Cells Flashcards
What are prokaryotic organism as
Prokaryotic cells - they’re single celled organisms
Prokaryotic cells are smaller and simpler
What are eukaryotic cells
Are complex and have more organelles
Eukaryotic cells
Animal plant algal and fungal cells are all eukaryotic
What organelles are in an animal cell
Cell surface (plasma) membrane Rough endoplasmic reticulum Smooth endoplasmic reticulum Lysosomes Ribosome Mitochondria Cytoplasm Golgi apparatus Nuclear envelope Nucleolus Nucleus
What extra things does a plant cell have
A cellulose cell wall with plasmodesmata
A vacuole (fluid filled compartment)
Chloroplasts
What do plants use starch Grains for
To store excess sugars
What is the main difference between plant cells and algal cells
They can be unicellular (Chlorella) or multicellular (seaweed)
Have the same organelles including a cellulose cell wall and chloroplasts. However the chloroplasts are a different shape and size to plant chloroplasts eg some algae have one large chloroplast rather than several smaller chloroplasts
How are fungal cells different from plant cells
Can be multicellular (mushrooms) or unicellular (yeast) fungal cells are a lot like plant cells but different :
Their cell walls are made of chitin not cellulose
They don’t have chloroplasts because they don’t photosynthesise
What is the cell surface membrane
Also called the plasma membrane
The membrane found on the surface of animal cells and just inside the cell wall of other cells
It’s made mainly of lipids and protein
Function - regulates the movement of substance into and out of the cell also has receptor molecules on it which allow it to respond to chemicals like hormones
What is the nucleus
Consists of the nuclear envelope, nucleolus, nuclear pore, chromatin
Large organelle surrounded by a nuclear envelope (double membrane) which contains many pores.
Contains chromosomes ( made from protein bound linear DNA) and one or more structures called a nucleolus
Function - Controls the cells activities ( controlling the transcription of dna ) dna contains instructions to make proteins
The pores allow substances (eg RNA);to move between the nucleus and the cytoplasm
The nucleolus makes ribosomes
What is the mitochondrion
Usually oval shaped
Have a double membrane the inner one is folded to form structures called cristae. Inside is the matrix which contains enzymes involved in respiration. So have an outer membrane, inner membrane, cristae and the matrix
Function- the site of aerobic respiration
Aerobic respiration produces ATP - a common energy source in the cell. Mitochondria are found in large numbers in cells that are very active and require a lot of energy.
What is the chloroplast
Small flattened structure found in plant cells and algal cells
It’s surrounded by a double membrane and also has membranes inside called thylakoid membranes
These membranes are stacked up in some parts of the chloroplast to form grana
Grana are linked together by lamellae- thin flat pieces of thylakoid membrane
Function- the site where phs takes place. Some parts of phs happen in the grana and other parts happen in the stroma ( a thick fluid found in chloroplasts) .
What is the Golgi apparatus
A group of fluid filled membrane bound flattened sacs.
Vesicles are often seen at the edge of the sacs
Function - it processes and packages new lipids and proteins. It also makes lysosomes
What is the Golgi vesicle
A small fluid filled sac in the cytoplasm, surrounded by a membrane and produced by the Golgi apparatus
Function- stores lipids and proteins made by the Golgi apparatus and transports them out of the cell ( via the cell surface membrane)/
What is the lysosome
A round organelle surrounded by a membrane , with no clear internal structure. It’s a type of Golgi vesicle.
Function- contains digestive enzymes called lysozymes. These are kept separate from the cytoplasm by the surrounding membrane and can be used to digest invading cells or to break down worn out components of the cell
What is the ribosome
A very small organelle that floats free in the cytoplasm or is attached to the rough endoplasmic reticulum. It’s made up of proteins and RNA it’s not surrounded by a membrane
Function - the site where proteins are made
What is the ROUGH endoplasmic reticulum
A system of membranes enclosing a fluid filled space the surface is covered with ribosomes
Function - folds and processes proteins that have been made at the ribosomes
Protein synthesis
What is the Smooth endoplasmic reticulum
Similar to red but with no ribosomes
Function - synthesises and processes lipids / carbohydrates
What is the cell wall
A rigid structure that surrounds cells in plants, algae and fungi. In plants and algae it’s made mainly of the carbohydrate cellulose. In fungi it’s made of chitin
Function- supports cells and prevents them from changing shape.
What is the cell vacuole in plants
A membrane bound organelle found in the cytoplasm
It contains cell sap - a weak solution of sugar and salts. The surrounding membrane is called the tonoplast
Function - helps to maintain pressure inside the cell and keep the cell rigid this stops the plant wilting it’s also involved in the isolation of unwanted chemicals inside the cell
Provides support and strength
What is the equation for microscope calculations
I. Image size
A M. Actual Magnification
mm to microneters
1mm =1000 micrometers
Micrometers -> x1000
What is resolution
How detailed the image is. More specifically, it’s how well a microscope distinguishes between two points that are close together. If a microscope lens can’t separate two objects, then increasing the magnification wont help.
What is magnification
Is how much bigger the image is than the specimen (the sample you’re looking at).
What is an optical ( light microscope)
Use light to form an image Max resolution of 0.2 micrometers View ribosomes, endoplasmic reticulum , lysosomes and mitochondria but not in perfect detail Also see nucleus Maximum useful mag - 1500 Lens type- glass Specimen - living or dead Prep- easy process thin sections add stains and dye Limitations- low mag, poor resolution Image - 2D
Transmission electron microscope
Use electromagnets to focus a beam of electrons which is then transmitted through the specimen. Denser parts of the specimen absorb more electrons, which makes them look darker on the image you end up with.
