GCSE Biology

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  • Created by: akarim1
  • Created on: 13-03-17 16:28
What is a light microscope?
a microscope that uses a beam of light to form an image of an object and can magnify around 2000 times. They are cheap and can be used anywhere. Resolving power: 200 nm
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What is an electron microscope?
a microscope that uses a beam of electrons to form an image of an object and can magnify around 2000000 times. They are very large, expensive and have to be kept in special condition. Resolving power: 0.2 nm
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Calculate magnification:
size of image / size of real object or eyepiece lens x objective lens
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Size of real object:
size of image / magnification
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What is resolution?
the ability to distinguish between two separate points
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What is resolving power?
a measure of the ability to distinguish between two separate points that are very close together
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Plants and Animal cell Diagram:
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What is the function of the nucleus?
controls all activity of the cell and is surrounded by the nuclear membrane. It contains the genes on the chromosomes that carry the instructions for making the proteins needed to build new cells / organisms. Diameter: 10 micrometres
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What is a cell membrane?
a liquid gell in which the organelles are suspended and where most of the chemical reactions needed for life take place
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What is the function of the cell membrane?
controls the passage of substances such as glucose and mineral ions into the cells. It also controls the movement of substances such as urea or hormones out of the cells
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What is the function of the mitochondria?
structures in the cytoplasm where aerobic respiration takes place, releasing energy for the cell. They are very small
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What is the function of the cell wall?
made of cellulose that strengthens the cell and gives it support
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What is algae?
simple aquatic organisms
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What is the function of the chloroplasts?
contain chlorophyll making them green. They absorb light so the plant can make food by photosynthesis.
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What is the function of a permanent vacuole?
space in the cytoplasm filled with cell sap. This keeps cells rigid to support the plant
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Parts of animal cells:
• a nucleus • cytoplasm • a cell membrane • mitochondria • ribosomes.
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Parts of plant cells:
• chloroplasts • a permanent vacuole filled with cell sap.
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What is a Eukaryotic cell?
Plant and animal cells (eukaryotic cells) have a cell membrane, cytoplasm and genetic material enclosed in a nucleus.
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What is a Prokaryotic cell?
Bacterial cells (prokaryotic cells) are much smaller in comparison. They have cytoplasm and a cell membrane surrounded by a cell wall. The genetic material is not enclosed in a nucleus. It is a single DNA loop and there may be one or more small ring
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What is the order of magnitude?
making approximate comparisons between numbers or objects
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Nerve cells specific functions:
Transmit electrical nerve impulses and so carry information from one part of the body to another ie from receptor to an effector.
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Nerve cells specialised feature:
Dendrites extend from the cell body to make connections with other neurones. Have a long axon (nerve fibre) to carry the impulse to the target organ. End plate forms a synapse with an effector (a muscle or a gland).
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Muscle cells specific function:
They contract and relax in pairs to move bones of the skeleton. Form one of the layers of tissue in your digestive system and contract to squeeze the food the food through your gut.
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Muscle cells specialised feature:
Contain special proteins that slide over each other making the fibres contract.in mitochondria to transfer energy for chemical reactions. they can store glycogen, a chemical that can be broken down / used in respiration by mitochondria
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Sperm cells specific function:
To fertilise the ovum (female egg cell).
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Sperm cells specialised feature:
The tail enables it to swim to the ovum and fertilise it. The head is streamlined to aid swimming - contains genetic information / nucleus, has enzymes to penetrate the egg cell membrane for fertilisation. middle section - mitochondria for energy
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Xylem cells specific function:
transport water and mineral ions from the roots to the leaves and shoots
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Xylem cells specialised feature:
Long and tube-like hollow vessels to carry the water. Cells have no end walls between them so they form a 'pipeline' to carry the water. Spirals and rings of lignin in the cell walls strengthen them to withstand pressure of water.
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Phloem cells specific function:
transport tissues that carry food made by photosynthesis around plant
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Phloem cells specialised feature:
cell wall between the cell breaks down to form sieve plates which allow water carrying dissolved food move freely up and down the tubes.
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Root hair cells specific function:
Absorb water and mineral ions from the soil.
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Root hair cells specialised feature:
increase SA for water to move up the cell. Large permanent vacuole that speeds up movement of water by osmosis. Mitochondria that transfer energy needed for active transport of mineral ions into the root hair cells
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What is diffusion?
Diffusion is the spreading out of the particles of any substance in solution, or particles of a gas, resulting in a net movement from an area of higher concentration to an area of lower concentration.
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Why does diffusion take place?
because of the random movement of particles
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Net movement:
particles moving in - particles moving out
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Examples of diffusion:
Some of the substances transported in and out of cells by diffusion are oxygen and carbon dioxide in gas exchange, and of the waste product urea from cells into the blood plasma for excretion in the kidney.
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What are the different factors that affect the rate of diffusion?
• the difference in concentrations (concentration gradient) • the temperature • the surface area of the membrane.
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The effectiveness of an exchange surface is increased by:
• having a large surface area • a membrane that is thin, to provide a short diffusion path • (in animals) having an efficient blood supply • (in animals, for gaseous exchange) being ventilated.
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What is gas exchange?
diffusion of oxygen and carbon dioxide in opposite directions in the lungs
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What is Osmosis?
the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane.
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What is a dilute sugar solution?
high concentration of water - low concentration of sugar
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What is a concentrated sugar solution?
low concentration of water - high concentration of sugar
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What is a isotonic solution?
when the concentration of solutes in the solution outside the cell is the same as the internal concentration
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What is a hypertonic solution?
when the concentration of solutes in the solution outside the cell is higher than the the internal concentration
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What is a hypotonic solution?
when the concentration of solutes in the solution outside the cell is lower than the internal concentration
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What is meant by turgor?
pressure inside a plant cell exerted by the cell contents pressing on
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What is a turgid solution?
a plant cell fully inflated with water
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What is a flaccid solution?
a plant cell that is limp through a reduction of pressure inside the cell
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What is a plasmolysed solution
a plant cell that has lost water causing the cell membrane to be pulled away from the inside of the cell wall
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What is active transport?
Active transport moves substances from a more dilute solution to a more concentrated solution (against a concentration gradient). This requires energy from respiration.
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What are some examples of active transport?
Active transport allows mineral ions to be absorbed into plant root hairs from very dilute solutions in the soil. Plants require ions for healthy growth. It also allows sugar molecules to be absorbed from lower concentrations in the gut to the blood
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What are some adaptations for exchanging materials?
having a large SA, thin membrane for short diffusion path, efficient blood supply / ventilation maintains a steep concentration
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Card 2

Front

What is an electron microscope?

Back

a microscope that uses a beam of electrons to form an image of an object and can magnify around 2000000 times. They are very large, expensive and have to be kept in special condition. Resolving power: 0.2 nm

Card 3

Front

Calculate magnification:

Back

Preview of the front of card 3

Card 4

Front

Size of real object:

Back

Preview of the front of card 4

Card 5

Front

What is resolution?

Back

Preview of the front of card 5
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