2.1.1 - CELL STRUCUTRE Flashcards
List the components of a eukaryotic animal cell
- plasma (cell surface) membrane
- rough endoplasmic reticulum (RER)
- nucleolus
- nucleus
- smooth endoplasmic reticulum (SER)
- lysosome
- ribosome
- nuclear envelope
- Golgi apparatus
- cytoplasm
- mitochondrion
List the components of a eukaryotic plant cell
- plasma (cell surface) membrane
- rough endoplasmic reticulum (RER)
- nucleolus
- nucleus
- smooth endoplasmic reticulum (SER)
- lysosome
- ribosome
- nuclear envelope
- Golgi apparatus
- cytoplasm
- mitochondrion
- CHLOROPLAST
- CELL WALL
- VACUOLE
What is the function of the plasma membrane?
- Regulates the movement of substances into and out of the cell
- has receptor molecules on it, which allow it to respond to chemicals like hormones (COMMUNICATION)
What is the function of the cell wall?
Supports plant cells
What is the function of the nucleus
- Controls the cell’s activities (by controlling transcription of DNA). DNA contains instructions to make proteins. The pores allow substances (e.g. mRNA + substances) to move between the nucleus and the cytoplasm
^— The nucleolus makes ribosomes - Stores DNA
What is the function of lysosomes?
- Contains digestive enzymes to break down pathogens, old/worn out organelles, cells + food molecules
- These are kept separate from the cytoplasm by the surrounding membrane
What is the function of ribosomes?
The site where proteins are made (PROTEIN SYNTHESIS)
What is the function of the Rough Endoplasmic Reticulum (RER)?
- Folds and processes proteins that have been made at the ribosomes
- Provides large surface area for protein synthesis
What is the function of the Smooth Endoplasmic Reticulum (SER)?
Synthesises, stores, transports + processes lipids and carbohydrates
What is the function of vesicles?
Transports substances in and out of the cell (via the plasma membrane) and between organelles.Some are formed by the Golgi apparatus or the endoplasmic reticulum, while others are formed at the cell surface
What is the function of the Golgi apparatus?
- Processes and packages new lipids and proteins
^— Also makes lysosomes - Transports molecules around the cell
What is the function of the mitochondrion?
- Site of aerobic respiration, where ATP is produced
- Found in large numbers in cells that are very active and require a lot of energy
What is the function of the chloroplasts?
- Site where photosynthesis takes place.
^— Some parts of photosynthesis happen in the grana, and other parts happen in the stroma (a thick fluid found in chloroplasts)
What is the function of the centriole?
Involved with the separation of chromosomes during cell division
What is the function of cilia?
- The microtubules allow the cilia to move
^— This movement is used by the cell to move substances along the cell surface
What is the function of the flagellum?
- Microtubules contract to make the flagellum move
- Flagella are used like outboard motors to propel cells forward (e.g. when a sperm cell swims)
Describe the structure of the Rough Endoplasmic Reticulum (RER)
- System of membranes enclosing a fluid-filled space
- The surface is covered with ribosomes
Describe the structure of the Smooth Endoplasmic Reticulum (SER)
- A system of membranes enclosing a fluid-filled space
- The surface has no ribosomes
Describe the structure of the mitochondria
- Oval-shaped
- Double membrane —> inner membrane folded to form structures called cristae
- Inside is the matrix, which contains enzymes involved in respiration
Describe the structure of the chloroplasts
- Small, flattened structure in plant cells
- Double membrane
- Has membranes called thylakoid membranes
- Thylakoids stack up to form grana
- Grana are linked together by lamellae (thin, flat pieces of thylakoid membrane
- Contains thick fluid called stroma
Explain the steps behind protein production/synthesis
- Proteins are made at the ribosomes
- Ribosomes on the RER make proteins that are excreted or attached to the cell membrane. Free ribosomes make proteins that stay in the cytoplasm
- new proteins at the RER are folded and processed (e.g. sugar chains are added) in the RER
- Proteins then transported from RER to the Golgi apparatus in vesicles
- At Golgi, proteins may undergo more processing (e.g. sugar chains trimmed or more added)
- The proteins enter more vesicles to be transported around the cell (e.g. glycoproteins in mucus move to the cell surface and are secreted)
What is the cytoskeleton
A network of protein threads running through the cytoplasm
- in eukaryotic cells, protein threads arranged as microfilaments (small solid strands) and microtubules (tiny protein cylinders)
What is the function of the cytoskeleton?
