cell theory
all living things are composed of cells products |
new cells are formed only by the division of pre-existing cells |
the cell contains inherited information (genes), which is used as instructions for growth, functioning and development |
the is the functioning unit of life; the metabolic reactions of life take place within the cells |
Magnification equation triangle
Image size (I)= actual size (A) x magnification (M) |
Actual size (A) = image size (I) / magnification (M) |
Magnification (M) = image size (I) / actual size (A) |
bacteria cells
bacteria cells like many other animals and plants, produce and secrete toxins that have an effect on other organisms |
DNA is free in the cytoplasm of a prokaryotic cell in the area called the nucleoid |
A section of DNA containing a genetic code for a metabole unwinds and hydrogen bonds break. |
RNA nucleotides line up (complementary base pairing). Messenger RNA is formed. This process is known an transcription. |
The next process is the production of the bacterial protein. This is called translation and it occurs at the ribosomes. |
Transcription and translation can occur simultaneously because the genetic material is free in the nucleoid surrounded by ribosomes. |
The newly made protein toxin is moved to the surface membrane ready to be secreted to cause infection. |
red blood cells
Red blood cells or erythrocytes are a biconcave shape. This increases the surface area to volume ratio of an erythrocyte. They are flexible so that they can squeeze through narrow blood capillaries. Their function is to transport oxygen around the body. In mammals, erythrocytes do not have a nucleus or other organelles. This increases space for the haemoglobin molecules inside the cell that carry oxygen. |
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eukaryotic and prokaryotic
eukaryotic |
prokaryotic |
eukaryotic cells make up multicellular cellular organisms such as plants and animals. they are complex cells with a nucleus and membrane-bound organelles |
prokaryotic cells are single celled organisms. they are simple structures and do not have a nucleus or any membrane-bound organelles |
plants and animals |
bacteria |
Light microscopy vs electron microscopy
light microscopy |
electron microscopy |
Light microscopes use visible light and magnifying lenses to observe small objects |
They use a beam of electrons in a vacuum with a wavelength less than 1nm to visualise the specimen. |
Positives: can observe sub-cellular structures |
Positive: x500000 magnification, high resolution (0.1nm) electron micrographs produced. |
Limitations: lower magnification (x500) and resolution (x200nm) |
Limitations: destroy the sample. |
egg cells
Egg cells, or ova, are the female gametes in animals. An egg cell is one of the largest cells in the human body, and is approximately 0.12 mm in diameter. It contains a nucleus which houses the genetic material. The zona pellucida is the outer protective layer/membrane of the egg. Attached to this is the corona radiata, which consists of two or three layers. Its function is to supply proteins needed by the fertilised egg cell. |
white blood cells
Neutrophils are a type of white blood cell and they play an important role in the immune system. They have multi-lobed nuclei, which enables them to squeeze though small gaps when travelling to the site of infection. The cytoplasm holds lysosomes that contain enzymes that are used to digest pathogens that are ingested by the neutrophil. |
root hair cell
These cells are found at a plants roots, near the growing tip. They have long hair like extensions called root hairs. The root hairs increase the surfae area of the cell o maximise the movement of water and minerals from he soil into the plant root |
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key functions of a cell
one of the key functions of a cell is to synthesise proteins for use inside the cell, to lead to cell multiplication and for secretion out of the cell for example, insulin |
proteins are synthesised on ribosomes attached to rough endoplasmic reticulum |
the newly synthesised proteins are transported through the cisternae of the rough ER and packaged into vesicles |
they are transported to the golgi apparatus, where vesicles fuse with the surface of the golgi apparatus and the apparatus enter |
it is here that the newly synthesised proteins are modified and then packaged into vesicles. secretory vesicles will transport proteins that are to be released from the cell to the cell surface membrane |
they will fuse with the membrane and release the protein by exocytosis |
gram staining
gram positive |
gram negative |
if you see a purple stain when observing the smar under a microscope it shows that gram-positive bacteria are present |
if the smear has retained the pink safranin stain, this shows that gram-negative bacteria are present. this is because their thinner cell walls and lipid membranes allow ethanol (applied during the method) to wash off all the crystal violet purple stain and to then retain the pink safranin stain |
doesn' have an outer membra |
has an outer membrane |
Positive Purple |
squamous epithelial tissue
sperm cell
sperm cells are male gametes in animals. They have a tall like structure called a a undulipodium so hey can move. They also contain many mitochondria to supply the energy needed for his movement. The sperm head is 3 μm wide and 4 μm long. it is made up of an acrosome, which contains digestive enzymes . These enzymes are released when the sperm meets the egg, to digest the protective layer and allow the sperm to penetrate. The sperm’s function is to deliver genetic information to the egg cell or ovum (female gamete). This is fertilisation |
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Time line about the cell
1665 |
Robert Hooke first described a cell |
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Anton Van Leeuwenhoek was the person who observed bacteria and protoctists |
1674 - 1683 |
The first living cell was observed protoctists from pond water samples, after developing powerful glass lenses |
1831 |
The nucleus is observed |
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Robert Brown an English botanist was the first to observe and describe the nucleus in a plant cell |
1674 - 1683 |
Universal cell theory |
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Matthias Schleiden suggests that all plant material is composed of cells. Jan Purkyne observed that animal tissue is composed of cells and the structure is similar to plant tissue. The scientist credited for the universal cell theory is Theodore Schwann, a German physiologist. He proposed that ‘all living things are made of cells’. |
1852 |
Evidence of the origin of the new cell |
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Robert Remak observed cell division in animal cells. His findings were not accepted at the time, but in 1855 Rudolf Virchow published the findings as his own to show new cells form from existing ones |
1860 |
Spontaneous generation disproved |
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Louis Pasteur demonstrated that bacteria will only grow sterile nutrient broth after it has been exposed to air. This disproved the theory of spontaneous generation of cells. |
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