Bio Unit 1.2 (Cells) Flashcards
What are the membranes surrounding cells made of and why can’t a light microscope distinguish them?
Phospholipids and proteins, the membranes are too thin to be distinguished by a light microscope
What is the advantage of eukaryotic cells having membrane bound organelles?
Harmful chemicals can be isolated and molecules with a particular function can be concentrates to one area
Prokaryotic Cell Wall substance
peptidoglycan
Prokaryotes
(e.g bacteria cells), basic, smaller structure with no internal membranes and membrane bound organelles, DNA free in cytoplasm
Eukaryotic cells
(plants, animals, fungi, protoctists), distinct nuclei, several membrane bound organelles
Plant Cell Wall substance
cellulose
Respiration in Prokaryotic Cells
mesosomes, infoldings of plasma membrane where respiration occurs
Respiration in Eukaryotic Cells
mitochondria site of aerobic respiration
Ribosome size in prokaryotic and eukaryotic
70S and 80S
DNA present in Prokaryotic
Plasmids are present (rings of DNA)
DNA present in Eukaryotic
Chromosome strands in nucleus (linear)
Why can’t viruses be seen by a light microscope?
Too small so they can pass through the filters that trap the bacteria
Viruses are acellular
no cells, no organelles, no cytoplasm
Three components of a virus
nucleic acid, DNA, protein coat (capsid)
Viruses that attack bacteria
bacteriophages (eg. T2 virus attacks E.Coli)
Size of nucleus
10-20 micrometres
Viruses considered living thing?
Viruses can be crystallised, but can reproduce with host (e.g flu in humans, avian flue in birds, TMV in plants)
Function of nucleus
Contains DNA which with protein comprises the chromosomes, chromosomes direct protein synthesis
Nucleus bounded by…
(2 membranes) nuclear envelope with pores to allow passage of larger molecules(mRNA and ribosomes)
The outer membrane of nucleus is continuous with…
endoplasmic reticulum
Granular material in nucleus
Nucleoplasm
What is nucleoplasm
contains chromatin (coils of DNA bound to protein) - during cell division chromatin condenses into chromosomes
Nucleolus
spherical bodies which are the sites of formation of rRNA (constituent of ribosomes)
Mitochondria Size
1- 10 micrometres
Mitochondria membrane
2 membranes separated by narrow, fluid filled inter membrane space
Organic Matrix of Mitochondria
Solution containing many compounds like lipids, proteins, etc.
Why is there a small circle of DNA in mitochondria?
So mitochondria can replicate and code for some of its proteins and RNA
Size of ribosomes in mitochondria and function?
70S which allow protein synthesis
Mitochondria Function
to produce ATP in aerobic respiration (reactions occur in matrix and aerobic respiration)
Function of Cristae
Provides large surface area for attachment of enzymes involved in respiration
More mitochondria will be in..
Metabolically active cells (muscle cells) as they need lots of ATP so more mitochondria
Mitochondria being cylindrical provides…
Large surface area (surface area to volume ratio is bigger than sphere)
Reduces diffusion distance between edge and centre (more efficient aerobic respiration.)
Where do you find chloroplasts?
In cells of photosynthesising tissue (in plants highest concentration is in palisade mesophyll cells)
Chloroplasts surrounded by
chloroplast envelope
Stroma contains…
fluid filled (contains products of photosynthesis such as liquid droplets, starch grains) and takes up large space
Ribosomes in chloroplasts are
70S
What is found in thylakoids?
chlorophyll
DNA in chloroplasts are
circular
Each granum has between:
2 and 100 parallel sacs
Within stroma
closed, flattened sacs called thylakoids (one stack of thylakoids is a geranium.)
Why are thylakoids useful?
Large surface area, efficient from trapping light energy
What is endosymbiotic theory?
Describes origin of mitochondria and chloroplasts: 1920’s - mitochondria were once independent bacteria, ancient bacteria engulfed others (maintaining symbiotic relationship) and some of this engulfed bacteria was good at turning glucose and oxygen into ATP (chloroplasts.) Evidence now that chloroplasts and mitochondria have their origins in prokaryotes
Endoplasmic Reticulum
System of parallel double membranes forming flattened sacs with cisternae (interconnected fluid filled spaces)
Rough ER
ribosomes on outer surface, transports proteins made there, present in large amounts in cells (makes a lot of protein e.g cells making amylase in salivary glands)
Smooth ER
membranes lack ribosomes, synthesis and transport of lipids, cells that store carbs, proteins, lipids (e.g in liver, secretory cells) have extensive ER
Where do ribosomes assemble?
Nucleolus from rRNA and protein
2 subunits of ribosomes
rRNA and protein
Where do ribosomes attach to?
RER membrane
What do ribosomes do?
Protein synthesis, mRNA and tRNA used to assemble polypeptide chain
Ribosomes in cytoplasm…
Synthesise proteins kept in the cell
What are 2 centrioles at right angles called?
Centrosomes
What is ‘read’ at ribosomes?
triplet codes of bases on mRNA
Where are centrioles found?
Animal cells and protoctistans (in cytoplasm next to nucleus)
What are centrioles made of?
9 microtubule triplets in a cylindrical arrangement (made from protein - tubulin)
What happens to centrioles before cell division?
Replicate, move to opposite poles of the cell
What do centrioles do?
synthesise microtubules of the spindle apparatus
What does Golgi body do?
Packages and processes proteins (encloses them in membranes) to form vesicles/lysosomes
What does Golgi body do to secretory enzymes?
