Cells 1 Flashcards
How are algal cells different to plant cells?
They tend to have one elongated chloroplast instead of several smaller ones
How are fungal cells different to plant cells?
They don’t have chloroplasts and their cell walls are made of chitin
What are all the organelles in an animal cell?
Cell membrane, mitochondria, cytoplasm, golgi aparatus, lysosome, nucleus, rough endoplasmic reticulum, smooth endoplasmic reticulum, ribosomes
What are all of the organelles in a plant cell?
Cell membrane, cell wall, cytoplasm, chloroplast, rough endoplasmic reticulum, smooth endoplasmic reticulum, mitochondria, golgi apparatus, vacuole, nucleus, ribosome
What is plasmodesmata?
Channels in a cell wall for exchanging substances between adjacent cells
What is the function of cell membrane?
It regulates the movement of substances into and out of the cell
What is the structure of the nucleus?
Surrounded by a double membrane nuclear envelope which contains many pores - the pores allow substances like RNA to move between the nucleus and the cytoplasm
The nucleus contains chromosomes, chromatin and a nucleolus - which makes ribosomes
What is the function of the nucleus?
Controls the cell’s activities
Holds the genetic information which contains instructions to make proteins
What is the structure of mitochondria?
Oval shaped with a double membrane
The inner membrane is folded to form the cristae which also forms the matrix
(In photos the matrix looks like wiggly lines)
What is the function of mitochondria?
The site of aerobic respiration
What is the structure of a chloroplast?
Surrounded by a double membrane
Contains grana (the little lines)
Contains lamella (the bigger lines)
Contains stroma (the little dots)
What are lamellae?
Thin flat pieces of thylakoid membrane
What is the function of chloroplasts?
The site of photosynthesis (some parts of photosynthesis happen in the grana and others in the stoma)
What is the structure of the golgi aparatus?
A group of fluid-filled membrane-bound flattened sacs
Vesicles (little circles) are often seen at the edges of the sacs
What is the function of the golgi aparatus?
It processes and packages new lipids and proteins
It also makes lysosomes
What is a golgi vesicle?
A small fluid filled sac produced by the golgi aparatus that stores lipids and proteins made by the golgi and transports them out of the cell
What is the structure of a lysosome?
A round organelle with no clear internal structure - it’s a type of golgi vesicle
What is the function of a lysosome?
They contain digestive enzymes called lysozymes which are used to digest invading cells or break down worn out components of the cell
What are ribosomes and their function?
A very small organelle that can float free in the cytoplasm or be attached to the rough ER
It’s made up of proteins and RNA and is not surrounded by a membrane
It’s the site of protein synthesis
What is the rough endoplasmic reticulum (RER) and its functions?
A system of membranes covered in ribosomes (they look like noodles)
The RER folds and processes proteins that have been made at the ribosomes
What is the function of the smooth endoplasmic reticulum (SER)?
To synthesise and process lipids
What is the structure of the cell wall?
A rigid structure that surrounds cells in plants, algae and fungi
What is the cell wall usually made of?
In plants and algae it’s made of cellulose but in fungi it’s made of chitin
What is the function of the cell wall?
To support cells and prevent them from changing shape
What is the structure of the vacuole?
A membrane bound organelle found in the cytoplasm that contains cell sap (a weak solution of sugar and salts)
The surrounding membrane is called the tonoplast
What is the function of the vacuole?
It helps maintain pressure inside the cell and keeps the cell rigid to stop plants wilting
It’s also involved in the isolation of unwanted chemicals inside the cell
How is an epithelial cell from the small intestine adapted for its function?
The walls have finger like projections called villi which also have folds in their membranes called microvilli which increase the surface area
They also have lots of mitochondria which are needed to provide energy for active transport and digest food molecules into the cell
How are red blood cells adapted for their function?
They have no nucleus make more room for haemoglobin
They have a biconcave disc shape to increase surface area
How are root hair cells adapted for their function?
They each have a hair like projection to increase surface area
They have lots of mitochondria to provide energy for active transport
What are the three most common adaptations of specialised cells?
Folded membrane to increase surface area
An excellent capillary network to maintain a good concentration gradient for efficient rate of diffusion
Thin exchange surface for a faster rate of diffusion as the distance is reduced
What are all of the structures in a bacterial cell?
Flagella, circular strand of DNA, cytoplasm, ribosomes, capsule, cell wall, cell membrane, plasmids
What is different about ribosomes in prokaryotic cells?
They are smaller than ribosomes in eukaryotic cells
What is the capsule in a bacterial cell?
A layer of slime that goes around the cell wall
What do the cell wall and cell membrane in bacterial cells contain?
A glycoprotein called murein
What are all of the structures in a viral particle?
