How Cells Function Brief Flashcards
What is a prokaryote?
A cell with no membrane-bound organisms
What is a eukaryote?
A cell with membrane-bound organisms
What is the size of a prokaryote?
1-10um
What is the size of a plant cell?
30-50um
What is the size of an animal cell?
10-20um
What is the cell wall in eukaryotes made of?
Present - plants (cellulose), fungi (chitin)
Absent - animals
What is the cell wall of a prokaryote made of?
Murein: carbohydrate and protein mix
How do prokaryotes store DNA?
mostly circular single DNA
How do eukaryotes store DNA?
DNA in linear chromosomes
Are prokaryotes unicelluluar?
Yes
How many cells do eukaryotes have?
Multi or unicellular
What is cell division used for in prokaryotes?
Reproduction
What is cell divison used for in eukaryotes?
growth and repair
What are the benefits of compartmentalisation/having organelles?
Can carry out multiple processes at once with optimal conditions, enzymes and reactants are close together so processes can be efficient, cell is less vulnerable to change b/c cytosol is affected not organelles
What is the function of a nucleus?
Controls activities of the cell and directs protein production
What is the function of a cell membrane?
Encloses cell contents, controls cell input and output
What is the cytosol?
Cell contents: dissolved ions, water, salt, enzymes, organelles. It is the area from the nuclear membrane to the plasma membrane
What is the endoplasmic reticulum?
Network of membranes involved in the transportation of proteins
What is a ribosome?
Cite of protein production
What is a golgi apparatus?
Stacks of flattened membranous sacs involved in modification and packaging of materials for exportation out of a cell
What is a mitochondria?
Cite of cellular respiration
What is the purpose of a cell wall?
Provides structure, prevents lysis
What is the purpose of a vacuole?
Membrane-bound compartment containing fluid with dissolved minerals
Do plants and animals have a vacuole?
Yes, just larger in plants
What is the purpose of a chloroplast?
Photosynthesis
Do animals have chloroplasts?
No
What are lysosomes?
Vesicles that contain enzymes for the breakdown of wastes
DO plant and animal cells have lysosomes?
Only animal
What is the fluid mosaic model?
The idea that a cell membrane has a phospholipid bilayer studded with proteins, that is fluid and moves around
What is the head of the phospholipid?
Water soluble, hydrophilic, polar, glycerol, phosphate containing
What is are the fatty acid tails of the phospholipid?
Water insoluble, hydrophobic, non-polar
What is an integral protein?
A protein embedded inside the phsopholipid bilayer
What is a transport protein?
Carrier and channel protein molecules that allow substances to pass through
What is a receptor protein?
An integral protein that binds to hormones and other substances
What is a peripheral protein?
A protein on the outside of the phospholipid bilayer
What is a recognition protein?
Attachs to carbohydrate molecules (glycoproteins) that act as markers (antigens)
What is an adhesion protein?
Links cells together
Where is a carbohydrate chain found?
Linked to proteins or lipids on the outer surface of the membrane
What is a purpose of a carbohydrate chain?
They are involved in cell recognition and cell adhesion and in the recognition of antibodies, hormones and viruses by cells.
What do cholestrol molecules do?
Provide stability to the membrane and reduce permeability to small water soluble molecules
What depends on surface area?
The rate at which materials enter and leave the cell
What depends on volume?
The rate at which materials are used
What are some substances that use diffusion?
Gases, water-soluble substances, small uncharged particles
WHat is osmotic pressure?
The pressure causing water to move along the concentration gradient
What is plasmolysis?
when water shrinks out of the vacuole in plants
What is crenation?
when water leaves the cells, causing death/damage
What is turgor?
Swelling of vacuole in plants
What is haemolysis?
Swelling of vacuole in animals
What is facilitated diffusion?
Diffusion through a protein channel, no energy used
What molecules use facilitated diffusion?
Ions, amino acids, glucose, certain water soluble molecules
What is active transport?
Movement against concentration gradient that uses energy
What type of molecules use active transport?
Proteins, sugars, ions, most water soluble molecules
What do prokaryotes have instead of a nucleus?
A single DNA chromosome attached to the plasma membrane
Where does replication begin in prokaryotes?
the origin
What happens in binary fission?
The chromosome is duplicated and the two DNA molecules are pulled to separate poles as the cell increases in size. A new cell wall and plasma membrane forms, pinches and creates new daughter cells
How do eukaryotes divide?
mitosis, then cytokinesis
what do multicellular organisms rely on mitosis for?
Growth, repair, development from a fertilised cell
What happens in G1?
Cell growth: Cellular contents, not chromosomes, are duplicated
What happens in S phase?
DNA synthesis: 46 chromosomes is duplicated by the cell, so they now are double-stranded with each strand being a chromatid
What happens in G2 phase?