Packages them to be exported out of cell as well as hormones like insulin.
What does Golgi body do to lipids?
Transports and stores lipids from SER (makes glycolipids)
Golgi body made from…
Flattened stacks of cisternae
What do lysosomes do?
Contains many enzymes (mostly digestive) to prevent them from digesting cell contents.
When is function of digestion in lysosomes utilised?
Digestion of bacteria previously engulfed by phagocytes, digestion of worn out cell organelles, lysosomes also break down dead cells (lysis)
How does lysosomes digest material which has been taken into cell?
Lysosome fuses with vesicle made when phagocyte engulfs bacteria by phagocytosis and enzymes digest bacteria
What are lysosomes?
Spherical vesicles bounded by a single membrane, originated from the Golgi body containing enzymes
Why is vacuole temporary in animals?
Waste products can accumalate
Vacuoles in animals are…
temporary store for sugars, amino acids and minerals
How does vacuole support cell?
Takes in water, making cell turgid as pushes against cell wall, prevents plant cells from wilting
What are cellulose molecules held together in?
Microfibrils embedded in peptin
Tonoplast
single membrane of vacuole
Cell Wall Function 2
Mechanical Strength - structure of microfibrils/laminated arrangement makes cell wall very strong, vacuole full of solution pushes against cell wall (turgidity)
Cell Wall Function 1
Transport - gaps in cellulose fibres make cell wall fully permeable to water and dissolves molecules and ions. Spaces called apoplasts. Apoplast pathway is main route of water across plant roots
Cell Wall Function 3
Plasmodesmata passes through pits (strands of cytoplasm), Network of cytoplasm called symplast, Symplast pathway important in water transport
Energy Store In Animals
Glycogen
OAI) Nucleus contains chromosomes in which…
DNA encodes proteins
Energy Store in Plants
Starch
OAI) What happens to mRNA molecules from nucleus?
Nuclear pores in nuclear envelope allow mRNA molecules to leave nucleus and attach to ribosomes in cytoplasm/rough ER
OAI) What do ribosomes contain?
rRNA - transcribed from DNA at nucleolus
OAI) What happens to rRNA at ribosomes?
Protein synthesis - forming polypeptides
OAI) Route of polypeptides from ribsosomes?
Moved through RER and packaged into vesicles
OAI) From RER what happens to vesicles?
Vesicles bud off RER and carry polypeptides to Golgi body to be chemically modified and folded
OAI) From the Golgi body what happens?
Newly synthesised proteins are packaged into vesicles
OAI) 3 Vesicles from Golgi Body Examples
Lysosomes containing digestive enzymes used within cell, secretory vesicles carry proteins to cell membrane for exocytosis, phospholipids+triglycerides move through SER to various destinations
OAI) Route Through Organelles
Nucleus, Ribosomes on RER, Through RER, Golgi body, Various destinations
Where do single celled organisms carry out all life functions?
In one cell
How do multicellular organisms carry out life functions?
Specialised cells forming tissues and organs
Development of a cell into specific type is called….
differentiation
As differentiation occurs what happens to the cell?
Structure becomes more specialised and chemical reactions performed are more specialised
Tissue Basic Explanation
Cells near each other in the embryo differentiate in the same way and group together as a tissue
All Epithelial Tissues have these three things.
Forms a continuous layer on the lining of internal/external surfaces of the body
No blood vessels but may have nerve endings
Cells (varied in shape and complexity) sit on basement membrane (collagen+protein)
What functions do epithelial tissues usually have?
Secretory/protective
Shape of cuboidal epithelium and where can you find it?
Cube shape cells on basement membrane - one cell thick (one layer)
Can be found in proximal convoluted tube of kidney nephron and in salivary gland ducts
Shape of squamous epithelium and where can you find it?
Multiple layers, flattened cells on basement cells
Can be found in alveoli walls. Bowman’c capsule lining of nephron
Shape of columnar epithelium and where can you find it?
Elongated cells, cilia, on basement membrane, nucleus toward the bottom
Can be found in fallopian tube and trachea
3 Types of Muscle Tissues
Smooth, Skeletal, Cardiac
What do skeletal muscle tissue do?
Attached to bones and generates locomotion
Why do skeletal muscles have powerful contraction?
Bands of fibres present
What kind of muscle is it as they tire easily?
Voluntary Muscle (choose to contract)
How does skeletal muscle tissue look under the microscope?
Striated/Striped
How do smooth muscles contract?
Rhythmically but less powerful than skeletal
Where can you find smooth muscles?
Skin, blood vessel walls, digestive/respiratory tracts
Smooth muscles move by themselves making them?
Involuntary
How do smooth muscles look under the microscope?
Unstriated (no stripes)
Where are cardiac muscles found?
In the heart
Function of cardiac muscle (shares skeletal and smooth properties)
rhythmically contracts without any nerve stimulation but nerves/hormones can modify contraction
Does not tire
Role of Connective Tissue
Connects, supports or separates tissues/organs
What fibres does connective tissue have?
Elastic and collagen fibres in an extracellular matrix
What are between the fibres of the connective tissue?
Adipocytes and cells of immune system
Organ definition
groups of tissue in a structural unit working together to perform a specific function
Leaf Example of an Organ Description
Leaf contains epidermal tissue, vascular tissue, packing tissue between vascular bundles - specialised for photosynthesis
Organ System Definition
Group of organs working together with a particular role
