Biology summer exam revision

*Do practice question on One note”

Cell structure

Eukaryotes (5-100um)are larger than prokaryotes(0.2-2um)

prokaryotic:

  • cells of bracteria

  • cell membrane on the outer layer of the cell

  • cell contains cytoplasm, ribbosome but no mitochondria or chloroplast

  • Dna is a single molecule found free in the cytoplasm - additional DNA is found on one or more rings called plasmids

  • divides by binary fission

Eukaryotes:

  • cells of animals, fungi, and plants

  • outer layer of cell membranw - surrounded by cell wall in plants and fungi

  • cell contains cytoplasm, cell organelles include mitochondria, cholorplasts in plants and ribosomes

  • DNA in nucleus

  • cell division by mitosis

Smallest to largest:

Organells

  • Cell

  • Tissue

  • Organ

  • Organ system

  • Organism

tissue - is a group of cells that work together for a common goalmm → um = x1000

um → mm = /1000

culture medium: is a liquid or gel that contains carbohydrates for energy and nitrogen for building proteins

tempretures above 25 degrees can cause dangerous bacteria to form

bacteria at the end of growth = number bacteria at begininning x 2 to the power of number of divisions

to prevent bacteria growth:

  • lowering or raising tempreture

  • disinfecting kills bacteria

  • antiseptics kills bacteria

  • Antiseptics kills bacteria

  • Antibiotics are used to kill bacteria inside humans.

the larger the inhibition zone is the more effective the disinfectant is


Cell division

genes - a section of DNA that contains information that controls specific characteristics

DNA - (Deoxyribonucleic acid) contains your entire genome that make up all of your characteristics

Allele - One of two or more versions of DNA sequence (a single base or segment of bases) at a given genomic location

Mitosis - a process by which a cell produce identical copies of itself for growth or repair

Meiosis

Mitosis

  • Creates DIPLOID daughter cells

  • Mitosis makes a cell Identical to itself

  • Mitosis is asexual reproduction

Meiosis

  • Creates HAPLOID daughter cells

  • meiosis makes cell with the chromosomes of the parent

  • Meiosis is sexual reprodcution

Diploid = 46 chromosomes

Haploid = 23 chromosomes

Size order: (smallest to largest)

  1. Gene

  2. DNA strand

  3. Chromosome

  4. Nucleus

  5. Cell

why is variation important?

variation is important because it makes us less vulnerable to environmental change which allows us to adopt to change in the environment

Stem cells

  • Stem cells are undifferentiated cells that are able to differentiate into specialized cell types

  • a single stem cell can replicate itself or differentiate into many cell types

  • Locations - Bone marrow, skin, Brain, eye, embryo’s

  • However from adults the can only differentiate into a small number of cells,

  • For embryo’s they can differentiate into anything

  • scientist had found embryotic stem cells in the umbilical cord blood of new born babies which means in the future it might be possible to get embryotic stem cells without destroying the embryo (future)

  • For adults its an easy process

  • For embryo’s its a difficult process

  • Can cure diseases such as diabetes, eye conditions, heart damage after attack, spinal cord injuries

stem cells in plants

  • found in the meristems of plants.

  • disease resistant

  • prevent rare species going extinct

  • Cheap and quick production of food


Movement of substances (transport)

Diffusion is the passive movement of molecules from a region of high concentration to a region of lower concentration down the concentration gradient

Accuracy - how close a measurement is to the true value

Precision - how close the measurement are to each other

Validity - are the values describing what was supposed to be measured?

Resolution of equipment is the degree at which a piece of equipment can measure to.

Solute + Solvent = Solution

Solute: a dissolved substance in the solvent

Solvent: a liquid used to dissolve a solute

Solution: a liquid mixture in which the solute is uniformly distributed within the solvent

Osmosis is the passive movement of water molecules from an area of high water potential to an area of low water potential across a partially permeable membrane

HWP: Low concentration of solute (dilute solutions)

LWP: High concentration of solutes (concentrated solution)

Active transport - substances that are absorbed against the concentration gradient, from low to high concentration.

ATP - Adenosine trisphosphate

Active transport requires energy which is released via aerobic respiration in the mitochondria in the form of ATP

Glucose sugar in the gut

Often absorbed against the concentration gradient

Glucose if used to produced energy via aerobic respiration

Glucose + oxygen → carbon dioxide + water + (enerygy)

Surface area to volume ration

High surface area: volume ratio = efficient transfer of substances e.g Jellyfish 6:1

Low surface area : volume ration = inefficient transfer of substances e.g hippo 2:1


Bioenergetics

Photosynthesis is the process that plants use to convert carbon dioxide and water into glucose and oxygen

Glucose is turned into starch for late use

Starch is insoluble which makes it much better for storing in plants

to test for starch in plants iodine solution turns from orange to blue

In humans:

Aerobic respiration:

oxygen + glucose → carbon dioxide + water

complete oxidation of glucose

produces more energy

Anaerobic respiration in humans:

glucose → lactic acid

Incomplete oxidation of glucose released less energy

oxygen debt - after exercise, lactic acid must be removed. Lactic acid is oxidised to carbon dioxide and water. This process requires oxygen which can increase a persons breathing and heart rate and lead it to take longer to return to normal

aerobic respiration in plants (also known as fermintation)

glucose → ethanol + carbon dioxide

carbon dioxide makes the bread rise.

ethanol is the alcohol

glycogen is a stored form of glucose