Genetic material (made of RNA), reverse transcriptase (enzyme), attachment proteins, capsid, lipid envelope, matrix
What are the three steps of cell fractionation?
Homogenisation
Filtration
Ultracentrifugation
What is homogenisation?
When cells are broken up by a homogeniser (blender) to break up the plasma membrane and release organelles into solution
What is filtration?
When large cell or tissue debris is filtered from the organelles through a gauze so only the homogenised cell solution will pass through
What is the process of ultracentrifugation?
- The cell fragments are poured into a tubee which is put into a centrifuge and spun at a low speed
- The heaviest organelles get flung to the bottom of the tube forming a thick sediment (called a pellet) and the rest of the organelles stay suspended in the fluid above (called the supernatant)
- The supernatant is poured into another tube and spun in the centrifuge at a higher speed until another pellet of the heaviest organelles is formed at the bottom of the tube and the process repeats at higher and higher speeds until all of the organelles are separated out
What is the order of mass of the organelles?
Nuclei –> chloroplasts (in plant cells) –> mitochondria –> lysosomes –> endoplasmic reticulum –> ribosomes
Before cell fractionation, what are the three properties that the solution must have?
Cold
Isotonic
Buffered
Why must the solution for cell fractionation be cold?
To reduce enzyme activity that might break down the organelles
Why must the solution for cell fractionation be isotonic?
To prevent organelles bursting or shrinking as a result of osmotic gain or loss of water
Why must the solution for cell fractionation be buffered?
To maintain a constant pH variation as pH will affect enzymes and the structure of organelles
What is magnification?
How many times bigger the image is than the object
How do you work out total magnification?
The magnification of the eyepiece lens multiplied by the magnification of the objective lens
What is resolution?
The smallest distance between two particles which allows them to be distinguished from one another
How does a scanning electron microscope (SEM) work?
It scans a beam of electrons across the specimen, knocking electrons off of the specimen which are gathered in a cathode ray tube to form an image
What are the advantages and disadvantages of SEMs?
Advantages
- Can be used on thick specimens
- Image is 3D
Disadvantages
- Give a lower resolution than TEMs
- Can only be used on non-living specimens
How do transmission electron microscopes (TEMs) work?
They use electromagnets to focus a beam of electrons which is transmitted through the specimen
What are the advantages and disadvantages of TEMs?
Advantages
- Give very high resolution images
- Can see the internal structure of organelles like chloroplasts
Disadvantages
- Can only be used on thin specimens
- Can only be used on non-living specimens
- Images are in black and white
What is the resolution of a TEM?
0.1nm
What is the resolution of an SEM?
20nm
What is the resolution of an optical microscope?
200nm / 0.2 micrometers
Why do light / optical microscopes have a poorer resolution compared to electron microscopes?
Because of the relatively long wavelength of light
What is the calculation for magnification?
Image size = actual size x magnification
What are the three stages of interphase?
Gap phase 1
Synthesis
Gap phase 2
What happens during gap phase 1?
The cell grows and new organelles and proteins are made
What happens during synthesis?
The cell replicates its DNA
What happens during gap phase 2?
The cell keeps growing and proteins needed for cell division are made
What increases during interphase?
The cell’s ATP content (provides the energy needed for cell division)
How long is a cell in interphase and mitosis for?
Interphase - 90% of the time
Mitosis - 10% of the time
What are the four stages of mitosis?
Prophase
Metaphase
Anaphase
Telophase
What happens during prophase?
The chromosomes condense and centrioles start moving to opposite ends of the cell, forming the spindle equator
The nuclear envelope also breaks down so the chromosomes are free in the cytoplasm
What does prophase look like in a picture?
The chromosomes just floating about in there
What happens during metaphase?
The chromosomes line up along the middle of the cell and become attached to the spindle equatore by their centromere
What does metaphase look like in a picture?
All the chromosomes lined up along the middle
What happens during anaphase?
The centromeres of the chromosomes divide, separating each pair of sister chromatids, pulling them to opposite poles of the spindle
What does anaphase look like in a picture?
The chromosomes now look v shaped and are moving to opposite ends of the cell
What happens during telophase?
The chromatids reach opposite ends of the poles and uncoil so they are now chromosomes again
A nuclear envelope forms around each group of chromosomes to create two nuclei
The cytoplasm now divides by cytokenesis so form two identical daughter cells
What does telophase look like in a picture?
Two cells forming
What is the calculation for binary fission?
Bacteria at the end = bacteria at the start × 2 to the power of the number of divisions
How do you use an eyepiece graticule and stage micrometer to calculate the actual size of cells?
- Eyepiece graticule is in the eyepiece
- Stage micrometer is on the stage
- Align the two scales
- Each division on the stage micrometer is worth 0.1mm
