Cells Flashcards
Magnification equation
Magnification = image size / real object size
What is resolution?
- Minimum distance apart that two objects can be distinguished as separate objects in an image.
- The greater the resolution the more clear the image will be
Properties of optical microscopes
- Use light
- Cannot see small internal organelles eg, ribosomes
- Low resolution and magnification
Properties of SEM (scanning electron microscope)
- Can use thick specimen
- Lower resolution than TEM
- 3D image
Properties of TEM (transmission electron microscope)
- High resolution, so you can see internal organelles
- Only used on thin specimens
- No living specimens
Why should a solution be kept ice cold?
To reduce enzyme activity that breaks up organelles
Why should the solution be isotonic?
To prevent the osmotic pressure of the cell changing and destroying the organelles
Why is a buffer solution used?
To maintain the pH
What do eukaryotic cells have?
A nucleus and membrane bound organelles
Function of the nucleus
- Controls the cell’s activity
- The nuclear pores allow substances to pass in and out of the nucleus
- The nucleolus makes ribosomes
Function of RER (rough endoplasmic reticulum)
- Folds and processes proteins
Function of SER (smooth endoplasmic reticulum)
- Synthesises and processes lipids
Function of Golgi apparatus
- Processes and packages new lipids and proteins
- Also makes lysosomes
Function of Golgi vesicles
- Stores lipids and proteins
- Transports it out of the cell
Function of Mitochondria
- Site of aerobic respiration where ATP is produced
Function of Ribosomes
- Site where proteins are made
Function of lysosomes
- Contain lysozymes which are digestive enzymes
Function of cell membrane
- Regulates the movement of substances in and out the cell
- Also has receptor molecules
Function of the cell wall
- Supports cell
Function of chloroplasts
- Site where photosynthesis takes place
Function of cell vacuole
- Helps maintain pressure and keep cell rigid
- Involved in isolation of unwanted chemicals
Function of capsule
- Protect bacteria from attacks from the cells of the immune system
What are viruses?
- Non living structures which contain nucleic acid enclosed in a capsid
The role of mitosis?
To produce identical daughter cells for growth and asexual reproduction
Stages of cell cycle
- Mitosis
- Interphase
- Cytokinesis
What is mitosis?
- A form of cell division that produces identical cells,
- There are four stages of mitosis: prophase, metaphase, anaphase and telophase
What happens in interphase?
- The cell grows & then prepares to divide
- Chromosomes & some organelles are replicated
- Chromosomes also begin to condense
What happens in cytokinesis?
- The parent & replicated organelles move to opposite sides of the cell
- The cytoplasm divides thus producing two daughter cells
Why is mitosis important?
- Growth: all cells produced are identical so organisms can grow using mitosis.
- Repair: all cells produced are identical so organisms can replace dead tissues using mitosis.
- Reproduction: some single-celled organisms, like yeast, reproduce by dividing into two identical daughter cells by mitosis.
What occurs in prophase?
- Chromosomes condense
- Centrioles move to opposite ends of the cell forming spindles
- Nuclear envelope breaks down
What occurs in metaphase?
- Chromosomes line up along the middle of the cell
- They become attached to the spindle by the centromeres
What occurs in anaphase?
- Centromeres divide, separating each pair of sister chromatids
- Spindles contract, pulling chromatids to opposite poles of the spindle
What occurs in telophase?
- Chromatids reach the opposite ends on the spindle
- They uncoil and become chromosomes
- Nuclear envelope forms around each group of chromosomes creating 2 nuclei
- Cytokinesis finishes leaving two genetically identical daughter cells
Steps of Required Practical 2- Mount slide
- Cut 2 cm tip of the root and place in HCl for about 15 minutes
- Rinse the tip with distilled water
- Cut off 1 mm of the tip and place on a slide
- Cover the sample with toluidene blue and macerate with amounted needle
- Add cover slip and squash the material gently and place under a microscope
- Calculate the mitotic index
How to calculate the mitotic index
Number of cells undergoing mitosis / total number of cells observed
How do you calculate the size of cells?
- Using a eyepiece graticule
- Or the IAM equation
What happens in G1?
- Cell growth and protein production
What happens in the S phase?
DNA replication
What is binary fission?
- The process at which prokaryotic cells divide
The stages of binary fission
- The circular DNA in the cells replicates & both copies attach to the cell membrane. Plasmids replicate.
- The cell membrane begins to grow between the two DNA molecules & begins to pinch inwards, dividing the cytoplasm in two.
- A new cell wall forms between the two DNA molecules dividing the original cell.
What is a cell membrane made up of?
- Phospholipids with proteins in between
- Also contains receptors
Why are cell membranes described as fluid mosaic?
- The phospholipids are constantly moving
- The proteins are scattered
The role of cholesterol
- Make the membrane more rigid and reduce the lateral movement of the phospholipids.
- It also prevents the leakage of water and dissolved ions from the cell as it is very hydrophobic.
The role of glycolipids
- Acts as cell surface receptors for certain molecules.
- They also allow cells to adhere(stick) to one another to form tissues
The role of glycoproteins
- Acts as cell surface receptors and neurotransmitters.
- These allow cells to recognise one another as well as attach to form tissues
What is diffusion?
- Passive movement of small, non-polar, lipid soluble molecules such as carbon dioxide and oxygen from an area of high concentration to an area of low concentration
What is osmosis?
- Diffusion of water molecules from an area of high water potential to an area to low water potential through a partially permeable membrane
Active transport
- Can transport all types of molecules through carrier proteins from an area of low concentration to an area of high concentration.
- However, this process requires energy in the form of ATP
Factors that increase the rate of diffusion
- Large surface area
- Short diffusion pathway
- Steep diffusion gradient
- An increase in temperature
