Key Concepts in Biology Flashcards
Describe how sperm cells are adapted to their function. ( 4 points)
- haploid nucleus (contains the genes- 23 chromosomes)
- long tail & streamlined to aid swimming
- top of head has digestive enzymes to help break down the outer membrane of the egg cell
- lots of mitochondria to supply the energy to allow the sperm to move
Describe how egg cells are adapted to their function. (3 points)
- surrounded by special cell membrane which can only accept one sperm cell
- lots of mitochondria to provide energy for the developing embryo
- large size and cytoplasm allow quick repeated division as the embryo grows
Describe how ciliated epithelial cells are adapted to their function. (1 point)
- long hair like structures called cilia which trap bacteria on their sticky mucus surface and killed by stomach acid
Identify the common parts of bacteria. (6 points)
- cytoplasm
- cell membrane
- cell wall
- chromosomal DNA (circular)
- plasmids
- flagella
Describe the function of the cytoplasm
liquid substance where chemical reactions occur, contain enzymes and organelles are found in it
Describe the function of the cell membrane
controls what enters and leaves the cell
Describe the function of the cell wall
provides structure to the cell and is made from cellulose
Describe the function of the chromosomal DNA
have no nucleus, this floats in cytoplasm
Describe the function of the plasmids
small rings of DNA, code for extra genes
Describe the function of the flagella
long, thin tail that allows them to move
Describe why bacteria are classified as being prokaryotic.
small and lack membrane-bound nuclei
Definition of an enzyme
biological catalyst that speeds up the rate of reaction without being used up
Differences between prokaryotic and eukaryotic cells
prokaryotes don’t have
- a nucleus
prokaryotes have:
- chromosomal DNA
- flagellum
- cell wall
Give examples of enzymes (3 points)
- carbohydrases-> amylase breaks down into maltose
- lipases
- proteases-> pepsin
What do carbohydrases do?
convert carbohydrates into simple sugars
what do proteases do?
Convert proteins into amino acids
what do lipases do?
convert lipids (fats) into fatty acids and glycerol
where is amylase found?
salivary glands, pancreas and small intestine
where is pepsin found?
produced in the stomach
where is lipase produce?
in the small intestine and pancreas
Explain why catalysis by enzymes is important for life processes
to speed up reactions
Describe how to test for starch in food.
iodine reaction -> orange to blue black
Describe how to test for reducing sugars in food.
Benedicts solution-> blue to reddish brown
State what enzyme specificity means
lock and key hypothesis
an enzyme’s action is due to its…
active site.
Stages of the lock and key hypothesis
Substrate diffuses into the active site and binds to it – the substrate must be a specific shape to fit into the enzyme
The substrate forms temporary bonds with the AA’s in the enzyme to produce an ENZYME – SUBSTRATE COMPLEX
The reaction takes place and the bonds in the substrate are broken – in this case, the larger molecule has been broken down into smaller molecules. An ENZYME – PRODUCT COMPLEX has formed
The products unbind from the active site and diffuses out
The enzyme is ready to be used again
Definition of an enzyme
a biological catalyst
How do enzymes become denatured?
Temperature, pH
Describe the effect of substrate concentration on enzyme activity.
as substrate conc increases, rate of reaction increases to a saturation point
Describe the effect of pH on enzyme activity.
too high or to low will affect amino acid chains and denature the protein
What is diffusion
a form of passive transport- movement of high conc to low
What is osmosis
a form of passive transport- movement of high conc to low- only applies to water across a selectively permeable membrane
what is active transport
a form of transport that does require energy
Describe what effect a mutation could have on the action of an enzyme.
a mutation is a change in a gene sequence, which changed the amino acid sequence, changes the shape of the protein/active site, preventing binding
Explain the role of the active site of an enzyme.
specific shape, bind to substratem catalyse reactions, lock and key hypothesis
Explain why phenolphthalein turns colourless when lipase breaks down the lipids in milk.
fatty acids are formed when the lipids are broken down
by lipase,and fatty acids are acidic (so the pH decreases)
Explain why the activity of lipase changes above a temperature of 40°C.
an increase in temperature above 40 °C causes changes
in the shape of the active site of the enzyme.therefore the enzyme becomes denatured and no
longer functions
Explain why enzymes can only catalyse specific reactions.
the active sit of an enzyme has a specific shape because of the order of amino acids, the substrate must have a shape which is complementary to the active site
Describe what happens to the molecule produced by transcription before it is translated.
leaves the nucleus, through the nuclear membrane and attached to ribosome
Explain how the lock and key hypothesis models how enzymes work.
(enzyme and substrate have) complementary shapes
substrate fits into enzyme / enzyme substrate complex formed
reference to active site
enzymes break (chemical) bonds / form chemical bonds / (causes) reaction to occur / make products
Idea of products leaving enzyme (so that enzyme can be used again)
Describe how named factors affect the rate of enzyme-catalysed reactions.
A description to include some of the following points Temperature
(temperature) too low – not enough energy to make reactions occur (fast enough)
reference to optimum temperature
optimum for most (humans) - 37oC
over 37oC changes enzyme shape / changes active site
shape of enzyme
therefore rate of reaction decreases / stops
enzymes denatured (if temperature too high)
pH
optimum pH – around 7.3 / 6 to 8 for most enzymes
specific optimum quoted eg pepsin – pH 2 to 3
pH either side of optimum – changes the shape of the
enzyme / shape of the active site
therefore rate of reaction decreases / stops
enzymes denatured (if pH too high / too low)
substrate / enzyme concentration
higher concentrations faster reactions
due to more collisions
until maximum rate reached / all enzymes being used
