AS-level - AQA
state 2 examples of eukaryotic cells:
animal cells and plant cells
state 1 example of a prokaryotic cell
bacterial cell
state the organelles found in an animal cell
cell wall
cell membrane
Golgi apparatus
lysosomes
rough and smooth endoplasmic reticulum
nucleus
mitochondria
ribosomes
state 2 organelles found in plant cells and not animal cells
cell wall
chloroplasts
vacuole
state the cell surface membrane function
controls the movement of substances in and out of the organelle
state the function of the nucleus
contains genetic information for the organism
makes mRNA and tRNA
makes rRNA and ribosomes
state the structure of the nucleus
nuclear envelope → controls the movement of substances in and out the nucleus
nucleoplasm
nuclear pore → allow large substances to exit the nucleus e.g. mRNA
nucleolus → makes rRNA and ribosomes
chromosomes → protein-bound linear DNA
state the function of the mitochondria
site of aerobic respiration, produces ATP for energy
state the structure of the mitochondria
double membrane → controls the movement of substances in and out of the organelle
Cristae → extensions of the inner membrane increases surface area for enzymes in respiration
matrix → contains proteins, DNA, lipids and ribosomes
state the function of chloroplasts
absorbs light energy for photosynthesis
state the structure of chloroplasts
chloroplast envelope → controls the movement of substances in and out of the organelle
thylakoid → light dependent stage takes place
granum → stacks of thylakoids
stroma → light-independent stage takes place (Calvin cycle)
state the function of Golgi apparatus
packs lipids and proteins into vesicles
stores and transports lipids and proteins
synthesises lysosomes
(modifies proteins)
state the function of lysosomes
breaks down toxins
state the function of ribosomes
protein synthesis
state the structure of ribosomes
contains a large subunit and a small subunit
contains rRNA
state the function of rER
synthesises and transports proteins
state the function of her
synthesises, stores and transports lipids and carbohydrates
state the function of cell wall in plant cells
supports cell
prevent cell from bursting
allows exchange of substance between cells
state the function of cell vacuole in plant cells
maintains osmotic pressure within the cell
tissue definition
a group of cells that work together to perform a specific function
organ definition
a group of tissues that work together to perform a specific function
organ system definition
a group of organs that work together to perform a specific function
features of eukaryotic cells:
nucleus
DNA associated with histone proteins
DNA is linear
has membrane-bound organelles
80s ribosomes
DNA has exons and introns
features of prokaryotic cells:
no nucleus
DNA not associated with proteins
circular DNA
no membrane-bound organelles
70s ribosomes
DNA has exons only
parts of a bacterial cell:
circular DNA →contains genetic info
plasmid →contains gneetic info for adverse survivial conditions
cytoplasm →contains enzymes for chemical reactions
ribosomes → protein synthesis
cell mmbrane → controls movement of chemical in and out of cell
cell wall → protects against damage from other cells and osmotic lysis
capsule → allows bacteria to stick together for protectiona nd protects against other cells
pilli → attatchment to cell substances
flagella → locomotion
viruses are…
acellular and non-living
state the features of a virus:
reverse transcriptase
genetic material
lipid envelope
attachment proteins
capsid
matrix
why are the specimens stained when preparing slides?
to increase contrast and make organelles visible
describe the steps for preparing a mounted slide
add a drop of water onto a glass slide
add a thin section of specimen to slide
add a few drops of stain e.g. iodine
lower a coverslip on specimen using a mounted needle
describe the features needed for a biological drawing
magnification labelled
smooth continuous lines
labels which don’t cross
state what type of resolution light microscopes have and why?
they have a low resolution due to long light wavelength
features of light microscopes
light wavelength
live specimens
low resolution
shows colour
can use thicker specimens
uses lenses to focus light
features of TEM microscopes
electron beam
greater resolution
can see smaller organelles
views only dead specimens
doesn’t show colour
thinner specimens
more complex and time consuming
uses magnets to focus beam
give 3 similarities between TEM and SEM microscopes
both are expensive
both involve complex sample preparation
both produce black and white images
both view only dead specimens
magnification definition
a measure of how many times bigger the image is to the object
resolution definition
the ability to distinguish between 2 objects that are close together
magnification formula
image size/ actual size
why does the tissue sample need to be homogenised?
to break open cells and release the organelles
why does the solution need to be filtered
to remove large cell debris
why must the tissue be placed in an ice-cold solution
to slow down enzyme activity to prevent digestion of organelles
why must the tissue sample be placed in a buffered solution
to maintain pH to prevent enzymes being denatured
why must the tissue sample be placed in an isotonic solution
to prevent osmosis so osmotic lysis doesn’t occur
state the process of centrifugation for obtaining mitochondria
place tissue sample in a blender and filter
place in an ice-cold, buffered, isotonic solution
centrifuge at a low speed and remove nucleus pellet
centrifuge at a higher speed to obtain mitochondria
what are the 5 stages of mitosis
interphase
prophase
metaphase
anaphase
telophase
describe the structure of a chromosomes after its been replicated
made up of 2 sister chromatids attached by a centromere
interphase
DNA replication occurs
prophase
chromosomes condense and become visible
nuclear envelope breaks down and nucleolus disappears
centrioles move to opposite poles of cells
metaphase
chromosomes line up at the equator
spindle fibres attach to centromeres
anaphase
sister chromatids separate and move to opposite poles of cells
by spindle fibres contracting
centromeres divide
telophase
chromatids reach opposite poles of cell and decondense
nuclear envelope forms and nucleolus forms
spindle fibres break down and disappear
give three reasons why mitosis is important for living organisms?
growth
replacement of dead/damaged tissue
cloning ar
product of mitosis
2 genetically identical diploid daughter cells
give 2 examples how cancer drugs might affect cell cycle:
prevent DNA replication
prevent spindle fibre formation
what can mutations in mitosis lead to
uncontrolled cell division causing a tumour
describe the process for binary fission:
replication of circular DNA
replication of plasmids
division of cytoplasm
describe the appearance and behaviour of chromosomes during mitosis
chromosomes condense
appear as 2 sister chromatids attached by a centromere
chromosomes line up across the equator
attach to spindle fibres by centromeres
centromere divides
sister chromatids pulled to opposite poles of cell
chromosomes unwind
outline the role of organelles in the production, transport and release of proteins