Cells
- Created by: wilby99
- Created on: 07-10-15 14:10
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- Cells
- membranes
- factors affecting permeability
- temperature
- Phospholipids get more kinetic energy and move around more, increasing membrane permeability
- As temp increases it will affect the way that the proteins are positioned. And if they are enzymes then it could alter the rate of the reactions that they catalyse.
- Increased fluidity may affect plasma membrane infolding during phagocytosis
- As temp decreases, the fatty acids are compressed (in unsaturated ones this means that the kinks in the tails increase and push other molecules away which maintains membrane fluidity.)
- This means that the proportions of unsaturated and saturated fatty acids at colder temps determine its fluidity.
- any extra cholesterol at the lower temp will also affect permeability ast it will separate the fatty acids
- Increased kinetic energy can make the molecules vibrate more which will then break any ionic or hydrogen bonds.
- High temp can affect the proteins of the cytoskeleton, plasma membrane and membrane embedded proteins.
- solvents
- When an organic solvent comes in contact with a lipid, then the lipid will dissolve in it. So the cell membrane will then lose its structure
- Increasing the solvent concentration will also increase membrane permeability.
- temperature
- structure
- the fluid mosaic model has five main components: ~Phospholipid bilayer ~cholesterol ~Proteins ~Glycolipids ~Glycoprotein
- Phospholipids: Hydrophobic tails repel water; Hydrophilic heads attract water;these move together to form a bilayer;this bilayer has a hydrophobic center which means that water soluble molecules will not be allowed to pass through.
- Cholesterol (lipid): gives membrane stability by binding to the hydrophobic tails pushing them closer together which makes the membrane less fluid and more rigid.
- The hydrophobic regions also provides a further barrier to any polar molecules coming through
- Proteins: control; what enters and leaves a cell:carrier proteins:channel proteins:receptors in cell signalling
- Glyc-olipids and Glyco-proteins: stabilise the membrane by forming hydrogen bonds with the surrounding water . Receptors in cell signalling:site of binding for drugs hormones and antibodies: Antigens
- the fluid mosaic model has five main components: ~Phospholipid bilayer ~cholesterol ~Proteins ~Glycolipids ~Glycoprotein
- factors affecting permeability
- structure
- Plasma membrane
- mainly made of lipids and proteins
- monitors movement in and out of cells and also is the site for cell signalling
- nucleus
- Nucleolus; Nuclear pores;Nuclear envelope ;Chromatin
- controls cells activities;DNA contains instructions for protein synthesis; pores allow movement between cytoplasm and nucleus; make ribosomes
- RER & SER
- membranes enclose a fluid filled space (RER is covered in ribosomes)
- SER: synthesises and processes lipids RER:folds and processes proteins made at ribosomes
- Golgi Apperatus
- fluid filled, membrane bound, flattened sacks
- processes and packages new lipids and proteins also makes lysosomes.
- Mitochondria
- Usually oval shaped; double membrane; inner membrane is folded to form cristae; in side cristea is matrix which contains enzymes
- site of aerobic respiration, where ATP is produced. found in large numbers in cells that are active and require a lot of energy
- chloroplast
- double membrane; stacked thylakoid membranes form grana; lamella join grana together.
- site of photo-synthesis, some happens in the gran and others in the stroma fluid
- vesicle
- small fluid filled sack surrounded by membrane; formed at golgi, ER and cell surface.
- transports substances between organelles and the membrane and between each other
- ribosomes
- made up of proteins and RNA and has no membrane
- site where proteins are made
- lysosome
- has a membrane but no clear internal structure
- contains digestive enzymes;used to digest invading cells and worn out components of a cell.
- Centriole
- small hollow cylinders made of microtubules
- involved in the separation of chromosomes during cell division
- cillia
- hair like structures; outer membrane; nine microtubules in the ring; two in the middle
- move substances along cell surface
- cytoskeleton
- network of protein threads arranged as microfilliments or microtubules
- support the cells organelles; strengthen and maintain cells shape; transport organelles and materials within the cell
- Plasma membrane
- membranes
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