- Microtubules + microfilaments support the cell’s organelles, keeping them in position
- Help strengthen cell + maintain shape
- Responsible for movement of materials within the cell (e.g. movement of chromosomes when they separate during cell division depends on contraction of microtubules in the spindle
- Proteins of the cytoskeleton can cause cell to move (e.g. movement of cilia + flagella caused by cytoskeletal protein filaments that run through them)
State the characteristics of prokaryotic cells
- small (less than 2 µm diameter)
- circular DNA
- no nucleus (free DNA)
- cell wall made of polysaccharide - but not cellulose or chitin
- few organelles and no membrane-bound organelles (no mitochondria)
- flagella (if present) made of the protein flagellin, arranged in a helix
- small ribosomes
e.g. E. coli bacteria
State the characteristics of eukaryotic cells
- larger cells (10-100 µm diameter)
- linear DNA
- nucleus (DNA inside nucleus)
- no cell wall (animals), cellulose cell wall (plants), chitin cell wall (fungi)
- many organelles - has membrane-bound organelles
- flagella (if present) made of microtubule proteinsarranged in a ‘9 + 2’ formation
- larger ribosomes
e.g. human liver cell
What is the equation for magnification?
Magnification = Image size/Actual size
Define magnification
How much bigger the image is than the specimen (actual size)
Define resolution
How well a microscope distinguishes between two points that are close together
How do light microscopes operate?
- They use light to produce photograms
What is the max resolution and magnification of a light microscope?
Resolution: 0.2 µm
Magnification: x 1500
How does a Laser Scanning Confocal Microscope operate?
- use laser beams to scan a specimen, which is tagged with fluorescent dye
- laser causes dye fluoresce (give off light)
- light then focused through a pinhole onto a detector
- detector hooked up to computer to generate image (can be 3D)
- can look at objects at different depths in thick specimens
What are the two kinds of electron microscope?
- Transmission Electron Microscope (TEM)
- Scanning Electron Microscope (SEM)
How does a TEM operate?
- use electromagnets to focus a beam of electrons which is transmitted through the specimen
- denser parts of the specimen absorb more electrons, which make them look darker on the image
What are the advantages and disadvantages of TEMs?
+ provide high resolution images
- can only be used on thin specimens
What is the maximum resolution and magnification of TEMs?
Resolution: 0.0002 µm
Magnification: more than x 1 000 000
How does a SEM operate?
- scans a beam of electrons across the specimen
- knocks off electrons from the specimen, which are gathered in a cathode ray tube to form an image
What are the advantages and disadvantages of SEMs?
+ can be 3D and show specimen surface
- give lower resolution images
What is the maximum resolution and magnification of SEMs?
Resolution: 0.002 µm
Magnification: less than x 500 000
Explain the Dry Mount method of preparing a microscope slide
- take thin slice of thick specimen
- use tweezers to pick up specimen and put it in the middle of a clean slide
- place a cover slip on top
Explain the Wet Mount method of preparing a microscope slide
- pipette a small drop of water onto the slide
- use tweezers to place the specimen on the water drop
- stand the slip upright on the slide, next to the water droplet, then title and lower it so it covers the specimen (BE CAREFUL OF AIR BUBBLES)
- once the slip is in position, add a stain (it’ll get drawn under the slip, across the specimen)
Why is it sometimes necessary to stain an object before viewing it through a microscope?
Sometimes the object being viewed may be completely transparent, making the whole thing look white
- different stains to make different things show up (e.g. eosin stains cell cytoplasms + methylene blue stains DNA)
What if the function of the permanent vacuole?
- Maintains cells structure
- Acts and temporary energy store
How is the size of ribosomes measured?
- Svedberg unit (S)
