1. Cells Flashcards by Erin Bailey

How has greater resolution of electron microscopes increased our understand of cell structures?

Electron microscopes use a beam of electrons to allow us to see structures that can be as close as a 10000th of a micrometer, meaning we can see more detail of a structure and better understand how it might function

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How do you calculate magnification ?

Magnification : size of image divided by size of real object using a scale bar

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Explain the function of the cell membrane

Controls entry and exit of substances from the cell

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Explain the function of chromosomes

Thread-like structures composed of DNA that carry genes

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Explain the function of the nuclear membrane

Enclosed the genetic material inside the nucleus

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Explain the function of the cytoplasm

Site of chemical reactions in the cell

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Explain the function of the nucleus

Control centre of the cell

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Explain the function of the mitochondria

Structures in the cell responsible for releasing energy during respiration

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Draw an animal cell

Nucleus
Cell membrane
Mitochondria
Cytoplasm

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Explain the function of the Cellulose cell wall

Provides strength and shape to the cell

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Explain the function of of chloroplasts

Contain the green pigment, chlorophyll to absorb light for photosynthesis

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Explain the function of the permanent vacuole

Stores water, salt and sugars

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Draw a plant cell

Cell wall
Cell membrane (inside cell wall)
Vacuole
Cytoplasm
Mitochondria
Chloroplasts 
Nucleus

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Name four differences between the bacterial cells and other cells

they do not contain a nucleus
they have 1 large circular chromosome and extra small rings of DNA (plasmids)
they have a cell which isn’t made of cellulose
they are much smaller compared to plant and animal cells

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What happens to the area you see as magnification increases?

The area of the field of view decreases and the resolution of the image isn’t as clear

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How do you calculate the actual size?

Actual size = image size divided by magnification

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What are stem cells?

A group of unspecialised cells which have the ability to divide to produce more stem cells and become any type of cell required by the body

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Where are stem cells found on a plant?

The meristems at the apices of roots and stems. Many if these cells retain the ability to divide and so can be used in cloning techniques

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Name one ethical concern for the use of adult bone marrow

Theoretically the technology could allow humans to be cloned

Name 3 limitations for adult bone marrow stem cells

Not all cell types can be produced, only specific types of blood cell
Cells have a limited life span
Cells can be hard to grow

Name ethical concerns for the use of stem cells in medicine (3)

Harvesting of the cells may result in the abortion of the embryo
Theoretically humans could be cloned
Creation of embryos artificially for the sole purpose of generating stem cells and then killing them raises similar debates to abortion of embryos

Give an example of when stem cells may be used

With leukaemia patients, a bone marrow transplant containing donor stem cells can be given after chemotherapy to replace the white blood cells and bone marrow that was destroyed

Define diffusion

Diffusion is the random molecular movement of molecules from a region of high concentration to a region of lower concentration alone a concentration gradient

Give three examples of diffusion in biology

gas exchange in the lungs
gas exchange in leaves during photosynthesis
absorption of digested food molecules in the gut

When does a rapid rate of diffusion occur?

A rapid rate of diffusion is allowed when the temperature is warm, the difference in concentration is greater and the surface area is high

List the levels of organisation

Cell - tissue - organ - organ system - organism

Explain why as organisms increase in size they have more difficultly exchanging and transporting substances

As an organisms size increases, it’s surface area to volume radio decreases

Name two systems that make exchange and transport more efficient

- The respiratory system | - The circulatory system

Where can stem cells be harvested from in an animal ?

Stem cells have be harvested from the embryonic umbilical chord or bone marrow (adult)

Why is it important to use the fine focus knob?

Using other knobs focuses the image in and out top quickly and it is difficult to adjust with precision

What structures do plant cells have that others don’t? (3)

- Cellulose Cell Wall - Large Permanent vacuole - chloroplasts

Describe what Leukaemia is and how stem cells are used to treat it: (4)

- Leukaemia is a form of cancer affecting white blood cells. - White blood cl so are unable to function correctly and so diseases cannot be fought off - Treatment involves the patients unhealthy white blood cells and bone marrow being destroyed by chemo and radiotherapy - The patient is then given a bone marrow transplant that contains donor stem cells

Risks of treating patients with stem cells vor Leukaemia : (3)

- Patients can be left with no immunity and therefore susceptible to infection - This leads to patients being treated in highly specialised medical units and have limited contact with family / friends - The donated stem cells could divide in an uncontrolled way producing tumours and unwanted cells types

Why do plant cells tend to have a more fixed shape and rigid structure than animal cells ?

The cell wall of the plant cell makes it rigid

The more active a cell the more mitochondria. Which types of cells have the largest numbers of mitochondria ?(3)

- Muscle - Liver - Sperm

What are the advantages of cells having cell organelles ?

It isolated cells that might be damaging

Why are Ring shapes sometimes observed on cells in the microscope ?

Air bubbles have been trapped in the coverslide

Name the steps to calculate magnification of a leaf cell | Measure bar in mm = 20mm

1. Convert mm to micrometer ( 20 x 1000 = 20000 micrometers ) 2. divide measured length by the printed measurement ( 20000 divided by 5 = x 4000)

Why must the onion tissue used only be 1 cell thick?

- Onion cells more than 1 cell thick would overlap and the cells wouldn’t be clear to see under the microscope

How is a Petri dish sterilised ?

Heat up to a temperature above the water

Why is iodine and methylene blue used in the onion practical ?

They stain the starch granules and make them visible

Risks of using stem cells in Leukaemia treatment (3)

- Patients can be left with no immunity during the process making them susceptible to infection - Patients May have to be treated in highly specialised medical units and have limited contact with family/friends - Donated stem cells could divide in an uncontrollable way producing tumours

Two structure in the bacterial cells that contain DNA

- In the form of a circular chromosome in the cytoplasm | - In the plasmids

Describe making a slide (6)

- Forceps are used to peel the thin, transparent layer of epidermis cells - Epidermis cells are then placed on a microscope slide with a few drops of Iodine solution or methylene blue - These chemicals stain the cells and make certain parts more obvious - A coverslide is then lowered onto the onion epidermis using a mounted needle or forceps - Lower coverslip one end first as this helps to prevent trapping air bubbles - Coverslip prevents the cell drying out

Factors affecting diffusion

- Concentration gradient - Temperature - surface area

Why does being multi-called not contribute to efficient exchange of substances ?

The body cells are closely packed together which increases volume but not surface area

Stem cells two important abilities (2)

- to continue dividing by cell division to produce more stem cells - to differentiate into a wide variety of specialised cell types