cells 3.2 Flashcards
aqa biology as level
what organelles are present in a eukaryotic cell?
- cell surface membrane
- nucleus
- mitochondria
- chloroplast (plant only)
- Golgi apparatus and vesicles
- lysosomes
- ribosomes
- RER and SER
- cell wall
- vacuole (plant only)
what is the structure of the nucleus?
- nuclear envelope
- nuclear pores
- nucleoplasm
- chromosomes
- nucleolus (site of RNA production)
what is the function of the nucleus?
it contains the genetic code of each cell and site of DNA replication and transcription (mRNA)
what is the difference between RER and SER?
both are folded cisternae with RER having ribosomes on its surface
what is the function of the RER?
protein synthesis
what is the function of the SER?
synthesis and storage of lipids and carbohydrates
what is the structure of the Golgi apparatus?
folded membranes forming cisternae from which vesicles pinch off from
what is the function of the Golgi apparatus?
- adds carbohydrates to proteins to form glycoproteins
- produce secretory enzymes
- secrete carbohydrates
- transport modify and store lipids
- form lysosomes
- labels molecules for destination
- finished products transported to surface in Golgi vesicles fusing with membrane
what is the function of lysosomes?
bag of digestive enzymes that
- hydrolyse phagocytes
- break down dead cells fully
- release enzymes to outside of cell to destroy material (exocytosis)
- digest worn out organelles
what is the structure of mitochondria?
double membrane inner membrane called cristae filled with matrix and loops of mitochondrial DNA
what is the function of mitochondria?
it is the site of aerobic respiration and ATP production and contains DNA needed to code for enzymes in respiration
what is the structure of ribosomes?
small and made up of two parts a protein and a rRNA
80s - larger ribosome found in eukaryotic
70s - smaller ribosomes in prokaryotic mitochondria and chloroplast
what is the function of ribosomes?
protein synthesis
what is the structure of vacuole?
cell sap filled sac surrounded by single membrane called tonoplast
what is the function of the vacuole?
its turgid so provides support for the cell and is a temporary store for sugar and amino acids provides pigment for petals
what is the structure of chloroplast?
surrounded by a double membrane contains thylakoids (has chlorophyll/pigment inside it) and stroma
what is the function of chloroplast?
site of photosynthesis
what is the cell wall made of in plants and animals?
plants - cellulose
animals - chitin
what is the function of the cell wall?
provide structural strength for cell
what is the function of the phospholipid bilayer?
controls exit and entrance of molecules
what are the differences between prokaryotes and eukaryotes?
- prokaryotes are smaller
- have no membrane bound organelles
- 70s ribosomes
- no nucleus
- cell wall made of murein
what are other structural features of prokaryotes?
plasma and flagella and capsule around cell
what is the specialisation order?
specialised cells form tissues
tissues form organs
organs form organ systems
what are viruses?
viruses are acellular and non living
what is the structure of a virus?
attachement proteins, lipid envelope, genetic material and capsid
where do viruses replicate?
inside the cells so difficult to destroy
what are the types of microscopes?
optical transmission electron and scanning electron
what is the definition of magnification?
how many times larger the image is compared to the actual size
what is the definition of resolution?
the minimum distance between two objects to be seen as separate
what are the pros and cons of optical microscope?
pros
- coloured image
- easier preparation
- can view living samples
- thicker samples
cons
- poor resolution as light has longer wavelength
- lower magnification
- can’t see organelles
what are the pros and cons of electron microscope?
pros
- high resolution as electrons have shorter wavelength
- high magnification
- can see organelles
cons
- long preparation
- black and white images
- non living samples
- thinner samples (TEM)
what is the difference between TEM and SEM?
TEM shows the organelle structure of sample whereas SEM shows the 3D structure of sample
what is the magnification formula?
image size = actual size x magnification
how do you calibrate the eyepiece graticule?
- Calculate the distance of each stage micrometer division.
- Line up the micrometer with your eyepiece reticle scale bar.
- Count divisions and calculate size for that magnification.
- Increase magnification and repeat calculations for each click stop.
- Create a sizing chart to keep at your workstation.
what is the process of cell fractionation?
homogenisation then ultracentrifugation
why are cells homogenised?
cells are broken apart to release the organelles and separate them in a solution
where are cells prepared?
in an ice cold isotonic and buffered solution
why is the solution ice cold?
to reduce enzyme activity
why is the solution isotonic?
must be same water potential to prevent osmotic gain or less of water
why is the solution buffered?
to prevent enzymes denaturing