biology 1

cell structure

cells are the smallest unit of life that can replicate independently

animal

• eukaryotic

• cell membrane → control which substances pass in and out of the cell

• nucleus → contains DNA

• cytoplasm → where chemical reactions take place

• mitochondria → provide cells with energy

• ribosomes → site of protein synthesis

plant

• eukaryotic

• cell wall → support and structure

• vacuole (permanent) → contains cell sap

• chloroplasts → where photosynthesis happens (contains chlorophyll to absorb light energy for photosynthesis)

bacteria

• prokaryotic

• single-cellular

  

• don’t have a nucleus instead have strands of DNA (nucleiod)

• don’t have chloroplasts or chlorophyll

• some have plasmids → extra small loops of DNA

• flagella → tails to propel the bacteria forwards

diffusion

DIFFUSION IS A PASSIVE PROCESS

→ diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration

• diffusion can occur in gases and liquids

diffusion can also take place THROUGH partially permeable membranes (usually only very small molecules can diffuse through)

    factors affecting rate of diffusion (increasing these factors increases rate of diffusion)

• concentration gradient

• temperature

• surface area

osmosis

osmosis is the diffusion of water molecules

→ it is defined as the net movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration

→ water concentration means the amount of water as compared to other molecules, called ‘solutes’ that are dissolved in the water

IT IS NOT ABOUT VOLUME OF WATER BUT ABOUT THE RATIO OF WATER TO SOLUTES

inside a cell we have lots of water and solute particles

outside we have almost pure water

therefore water particles will diffuse from the outside of the cell to the inside of the cell

active transport

→ defined as the net movement of molecules from a lower concentration gradient to a higher concentration requiring energy from cellular respiration

→ therefore it requires energy from the cell

• active transport always takes place across a cell membrane and it also requires special proteins

IN ROOT HAIR CELLS (which have large surface area due to their shape)

root hair cells need to absorb water (by osmosis) and mineral ions (by active transport because it needs to go against the concentration gradient)

• root hair cells need lots of mitochondria

balanced diet

we need:

• carbohydrates (bread, pasta) → provide us with energy

• lipids (oily fish, avocados, dairy → provide longer term energy to store as fat which also keeps us warm

• proteins (legumes, meat and fish) → need them to grow

• vitamins (fruit and vegetables, sunlight) → helps us absorb calcium

• mineral ions (calcium, iron) → needed for bones and haemoglobin

• fibre (whole bread, brown rice) → helps food move through our intestines more easily

• water (fruit, water) → chemical reactions, most of our body is made of water

biological molecules

biological molecules are molecules found in living organisms and are produced by cells

nutrients are substances that are needed for growth, repair and metabolism

• carbs made of C, H, O

  • monomers like fructose and glucose can bind together to form polymers like starch

• protein is made of amino acids

  • C, H, O, N

• lipids are NOT polymers

  • fat is a lipid which is solid at room temperature

  • made of C, H, O

enzymes

enzymes are biological catalysts

→ catalyst is a substance which increases the speed of a reaction without being changed in the process

enzymes have an active site which is complementary to the shape of the substrate (reactant)

• it has to fit

LOCK AND KEY MODEL (LESS REALISTIC)

we thought a substrate had to be the exact right shape to fit into the active site

INDUCED FIT

we now know the enzyme changes shape a little bit to fit the substrate

temperature - originally enzyme activity increases with temperature because of energy but once we reach 37 degrees some of the bonds in the enzyme begin to break so it starts to change shape or ‘denature’

at first it will not fit as well and rate of reaction will be slower

eventually it will no longer be able to bind to the substrate at all (the damage is also permanent)

optimum temp - the temp where the rate of reaction is highest

pH - same as temperature, most have an optimum temp of 7

digestive enzymes:

→ proteins carbs and lipids are too big to be digested so they need to be broken down by enzymes

• carbs → starch then amylase makes it into maltose then maltase breaks it down into glucose

• proteins → protease breaks it down into amino acids

• lipids → lipase breaks them down into glycerol and fatty acids

  • bile also helps in the breakdown of lipids because it emulsifies them which increases their surface area

• all of the enzymes are made in the pancreas and small intestine

• amylase is made in salivary gland

• protease made in stomach

microscopy

first objective lens - 4x

second - 10x

eye piece lens - 10x

third - 40x

image refers to the image we see when we look down the microscope

real refers to the actual onion cells

magnification means how many times larger the image is than the actual

→ mag = image size/object size

resolution means the shortest distance between two points on an object that can still be distinguished as two separate entities

a cell is 1 - 100 micrometres