2a) Cells, Organs and Populations Flashcards
What things do a plant cell contain that an animal/human cell doesn’t?
Rigid cellulose cell wall - supports the cell and strengthens it
Permanent vacuole - contains cell sap (weak solution of sugar + salts)
Chloroplasts - where photosynthesis occurs to make food, contain chlorophyll
What does a human/animal cell have? (+plant cells)
Nucleus - contains genetic material that controls activities of the cell
Cytoplasm - where chemical reactions happen, has enzymes
Cell membrane - controls in and out
Mitochondria - where respiration
Ribosomes - proteins made
What does a yeast cell contain?
Yeast = single celled organism Nucleus - genetic material to control Cytoplasm - chemical reactions Cell membrane - control in and out Cell wall - support and strengthen
What do Bacteria cells contain?
Bacteria = single celled organism
Cytoplasm - chemical reactions
Cell membrane - control in and out
Cell wall - support and strengthen
NO nucleus - genetic material floats in the cytoplasm
What are all living things made of?
Cells
What is the role of the nucleus in a cell?
Contains genetic material
Controls the activities of the cell
What is the cytoplasm?
Gel-like substance
Where chemical reactions happen
Contains enzymes that control these chemical reactions
What’s the importance if the cell membrane?
Hold the cell together
Controls what goes in and out
Why do cells need mitochondria?
Where most of the reactions for respiration take place
Respiration releases energy that the cell needs to work
What is the purpose of ribosomes in the cell?
Where proteins are made
Why do plant cells have a rigid cell wall?
Supports and strengthens the cell
Made of cellulose
What is cell sap and where is it found?
A weak solution of sugar and salts.
Inside vacuole in plant cells
Why do plant cells have chloroplasts?
Contain a green substance called chlorophyll (to absorb sunlight)
Where photosynthesis occurs which makes food for the plant
Define diffusion
Overall net movement or spreading out of particles from an area of high concentration to an area of low concentration
(Honey Lumps)
Why does diffusion only happen in solutions and gases
Particles in these substances are free to move about randomly
If the difference in concentration is big, what happens to the rate of diffusion?
The bigger difference in concentration, faster the diffusion rate
Why can’t molecules like starch and proteins diffuse through cell membranes?
Big molecules - won’t fit through cell membrane
Give some examples of molecules that can diffuse through cell membranes
Small molecules:
Oxygen, glucose, amino acids, water
How are Palisade leaf cells adapted for photosynthesis?
Packed with chloroplasts - crammed at the top of the cell so closer to light
Tall shape - surface area exposed to absorb CO2 from air
Thin shape - packed at top of leaf where photosynthesis happens
How are red blood cells adapted to carry oxygen?
Concave shape - big surface area to absorb oxygen, can pass smoothly through capillaries
Haemoglobin - red pigment that’s absorbs the oxygen
No nucleus - more room for haemoglobin
How are sperm cells specialised for reproduction?
Long tail and streamlined head - help it swim to egg
Mitochondria - provide energy
Enzymes - digest through egg cell membrane
How are guard cells adapted to allow gas exchange and control water loss within a leaf?
Kidney shape - to open and close the stomata
Turgid - stomata opens so gases can exchange for photosynthesis
Flaccid - stomata close go stop water vapour escaping
Thin outer walls, thick inner walls
Sensitive to light - close at night to save water
How is an egg cell specialised for reproduction?
Food reserves to nourish embryo
Membrane instantly changes structure to stop more sperm entering - so offspring end up with right amount of DNA
Define differentiation
The process by which cells become specialised for a particular job
Occurs during the development of a multicellular organism
What are tissues?
Groups of similar cells that work together to carry out a particular function
Can include more than one type of cell
E.g. Muscular tissue
What is an organ?
Group of different tissues that work together to perform a certain function
E.g. Stomach
What is an organ system?
Groups of organs working together to perform a particular function
E.g. Digestive system
What is the leaf made up of?
Mesophyll tissue - where photosynthesis occurs
Xylem and Phloem - transport
Epidermal tissue - covers plant
What is the photosynthesis equation?
Carbon dioxide + water ~> glucose + oxygen (+energy)
Arrow stands for chlorophyll/sunlight
What is photosynthesis?
The process of producing food (glucose) in plants and algae inside chloroplasts
Where is chlorophyll found?
Chloroplasts in plant cells
What is chlorophyll?
Green substance in chloroplasts
Absorb sunlight and uses energy to covert carbon dioxide (air) and water (soil) into glucose
Oxygen in produced as a by-product
What is produced as a by-product of photosynthesis?
Oxygen (+energy)
Why is sunlight needed for photosynthesis?
Provide energy for the process
What is an organelle?
Parts of the cells which have a distinct structure and function
What is the rate of photosynthesis affected by?
Limiting factors:
Intensity of light - provides energy
Volume of CO2 - raw material
Temperature - for enzymes
What is a limiting factor?
Something that slows down the rate of photosynethesis
How can you measure how fast photosynthesis is happening?
Measure amount of oxygen produced in a time period
Either count bubbles or collect oxygen in a gas syringe
How can you change light intensity in a lab?
Move the lamp closer of further away from the plant
Describe one way of increasing the amount of CO2
Dissolve some sodium hydrogen carbonate in the water which gives off CO2
Using a paraffin heater - CO2 created as a by-product
Describe one way of controlling the temperature
Put the flask in a water bath
At what temperature do enzymes usually get damaged?
45 degrees Celsius
Name 5 ways plants use glucose
For respiration - provide energy
Making cell walls - glucose is converted into cellulose
Making proteins - combined with nitrate ions to make amino acids
Stored in seeds - turned into lipids
Stored as starch - energy store
What environmental factor affect where an organism might live?
Temperature Availability of water Availability of oxygen and CO2 Availability of nutrients Amount of light
How do you work out the mean number of organisms per quadrat?
Total organisms divided by number of quadrats
How do you work out the population size of an area?
Mean no. Of organisms per m squared times by total area of habitat
How can you measure the distribution of organisms?
Quadrats
Transect line