Post-DNA synthesis: the cell increases in size, accumulates materials for mitosis, checks chromosomes for errors and fixes these
What is interphase?
The phase where chromosomes are duplicated and cell growth occurs
What is mitosis?
The process by which the nucleus of a cell divides, creating two new nuclei each creating an indentical copy of DNA
What is cytokinesis?
Division of the rest of the cell
What are the features of interphase?
Nucleus is well defined, chromosomes are not visible
How long does interphase last?
12-24 hours
What is the order of mitosis?
Prophase, Metaphase, Anaphse, Telophase
What are the features of prophase?
Chromosomes become visible, as they shorten and thicken. They are held together by centromeres. Centrioles move apart, with microtubules of the mitotic spindle continuing to extend from the centrioles. The spindle fibres attach to the kentichores of the chromatids
What are the features of metaphase?
Miotic spindle is fully formed between the pairs of centrioles at the two poles of the spindle. The double-stranded chromosomes line up at the equator of the cell
What happens in anaphase?
Each centromere divides, so the chromatids separate to either side of the cell as the tubules shorten.
What happens in telophase?
The spindle fibres become thinner and less obvious. A new nuclear membrane forms around each group of chromosomes.
What happens in cytokinesis?
In animal cells, plasma membrane moves inwards, pinching the daughter cells apart. In plant cells, a new cell wall and membrane is formed
What is checked at the G1 checkpoint?
Cell growth checkpoint: if the cell is healthy and is at a suitable size, S phase is initiated. If DNA replication is not going to work, G0 is initiated
What happens at the G2 checkpoint
DNA synthesis checkpoint:
Occurs after DNA has replicated itself
DNA repair enzymes are triggered to check the results of DNA replication for errors
If this checkpoint is passed, proteins signal the cell to begin mitosis
What happens at the mitosis checkpoint?
If a cell passes this checkpoint, proteins signal the cell to exit mitosis and enter G1 phases once again
What is apoptosis?
Controlled cell death
What is the role of apoptosis?
Maintenance of adult cell numbers, defense against damaged or dangerous cells, sculpting of embryonic tissue (forming fingers, menstruation, synapses formed)
How does apoptosis occur?
The cell membrane shrinks, DNA fragments, lysosomes empty their contents into the cell causing cellular components to be broken down. The remains are then consumed by phagocytes
What can too little apoptosis lead to?
Cancer
What can too much apoptosis lead to?
Alzeimhers
What is necrosis?
Premature death of cells caused by external factors (e.g. toxins, trauma, infection, etc)
What is the problem with necrosis?
Internal contents may be released and poison surrounding cells
What is the problem with cancer?
Grow when they should not, don’t die when they are meant to
What to cancer cells often have?
Mutated versions of
- proto-oncogenes: regulation of cell division
- tumour suppressor genes: genes involved in the slowing down of cell divison, repair of DNA, apoptosis
What are mutagens?
Agents that modify/alter the DNA sequence
What can mutagens cause?
Developmental abnormalities/cancer because of interfering with regulatory role
How are stem cells different to other cells?
They can self-renew (make copies of themselves) and differentiate (make other types of specialised cells for the body)
Why are stem cells important?
Specialised cells can’t replace themselves
What is a zygote?
A structure that forms when a sperm fertilises an egg
How does a zygote become an embryo?
Divides many times by osmosis
What are embryonic stem cells?
The first eight cells of an embryo. Identical.
Embryonic stem (ES) cells include those found within the embryo, the foetus or the umbilical cord blood. Depending upon when they are harvested, ES cells can give rise to just about any cell in the human body.
What does the blastocyst develop into?
A gastrula with three primary layers called germ layers
What is a blastocyst?
A rapidly dividing ball of cells
What is the outer layer of a gastrula?
Ectoderm
What is the middle layer of a gastrula?
Mesoderm
What is in the inner layer of a gastrula?
Endoderm
What are the two types of stem cells?
Tissue/adult stem cells, embryonic stem cells
What does the outer layer of the blastocyst form?
the placenta
How are embryonic stem cells found?
Taken from inner cell mass and put in fluid with nutrients to cultivate in a lab
What is the potency of embryonic stem cells?
Pluripotent: every cell inside the body
Where are tissue stem cells found?
surface of eye, skin, testicles, brain, breast, bone marrow, intestines, muscles
What does multipotent means
Can specialise into many different types, usually the ones in their germ layer
What is the potency of a blood stem cell?
Multipotent
What does iPS mean?
Induced pluripotent stem cells
How are iPS made?
get stem cells, add particular genes to cells to make them pluripotent. this is genetic reprogramming
What does totipotent mean?
Can become any cells (only first eight in zygote), including placenta
What potency are adult stem cells?
Multipotent
What does unipotent mean?
Can only become one specialised cell