High resolution image- you see internal structures of organelles like chloroplasts
Limitations- expensive , dead specimen, have to operate in a vacuum, only used on thin specimens, black and white ,
Artefacts
Scanning electron microscopes
Electron beams bounce of specimen, electrons gathered in a cathode rah tube to form an image. Images you end up with show the surface of the specimen and they can be 3D.
Can be used on thick specimens
Limitations- dead specimen, difficult and time consuming preparation , expensive, give lower resolution than tems
Have to operate in vacuum
Produce artefacts
Detectors pick up scattered electrons to form 3D image often falsely coloured
How would you prepare a microscope slide
Put on a slide using a temporary mount eg water
Pippette a small amount of water on a slide
Put on slide and add a stain like iodine for plants to show starch grains and eosin to make cytoplasm snow up
Add a cover slip
Microscope artefacts
You can see in a microscope but not part of the cell or specimen you’re looking at can be anything from bits of dust, air bubbles, fingerprints
They’re usually made during the preparation of your specimen
Common in electron micropgraphs because specimens need a lot of prep before viewing under an electron microscope
The first scientists to use electron microscopes could only distinguish between artefacts and organelles by repeatedly preparing specimens in different ways. If objects could be seen with one preparation technique, but not another, it was more likely to be an artefact than an organelle.
Hag would you do to look at organelles under an electron microscope
Cell fractionation
What does homogenisation do
Breaking up cells
By vibrating cells or by grinding up cells in a blender
This breaks up the plasma membrane and releases the organelles into solution
The solution must be kept ice cold, to reduce the activity of enzymes that break down organelles
Isotonic - should have the same concentration of chemicals as the cells being broken down to prevent damage to the organelles through osmosis
Buffer solution should be added- maintain the pH
What’s the next step
Filtration
Homogenised cell solution is filtered through a gauze to separate any large cell debris or tissue debris, like connective tissue from the organelles
The organelles are much smaller than the debris so they pass through the gauze
What’s the third step
Ultracentrifugation
After filtration you’re left with a solution containing a mixture of organelles
To separate a particular organelle from all the others u use ultracentrifugation
-The cell fragments are poured into a tube the tube is put into a centrifuge ( a machine that separates material by spinning) and is spun at a low speed. The heaviest organelles, like nuclei, get flung to the bottom of the tube by the centrifuge. They form a thick sediment at the bottom - the pellet. The rest of the organelles stay suspended in the fluid above the sediment- the supernatant
- the supernatant is drained off, poured into another tube and spun in the centrifuge at a higher speed. Again, the heaviest organelles form a pellet at the bottom of the tube. The supernatant containing the rest of the organelles is drained off and spun in the centrifuge at an even higher speed.
- this process is repeated at higher speeds, until all the organelles are separated out. Each time, the pellet at the bottom of the tube is made up of lighter and lighter organelles.
How are the organelles separated out
Separated in order of mass ( from heaviest to lightest) this order is usually: nuclei, then mitochondria, lysosomes, endoplasmic reticulum and finally ribosomes
In plant cells the chloroplasts come out after the nuclei but before the mitochondria
Naughty clever monkeys like eating red raspberries
What is a prokaryotic cell
Single celled organisms
They are much smaller and simpler than eukaryotic cells and they don’t have any membrane bound organelles ( like nucleus ) in their cytoplasm
What is the dna like in a prokaryotic cell
Doesn’t have it’s dna enclosed in a nucleus
The dna floats free in the cytoplasm. It’s circular dna is one coiled up strand, it’s. it attached to any histone proteins
What are the plasmid
Small loops of dna that aren’t part of the main circular dna
Plasmids contain genes for things like antibiotic resistance and can be passed between prokaryotes
They’re not always present
Some prokaryotic cells have several
What does the cell wall do in a eukaryote cell
Supports and strengthens prevents it from changing shape made up of a polymer murein.
Murein is a glycoprotein ( protein with a carbohydrate attached)
What does the cell surface me,brand do in a pro cell
Mainly made of lipids and proteins
It controls the movement of substances into and out of the cell
What’s the ribosomes in a pro cell
They’re smaller than those in a eukaryotic cell
70s
What’s the slime capsule
Made up of secreted slime it helps to protect the bacteria for arrack by cells of the immune system
The flagellum
Long hair like structure that rotates to make the prokaryotic cell move
Not all prokaryotes have a flagellum some have more than one
The cytoplasm
Contains all the enzymes needed for all metabolic reactions
When do cells become specialised to carry out specific functions
In multicellular eukaryotic organisms
A lot of energy
Lots of mitochondria
Cell needs to make protein
Lots of ribosomes
Epithelial cells
Are adapted to absorb food efficiently
- the walls of the small intestine have finger like projections called villi the increase surface area for absorption
- epithelial cells on the surface of the villi have folds in their cell surface membranes called microvilli microvilli increase surface area even more
- have lots of mitochondria to provide energy for the transport of digested food molecules into the cell.
Red blood cells
They have no nucleus to make more room for haemogolobin
Sperm cells
Lots of mitochondria to provide large amounts of energy to propel themselves towards the egg
What is cell organisation
Specialised cells are grouped together to form tissues. A tissue is a group of cells working together to perform a particular function
Different tissues work together or form organs
Different organs make up an organ system
Name different types of tissue
Epithelial tissue, muscular tissue, glandular tissue
All work together to form the stomach which is the organ and part of the digestive system including small intestine large intestine and liver
