Topic 1 - Key concepts Flashcards
Eukaryotic cells
Plant or animal cells. Eukaryotic cells have a nucleus which contains the generic material
Prokaryotic cells
Bacterial cells. Prokaryotic cells don’t have a true nucleus and their genetic material is stored in a circular loop of chromosomal DNA.
nucleus
contains genetic material that controls activities of the cell
cytoplasm
gel-like substance where most of the chemical reactions happen
cell membrane
holds cell together and controls what goes in and out
mitochondria
site where most of aerobic respiration reactions take place, which releases energy that the cell needs to work
ribosomes
involved in protein synthesis - making proteins
cell wall
a rigid structure that supports and strengthens the cell. it is made of cellulose
large vacuole
contains cell sap and maintains internal pressure to support cell
chloroplasts
contain a green pigment called chlorophyll which absorbs light needed for photosynthesis
chromosomal dna
a circular loop that contains all of the cell’s genetic information, which controls the cells’ activities.
plasmid
small lops of DNA which contain genes for things like drug resistance, and can be passed between bacteria
flagellum
hair like structure that rotates to make the bacterium move away from harmful substances
What is a specialised cell?
A specialised cell is a cell that has differentiated so that its organelles are suited to perform a specific function.
sperm cells
- long tail to swim to the egg
- middle section is packed with mitochondria to supply energy so the sperm can swim faster/ long distance
-acrosome contains enzymes needed to digest through egg’s membrane - haploid nucleus
egg cells
- nutrients in the cytoplasm to feed the embryo
- membrane changes structure after fertillisation to stop any more sperm entering
- haploid nucleus
haploid nucleus
both sperm and egg cells have haploid nuclei.
contains half the number of chromosomes normal cells have ( 23).
when they combine the resulting embryo will have the right amount of chromosomes
ciliated epithelial cells
- they have cilia on the top surface that beat to move substances in one direction
- they have a lot of mitochondria to supply energy through aerobic respiration so the cilia can beat
What are enzymes?
a biological catalyst that speeds up the rate of reaction without being used up.
Why are enzymes so useful in the human body?
only catalyse useful reactions in body
reduces need to increase temp to speed up useful reactions, as cells would be damaged
What are active sites?
They have a unique shape that is complimentary to only 1 specific substrate shape.
Why do enzymes only catalyse 1 reaction?
for the enzyme to catalyse a reaction, the substrate has to fit inside its active site
How does increasing temp change enzyme activity
- at first a higher temp increases the rate of the enzyme’s reaction until the optimum temp, where the rate is at its peak
- this is because the reactants have more energy and so move more rapidly and collide with enzymes more frequently
What happens when the temp becomes too high
-when the temp becomes too high, the bonds holding the enzyme together break.
-this causes a change in the shape of the active site, which means the substrate cannot bind to the active site.
-the enzyme becomes denatured and cannot catalyse the reaction anymore
how does substrate concentration affect enzyme activity
-the higher the substrate concentration, the faster the reaction.
-this is because it’s more likely the enzyme react with a substrate molecule
- however after a certain point all the active sites are full so adding more substrate makes no difference
how does pH affect enzyme activity
if the ph is too high or too low the ph interferes with the bonds holding the enzyme together, causing a change in the active site’s shape and denaturing it
- all enzyme have an optimum pH in which the rate of reaction is highest
why are enzymes needed for digestion?
-many of the molecules in our food are too large to pass through the walls of our digestive system
- enzymes break them down into smaller soluble molecules
- these pass easily through the walls of digestive system and are absorbed into the bloodstream
carbohydrases
carbohydrates -> simple sugars
proteases
proteins -> amino acids
lipases
lipids -> glycerol + 3 fatty acids
What do fatty acids do to solutions
lower their ph as they are acidic.
Synthesis reactions
make carbohydrates, proteins and lipids back from their smaller components
how to prepare a food sample
- get a piece of your food and break it up using pestle and mortar
- transfer to beaker + distilled water
-give mixture a stir - allow mixture to settle out then pipette out some liquid
test for reducing sugars
- transfer 5cm3 of food sample to test tube
- prepare water bath and set to 75°
- add 10 drops of benedict’s reagent
- place test tube in water bath for about 5 mins
- a coloured precipitate ( green, orange, red ) will form in presence of reducing sugars
test for starch
- transfer 5cm3 of food sample to test tube
- add few drops of iodine solution
- if it contains starch :
brown-orange -> blue-black
Biuret solution
potassium hydroxide + copper sulfate
test for proteins
-transfer 2cm3 of food sample to test tube
-add biuret solution
blue -> pink or purple
test for lipids
- transfer some food sample into test tube
- add 2cm3 of ethanol to test tube
- shake well until it dissolves
- pour solution into test tube containing distilled water
- lipid will precipitate out the liquid -> milky emulsion
what is diffusion?
The net movement of particles from a high concentration to low concentration down the concentration gradient
Diffusion across cell membranes
cell membranes are partially permeable which means they only let some molecules diffuse through it while bigger ones can’t pass through
what is osmosis
The net movement of water molecules from a high water concentration to low water concentration across a partially permeable membrane
What happens when a plant cell is put in a concentrated solution
-it loses water as the concentration of water is lower across its membrane, so water will move out of it into the solution
- it becomes flaccid
What happens when a plant cell is put in a dilute solution
-it gains water as the concentration of water is higher across its membrane, so water will move into it
- it becomes turgid
flaccid
the contents of the plant cell shrink and move away from the cell wall
turgid
the contents of the plant cell expand and the cell wall becomes stronger
active transport
The net movement of particles from a low concentration to high concentration up the concentration gradient
difference between A.T and diffusion
active transport requires energy released from respiration but diffusion is a passive process, happens by itself
Example of active transport in use
it allows the bloodstream to take nutrients from the gut, despite the gut having a lower concentration of nutrients than the bloodstream
