Flashcards in Topic 1: Key Concepts In Biology Deck (54)
What’s a eukaryotic cell?
A complex cell. All plants + animals
What’s a prokaryotic cell?
Smaller, simpler cell. Prokaryotes are single celled organisms. Bacteria are prokaryotes.
What’s a nucleus?
Contains genetic material arranged in chromosomes, controls activities of cell
What’s a cytoplasm?
Contains enzymes which control chemical reactions that take place here
What’s a cell membrane?
Holds cell together, controls what enters and exits cell
Where reactions for respiration (transfers energy cells need to work) take place
Involved in translation of genetic material in synthesis of proteins
What’s the rigid cell wall?
Made of cellulose, supports and strengthens cell
What’s a large vacuole?
Contains cell sap (weak solution of sugar and salts) maintains internal pressure of cell
Where photosynthesis occurs, contain green chlorophyll
What’s chromosomal dna?
Controls activities and replication, floats free in cytoplasm
Rotates to move bacterium away from harmful and towards good substances
What’s plasmid dna?
Small loops of extra dna, can be passed between bacteria, contains genes
What are specialised cells?
Specialised cells have a structure adapted to their function
What’s an acrosome?
At front of sperm cell, stores enzymes to digest membrane of egg cell
How are egg cells specialised for reproduction?
Have nutrients in cytoplasm to nourish early developing embryo
Has haploid nucleus
After fertilisation membrane changes structure
What is resolution?
How well microscope distinguishes between two points thats are close together
How do light microscopes work?
Invented in 1590, they pass light through specimen
How do electron microscopes work?
Invented in 1930, use electrons. Can’t be used to view living cells
Describe the practical ‘how to view a specimen using a light microscope’
1) take things slice (lets light through) of specimen
2, pipette 1 drop of water onto clean slide (secures specimen) and tweezer specimen onto slide
3, add stain to colourless specimen (so you can see it, different stain highlights different structures within cells)
4, hold cover slip at angle using mounted needle, carefully lower onto slide over specimen (So no air bubbles)
5, clip slide onto stage + choose lowest powered objective lens
6, use coarse adjustment knob, move stage up so slide just underneath objective lens. Look down eyepiece, move stage down until specimen almost focused (avoids collision)
7, adjust focus with fine adjustment knob, until image is clear. Position clear ruler on stage, measure diameter of visible circular area
8, greater magnification > higher powered objective lens
Describe the practical ‘scientific drawing of specimen’
1, Outline main features with unbroken lines
2, keep all parts in proportion
3, label important features using straight lines that don’t cross over each other. Include magnification used and a scale.
What is magnification?
How many times bigger the image is
What’s the two equations for total magnification?
Total magnification = eyepiece lens magnification x objective lens magnification
magnification = image size / actual size
Order the units picometer, micrometer, millimetre, nanometre from largest unit of measurement to smallest. How do you convert between them?
Larger > smaller, x 1000
Smaller > larger, divide by 1000
What are enzymes?
Enzymes are biological catalysts that speed up useful chemical reactions in the body without being changed
What’s a substrate?
Molecule changed in the reaction
What’s active site?
Where enzyme joins onto substrate
What do enzymes and substrates have?
Enzymes have a high specificity for their substrate (lock and key)
Some bonds holding enzyme together break, causing shape of enzymes active site to change. Substrate will no longer fit.