Unit 1 - Topic 1 Cells basis of life Flashcards
Describe the cell membrane
It is very thin and the basic structure is known as the phospholipid bilayer. It consists of two polar phospholipids which has a negatively charged phosphate ‘head’ and two fatty acid ‘tails’. The phosphate head is hydrophilic while the tails are hydrophobic
What does it mean by the fluid mosaic model?
It is a model used to describe the cell membrane as molecules are constantly moving
What is a protein channel?
a channel passing through the Centre of a protein, the lining of which is hydrophilic
What are glycoproteins?
a protein with attached polysaccharides that reacts predominantly as a protein
they act as specific markers when the body is trying to defend itself, for example antigens in the immune system
What is role of cholesterol in the cell membrane?
Regulates fluidity of the membrane so that it is neither too rigid or too fluid for functioning of a cell
How does the cell membrane maintain a constant internal environment?
The fluid nature of the membrane ensures it is in constant motion, allowing small molecules to pass between the lipid molecules.
Material pass through active and passive transport
Contrast passive and active transport
passive transport does not require energy, it includes simple diffusion, facilitated diffusion and osmosis. Passive transport occurs from a high concentration to low concentration (with the concentration gradient)
Active transport requires energy as it goes against the concentration gradient. It includes exocytosis and endocytosis
What is involved in endocytosis?
phagocytosis (engulf particle matter), pinocytosis (fluid and its contents)
What is turgor pressure?
the inward pressure exerted on plant cells due to the presence of a cell wall
The cell is fully turgid when no net movement of water can occur because of the water already in the cell
Define monosaccharides, disaccharides and polysaccharides
monosaccharides - basic building block of carbohydrates
polysaccharide - a complex carbohydrate composed of many monosaccharides bonded together
disaccharide - molecule composed of two chemically bound monosaccharides (e.g. sucrose)
Give an example of how the arrangement of internal membranes can control biochemical processes
Folding of mitochondria increases the surface area for enzyme-controlled reactions
What is the role of enzymes?
To control and regulate biochemical processes
Describe the structure and role of an active site in enzymes
The shape of an enzyme is complementary to the shape of its substrate, therefore the substrate molecules fit almost perfectly into to the enzyme. The part of the enzyme in contact with the substrate is known as the active site.
Describe the structure and role of an active site in enzymes
The shape of an enzyme is complementary to the shape of its substrate, therefore the substrate molecules fit almost perfectly into to the enzyme. The part of the enzyme in contact with the substrate is known as the active site. After the product molecules are formed, they no longer fit into the active site and escape leaving the site free to receive further substrate molecules.
What affects enzymes?
They are heat-sensitive - too hot they will be destroyed, too cold action may be inhibited but protein structure is not altered
pH sensitive - only work within optimum range
concentration of enzymes and substrate increase, rate of action also increases
inhibited by poisons which compete for active site of block the active site
