structure and functions in living organisms Flashcards
describe the nucleus/function of the nucleus
- controls activity of cell (by making proteins)
- contains chromosomes - strands of DNA which carry genes (each gene codes for a protein)
describe the cell membrane/function of it
the boundary between cytoplasm & the cell’s surroundings, controls what substances enter/leave cell (selectively permeable)
describe cytoplasm/function of it
jelly-like liquid where chemical reactions occur
describe the mitochondria/function of it
carries out some reactions of aerobic respiration, producing ATP (energy carrier molecule)
describe ribosomes/function of it
synthesise (assemble) proteins from amino acids
describe chloroplasts/function of them
they absorb light energy and use it to carry out the chemical reactions of photosynthesis, making biological molecules for plant cells
describe the cell wall/function of it
made of cellulose (a carbohydrate) in plants, helps to keep plant cells in a fixed shape (so keeps the plant upright)
describe the vacuole/functions of the vacuole
it’s filled with a watery liquid called cell sap; stores dissolved sugars, mineral ions and other substances
similarities in structure of plant and animal cells?
- nucleus
- cell membrane
- cytoplasm
- mitochondria
- ribosomes
differences in structure of plant and animal cells?
only plant cells have chloroplasts, vacuoles, and cell walls
2.7 identify the chemical elements present in carbohydrates
carbon, hydrogen, oxygen
2.7 identify chemical elements present in proteins
carbon, hydrogen, oxygen, nitrogen
2.7 identify chemical elements present in lipids
carbon, hydrogen, oxygen
2.8 describe the structure of carbohydrates
- simple sugars (e.g. glucose & fructose) smallest units of carbohydrates
- 2 sugar molecules can be joined together, e.g. glucose + fructose makes sucrose - a complex carbohydrate
- many sugar molecules (1000s) joined together to make complex carbohydrates
- starch & glycogen made from simple sugars
what is starch used for?
used to store glucose in plants
what is glycogen used for?
used to store glucose in animals & fungi
2.8 describe the structure of proteins
- large molecules made up from smaller basic units - made of many amino acids joined together
- 20 different amino acids which can be combined in any order, resulting in millions of different protein structures
- shape of a protein helps it to carry out its job
what are the functions of protein in the body?
- structural molecules (e.g. collagen & keratin)
- controlling chemical reactions - these are enzymes
- messenger molecules - hormones
- combating disease - antibodies
- transport - e.g. haemoglobin & cell membrane proteins
2.8 describe the structure of lipids
- large molecules made up of 3 fatty acids joined to 1 glycerol molecule
functions of lipids?
- energy storage (can also be used in respiration)
- part of cell membranes
- thermal insulation
- electrical insulations - around nerve cells
- buoyancy - helps marine animals like whales to float
2.9 practical: investigate food samples for presence of glucose/reducing sugars
- crush up food sample
- add benedict’s solution to it (in solution)
- place in a water bath at 80°C for 5 mins
- if a reducing sugar is present the colour will change from blue to—> brick red
- if it’s green, yellow, orange it’s still positive result but lower concentration of the sugar
2.9 practical: investigate food samples for presence of starch
- add few drops of orange iodine solution to sample on a spotting tile
- a blue-black colour indicates presence of starch
2.9 practical: investigate food samples for presence of protein
- add 2cm squared water to food sample & shake (if not already liquid)
- add equal volume of dilute potassium hydroxide & shake
- add 2 drops of 1% copper sulfate solution
- if protein present then pale purple colour will develop
2.9 practical: investigate food samples for presence of lipids
- emulsion
- food sample placed in test tube
- add small volume of absolute ethanol & shake to dissolve any lipid in the alcohol
- add equal volume of water
- a cloudy white colour (caused by an emulsion forming) indicates presence of lipid
2.10 what is the role of enzymes?
biological catalysts in metabolic reactions
definition for a catalyst
a catalyst is a chemical which increases the rate of a reaction without being used up itself in the reaction
2.11 how does temperature affect enzyme function?
- temperature increase = enzyme & substrate have more KE, move faster & so more successful collisions
- all proteins held together by forces between different parts of amino acid chain. high temps & changes of ph disrupt these forces, so shape changes
- protein is denatured
- in enzymes, active site changes shape so no longer complementary to substrate
2.12 practical: investigate how enzyme activity can be affected by changes in temperature
- add 5cm cubed starch solution to test tube & heat to temp being investigated using water bath
- add drop of iodine to each of the wells of a spotting tile
- use syringe to add 2cm cubed amylase to starch solution & mix well
- every min, transfer droplet of solution to new well of iodine solution (which should turn blue-black)
- repeat this transfer process until iodine solution stops turning blue-black (this means amylase broken down all starch)
- record time taken for reaction to be completed
- repeat investigation for range of temps (20°C-60°C)
2.12 practical explanation (investigate how enzyme activity can be affected by changes in temp)
- amylase enzyme which breaks down starch
- quicker reaction completed, faster enzyme is working
investigation shows:
1. at optimum temp, iodine stopped turning blue-black the fastest: this bc enzyme working at its fastest rate & has digested all starch
2. at colder temps (below optimum), iodine took longer time to stop turning blue-black: this bc amylase enzyme working slowly due to low kinetic energy & few collisions between amylase & starch
3. at hotter temps (above optimum) iodine turned blue black throughout whole investigation: this bc amylase enzyme denatured & so can no longer bind w starch or break it down
2.13 how can enzyme function be affected by changes in pH?
all proteins held together by forces between different parts of the amino acid chain. changes of pH disrupt these forces, so shape changes
- protein is denatured
- in enzymes, active site changes shape so no longer complementary to substrate
2.1 describe levels of organisation in organisms: organelles
structures that carry out specific processes the cells need to survive
2.1 describe levels of organisation in organisms: cells
the smallest functional unit of life & contain a number of organelles
2.1 describe levels of organisation in organisms: tissues
groups of similar cells, which work together to carry out the same function
2.1 describe levels of organisation in organisms: organs
made up of several different tissues working together to carry out a more complex function
2.1 describe levels of organisation in organisms: organ systems
made up of several different organs working together to carry out a complex function essential to life
