Unit 1 - All Notes with Specification Points

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  • Created on: 11-03-15 20:46
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1.1.1 Cell Organelles
(a) state the resolution and magnification that can be achieved by a light microscope, a
transmission electron microscope and a scanning electron microscope;
Light Microscope - 1500x
TEM -
SEM -
(b) explain the difference between magnification and resolution;
(c) explain the need for staining samples for use in light microscopy and electron microscopy;
Light microscopy - Most biological materials are colourless and so need a stain to enable
struxctures to stand out. Iodine in potassium iodide solution or methylene blue.
Electron microscopy ­ Samples need staining with heavy metal salts in order to reflect the
electrons off to produce an image.
(d) calculate the linear magnification of an image (HSW3);
(e) describe and interpret drawings and photographs of eukaryotic cells as seen under an electron
microscope and be able to recognise the following structures: nucleus, nucleolus, nuclear envelope,
rough and smooth endoplasmic reticulum (ER), Golgi apparatus, ribosomes, mitochondria,
lysosomes, chloroplasts, plasma (cell surface) membrane, centrioles, flagella and cilia;
(f) outline the functions of the structures listed in (e);
(a) outline the roles of membranes within cells and at the surface of cells;
Cell plasma membrane - Separate inside of cell from outer environment. Regulate transport of
materials into and out of cells. Roles in cell recognition and cell signalling.
Other membranes in the cell - Compartmentalisation. Regulate transport of materials into and out
of organelles. Hold in place some components of metabolic pathways. Contain potentially harmful
things inside the cell e.g. hydrolytic enzymes of the lysosomes.
(b) state that plasma (cell surface) membranes are partially permeable barriers;
Plasma membranes are partially permeable barriers that selectively allow materials in and out of
the cell.
(c) describe, with the aid of diagrams, the fluid mosaic model of membrane structure (HSW1);
Proposed by Singer and Nicholson
Fluid ­ The phospholipids can move about in their plane due to heat and they also slowly move
the proteins in the membrane too. This was proved by the protein fusion experiment. However
some proteins are attached to the cytoskeleton and so cannot move.

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Mosaic ­ There are glycoproteins, lipoproteins and proteins on the membrane make "patches"
which give it a mosaic appearance.
(d) describe the roles of the components of the cell membrane; phospholipids, cholesterol,
glycolipids, proteins and glycoproteins;
Phospholipids ­ Form a fluid barrier. Short chain and unsaturated fatty acids increase its fluidity.
Cholesterol ­ Helps to regulate membrane fluidity as it gives mechanical stability and reduces
leakage of polar molecules through the bilayer but is found in eukaryotes only.
Glycolipids ­ Involved in cell recognition.…read more

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No calculations of water
potential will be required);
(j) recognise and explain the effects that solutions of different water potentials can have upon
plant and animal cells (HSW3).
1.1.…read more

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Telophase ­ Nuclear envelope reforms. Spindle breaks down. Chromosomes uncoil so can no
longer be seen in a light microscope. (2 cells in 2n)
(c) explain the meaning of the term homologous pair of chromosomes;
Homologous pair of chromosomes - Apairof chromosomeshaving the same genesequences
,
each derived from one parent.
(d) explain the significance of mitosis for growth, repair and asexual reproduction in plants and
animals;
Growth of organisms. Repairof tissues. Replacementof cells. Growthin population for asexually
reproducing organisms.…read more

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HSW4).
1.2.1 Exchange surfaces and breathing
(a) explain, in terms of surface area:volume ratio, why multicellular organisms need specialised
exchange surfaces and single-celled organisms do not (HSW1);
Diffusion is not fast enough, especially for highly metabolically active organisms, and there are too
many cells. Also, with larger organisms, a concentration gradient for diffusion is not significant
enough as all cells require oxygen and nutrients ­ tissue fluid assists with this.…read more

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Cartilage ­ Is in C-rings to support the trachea and bronchi to hold them open. The C shape is to
allow movement and the expansion of the oesophagus when swallowing.
Cilia ­ Contain microtubules which slide over each other to make the cilia bend in a sweeping
action. They sweep the mucus containing foreign particles and pathogens up and out of the
airways.…read more

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Single circulatory system ­ Fish have a single circulatory system meaning the blood passes
through the heart only once in a complete cycle.
Double circulatory system ­ Mammals have a double circulatory system meaning that the blood
passes through the heart twice in a complete cycle. Oxygenated and deoxygenated blood are kept
separate with the pulmonary circulation and the systemic circulation.…read more

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Arteries
Structure:
Very narrow lumen ­ Enables blood to be carried at a sustained high pressure.
Tunica intima ­ Endothelium layer that is very smooth to reduce friction of blood flow to maintain
high pressure, made of squamous epithelium. It is folded to allow expansion.
Tunica media ­ Smooth muscle, elastic fibres and collagen fibres. These all contribute to the
strength of the artery wall.…read more

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Proteins Plasma proteins Proteins secreted by body Proteins secreted by body cells
and hormones cells and some small (cannot go through capillaries
hormones. into blood so must be carried
by lymph)
Fats Some transported None More than in blood such as
as lipoproteins. reconstituted fatty acids and
glycerol which are absorbed
into the lacteals of the
lymphatic system in the
intestine.
Glucose 80-120 Less than in blood because Less than in tissue fluid.
mg/100cm3 it is used by the body cells
by facilitated diffusion.…read more

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Candidates should be able to:
(a) explain the need for transport systems in multicellular plants in terms of size and surface
area:volume ratio;
Need for transport systems:
Diffusion is too slow ­ Not a large enough surface area if surface area to volume ratio is small
Layers of cells can make it difficult.…read more

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