2. Structure and Functions in Living Organisms: Levels of organisation + Cell structure

what are the levels of organisation?

organelle

cell

tissue

organ

organ system

organism

what is an organelle?

a component within a cell that carries out a specific task

what is a cell?

a basic functional and structural unit in a living organism

what is a tissue?

a group of cells of similar structure working together to perform a specific function

what is an organ?

a group of tissues working together to perform a specific function

what is an organ system?

a group of organs with related functions working together to perform body functions within an organism

give some examples of organ systems in animals and plants

shoot system

root system

digestive system

circulatory system

immune system

respiratory system

excretory system

nervous system

reproductive system

what is the function of the nucleus?

• contains genetic material in chromosomes which control how cells grow and work

• controls cell division

what is the function of the cytoplasm?

• supports cell structures

• site of chemical reactions

• contains water and many solutes

what is the function of the cell membrane?

• holds the cell together

• controls substances entering and leaving the cell

what is the function of the cell wall?

• gives the cell extra support and defines its shape

what is the function of chloroplasts?

• site of photosynthesis, providing food for plants

• the chlorophyll pigments absorb light energy needed for the reaction to occur

what is the function of the vacuole?

• contains cell sap

• used for storage of certain material

• helps support the shape of the cell, keeping it turgid

what is the function of the mitochondria?

• site of aerobic respiration, providing energy for the cell

• cells with high rates of metabolism (carrying out many different cell reactions) will have significantly higher numbers of mitochondria than cells with lower metabolism

what is the function of ribosomes?

• site of protein synthesis

what is the function of the vesicles?

• used to safely transport substances from one part of the cell to another

what are the main organelles found in animal cells?

• nucleus

• cell membrane

• mitochondria

• ribosomes

• cytoplasm

what organelles are found in plant cells?

• nucleus

• cell membrane

• mitochondria

• ribosomes

• cytoplasm

• cell wall made of cellulose

• permanent vacuole

• chloroplasts

what is cell differentiation?

the process by which a cell changes to become specialised

when a cell differentiates, it developes a structure and composition of sucellular structures which enables it to carry out a certain function

what are specialised cells?

those that have devloped certain characteristics that allow them to perform particular functions. these differences are controlled by genes in the nucleus

animal cell differentiation vs plant cell differentiation

in animals, most cells differentiate at an early stage of development, so lose their ability to differentiate

in plants, many types of cells retain the ability to fully differentiate throughout the life of a plant

what are some examples of specialised cells?

ciliated epithelial cell

nerve cell

red blood cell

root hair cell

palisade mesophyll cell

where are ciliated epithelial cells found?what do they do, and how are they adapted?

• in trachea and bronchi

• hair-like extensions called cilia, which beat and transport mucus and trapped particles toward the throat

what do nerve cells do, and how are they adapted?

• nerve cells conduct impulses

• long, allowing for fast communication between different parts of the body and the CNS

• their axons are covered in a fatty sheath that insulates and speeds up nerve transmission

what do red blood cells do, and how are they adapted?

• they transport oxygen

• bioconcave shape, increasing surface area for oxygen diffusion

• contain haemoglobin and lack a nucleus, maximising space for oxygen transport

what do root hair cells do and how are they adapted?

• root hair cells absorb water and mineral ions found in the soil

• their long extensions increase surface area for maximum absorption

• thin walls help move water quickly

what do palisade mesophyll cells do, and how are they adapted?

• palisade mesophyll cells perform photosynthesis

• column-shaped to maximise light absorption

• contain lots of chloroplasts to maximise photosyntheis

• tightly packed to optimize photosynthesis

what is a stem cell?

an undifferentiated cell of an organism that is capable of dividing an unlimited number of times

stem cells can give rise to other cell types through differentiation

what are embryonic stem cells?

they are important as they help to form all of the different tissues and organs needed during development to form an individual - they are totipotent

what are adult stem cells?

they replace cells lost through damage or produce new cells for growth

(bone marrow continually makes new blood cells throughout life)

what are meristem cells?

found in plants, meristem cells are unspecialised cells that differentiate into cells in the plant where growth is occurring

what can stem cells be used for in medicine?

• use embryonic stem cells to repair damaged organs

• adult stem cells can also be used for this (but differentiate into fewer cells)

• used to cure diseases in the future

what is therapeutic cloning? where is it used?

• an embryo is produced from a patient

• stem cells are taken from the embryo and cultured in a petri dish

• because they are genetically identical, the cells will not be rejected by the patient

• is used to make pancreatic cells which produce insulin for diabetic patients

what are some benefits and issues of using stem cells in medicine?