magnifies the object
- magnify up to 2000x
- relatively cheap
- can be used almost anywhere and can magnify live specimens
- limited resolution (blurry)
When was the electron microscope available?
1930s
Why the electron microscope is an important development for science?
Allows scientists to understand more about the sub-cellular structures
What are the features of a electron microscope?
- forms a beam of electrons and can magnify up to 2 million times
- transmission electron microscope gives a 2D images with a high magnification
- scanning electron microscopes give dramatic 3D images but a low magnification.
- very large , expensive, kept at a specific temperature, pressure and humidity
How to calculate magnification ?
Magnification = Image size/ size of real object
How to work out magnification on a light microscope?
Multiply magnification of the eyepiece lens by the magnification of the objective lens
What is the definition of resolution?
The ability to distinguish between two separate points and is resolving power of a microscope that effects the detail shown
What is the resolution of a light microscope?
200nm
What is the resolution of an electron microscope ?
10nm
What has a higher resolution , light or electron microscope?
Electron
How big is the average animal cell?
10-30 um long
What is the definition of the nucleus ?
Controls the cell activities. Contains the genes on the chromosomes that carry the instructions for making proteins needed to build new cells
What is the definition of the cytoplasm?
Liquid gel in which organelles are suspended, it is where chemical reactions take place.
What is the definition of the cell membrane?
Controls the passage of substances such as glucose and mineral ions into the cell. Also urea and hormone passage
What is the definition of the mitochondria?
Structures in the cytoplasm where aerobic respiration takes place, releasing energy for the cell.
What is the definition of a ribosome?
Protein synthesis, makes all protein needed in the cell.
How do plants make food ?
Photosynthesis
Are animal or plant cells bigger?
Plant cells are bigger and contain more features
What is algae?
Simple aquatic organism , make food through photosynthesis
What is the cell wall?
Made of cellulose, strengthens the cell and gives it support
What are chloroplasts?
Found in green part of the plant . Contain chlorophyll that absorbs light to create food through photosynthesis
What is the permanent vacuole?
Space in the cytoplasm filled with cell sap , helps keep the cell rigid
What are eukaryotic cells?
- Animal and plant cells
- has a nucleus and other organelles like cell membrane and cytoplasm
- have DNA that forms structures called chromosomes
- larger (10-100 um)
- example:human skin cell
What are prokaryotic cells?
- bacteria
- 0.2-2um in size
- no nucleus
- few organelles
- example: ecoli bacterium
What is the size of DNA?
10nm
A fox is around 40 cm long. A rick living on the fox is around 0.4cm long . How many order of magnitude is the fox longer than the tick?
40/0.4 = 100x
100x is two orders of magnitude, the number of 0s is the amount of magntiude
What are nerve cells?
- specialised to carry electrical impulses around the body of an animal
- provide a rapid communication system
What adaptions do nerve cells have?
- dendrites that make connection to other cells
- axon carries nerve impulses from one place to another
- synapses are adapted to pass impulses through neurotransmitters
What are muscle cells?
- specialised cells that can contract and relax
- striated muscles cells work together in tissues called muscles
- muscles move the skeleton
- muscles cells help squeeze food through gut , in digestive system
How are muscle cells adapted?
- special proteins that slide over each other making the fibres contract
- mitochondria that transfers energy needed for chemical reactions to take place during contraction and relaxing
- store glycogen , chemical broken down and used for respiration, energy transferred to fibres for contraction.
What are sperm cells?
- contain genetic information from the male parent
- need to move through female reproductive system to break an egg
How sperm cells are adapted ?
- long tail helps sperm move through reproductive system
- middle section full of mitochondria , transfers energy needed for tail to work
- acrosome stores digestive enzymes for breaking down the outer layers of an egg
- has nucleus that contains genetic information.
What are root hair cells?
- grow on roots of tip
- helps bring water up more efficiently
- close to xylem tissue
- active transport helps move water into cells
What are root hair cells adaptions?
- increase surface area for water to move into cells
- large permanent vacuole speeds up movement of water by osmosis from the soil across the root hair cell
- mitochondria gives energy needed for active transport of mineral ions into root hair cell
What are photosynthesis cells?
Plant cells that make food through photosynthesis
What adaptions do photosynthesis cells have?
- chloroplasts, contain chlorophyll that trap sunlight for photosynthesis
- positioned on leaves and outer layer of stem
- large permanent vacuole keeps cell rigid
What are xylem cells?
- transport tissue for water and minerals from the roots to the highest leaves and shoots
- helps support plant , runs through stem
How the xylem tissue was formed?
Xylem cells are alive at first , but die when chemical called lignin builds up in the cell walls. It kills the cells forming a hollow tube able to transport water more easily from end to end
What adaptions do the xylem cells have?
- spirals and rings of lignin in xylem cells make the very strong and help them withstand pressure of water moving up plant
- help support plant stem
What are phloem cells?
- specialised transport tissue that carries food made by photosynthesis around the body
- forme tube like xylem but is not lignified
- goes to where is needed.
