biology - key concepts in biology

Created by

Phoebe Stanway

Cards (46)

What is a prokaryotic cell? 
A cell without a nucleus
What is a eukaryotic cell?
cell with a nucleus
What is the function of the nucleus?
Contains the cell's genetic material.
What is the function of the mitochondria?
use aerobic respiration to transfer energy
What is the function of the cytoplasm?
Where chemical reactions take place
What is the function of the ribosomes?
site of protein synthesis
What is the function of the chloroplasts?
Site of photosynthesis (green pigment chlorophyll absorbs necessary sunlight)
What is the function of chromosomal DNA? 
It is one long circular chromosome which controls the cells activities and replication. It floats in the cytoplasm.
What is the function of plasmid DNA?
Small loops of extra DNA which aren't part of the chromosome; contain genes for things like drug resistance and can be passed between bacteria
What is the function of the flagella?
rotates to help the bacterium move
How are egg cells specialised?
They have a large store of nutrients in the cytoplasm, a haploid nucleus and changes in the cell membrane after fertilisation to stop any more sperm getting in
How are sperm cells specialised?
long tail and streamline head to help it swim to the egg
lots of mitochondria in the cell to provide the energy needed
carries enzymes in its head to digest through the egg cell membrane
What are the disadvantages of light microscopes?
limited magnification and limited resolution
What are the disadvantages of electron microscopes?
Expensive, can only view dead specimens, no colour
How can you calculate magnification?
magnification = image size/actual size
How do you view a specimen using a light microscope?
- thin slice to let light through
- put drop of water (pipette) on a slide to secure specimen in place
- place specimen on slide, and place cover slip at an agle to prevent air bubbles
- put the slip on the stage
-set to lowest-powered objective lens
- use coarse wheel to move stage up to just below the obejective lens
- use fine wheel to bring into focus
What is an enzyme?
biological catalyst
How do enzymes work?
Lower activation energy needed to start a chemical reaction
Describe the lock and key model
The enzyme and the substrate have specific complementary geometric shapes that fit exactly into one another - the substrate fits exactly into the active site. The large insoluble molecules are then broken down into small soluble molecules.
What happens to enzyme activity as temperature increases?
At first, enzyme activty increases with temperature, until the optimum is reached. The enzymes and substrates gain more kinetic energy, increasing the likelyhood of a successful collision. Past the optimum, the active site denatures and the substrate no longer fits.
What happens to enzyme activity as pH increases?
At first, enzyme activty increases with pH, until the optimum is reached. Past the optimum, the active site denatures and the substrate no longer fits.
How can you investigate the effect of pH on enzyme activity?
- drop of iodine into every spot on a tile
- heat beaker of water to 35 degrees and keep constant
- add amylase solution and pH 5 buffer to boiling tube, heat in beaker for 5 minutes
- add starch solution , mix and start stop clock.
- everu tne seconds, take a sample and add to a drop, when iodine remains browny yellow instead of blue-black, all the starch has been broken down.
- stop the stop clock, record time and calculate rate before repeating with buffer solutions of a different pH
What enzymes break down proteins?
proteases
What enzymes break down carbohydrates?
Carbohydrases eg amylase
What enzymes break down lipids?
lipase
What is starch broken into?
simple sugars like glucose
What are proteins broken into?
amino acids (polypeptides)
What are lipids broken into?
fatty acids and glycerol
What does glycogen sythase do?
joins together chains of glucose molecules to make glycogen.
How can you test for sugars?
Using Benedict's Reagent (blue - green - yellow - brick red)
- add the reagent to a sample, and heat in a water bath set to 75 degrees.
- if positive, a coloured precipitate will form
- higher concentration, more red
How can you test for proteins?
Biuret test: use Biuret reagent. Blue to purple if protein is present
You first need to add potassium hydroxide to make the solution alkaline
How can you test for lipids?
Emulsion test - shake sample with ice-cold ethanol, then pour into water. If a precipitation (a milky emulsion) forms, there will be lipids present
How can you test for starch?
Add sample to iodine - blue black = starch present
What is the formula for energy in food (J)
mass of water (g) x Temperature change of water (°C) x 42
How can you find the amount of energy in food?
Burn food under a known volume of water, find temperature change, calculate using formula.
What is diffusion?
The net movement of particles from an area of high concentration to an area of low concentration until equilibrium is reached.
What is active transport?
the movement of ions or molecules across a membrane into a region of higher concentration, requiring energy.
What is osmosis?
diffusion of water across a partially permeable membrane, from higher to lower concentration
How can you investigate osmosis?
- use a cork borer to cut cylinders of potato (cut off skin). Cut to same length, and divide into groups of three.
- find the mass of each group
- place one group in a different concentration of sucrose solution
- leave cylinders for 40 minutes
- remove and pat dry gently to remove excess water which could affect the weight
- weigh each group again and record the results
- calculate percentage change in mass
-water gained = higher sucrose conc. in potato
- water lost = lower sucrose conc. in potato
- no change = same sucrose conc. in solution and potato
the starch grains in the potatoes become smaller and starch was converted to glucose
state why the potatoes need glucose
for energy/respiration