3.2 Cell Replication Flashcards
Describe the structure and function of the cell surface membrane
- phospholipid bilayer with embedded proteins
- Selectively permeable - enables control of substances passing in and out of the cell
- Barrier between internal and external environment of cell
Describe the structure and function of the Nucleus
- Nuclear envelope, nuclear pores, nucleolus, DNA/chromatin
- Controls cell activity through transcription on mRNA
- Nuclear pores allow substances like mRNA to move between the nucleus and cytoplasm
- Nucleolus makes ribosomes which are made up of proteins and ribosomal RNA
Describe the structure and function of the Mitochondria
Double membrane - inner membrane folded to form cristae
Matrix containing small 70s ribosomes, small circular DNA and enzymes involved in aerobic respiration (glycolysis)
Site of aerobic respiration producing ATP for energy release
Describe the structure and function of the Golgi apparatus
- 3 or more fluid filled membrane bound sacs with vesicles at the edge
- Receives protein from RER
modifies/processes protein e.g. adds carbohydrates/sugars - Packages into vesicles e.g. for transport to cell surface membrane for exocytosis
- Also makes lysosomes
Describe the structure and function of the Lysosomes - link to phagocytosis in immunity
- Type of golgi vesicle containing lysosomes - hydrolytic enzymes
- Release of lysozymes to break down/hydrolyse pathogens or worn out cell components
Describe the structure and function of the Rough Endoplasmic Reticulum
- Float free in cytoplasm or bound to RER. not membrane bound. Made from 1 large and 1 small subunit
- Site of protein synthesis, specifically translation
Describe the structure and function of the Rough Endoplasmic Reticulum
Ribosomes bound by a system of membranes
Folds polypeptides to secondary/tertiary structure
Packages to vesicles, transport to the golgi apparatus
Describe the structure and function of the Rough Endoplasmic Reticulum
Ribosomes bound by a system of membranes
Folds polypeptides to secondary/tertiary structure
Packages to vesicles, transport to the golgi apparatus
Describe the structure and function of the Smooth Endoplasmic Reticulum
Similar to RER but without ribosomes - system of membranes
Synthesises and processes lipids
Describe the structure and function of Chloroplasts (plants and algae) - link to photosynthesis
- Thylakoid membranes are stacked up in some parts to form grana, which are linked by lamellae. - - These sit in the stroma and are surrounded by a double membrane. Also contains starch granules and circular DNA
- Chlorophyll absorbs light for photosynthesis to produce organic substances
Describe the structure and function of the cell wall (plants, algae, fungi) - link to structure and function of cellulose
Made of cellulose in plants and algae, and of chitin in fungi
Rigid structure surrounding cells in plants, algae, and fungi. Prevents the cell changing shape and bursting (lysis)
Describe the structure and function of the cell vacuole (plants)
Contains cell sap - a weak solution of sugars and salts. Surrounding membrane is called the tonoplast
Maintains pressure in the cell to help prevent wilting
Stores unwanted chemicals in the cell
Explain how epithelial cells in the small intestine are specialised for efficient absorption
- Villi and microvilli increase surface area
- Lots of mitochondria to provide energy for processes like active transport
Differences between prokaryotic and eukaryotic
-Prokaryotic has no membrane bound organelles, while eukaryotic has it
-Prokaryotic has no nucleus
-Prokaryotic DNA is circular; Eukaryotic DNA is linear
-Prokaryotic cell wall contains murein while eukaryotic is made of cellulose
-Prokaryotic has 70s ribosomes; eukaryotic has 80s
-Prokaryotic has a capsule; Eukaryotic does not
Explain why viruses are non living
Acellular - not made of/able to divide into cells
Non living - unable to reproduce without a host cell
Optical microscopes
-Light microscopes have a poor resolution due to the long wavelength of light
-Small organelles in a cell are not visible, but they can see large samples
Electron microscopes
Electrons are absorbed by air, which is why samples must be in a vacuum. Therefore, dead samples can be examined. The image remains black and white although the samples are stained
Transmission microscope process
Very thin specimens are stained and placed in a vacuum. An electron gun produces a beam of electrons that pass through the specimen. Some parts absorb the electrons and appear dark. The image produced is 2D and shows detailed images of the internal structure of cells
Scanning electron microscope
The electrons are beamed onto the surface and the electrons are scattered in different ways depending on the contours on the surface. This produces a 3D image.
what is magnification and resolution
Magnification - how much bigger the image of a sample is compared to the real size
M=I/A
Resolution - how much distance it takes to distinguish 2 points as separate objects
Explain how you would use cell fractionation and ultracentrifugation to separate cell components
- Homogenise tissue using a blender
- Disrupts cell membrane / break open cell
- Release contents / organelles - Place in a cold, isotonic, buffered solution
- Cold reduces enzyme activity so organelles aren’t broken down
- Isotonic so water doesn’t move in/out of organelles by osmosis so they don’t burst / shrivel
- Buffered keeps pH constant so enzymes don’t denature - Filter homogenate
- Remove large, unwanted debris e.g. whole cells, connective tissue - Ultracentrifugation
a) Centrifuge homogenate in a tube at a low speed
b) Remove pellet of heaviest organelle and spin supernatant at a higher speed
c) Repeated at higher and higher speeds until organelles separated out, each time pellet is made of lighterorganelles
d) Separated in order of mass/density: nuclei → chloroplasts → mitochondria → lysosomes →endoplasmic reticulum → ribosomes
What happens during interphase of the cell cycle
S phase - DNA replicates semi conservatively leading to 2 sister chromatids
G1 and G2 - Number of organelles and volume of cytoplasm increases; protein synthesis; ATP content increased
describe mitosis
Prophase
-Chromosomes condense
-Nuclear envelope breaks down and centrioles move to opposite poles, forming spindle network
Metaphase
-Chromosomes align along the equator
-Spindle fibres attach to chromosomes by centromeres
Anaphase
-Spindle fibres contract, pulling sister chromatids to opposite poles of the cell
-Centromere divides
Telophase
-Chromosomes uncoil
-Nuclear envelope reforms = two nuclei
-Spindle fibres and centrioles break down
Cytokinesis
-The division of the cytoplasm, usually occurs, producing 2 new cells
Importance of mitosis in the life of an organism
Repairing damages tissues or replacing cells
Asexual reproduction
How does prokaryotic cells replicate
Binary fission:
1) Circular DNA and plasmids replicate
2) Cytoplasm expands as each DNA molecule moves to opposite poles of the cell
3) Cytoplasm divides
4) 2 daughter cells. Each with a single copy of DNA and a variable number of plasmids
Describe what is meant by the fluid mosaic model
Molecules within membrane can move laterally
Mixture of phospholipids, proteins glycoproteins and glycolipids
Structure of cell membrane
Phospholipid bilayer
Phosphate heads are hydrophilic and so are attracted to water. Tails are hydrophobic and repel water
Embedded proteins
Channel and carrier proteins
Glycolipids and glycoproteins
Cholesterol
Importance of mitosis in the life of an organism
Parent cell divides to produce 2 genetically identical daughter cells for:
- Repairing damaged tissues/replacing cells
- Asexual reproduction
How does cancer treatement control cell division