What adaptions do phloem cells have?
- cell walls between cells break down to form special sieve. Helps free up movement
- companion cells help phloem stay alive. Mitochondria and companion cell transfers energy needed to move dissolved foods.
What is diffusion?
Spreading out of the particles of any substance in solution, from a high to low concentration
Why does diffusion take place?
Random movement of particles , causes collision , so molecules move about
Formula for net movement of particles?
Net movement =particles moving in -particles moving out
How the concentration of particles effects the rate of diffusion?
Greater the difference in concentration the higher the rate of diffusion
What is the concentration gradient?
Difference between two areas of concentration . Bigger the difference the steeper the concentration gradient.
Does temperature effect the rate of diffusion?
Yes, particles move around rapidly increasing the rate of diffusion.
How does diffusion work moving in and out of cells?
Move in and out of cells by diffusion across the cell membrane
What substances move in and out of cells?
- simple sugars(glucose)
- gases(oxygen, carbon dioxide)
- waste products (urea)
What is urea?
Waste product from the breakdown of amino acids in the liver. It is put into blood plasma for excretion in the kidney
How does urea transport from the liver ?
From the liver it diffuses to the blood cells
How gas exchange works?
Oxygen needed for respiration passes from lungs to red blood cells through diffusion. Then it diffuses from the blood to the cells where it is needed. Carbon dioxide moves through body cells into red blood cells then into the air in the lungs through diffusion.
What is gas exchange?
Movement of oxygen and carbon dioxide in opposite directions in the lungs.
What is a partially permeable membrane?
Membrane that only lets some types of particles through
What is osmosis?
Movement of water molecules across a partially permeable membrane from a region of high concentration of water to a region of low concentration of water.
What is a dilute solution?
Dilute solution of sugar contains high concentration of water , low concentration of suagr
What is a concentrated solution?
Sugar solution contains low concentration of water and high concentration of sugar
What does isotonic mean?
Concentration of solutes outside the cell is the same as the internal concentration
What is does hypertonic mean?
Concentration of solutes outside the cel is higher than the internal concentration
What does hypotonic mean?
Concentration of solutes outside the cell is lower than the internal concentration.
How osmosis works in animals?
- cell uses up water in chemical reactions , cytoplasm becomes concentrated
- cytoplasm becomes too dilute water leaves the cell by osmosis
- maintaining constant internal conditions is vital as cell can burst or shrivel up
Why do plants rely on osmosis.
The support their stem and leaves
What does osmosis create?
A turgid cell.
What is a turgid cell?
When the cell is full of water. The vacuole swells, pushed against the cell wall, keeping plant rigid
What state do cells need to be ?
Hypotonic
What is a flaccid cell?
Soft cell is hypertonic and weak. No longer supports the plant
What is plasmolysis?
Where the cell membrane pulls away from the cell wall and the cell dies.
What is active transport ?
Movement of substances from a more dilute to a concentrated solution (against a concentration gradient)this requires energy from transpiration
Two ways substances move in and out of cells?
- diffusion
- active transport
What is needed for active transport?
Energy is needed , it is produced through respiration
What is needed for active transport to be efficient?
Lots of energy needs to be produced by the mitochondria
Why active transport is important in plants?
Mineral ions in the soil such as nitrate ions, are usually found in very dilute solutions . Mineral ions actively transport across the cell membrane of the root hair cells , ions are needed for plant growth
Why active transport is important in animals?
Active transport happens in the gut (lower concentration) to move into the blood (higher concentration) sugar is used for cell respiration.
What happens to the SA:V for a small object ?
If an object is smaller the sa:v increases as diffusion distances are smaller and simple diffusion is sufficient
What happens SA:V for a large object?
Object gets bigger the SA:V falls so the simple diffusion is no longer sufficient . It is a lot more difficult to exchange materials quickly
What happens if the surface area gets smaller?
- gasses and food no longer reach every cell. Inside the organism by simple diffusion
- metabolic waste isn’t removed as quickly.
What adaptions help exchange materials?
- larger surface area, where more exchange can take place
- thin membrane , allowing for a short diffusion path
- efficient blood supply in animals
- ventilation in animals makes gas exchange more efficient.
Why humans could not function with a simple diffusion system?
SA:V is too low
How adaptions for exchanging materials work in humans ?
Air is moved in and out of cells , ventilating tiny air sacs called alveoli. Alveoli has a large surface area and a rich blood supply . Villi in the small intestine also has a large surface area and rich blood supply and short diffusion paths.
How fish are adapted for exchange?
Exchange oxygen and co2 between blood and water. Happens across gils which are made of thin filaments that have a rich blood supply. Fish need a constant water flow . They get this nu pumping water over gills using operculum flap that covers the gills.
How are plant roots adapted for exchange?
Large surface area made bigger by root hair cells . Need to take up water and mineral ions
How plants leaves are adapted for exchange?
Thin leaves, the presence of air spaces and stomata all help provide a larger surface area. For the diffusion of substances like water, mineral ions and carbon dioxide.
