Biology paper 1

Created by

Kshitij Sapkota

Cards (471)

Cell 
The basic unit of life
Microscope 
Used to see cells and other tiny specimens
Light microscopes can magnify up to 2000 times
Electron microscopes can magnify up to 2 million times
Using a microscope 
1. Adjust the objective lens
2. Focus the specimen on the stage
3. View the specimen through the eyepiece
Units of measurement 
Kilometre (km)
Metre (m)
Centimetre (cm)
Millimetre (mm)
Micrometre (μm)
Nanometre (nm)
1 μm = 1000 nm
First light microscopes developed
Mid-17th century
Light microscopes use a beam of light to form an image
Electron microscopes use a beam of electrons to form an image
Transmission electron microscope 
Gives 2D images with very high magnification and resolution
Scanning electron microscope 
Gives dramatic 3D images but lower magnifications
Electron microscopes are large, very expensive, and have to be kept in special temperature, pressure, and humidity-controlled rooms
Calculating magnification with a light microscope 
Multiply the magnification of the eyepiece lens by the magnification of the objective lens
When labelling drawings made using a microscope, the magnification given should be the magnification at which the specimen was viewed
Calculating the size of an object
1. Know or can measure two of the factors
2. Find the third
Magnification triangle formula 
size of image / magnification = size of real object
The cell has a diameter of 25 μm
Magnifying power 
The ability of a microscope to make things look bigger
Resolving power 
The ability of a microscope to distinguish between two separate points
Light microscope has a resolving power of about 200 nm
Scanning electron microscope has a resolving power of about 10 nm
Transmission electron microscope has a resolving power of about 0.2 nm
The cells that make up your body are typical animal cells
Animal cells 
Have a nucleus that controls all the activities of the cell
Have a cell membrane that controls the passage of substances into and out of the cell
Have mitochondria where aerobic respiration takes place
Have ribosomes where protein synthesis takes place
Plant cells 
Have a cell wall made of cellulose that strengthens the cell and gives it support
Have chloroplasts that contain chlorophyll and allow the plant to photosynthesise
Have a permanent vacuole filled with cell sap that helps keep the cell rigid
Eukaryotic cells 
Have a cell membrane, cytoplasm, and genetic material enclosed in a nucleus
Prokaryotic cells 
Have cytoplasm and a cell membrane surrounded by a cell wall, but the genetic material is not enclosed in a nucleus
Bacteria are examples of prokaryotes
Bacteria may have a protective slime capsule, flagella to move around, and plasmids that code for specific features
Some bacteria are harmful and can cause diseases or decompose and destroy stored food
Many bacteria have little or no effect on other organisms and are very useful
Orders of magnitude 
Used to make approximate comparisons between numbers or objects, where each order of magnitude is about 10 times bigger
As an organism develops, cells differentiate to form different types of specialised cells
Relative sizes of different cells and whole organisms
e
dif
ba
100m-
giant redwood
10m
minke whale
1m
human
συ
er
human eye 10cm-
apple
e2
1 cm -
wasp
1mm
ant
100 μπ
light
microscope
eukaryotic cells
10μm-
prokaryotic cells
1 με
S
electron
microscope
100 nm
10 nm
PLOT
viruses
DNA
1 nm
a small molecule
Although the smallest living organisms are only single cells, they can carry out all of the functions of life. Most organisms are bigger and are made up of lots of cells. Some of these cells become specialised to carry out particular jobs.
As an organism develops, cells differentiate to form different types of specialised cells. Most types of animal cells differentiate at an early stage of development, whereas many types of plant cells retain the ability to differentiate throughout life. As a cell differentiates, it gets different sub-cellular structures that enable it to carry out a particular function. It has become a specialised cell
Some specialised cells, such as egg and sperm cells, work individually. Others are adapted to work as part of a Tissue, an organ, or a whole organism
Nerve cells 
They are specialised to carry electrical impulses around the body of an animal
They have several adaptations including lots of dendrites to make connections to other nerve cells, an axon that carries the nerve impulse from one place to another, and nerve endings or synapses that are adapted to pass the impulses to another cell or between a nerve cell and a muscle in the body using special transmitter chemicals
They contain lots of mitochondria to provide the energy needed to make the transmitter chemicals
Muscle cells 
They are specialised cells that can contract and relax
Striated muscle cells have three main adaptations: they contain special proteins that slide over each other making the fibres contract, they contain many mitochondria to transfer the energy needed for the chemical reactions that take place as the cells contract and relax, and they can store glycogen, a chemical that can be broken down and used in cellular respiration by the mitochondria to transfer the energy needed for the fibres to contract
Sperm cells 
They have a long tail that whips from side to side to help move the sperm through water or the female reproductive system, the middle section is full of mitochondria which transfer the energy needed for the tail to work, the acrosome stores digestive enzymes for breaking down the outer layers of the egg, and a large nucleus contains the genetic information to be passed on
Root hair cells 
They greatly increase the surface area available for water to move into the cell, they have a large permanent vacuole that speeds up the movement of water by osmosis from the soil across the root hair cell, and they have many mitochondria that transfer the energy needed for the active transport of mineral ions into the root hair cells