Topic 1 - Cells Flashcards
What are living things made of ?
Cells
Eukaryotic Cell
A cell with a membrane bound nucleus (Eg. Plants and Animals)
Prokaryotic Cell
A cell without a membrane bound nucleus (Eg. Bacteria)
What is the difference between a Eukaryotic and Prokaryotic Cell ?
Eukaryotic have a nucleus whilst Prokaryotic cells have free DNA and rings of DNA called plasmids
What is the size difference between a Eukaryotic and Prokaryotic cell
Eukaryotic cells are 100x larger
What are the differences between and animal and plant cell
Plant cells have; a vacuole filled with cell sap, chloroplasts for photosynthesis, a cell wall for structural integrity
Roles of chloroplast, mitochondria and ribosomes
Chloroplast - Site of photosynthesis
Mitochondria - Site of respiration
Ribosome - Site of protein synthesis
Roles of nucleus, cell membrane and cytoplasm
Nucleus - stores genetic information
Cell Membrane - Controls what goes in and out the cell
Cytoplasm - the site of chemical reactions
Roles of the cell wall, vacuole and flagellum
Cell wall - maintains the structure of the cell
Vacuole - contains cell sap (a mixture of dissolved ed sugar)
Flagellum - allows cells to move more efficiently
What is differentiation?
When a cell becomes specialised to a certain role
When does differentiation happen?
Animals - at the early stages of embryo development
Plants - at any point within their lives
What is a specialised cell? (and example)
A cell that has been adapted to enable it to complete a specific job (Eg. Sperm cell, Root hair cell)
How have sperm, nerve and muscle cells been adapted to their function?
Sperm - Lots of mitochondria to provide energy for the swimming and a flagellum to move faster.
Nerve - Surrounded by insulation (myelin sheith) to ensure electrical impulses stay in the cell
Muscle - Can change shape to contract and relax
How have root hair cells, the xylem and phloem adapted to their function?
Root hair - Long hair like structures to increase SA for absorbing nutrients from the soil
Xylem - Hollow cells to transport water
Phloem - companion cells to provide energy for active transport and sieve plates
What is magnification ?
Magnification is the ability of the microscope to make an object appear larger
What is resolution ?
The detail which can be seen in a magnified object, higher resolution means more detail.
What is the difference between a light and electron microscope ?
Electron - Much higher resolution and higher magnification so sub cellular structures can be seen
Light - Cheaper
Total magnification calculation
Total magnification = eye piece lens x objective lens
How thick should a specimen on a slide be ?
As thin as possible - ideally 1 cell thick
Why should specimens be as thin as possible ?
So that light can pass through the cell so we can see inside it.
Why do we use iodine to stain the cells ?
The stain helps us differentiate between the sub-cellular structures of the cell
How do you draw cells ?
No shading
Straight lines
Note down the magnification
Annotate what you can see
What is the process of making an onion cell ?
1) Place a thin sample on a slide (1 cell thick)
2) Add a drop of iodine
3) Carefully add cover slip at an angle to avoid bubbles
What is a micrometer ?
1/1000th of a millimetre
What is the equation that links magnification, image size and actual size?
magnification = image size / actual size
Difference between adult and embryonic stem cells
Adult - can only differentiated into certain types of cells
Embryonic - Can differentiate into any type of cell
What are stem cells ?
Undifferentiated cells
Where are stem cells found in plants ?
Meristem tissue - tips of roots and shoots
Where are stem cells found in humans ?
Bone marrow
Uses of stem cells in plants and animals
Animals - treating disease using bone marrow and therapeutic cloning
Plants - Produces lots of identical crops to prevent extinction.
Whta is therapeutic cloning ?
When an embryo is produced with the same genes as the patient, so they can be used for medical treatment without rejection
Risks of using stem cells
Viral diseases can be spread and there are ethical issues involving embryos.
What are chromosomes ?
Long stands of DNA
Where are chromosomes found ?
In the nucleus
Describe the 3 stages of the cell cycle
Stage 1: cell grows, DNA replicates and sub cellullar structures multiply.
Stage 2: Chromosomes and copies line up down centre of the cell and are pulled to either side. New nuclear membranes form.
Stage 3: cytoplasm divides and new cell membranes form.
What is the purpose of mitosis
The growth and repair of tissues
What are the products of mitosis ?
Two identical daughter cells (clones)
What causes cancer ?
Uncontrolled cell division
What are benign tumours ?
Abnormal growth of cells contained in one area which do not invade neighbouring tissues.
What are malignant tumours ?
Cancerous growths which invade neighbouring tissues and can spread to other parts of the body to form secondary tumours.
How does cancer spread ?
Parts of tumours which aren’t restricted to a membrane break off and travel through the bloodstream.
What can increase the chance of cancer ?
Genetics and Lifestyle
What is diffusion ?
The movement of particle form an are of high concentration to low concentration
Examples of diffusion in plants and animals
Plants - CO2 diffuses into the leaf, O2 diffuses out
Animals - O2 diffuses from lungs to blood, CO2 diffuses from blood to lungs
What 3 things can increase the rate of diffusion ?
1) Temperature
2) Surface area
3) Concentration gradient
How do you work of the the surface area to volume ratio ?
Surface area / volume
How are single cell organisms adapted for diffusion ?
High surface area to volume ratio so all parts of the cell are close to the outside, short diffusion pathway.
What is exchange in cells ?
Substances diffusing in and out of cells
Why do multicellular organisms need specialised exchange systems ?
They have small SA:V so need organs to bring substances from outside to the internal cells.
What are the three features of gills, lungs and the small intestine ?
Large surface area, lots of blood vessels and thin membranes
How do these feature help with diffusion?
Large surface area - lots of diffusion at once.
Thin membranes - short diffusion pathway/distance. Lots of blood vessels - maintain a concentration gradient.
What is osmosis ?
The movement of water molecules from a dilute solution to a concentrated solution through a partially permeable membrane.
What happens in dilute solutions ?
They absorb water by osmosis and expand. Animal cells will burst.
What happens in concentrated solutions
Water leaves the cells by osmosis and they will shrink
What happens to a plant tissue in a dilute solution ?
It will gain mass and length
What happens to plant tissue in a concentrated solution ?
It will lose mass and length
How do you find percentage change in mass ?
change in mass / starting mass x 100
What is active transport ?
The movement of particles from an area of low concentration to an area of high concentration.
What are the differences between diffusion and active transport?
Active transport requires energy
Active transport goes against a concentration gradient
Active transport in plants (example)
Some mineral ions are absorbed against the concentration gradient.
Active transport in humans (example)
Glucose is absorbed from the small intestine into the blood
