Cells (2) Flashcards
What are the 2 main groups of cells?
Eukaryote and prokaryote
What characterises a eukaryote?
Presence of a nucleus and cytoplasm containing many cell organelles
What are the 7 main eukaryotic cell organelles
Nucleus
Ribosomes
Endoplasmic reticulum
Golgi apparatus and vesicles
Lysosomes
Mitochondria and chloroplasts
What is the nucleus and it’s properties?
Contains the genetic material (linear DNA), it is bound by a double membrane called the nuclear envelope which has nuclear pores allowing communication with cytoplasm. The nucleus controls protein synthesis and thus the development and function of a cell.
What are ribosomes and their properties?
Very small organelles made up of protein and ribosomal RNA, they can be present in the cytoplasm singly or attached to the RER. They are used in protein synthesis joining AA together.
What are the 2 types of endoplasmic reticulum?
Soft and rough
What does the RER do?
Has ribosomes that produce secretory proteins which are sent to the Golgi apparatus for modification and/or packaging
What does the SER do?
Lacks ribosomes and is involved in the production and transport of lipids
What does the Golgi (apparatus) do?
Adds carbohydrates to proteins received from RER to form glycoproteins, modifying and packaging then into Golgi vesicles for secretion. This produces lysosomes (a vesicle that releases lysozymes aka hydrolytic enzymes)
What is the Golgi apparatus?
Flattened membrane sacs that are abundant in secretory cells eg in the pancreas
What are lysosomes?
Simple sacs containing hydrolytic enzymes surrounded by a single membrane these are formed by the Golgi apparatus
What are the functions of lysosomes?
1- digestion of material taken in by phagocytosis
2- digestion of engulfed non functioning organelles
3- releasing enzymes outside the cell
What is mitochondria used for?
Aerobic respiration (produces atp)
What are the functions/characteristics of mitochondria?
- bounded by 2 membranes forming an envelope around an inner matrix
- between 2 membranes is the inter membrane
- the folds of the inner membrane are called cristae
- matrix contains enzymes for respiration and DNA and ribosomes
What are the characteristics/properties of chloroplasts?
- only found in photosynthetic plant cells and algae
- within the chloroplast there is a membrane system consisting of many flattened sacs called thylakoids
- granum provides a large surface area for photosynthesis
- the stroma contains enzymes sugars and starch granules
What additional structures do eukaryotic plant cells have?
A cellulose cell wall consisting of cellulose microfibrils
Chloroplasts
A large permanent vacuole containing soluble sugars, salts and sometimes pigment
What cell wall does algae have?
Cellulose or/and glycoproteins
What cell wall does fungi have?
Chitin (polysaccharide) and a polysaccharide called glycan and glycoproteins
What is cell differentiation?
Specialised cells developed to perform specific functions, the development of cells into specialised types is cell differentiation
What are the 4 cell groups?
Cells
Tissues
Organs
Organ systems
What are prokaryotes?
Very small single called organisms with no nucleus and no membrane bound organelles in their cytoplasm
What do TYPICAL prokaryotes always contain?
- murein cell wall
- cell surface membrane
- circular DNA (free in cytoplasm)
- ribosomes (smaller than eukaryotes)
- cytoplasm
What structures MAY be present in prokaryotes?
- capsule surrounding cell wall
- one or more plasmids
- one or more flagella
What are viruses?
Acellular non living cells with no nucleus, no organelles, no cell surface membrane and no cytoplasm
What does a typical virus particle have?
- genetic material (DNA/RNA)
- capsid
- attachment proteins on outside
What are the 2 main branches of microscopes?
Light and electron
What are the 2 types of electron microscope?
Transmission and scanning
What does a light microscope do?
Light passes thru a specimen usually mounted on a glass slide; this is prepared quite easily and quickly. The specimen must be thin and stained
What does an electron microscope do?
Uses a beam of electrons focused by electromagnets to produce an uncoloured 2D or 3D Image
What is the average resolution and magnification of a light compared to electron microscope?
Light: 200nm resolving power, x1500 magnification
Electron: 0.5nm resolving power, x1,000,000 magnification
Why does electron have a greater resolution?
Shorter wavelength
What are the disadvantages of electron?
Vacuum requires
Complex to prepare specimens
Extremely large and expensive
What is the difference between TEM and SEM?
In tem: specimen is stained using electron dense substances as these deflect electrons, tem is higher resolution and gives a 2D image
In sem: specimens are coated with a thin film of a heavy metal such as gold, sem gives a 3D Image and sections can be thicker
What are artefacts?
Parts of the image with poor preparation
What is the general formula for magnification?
M = I/A
What is mitosis?
Type of nuclear division which produces cells that are genetically identical
What are the 3 sections of the cell cycle ?
Interphase, mitosis and cytokinesis
What are the 4 phases of mitosis?
Prophase
Metaphase
Anaphase
Telophase
What happens in interphase?
Rapid multiplication and replacement of cells; DNA content is doubled via DNA replication, increase in protein synthesis, cell organelles are replicated
What is prophase?
Chromatids become visible, centrioles move to opposite piles of the cell and the nuclear membrane breaks down
What happens in metaphase?
Centrioles form a spindle across the cell which consists of protein microtubules, each chromosome moves to the equator
What happens in anaphase?
The centromere splits and sister chromatids seperate, being pulled to opposite poles by the spindle
What happens in telophase?
Chromatids are at opposite poles and begin to uncoil, nuclear membrane reforms. The two cells are genetically identical to eachother and to the original parent
What is cytokinesis?
The splitting of the cytoplasm into two, two new cells form as a cell surface membrane forms (and a cellulose cell wall in plants)
What is cancer?
The uncontrolled and rapid cell division and growth (mitosis) results in a group of abnormal cells called a tumour.
How do cancer treatments work?
Inhibiting the enzymes DNA helicase or DNA polymerase OR to inhibit the formation of the spindle
The 2 causes of cancer are:
Proto-oncogenes - increase rate of mitosis and a mutation can cause cells to divide too rapidly
Tumour suppressor genes - decrease rate of mitosis and a mutation can cause cells to divide too rapidly
What is a benign and malignant tumour?
Benign- slow growing, remain in one place
Malignant- fast growing and can spread
