- All living organisms are made of cells - A semi-independent living unit within the organism/independent living unit in a unicellular organism which has the mechanisms for metabolism, growth and replication (by meiosis/mitosis/binary fission) - Consists of an aqueous solution (cytoplasm) of membrane bound/non-membrane bound organic molecules (organelles)

- uni-cellular/multi-cellular organism with chromosomes enclosed in the nucleus - have cytoplasmic membrane-bound organelles - DNA divided into a series of linear chromosomes - large differences between cells in the same organism - Animals, plants, fungi, protozoa (unicellular eukaryotes) and algae

- assembly of nucleic acid (DNA/RNA) and proteins which is parasitic on prokaryotes/eukaryotes. - Invade host cells, subvert protein synthesis mechanism to reproduce before escaping host cell to invade other cells. - NOT CELLS OR ORGANISMS-- lack plasma membrane and requires a host to survive

Cells and Organelles Flashcards by Aqeel Mohamed

What are “communities of cells”

Higher organisms (e.g. humans) 
Individual cells perform specialised functions

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What is a cell?

All living organisms are made of cells
A semi-independent living unit within the organism/independent living unit in a unicellular organism which has the mechanisms for metabolism, growth and replication (by meiosis/mitosis/binary fission)
Consists of an aqueous solution (cytoplasm) of membrane bound/non-membrane bound organic molecules (organelles)

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What is an organelle?

Sub-unit within a cell, with a defined structure and performing specific, integrated activities
Either membrane-bound/non-membrane bound

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What is tissue?

-assembly of cells and their extracellular products (extracellular matrix, connective tissue and lymphoid) co-ordinated to carry specific related functions in the body

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What is an organ?

-Assembly of related tissues coordinated to perform specific related functions within the body

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What is a system?

-Assembly of organs with specific related functions that are regulated the same way (e.g. respiratory) OR be diffused functional network of cells located around the body, with specific related functions (e.g. immune)

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What is the extracellular matrix?

-Extracellular matrix (collagen, enzymes and glycoprotein) provides strength and structural integrity to cells

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What is a prokaryote?

uni-cellular organism with the chromosome (genetic material) lying free in the cell as a circular strand
no membrane-bound organelles
bacteria

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What is a eukaryote?

uni-cellular/multi-cellular organism with chromosomes enclosed in the nucleus
have cytoplasmic membrane-bound organelles
DNA divided into a series of linear chromosomes
large differences between cells in the same organism
Animals, plants, fungi, protozoa (unicellular eukaryotes) and algae

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Why are the differences between prokaryotes and eukaryotes significant in terms of pathoogen site detection?

Prokaryotes are usually pathogens
Differences between prokaryotes and eukaryotes indicate target sites against the prokaryote pathogen without harming the infected eukaryote (human)

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What is a virus?

assembly of nucleic acid (DNA/RNA) and proteins which is parasitic on prokaryotes/eukaryotes.
Invade host cells, subvert protein synthesis mechanism to reproduce before escaping host cell to invade other cells.
NOT CELLS OR ORGANISMS– lack plasma membrane and requires a host to survive

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What is the drawback of EM?

Image produced may not be a 100% reality
Preperation of sample and the fact that the sample is deceased means that the image may not be 100% accurate to a normal living cell.
Preparation is labour intensive

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What is a Transmission Electron Microscope (TEM) used for?

To look inside cell specimen
electrons pass through the specimen (based on density)
Osmium tetroxide stabilsises lipids unlike in light microscope sample prep

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What is a Scanning Electron Microscope (SEM) used for?

To see the specimen cell surface

- electrons deflected off cell surface by heavy metal coating (which is applied during prep)

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At what distance is diffusion efficient?

50μm

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What limits the maximum size of a cell?

Diffusion is inefficient >50μm
As SA:Vol decreases (cell gets bigger), distance from nuclues to periphery to increases, causing less efficient diffusion hence why most cells are approx similar size

What do specialised cells with a large SA:Vol ratio have to overcome inefficient diffusion?

Thin permeable membrane
Transport of substances around cell via cytoskeleton and vesicles
Multinucleate so gene expression/transport can occur at multiple sites
Gap junctions which are channels between cells to allow movement of substances

What is the benefit of membrane-bound organelles?

Allows organelles to exist in a specialised environment so different cellular processes can operate under different conditions (e.g. a specific optimum pH for an enzyme)
Cell can have numerous different functional compartments

What is the cytoskeleton?

Arrangement of protein filaments (actin, microtubules and intermediate)
Control mechanical strength
Control shape
Guide movement of substances in vesicles
Control location of organelles

What is cytosol?

Aqueous environment within plasma membrane

What is cytoplasm?

Cytosol along with cellular organelles

What is the Nucleus?

Site of genetic material of the cell which is organised as chromosomes that exist as chromatin
Chromosomes only visible during cell division.

What is chromatin?

Chromosomes are condensed to form chromatin
Chromatin is a complex of DNA/histone and non-histone proteins
DNA packaged around histones to form nucleosome

Why is DNA packaged around histones?

Non-packaged DNA = 1.8m

Nucleosomes= 95mm

What is the nucleolus?

-Site of rDNA (hence rRNA synthesis) and ribosome assembly

What is the function of the nuclear envelope?

-Double membrane that surrounds the nucleolus that regulates the transport of substances in/out

What is the function of Smooth Endoplasmic Reticulum?

- Made up of cisternae - Biosyntheses if membrane lipids and steroids, start of N-linked glycosylation and detoification of xenobiotics (toxin) via peroxisomes

What is the function of Rough Endoplasmic Reticulum?

- Made of cisternae - SER + RER are continous set of endosomes - Consists of ribosomes on surface - Site of translation/protein synthesis/cleavage - Proteins are folded via Cys-Cys disulfide bridges - Vesicles consisting of newly synthesisied protein pinch of RER

What is the Golgi Apparatus?

4-8 closely stacked cisternae - Modifies protein (N-linked carbs + glycosylation of O-linked carbs and lipids) delivered from RER via vesicles - Synthesise secretory products - Direct newly synthesised protein to correct compartments - Transport substances around cell - produce lysosomes

Why can lysosomes be a target site against pathogens?

Because it is membrane bound, it creates a specific environment for the survival of that cellular component If that lyosome is destroyed, that cellular component wouldn't be able to surivive which can cause the pathogen to die.

What are secretory vesicles?

Membrane bound Pinch off golgi apparatus and coalesces with the inside of plasma membrane before contents are secreted via exocytosis Composition is similar to the plasma membrane hence allowing exocytosis

What are peroxisomes?

Membrane-bound Synthesised by SER Involved in detoxification incl. hydrogen peroxide Involved in phospholipid synthesis Oxidation of Very Long Chain Fatty Acids (VLFCA)

What are lysosomes?

Membrane-bound Involved in organelle autophagy (turnover/replacement) >50 different hydrolytic enzymes that can hydrolyse all major cellular macromolecules Has a low pH due to acidic hydrolytic enzymes

What is the mitochondria?

- Double membrane bound - Contains some DNA to encode some of its own proteins (own genome)-1% of overall genome - Site of Kreb's cycle and Electron Transport Chain - Inner membrane is tightlly folded to form cristae that extends into the matrix which increases SA for enzymes to embed in

How does fitness influence number of mitochondria

The more active you are, the greater the number of mitochondria as your body has an increased metabolic activity. This could explain why fitter people have better post-injury/op outcomes as their energy levels are not a limiting factor in recovery.

What is the use of a light microscope?

Overall tissue organisation can be seen and individual cells distinguished