Arrange these terms in order of size from smallest to largest: organism tissue organ cell molecule organelle organ system
molecule → organelle → cell→ tissue → organ → organ system → organism
Define a cell
The simplest living unit of all life forms
e.g. guard cell, goblet cell
Define a tissue and give an example of an animal tissue and a plant tissue
An collection of similar cells working together to carry out a specific function
- animal tissue: ciliated epithelium, connective tissue, muscle tissue and nervous tissue
- plant tissues: xylem, phloem
Define an organ and give an example of an animal organ and a plant organ (3)
A collection of different tissues working together to carry out specific functions
- animal organs : stomach, pacreas, eye, skin, liver, heart
- plant organs: leaf, flower, root
Define an organ system
A collection of different organs working together to carry out specific functions
E.g. digestive system consists of stomach, pancreas, small and large intestine
Define the term differentiation
As a cell differentiates it acquires different sub-cellular structures to enable it to carry out a certain function.
It has become a specialised cell.
Changes can include structural changes, chemical changes and changes to the number and type of organelles present in the cell.
Define the term magnification
The number of times bigger an image is compared the actual size of the specimen
Define the term resolution
The ability to distinguish between 2 separate points
The greater the resolution the sharper and clearer an image will appear
Describe an inhibition zone
An area where no bacteria are found to be living on an agar plate
Describe the differences in the genetic material in a prokaryotic cell and a eukaryotic cell
genetic material is not enclosed in a nucleus
it is a single DNA loop and there may be one or more small rings of DNA called plasmids
genetic material is found enclosed in a nucleus
there is more DNA in eukaryotic cells
Electron microscopes allow scientists to study the internal detail of some organelles. Give 2 organelles that this applies to.
Give 2 ways in which a muscle cell is specialised for function?
Cells contain many mitochondria (to produce ATP which is used by the cell the make the muscle contract)
Contains special proteins in the cytoplasm that can move (to enable the muscle to contract)
Give 2 ways in which equipment can be sterilised when making an agar plate
Give 3 examples of specialised cells found in animals
Red blood cell (found in the blood)
Motor neurone (found in the nervous system)
Cardiac muscle cell (only found in the heart)
Ciliated epithelial cells (found in the trachea, bronchi and bronchioles)
Give 3 examples of specialised cells found in plants
root hair cell (in the root TIPS)
guard cell (in the lower epidermis)
palisade mesophyll cell (in the leaf)
Give 3 ways in which a sperm cell (spermatocyte) is specialised for function?
Head only contains half the number of chromosomes in the nucleus (to enable the chromosome number to be kept correct after fertilisation)
Middle part of the cell has many mitochondria (to produce ATP used by the cell to enable it to swim)
Tail is a long extension to the cell (to enable it to move by propulsion)
Give 3 ways in which phloem cells are specialised for function?
End walls of cells are broken down (to link adjacent cells)
High number of mitochondria (to produce ATP for translocation)
The cytoplasm of adjacent cells is connected to allow passage of sucrose between cells (think about translocation!)
Give 4 ways in which a motor neurone is specialised for function?
Long extended cytoplasm and cell membrane (to form the axon)
Cell body has many extensions (to form dendrites)
Axon is covered in myelin sheath (to increase the speed that the nerve impulse travels)
Contains neurotransmitter chemicals (to enable the impulse to be passed to the effector)
Give 4 ways in which a red blood cell (erythrocyte) is specialised for function?
Shape is a biconcave disc (to increase the surface area to volume ratio to take up more oxygen by diffusion)
Biconcave shape also allows RBC to squeeze through the capillaries
No nucleus or mitochondria (to enable it to form a biconcave shape)
Contains a special protein called haemoglobin (to bind with oxygen to form oxyhaemoglobin
Give 4 ways in which the root hair cell is specialised for function?
Long extension to the cell wall, cell membrane and cytoplasm (to increase its surface area)
Thin cell wall (to reduce the distance water has to travel to enter the cell by osmosis)
Large permanent vacuole (to hold more water)
High number of mitochondria (to produce ATP for active uptake on mineral ions from the soil)
Give 5 ways in which xylem cells are specialised for function?
Thick cell wall (to strengthen the cell)
Cells are dead (to form hollow tubes)
Pits occur between cells (to link adjacent cells)
No organelles (to enable cells to become hollow)
Cells have a layer of lignin around them (to make them waterproof)
Give an example of an organ in a plant and an animal
Plant organs = leaf, flower
Animal organs = stomach, uterus, brain, liver, pancreas, eye
Give an example of an organ system in a plant and an animal
Plant organ systems = root system, shoot system
Animal organ systems = digestive system, reproductive system, circulatory system
How are inhibition zones used?
To determine which antibiotic is most effective at killing bacteria.
The antibiotic which results in the largest inhibition zone is the most effective at killing the bacteria
How can you calculate the actual size of the specimen?
Image size divided by magnification
How can you calculate the image size?
Actual size of the specimen multiplied by the magnification
How can you calculate the magnification of an image?
Image size divided by the actual size of the specimen
HINT: both sizes must be in the same units
How can you prevent contamination when setting up an agar plate to grow bacteria?
Sterilise the petri dish and culture medium
Inoculating loops used to transfer microorganisms to the media must be sterilised by passing them through a flame
Partially tape the lid of the petri dish to the base (do not fully tape it as this will prevent oxygen entering and the bacteria will die!)
Incubate the petri dish upside down (at 25oC for 48 hours)
How did electron microscopes help Biologists in their studies?
This means that it can be used to study cells in much finer detail.
This has enabled biologists to see and understand many more sub-cellular structures.
How do bacteria reproduce?
Bacteria multiply by simple cell division (binary fission) as often as once every 20 minutes if they have enough nutrients and a suitable temperature.